DoD STTR 22.A

OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Air Platforms;Human Systems

OBJECTIVE: Design, build, and demonstrate a vertical lift platform (i.e., helicopter or tiltrotor) cockpit visual display that mitigates spatial disorientation during brownout landings and takeoffs. The display must be compatible with DoD vertical lift/aircrew systems currently in use.

DESCRIPTION: The term “brownout” refers to degradation of out-the-window cockpit visibility during landings or takeoffs from areas with loose, dry, ground soil. During brownouts, loss of visibility occurs when a helicopter or tiltrotor’s main rotor blades stir up dirt, dust, or sand, which is then re-circulated through the blades and over the windscreen during low ground hover operations. The Joint Air Power Competence Centre (JAPCC) reported that the most dangerous action a helicopter pilot can take is land in brownout conditions. Additionally, it cited a USAF Institute of Technology report which states that the U.S. Department of Defense (DoD) had over 100 million USD in costs attributed to brownout mishaps. Furthermore, 65% of non-hostile fatalities have been from brownout hover and low speed flight. A final conclusion from the JAPCC’s report was that while many phases of helicopter flight can be performed with only instrument scanning, landing and hovering cannot [Ref 1].

During vertical hover landings or takeoffs with good outside visibility, rotary-wing and tiltrotor pilots maintain spatial orientation by using two types of outside visual cues. The first is a distant view of a horizontal reference that can be used for detecting unintended roll or pitch motions, and the second is a view of nearby fixed ground objects used as references for detecting unintended yaw, side drift, or forward and aft motion. With Visual Meteorological Conditions (VMC), primary spatial cues for rotary-wing and tiltrotor pilots are defined as fixed foveal views of distant (horizon) or near (ground) references. In contrast, secondary spatial cues have been defined as unstabilized peripherally viewed objects (such as cockpit components or outside airframe structures) that are perceived as being in motion as they change retinal position relative to the stabilized primary cue. Together, fixed primary and moving secondary spatial cues create a dynamic sight picture that allows pilots to use a VMC spatial strategy for determining aircraft attitude and directional rate of movement [Ref 2]. If visibility of either primary cue type is blocked by circulating particles within the rotor blade vortex ring, the pilot will suffer an immediate loss of critical spatial information, which unfortunately, also creates a high potential for spatial disorientation (SD) and incorrect control inputs.

When brownouts cause pilots to suddenly lose their outside visual cues seconds before touchdown, they are forced instantly to decide whether to attempt a rapid instrument transition or continue with an outside scan, hoping to see a visual ground reference seconds before setting down. Unfortunately, when transitioning from an outside view to head down instruments, the Federal Aviation Administration (FAA) has documented that establishing full instrument control after the loss of surface visual reference can take as much as 35 seconds [Ref 3]. With brownout conditions, sudden loss of the primary spatial cues (horizon and ground) and the limited time available to successfully transition to instruments, creates a high risk for SD.

Researchers have demonstrated that pilots exhibit specific reflexive head and eye movements that influence sight picture dynamics in a manner that aids with development of VMC spatial strategies [Refs 2, 4, and 5]. Brownout visual countermeasures that accommodate these normal pilot behaviors may help reduce pilot spatial problems known to occur with less than optimum display designs. To mitigate this risk, the DoD is seeking a non-energy signature emitting visual display system with a presentation that will mimic pilot outside spatial strategies when encountering degraded visual environments (DVE).

Proposed display designs should enable a seamless transition time between real-world spatial cues and display symbology and consideration should be given for incorporation of flight path predictor type symbology. Design proposals should also describe, in general terms, compatibility with existing rotary-wing and tiltrotor systems such as (but not limited to): weight issues, cost estimate assessment, display transition time, and usability with both day and night conditions.

The prototype display should be constructed in a manner compatible with both stationary (non-motion) flight simulator and a motion-based flight simulator with six degrees of freedom (6DOF). The first stage of the evaluation should involve non-motion flight simulation with brownout conditions and the second stage should repeat stage one in a simulated flight environment with full 6DOF motion. Since the combined motion and visual environments of rotary-wing and tiltrotor brownout usually involve 6DOF, the Navy Disorientation Research Device (DRD) at the Naval Medical Research Unit Dayton, Wright-Patterson Air Force Base, Ohio, may be considered as a potential test facility for Phases II and III efforts. It is expected that a fully operational and complete (hardware and software) brownout mitigation visual display prototype will not require input from airframe emitted sensory energy and will operate using open-source software that is compatible with desktop Microsoft CPU systems. Device prototype and test subject raw performance data collected in ASCII format during test and evaluation with motion and non-motion based brownout simulations. Phase II final report that contains a detailed schematic and a complete description for operation of the brownout mitigation visual display system. The final report should also include a detailed analysis of the performance testing data collected during motion and non-motion brownout simulations.

Test and evaluation should demonstrate the prototype display capability for preventing SD during sudden and unexpected encounters with brownout conditions during high workload conditions. The experimental design for evaluating the working prototype should include DoD rotary-wing and tiltrotor pilots as test subjects and have a statistical power of 0.80 or higher. Dependent variables for display assessment should include, but not be limited to, pilot landing and takeoff tracking performance (roll, pitch, yaw, ascent, descent, airspeed, and drift), Opto-Kinetic Cervical Reflex (OKCR) response, eye tracking, Control Reversal Errors (CRE), subjective workload assessment, and motion sickness susceptibility.

Note: NAVAIR will provide Phase I performers with the appropriate guidance required for human research protocols so that they have the information to use while preparing their Initial Phase II Proposal. Institutional Review Board (IRB) determination as well as processing, submission, and review of all paperwork required for human subject use can be a lengthy process. As such, no human research will be allowed until Phase II and work will not be authorized until approval has been obtained, typically as an option to be exercised during Phase II.

PHASE I: Develop, describe, and define potential methodologies and designs for a visual display system that will prevent loss of spatial awareness during DVE encountered with brownout conditions. During the Phase I process, plans for designing an optimum visual countermeasure for brownout should take into consideration the types of cognitive processing pilots use with inflight spatial strategies, during both VMC and Instrument Meteorological Conditions (IMC). Provide detailed Phase I final report that includes concepts and plans to develop and test a brownout mitigation visual display for rotary-wing aircraft in stationary and 6DOF simulators. The Phase I effort will include prototype plans to be developed under Phase II.

Note: Please refer to the statement included in the Description above regarding human research protocol for Phase II.

PHASE II: Develop a working prototype visual display for mitigating or eliminating pilot SD during brownout takeoffs and landings.

Note: Please refer to the statement included in the Description above regarding human research protocol for Phase II.

PHASE III DUAL USE APPLICATIONS: Integrate display design into a 6DOF motion simulator and vertical lift platform. Final end user testing, validation, and verification of the display system in DVE conditions.

Private sector or corporate transportation services that utilize vertical lift platforms (i.e., helicopters) can experience degraded visual environments due to unexpected weather conditions or terrain challenges. These conditions can lead to mishaps due to resulting spatial disorientation. In addition, federal (e.g., USCG, DHS, FBI), state (National Guard units, Civil Air Patrol), or local (e.g., Firefighter/Paramedics, life flight) government search and rescue that utilize vertical lift platforms may benefit from the use of an advanced display design to mitigate spatial disorientation associated with DVE conditions. A secondary application may be in the display system used with unmanned aerial systems with vertical lift capabilities.

REFERENCES:

1. Modesto, M. (2017). “Beating brownout: Technology helps, but training remains key.” Joint Air Power Competence Centre. https://www.japcc.org/beating-brownout/.
2. Patterson, F. R., Cacioppo, A. J., Gallimore, J. J., Hinman, G. E., & Nalepka, J. P. (1997). “Aviation spatial orientation in relationship to head position and attitude interpretation.” Aviation, Space, and Environmental Medicine, 68(6), 463–471. https://www.researchgate.net/publication/14033635_Aviation_spatial_orientation_in_relationship_to_head_position_and_attitude_interpretation.
3. Hunt, K. S. (1983, February 9). “Advisory circular: Pilot’s spatial disorientation.” AC No. 60-4A. Federal Aviation Administration. https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC60-4A.pdf.
4. Patterson, F. R., & Muth, E. R. (2010, September 9). “Cybersickness onset with reflexive head movements during land and shipboard head-mounted display flight simulation, Report Number 10-43.” Naval Aerospace Medical Research Laboratory. https://apps.dtic.mil/sti/pdfs/ADA528015.pdf.
5. Moore, S. T., MacDougall, H. G., Lesceu, X., Speyer, J. J., Wuyts, F., & Clark, J. B. (2008). “Head-eye coordination during simulated orbiter landing.” Aviation, Space, and Environmental Medicine, 79(9), 888-898. https://doi.org/10.3357/ASEM.2209.2008.
6. Naval Medical Research Unit Dayton. (n.d.). “Disorientation research device: The Kraken(TM).” Retrieved March 24, 2021, from https://www.med.navy.mil/sites/nmrc/NAMRUDayton/Directorates/Admin/Pages/Disorientation-Research-Device.aspx.

KEYWORDS: Degraded visual environment; DVE; future vertical lift; spatial disorientation; display symbology; display design; human factors

OUSD (R&E) MODERNIZATION PRIORITY: Directed Energy (DE);General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Air Platforms

OBJECTIVE: Develop an aerodynamic, multifunctional heat exchanger that is capable of dissipating a large amount of aircraft waste heat while improving inlet flow distortion upstream of a gas turbine engine.

DESCRIPTION: Inlet guide vanes offer a potentially attractive way to remove heat from aircraft and engine coolants. Doing so, however, adds complexity and volume to conventional guide vanes, which are also ill-suited for convoluted inlets with complex aerodynamics. The volume added to conventional guide vanes results in aerodynamic losses and weight penalties that can negate the gains from multifunctionality. More elegant, combined aerodynamic/heat exchanger solutions may be feasible given the current state-of-the-art in multi-objective optimization, additive manufacturing, and custom flow tailoring. Advanced diffuser designs often involve flow separation and large-scale unsteady flow features which reduce the diffuser efficiency and subject the downstream turbomachinery to extreme flow distortions. Solutions are sought for a new heat exchanger technology that can simultaneously improve inlet diffuser aerodynamic performance. The heat transfer and aerodynamic flow field characteristics of the proposed technology need to be fully understood to ensure gas turbine engine compatibility and enable future, advanced Navy propulsion systems.

The proposed solutions will be required to demonstrate the following criteria:

• Heat exchanger effectiveness greater than, or equal to, 0.4.
• A total pressure drop across the heat exchanger no greater than 8%.
• A decrease in the element average circumferential and radial distortions as defined in SAE AIR 1419C [Ref 5].
• The front face of the heat exchanger positioned no more than two (2) diameters upstream of the Aerodynamic Interface Plane (AIP).

Though not required criteria, proposed solutions are encouraged to consider impacts and capabilities on the air platform as a whole. Metrics such as weight, serviceability, propulsion performance, and working fluid are important aspects to overall feasibility and utility. Values are not imposed so that the design space is not overly constrained. It is advised that total system estimated weight (including installation and plumbing) not to exceed 50lbm, and must fit within an existing inlet geometry (Ref 3 may be used for a defined geometry).

It is recommended to collaborate with an original equipment manufacturer (OEM) for Phase II studies, and Phase III integrated testing to identify representative installation configurations and performance needs.

PHASE I: Demonstrate feasibility of the proposed technology through computational and system-level analysis of a proposed concept, and in a simplified flow environment at the bench level. Detailed benefits of this concept, relative to existing technologies, should be identified. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: A prototype device should be designed, built, and tested to evaluate heat exchanger effectiveness, pressure loss, and distortion reduction in a representatively complex inlet (serpentine, varying cross-sectional area and shape; Ref 3).

PHASE III DUAL USE APPLICATIONS: Integrated test should be performed to evaluate the impact the multifunctional heat exchanger has on power plant performance. Transition the technology to applicable naval platform or lab.

Heat dissipation and flow straightening are not military specific concerns. Commercial aircraft/rotorcraft could also take advantage of this topic. Improvements to air flow into engines provide great operational safety and reliance for air vehicles.

Commercialization of this technology may include industrial applications for flow conditioning and heat exchangers, as well as advanced concepts for commercial transport aircraft and automotive applications.

This technology could also be applied for regenerative engine cycles. The ability to utilize the waste exhaust thermal energy of a power cycle to heat incoming air can provide an increase in cycle efficiency and decrease in fuel consumption. Additive manufacturing could provide the opportunity to retrofit existing systems to take advantage of regeneration.

REFERENCES:

1. Guimarães, T., Lowe, K. T., & O’Brien, W. F. (2017, October 31). “StreamVane turbofan inlet swirl distortion generator: Mean flow and turbulence structure.” AIAA Journal of Propulsion and Power, 34(2), 340-353. https://doi.org/10.2514/1.B36422.
2. Nessler, C. A., Copenhaver, W. W., & List, M. G. (2013, January 7-10). “Serpentine diffuser performance with emphasis on future introduction to a transonic fan [Paper presentation].” In 51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, Grapevine (Dallas/Ft. Worth Region), TX, United States. https://doi.org/10.2514/6.2013-219.
3. Maghsoudi, I., Mahmoodi, M., & Vaziri, M. A. (2020, January 28). “Numerical design and optimization of mechanical vane-type vortex generators in a serpentine air inlet duct.” European Physical Journal Plus, 135(2), 139. https://doi.org/10.1140/epjp/s13360-020-00124-1.
4. Reichert, B. A., & Wendt, B. J. (1996). “Improving curved subsonic diffuser performance with vortex generators.” AIAA Journal, 34(1), 65-72. https://doi.org/10.2514/3.13022.
5. SAE International Aerospace Council Divisional Technical Committee S-16. (2017, November 20). “AIR1419C: Inlet total-pressure-distortion considerations for gas-turbine engines.” SAE International, November 20, 2017. https://www.sae.org/standards/content/air1419c/.

KEYWORDS: Thermal management; Inlets; Heat Exchangers; Propulsion Performance; Inlet Distortion; Additive Manufacturing

OUSD (R&E) MODERNIZATION PRIORITY: Artificial Intelligence (AI)/Machine Learning (ML)

TECHNOLOGY AREA(S): Air Platforms;Materials / Processes

OBJECTIVE: Develop a coupled electro-chemo-mechanical model to optimize electroplating parameters, and to predict the influence of surface roughness, porosities/defects, and residual stresses due to zinc-nickel (Zn-Ni) coating on fatigue strength of high strength steel (HSS) aerospace components.

DESCRIPTION: Naval aircraft operate routinely in a very severe saltwater environment, and corrosion damage is the leading cause affecting fleet readiness and total life cycle cost. The Navy spends about $3.7 billion a year on corrosion maintenance and repairs. Corrosion fatigue can also lead to catastrophic failures of aircraft primary structures. Electrodeposition of cadmium coating on high strength steel (HSS) components has been very effective in providing protection against corrosion. However, cadmium—a known carcinogen—creates environmental hazards, and occupational safety and health (OSH) risks. Recently, a new alkaline Zn-Ni coating process has been developed and shown promises as a suitable replacement for cadmium plating.

HSS alloys such as 300M and 4340 are susceptible to hydrogen embrittlement. During the electroplating process, the released hydrogen gas could be absorbed into the substrate, which can cause the loss of ductility, static, and fatigue strength of the base metal. Furthermore, hydrogen can also be absorbed into the HSS components when the coating corrodes in service. This hydrogen re-embrittlement (H-RE) mechanism could also lead to premature structural failures.

In addition, surface roughness, coating thickness/uniformity, porosities/microcracking, residual stresses, and pre- and post-treatment can have a significant impact on not only the effectiveness and durability of the coating system, but also on the components’ fatigue performance. Electrolyte chemical composition, current density, part geometries, and anode-cathode placement/spacing and surface areas are also contributors to the plating variations.

Current process characterization, optimization, and qualification are predominantly empirical based requiring extensive testing, a costly and very time-consuming effort. This must be repeated for each of the HSS alloys.

The Navy requires an integrated suite of software tools that accelerate the optimization and qualification process, and quickly assess the impacts of electroplating on the structural integrity, including material properties and fatigue performance of HSS aircraft components (e.g., landing gears) subjected to naval operating environments. The modeling approach should consider the interplay between residual stresses, porosities/defects, and microstructure evolution on fatigue strength of the metallic materials. The proposed research should also provide a two-way coupling between the corrosion damage and mechanical stresses (internal/residual and externally applied) for capturing the synergistic effects of mechanical loading and corrosion on the integrity of the electroplated parts.

The specific aims are: (a) modeling residual stress generation during electrodeposition, (b) predicting fatigue strength of the base metal considering surface roughness, porosities/defects, and residual stresses, and (c) developing multiobjective optimization algorithm for the plating process.

PHASE I: Develop a modeling concept and computational framework for electrodeposition and optimization of Zn-Ni coating on a HSS (300M or 4340) structural component (e.g., landing gears). Demonstrate feasibility of the proposed concept to predict residual stresses, coating thicknesses, and fatigue performance of the electroplated part under constant and variable amplitude spectra. Develop a qualification testing plan for the optimized coating. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Develop multiobjective optimization algorithm for electroplating process. Develop and demonstrate a beta software tool for electroplating Zn-Ni coating on HSS (300M or 4340) parts. Validate the model predictions with experimental test coupons and representative structural parts subjected to constant and variable amplitude spectra. Perform qualification testing for the optimized coating in accordance with the test plan developed in Phase I. Demonstrate by testing that the corrosion protection and fatigue performance of the optimized Zn-Ni plated component under constant amplitude and variable amplitude spectrum to be equivalent or better than the cadmium plated part.

PHASE III DUAL USE APPLICATIONS: Demonstrate the scalability and effectiveness of the tools for different HSS alloys such as Aermet100, 17-4PH and HYTUF. Perform qualification testing on a full-scale component to validate the software predictions. Transition the tools to U.S. Government depots and commercial industries.

In addition to aerospace, the transportation industry—such as automotive—will benefit greatly from this technology for optimizing plating of transmission gears made from high strength steel alloys for better corrosion and wear resistance performance.

REFERENCES:

1. Read, H. J. (1967). “Metallurgical aspects of electrodeposits.” Plating, 54(1), 33-42. https://www.nmfrc.org/pdf/2018/07harold_read1966.pdf.
2. Weil, R. (1982). “Material science of electrodeposits.” Material Science. https://www.nmfrc.org/pdf/stwp/2012-03-01.pdf.
3. Raub, C. J. (1993). “Hydrogen in electrodeposits: of decisive importance, but much neglected." Plating and Surface Finishing, 80(9), 30-38. https://www.nmfrc.org/pdf/2018/34christoph_raub1993.pdf.
4. Gabe, D. R. (1997). “The role of hydrogen in metal electrodeposition processes.” Journal of Applied Electrochemistry, 27(8), 908-915. https://doi.org/10.1023/A:1018497401365.
5. Stein, M., Owens, S. P., Pickering, H. W., & Weil, K. G. (1998). “Dealloying studies with electrodeposited zinc-nickel alloy films.” Electrochimica acta, 43(1-2), 223-226. https://doi.org/10.1016/S0013-4686(97)00228-4.
6. Weil, R. (1994). “Aspects of the mechanical properties of electrodeposits.” MRS Online Proceedings Library (OPL), 356. https://doi.org/10.1557/PROC-356-119
7. Hearne, S. J. (2008). “Origins of Stress During Electrodeposition (No. SAND2008-2533C).” Sandia National Lab.(SNL-NM), Albuquerque, NM (United States). https://www.osti.gov/servlets/purl/1145482.
8. Crotty, D., Lash, R., & English, J. (1999). “Performance of zinc-nickel alloy electrodeposits as affected by internal stress.” SAE transactions, 28-39. https://www.jstor.org/stable/44650584.
9. Felder, E. C., Nakahara, S., & Well, R. (1981). “Effect of substrate surface conditions on the microstructure of nickel electrodeposits.” Thin Solid Films, 84(2), 197-203. https://doi.org/10.1016/0040-6090(81)90469-7.
10. Voorwald, H. J. C., Rocha, P. C. F., Cioffi, M. O. H., & Costa, M. Y. P. (2007). “Residual stress influence on fatigue lifetimes of electroplated AISI 4340 high strength steel.” Fatigue & Fracture of Engineering Materials & Structures, 30(11), 1084-1097. https://doi.org/10.1111/j.1460-2695.2007.01178.x.
11. Sabelkin, V., Misak, H., & Mall, S. (2016). “Fatigue behavior of Zn–Ni and Cd coated AISI 4340 steel with scribed damage in saltwater environment.” International Journal of Fatigue, 90, 158-165. https://doi.org/10.1016/j.ijfatigue.2016.04.027.
12. (2016). “ASTM E8/E8M-16ae1, Standard test methods for tension testing of metallic materials.” ASTM International. https://www.astm.org/DATABASE.CART/HISTORICAL/E8E8M-16AE1.htm.
13. (2019). “ASTM E606/E606M-19e1, Standard test method for strain-controlled fatigue testing.” ASTM International. https://www.astm.org/Standards/E606.htm. 
14. Waalkes, M. P. (2003). “Cadmium carcinogenesis.” Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis, 533(1-2), 107-120. https://doi.org/10.1016/j.mrfmmm.2003.07.011.
15. Fernandes, M. F., dos Santos, J. R. M., de Oliveira Velloso, V. M., & Voorwald, H. J. C. (2020). “AISI 4140 steel fatigue performance: Cd replacement by electroplated Zn-Ni Alloy Coating.” Journal of Materials Engineering and Performance, 1-12. https://doi.org/10.1007/s11665-020-04669-1.
16. Barrera, O. et al. (2018). “Understanding and mitigating hydrogen embrittlement of steels: a review of experimental, modelling and design progress from atomistic to continuum.” Journal of materials science, 53(9), 6251-6290. https://doi.org/10.1007/s10853-017-1978-5.

KEYWORDS: electroplating; zinc-nickel coating; high strength steel; fatigue strength; corrosion protection; wear resistance

OUSD (R&E) MODERNIZATION PRIORITY: Networked C3

TECHNOLOGY AREA(S): Air Platforms

OBJECTIVE: Develop an advanced tool for automatically generating hexahedral meshes for high-fidelity simulation of electronically scanned array antennas on Navy platforms.

DESCRIPTION: Currently, many powerful fully automatic mesh generation tools are available that employ tetrahedral cells to mesh complex geometries, including full aircraft Computer-aided Design (CAD) models. These tetrahedral meshes are in general unable to provide the same level of solution accuracy as hexahedral meshes. Another important advantage of a hexahedral mesh over a tetrahedral mesh is the reduction in the number of elements for the same level of analysis accuracy. However, creating hexahedral meshes, especially for complex geometries such as full aircraft, is a tedious and time-consuming process that significantly burdens many realistic engineering analyses and design cycles.

Conducting performance analysis of very complex antennas on full aircraft configuration for Navy applications can be significantly improved by employing a hexahedral mesh. Such antennas include passive phased array (PESA), active electronically scanned array (AESA), hybrid beam forming phased array, and digital beam forming (DBF) array. These types of antennas have small-scale complex internal features that need to be precisely captured by a given mesh. At the same time, the location of these antennas on the aircraft is also important and needs to be optimized. As such, the combination of greatly varying mesh scales and the number simulations that need to be performed are significant factors that can take advantage of a hexahedral mesh that will allow for better accuracy with significantly reduced overall simulation time. The ability to produce highly accurate on-aircraft antenna responses at the element level (fractions of a dB in the main beam) while reducing run-time by adaptively meshing the model is critical. Taking advantage of the latest developments in hexahedral meshing technology [Refs 1–3] to create fully hexahedral or strongly hex-dominant (98% or more hex) meshes for applications involving installed phased array antennas on full aircraft configurations is a possible means to address this topic. The approach should provide capabilities to import CAD models (IGES, STEP, STL, etc.) and subsequent geometry cleanup and preparation for meshing. Provide capabilities to write out mesh in CGNS format for subsequent use with EM simulation tools.

PHASE I: Demonstrate the feasibility of an automatic hexahedral mesh, or a hexahedral dominant mesh generation tool, for simulation of complex phased array antennas on full aircraft platforms. Initiate development work on a user friendly Graphic User Interface (GUI) or integrate into an existing mesh generation tool to enable the user to efficiently (relative to that of existing commercial codes using tetrahedral meshing), set up a geometry model and create a hexahedral mesh capturing details of the antenna and aircraft geometry. The demonstration should compare accuracy of simulations using the hexahedral meshes with those using tetrahedral meshes for a variety of canonical electromagnetic problems.. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Develop a prototype hexahedral mesh generator tool. Continue work on further development and improvement of the algorithm initiated during Phase I. Complete the related GUI development work. Include performance metrics using advanced EM simulation tools to show expected performance efficiencies compared to conventional tetrahedral meshes. Show ease of use and operability utilizing realistic CAD models of installed phased array antennas on the aircraft. Provide the option of creating tetrahedral meshes as needed by the end user.

PHASE III DUAL USE APPLICATIONS: Complete development, and perform final testing of a commercial grade application for use by radar, antenna, and computational electromagnetics engineers.

The approach is applicable to any electrically large complex system including commercial aircraft or automobiles.

REFERENCES:

1. Livesu, M., Pietroni, N., Puppo, E., Sheffer, A., & Cignoni, P. (2020). “LoopyCuts: practical feature-preserving block decomposition for strongly hex-dominant meshing.” ACM Transactions on Graphics (TOG), 39(4), 121-1. https://doi.org/10.1145/3386569.3392472.
2. Li, Y., Liu, Y., Xu, W., Wang, W., & Guo, B. (2012). “All-hex meshing using singularity-restricted field.” ACM Transactions on Graphics (TOG), 31(6), 1-11. https://doi.org/10.1145/2366145.2366196.
3. Liu, H., Zhang, P., Chien, E., Solomon, J., & Bommes, D. (2018). “Singularity-constrained octahedral fields for hexahedral meshing.” ACM Transactions on Graphics, 37(4), Article No. 93, 1. https://doi.org/10.1145/3197517.3201344.

KEYWORDS: computational electromagnetics; Hexahedral Mesh; modeling and simulation; antennas; radome; antenna array

OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Air Platforms;Human Systems

OBJECTIVE: Develop and validate a survey-based assessment tool aimed at measuring perceptions regarding the experience and severity of a spatial disorientation-related illusion, as well as to evaluate the effectiveness of knowledge/skill acquisition and attitudinal changes from spatial disorientation training protocols.

DESCRIPTION: Spatial disorientation (SD) is one of the most cited accident-causing factors in aviation and accounts for 33% of all aviation accidents [Ref 2]. This trend has increased over time due to the rise in licensed pilots and hours flown; however, little research has been done to address the measurement of knowledge, skills, and attitudes required to combat an SD incident. Rather, the majority of current and prior literature focuses on improving the technology utilized to improve SD training. While technological updates to modern SD training simulations have been shown to improve SD-related outcomes [Refs 3–6] (i.e., subjective identification of SD illusions, successful simulation, and elicitation of illusions), the lack of observational and survey scales to assess the true effect that SD training methods have on aviators is concerning. Specifically, no current or prior literature attempts to analyze and present the specific knowledge, skills, and abilities (KSA) that their study's training conditions were meant to target. This systematic lack of KSA identification during training assessment is concerning as they remain the most predictive and valid metrics of competencies that relate to an individual’s abilities to perform a task [Ref 1].

Recent advances in the SD training domain have sought to mitigate this challenge by producing a set of training competencies that are believed to be associated with SD training outcomes. A recent Training Systems Requirements Analysis focused on advanced spatial disorientation was developed via a subject matter expert review of prior SD training and competency literature. Various current and prior SD training programs also informed this analysis in order to ensure that the information taught in future SD training programs, to both indoctrination and refresher aviators, will improve their knowledge of SD, their skills in employing tactics against it, and their attitudes towards utilizing training and safety procedures for SD. However, while previous analyses provide the most comprehensive list of competencies for SD training to date, the competencies and methods of measuring said competencies have not undergone documented validation. Psychometric validation is a statistically quantitative process concerned with determining if the metrics utilized to measure latent constructs (i.e., illusion identification ability) are measuring latent constructs reliably and consistently. Without the validation of questions and behavioral observations to underpin analysis results, it is unclear whether the protocols will truly target key SD avoidance, mitigation, and countermeasure competencies required by aviators. Further, it is possible that without appropriate psychometric validation, future efforts will have opposing effects on SD training by missing key components of the required KSA.

Developing a validated SD assessment and evaluation tool provides an opportunity to formulate a data-driven method to both measure SD mitigation and countermeasure knowledge and behavior, while also providing a differential measurement to assess training effectiveness resulting in validated training methods. A software-based assessment tool would assist trainers in not only developing more effective training protocols and procedures, but also personalizing SD training feedback to student aviators. The final decision support tool product will enable a standardized, reliable, and valid measurement of real-time training SD episode mitigation and reaction knowledge and skills. The hardware and software must meet the system DoD accreditation and certification requirements to support processing approvals for use through the policy cited in Department of Defense Instruction (DoDI) 8510.01, Risk Management Framework (RMF) for DoD Information Technology (IT) [Refs 7, 8], and comply with appropriate DoDI 8500.01, Cybersecurity [Refs 7, 8, 9]. Finally, research into the effectiveness of the instructional strategies and technologies developed based on these concepts is necessary to determine feasibility prior to transition.

PHASE I: Develop a psychometrically-based validation protocol to assess relevant SD competencies (e.g., application of procedures, communication, safety of flight management, automated and/or manual aircraft control, leadership, crew resource management, problem solving, decision making, situation awareness, workload management). Design the framework of the software-based tool to ensure a high level of end-user use reliability and usability. Develop the user-interaction architecture of the software tool for user input, output, and modification of the validated survey. Deploy psychometric validity testing. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Develop a validated questionnaire and observation tool of SD mitigation and countermeasure KSA from validity testing. Incorporate the initial questionnaire and observation tool into the software-based application for prototype demonstration and testing. Deploy confirmatory testing of validated questionnaire and observation tool. Finalize the questionnaire and observational assessment tool.

PHASE III DUAL USE APPLICATIONS: Obtain management framework certification for an authority to operate to successfully transition to a NAVAIR program office. Based on Phase II results, finalize and refine the methodology (questionnaire/observation tool) and software developed to meet training requirements for a wider variety of SD events/scenarios or platforms to support transition and commercialization of the product. Investigate the potential of expanding the software-based application to validate additional relevant training environments to extend transition applicability.

The validation framework and evaluation software has applicability to commercial industries including commercial airlines and corporate training. Demonstration of a methodologically sound software technology to validate training system needs has broader DoD and commercial applicability.

REFERENCES:

1. Bloom, B. S. (1956). “Taxonomy of educational objectives. Handbook 1: Cognitive domain.” Addison-Wesley Longman Ltd; 2nd edition. https://www.amazon.com/Taxonomy-Educational-Objectives-Handbook-Cognitive/dp/0582280109/ref=sr_1_2?crid=194EH99NIT4AZ&dchild=1&keywords=taxonomy+of+educational+objectives&qid=1616611649&s=books&sprefix=Taxonomy+of%2Caps%2C438&sr=1-2.
2. Gibb, R., Ercoline, B., & Scharff, L. (2011). “Spatial disorientation: decades of pilot fatalities.” Aviation, Space, and Environmental Medicine, 82(7), 717–724. https://doi.org/10.3357/ASEM.3048.2011.
3. Kallus, K. W., & Tropper, K. (2004). “Evaluation of a spatial disorientation simulator training for jet pilots.” International Journal of Applied Aviation Studies, 4(1), 4556. https://www.academy.jccbi.gov/ama-800/Spring_2004.pdf#page=45.
4. Tropper, K., Kallus, W., & Boucsein, W. (2009). “Psychophysiological evaluation of an antidisorientation training for visual flight rules pilots in a moving base simulator.” The International Journal of Aviation Psychology, 19(3), 270–286. https://www.worldcat.org/title/psychophysiological-evaluation-of-an-antidisorientation-training-for-visual-flight-rules-pilots-in-a-moving-base-simulator/oclc/770679956&referer=brief_results.
5. Kallus, W., Tropper, K., & Boucsein, W. (2011). “The importance of motion cues in spatial disorientation training for VFR-pilots.” The International Journal of Aviation Psychology, 21(2), 135–152. https://www.worldcat.org/title/the-importance-of-motion-cues-in-spatial-disorientation-training-for-vfr-pilots/oclc/710990109&referer=brief_results.
6. Stroud, K. J., Harm, D. L., & Klaus, D. M. (2005). “Preflight virtual reality training as a countermeasure for space motion sickness and disorientation.” Aviation, Space, and Environmental Medicine, 76(4), 352-356. https://www.ingentaconnect.com/content/asma/asem/2005/00000076/00000004/art00006
7. Department of Defense. (2014). Risk Management Framework (RMF) for DoD Information Technology (IT). Washington D.C.: Executive Services Directorate. https://www.esd.whs.mil/Portals/54/Documents/DD/issuances/dodi/851001_2014.pdf.
8. BAI Information Security Consulting & Training. (2020). BAI: Information Security RMF Resource Center. Retrieved from Risk Management Framework. https://rmf.org/.
9. Department of Defense Instruction 8510.01. https://www.acqnotes.com/wp-content/uploads/2016/08/DoDI-8510.01-Risk-Management-Framework-for-DoD-Information-Technology-%E2%80%93-24-May-2016.pdf.

KEYWORDS: Spatial disorientation; training; validated training methods; decision support tool; psychometric validation; training competencies

OUSD (R&E) MODERNIZATION PRIORITY: Networked C3

TECHNOLOGY AREA(S): Air Platforms

OBJECTIVE: Develop a simulation tool that will evaluate the risk to a platform given a component that has failed to meet its electromagnetic compatibility (EMC) test requirements (e.g., MIL-STD-461; [Ref 1]).

DESCRIPTION: In order to work toward successful platform level integration, there is a long-established workflow for EMC. In this procedure, individual electronic modules are designed and tested to certain standards, usually based on MIL-STD-461 [Ref 1], which impose limits on radiated and conducted emissions and radiated and conducted susceptibility. Any unit that passes those tests is assumed to be ready for integration onto the platform for its application with the expectation that it will not interfere with neighboring equipment and will operate in its intended electromagnetic environment.

As long as this process has been in place, there were countless examples of modules that failed to pass the mandated requirements. Each time this happens the standard process step was to instruct the supplier to redesign the module until it meets the specified requirements. However, there are often counter arguments that these redesigns can add cost, weight, and potentially jeopardize schedules. Engineers are often left to evaluate the potential risk of allowing a given noncompliant module to waive certain requirements based on past experience, personal judgement, and general heuristics.

The goal of this STTR effort is to give engineers in that position a tool that will allow them to take component-level testing data and model the potential effects when that module is placed in a realistically modeled platform. This involves developing a program to read in radiated emissions or susceptibility data from a test report. It would then create a model of a source or victim by backwards propagating the test data (usually taken at 1 m separation distance). That source or victim unit would then be placed in a model of the full platform with realistic grounding, bonding, and cable routing. A simulation would then be run to determine if emissions from the offending unit had negative impacts on neighboring systems or the external environment, or to see if the exterior electromagnetic environment would be likely to cause susceptibility upsets in the unit. The end result would not be to achieve an exact simulation result to compare to future testing, but instead to give engineers an analysis to show that the units’ behavior will likely be severely noncompliant, marginal, or very benign. This will allow for more accurate data-driven risk assessments in the cases of noncompliant modules seeking waivers to requirements. An objective is to identify at least 90% of severely non-compliant situations using this simulation.

PHASE I: Develop a workflow that ties together all the necessary steps for the analysis: reading in test report data; converting it to a usable format; mathematically back-propagating the source or victim that yields the emissions or susceptibility profile; assigning those properties to a module that can be placed in a CAD model of a full platform with worst-case assumptions about grounding, bonding, and cable-routing; and running a simulation to compare the unit’s performance to platform level requirements. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Develop a prototype new user interface and computational engine for the simulation capabilities and integrate the capabilities into an existing simulation product. Validate the workflow developed in Phase I with historical data sets that show measurements of noncompliant components and full platforms tests performed with those components installed. Demonstrate the prototype in a lab or live environment.

PHASE III DUAL USE APPLICATIONS: Complete development and perform final testing of a commercial grade application for use by platform level EMC engineers.

The simulation tool is suitable for electromagnetic compatibility evaluation of any civilian or military electronic system. Such system would be present on aircraft, ships, armored vehicles, space craft, automobiles, trucks, trains or even factories.

REFERENCES:

1. AFLCMC/EZSS. (2015, December11). MIL-STD-461G: Department of Defense interface standard: Requirements for the control of electromagnetic interference characteristics of subsystems and equipment Department of Defense. http://everyspec.com/MIL-STD/MIL-STD-0300-0499/MIL-STD-461G_53571/.
2. Joint Committee. (2010, December 1). MIL-STD-464C: Department of Defense interface standard: Electromagnetic environmental effects requirements for systems. Department of Defense. http://everyspec.com/MIL-STD/MIL-STD-0300-0499/MIL-STD-464C_28312/.

KEYWORDS: electromagnetic compatibility; electronic vulnerability; electromagnetic interference; radiated emissions; radiated susceptibility; modeling and simulation.

OUSD (R&E) MODERNIZATION PRIORITY: Cybersecurity;General Warfighting Requirements (GWR);Microelectronics

TECHNOLOGY AREA(S): Materials / Processes

OBJECTIVE: Design and develop a heteroepitaxy growth process that enables epitaxial growth of high-performance and high-reliability Indium Phosphide-based Quantum Cascade Lasers on silicon substrates.

DESCRIPTION: Monolithic integration of Quantum Cascade Lasers (QCLs) on silicon (Si) would enable a mechanically stable substrate that could take advantage of the best of both worlds: existing high-performance Si-based electronic and optical circuits (e.g., multiple-function, high-speed electronic circuitry; low-loss passive Si optical waveguides; active Si optical modulators and phase-shifters; etc.); and III-V semiconductor-based photonics (e.g., high-performance QCLs, and photo-detectors, etc.). Such compact systems with monolithically integrated mid-infrared sources with Si electronics have applications in infrared countermeasures, integrated transceivers for free-space optical communications, phased-array beam-steerable sources for laser detection and ranging, various passive- and active-optical sensing systems, etc. Moreover, two- and three-photon absorption losses are minimal in the mid-infrared wavelength range, thereby enabling low-loss optical transmission over integrated Si waveguides.

Fabry-Perot (FP) [Ref 1] and distributed-feedback (DFB) [Ref 2] QCLs emitting at 4.6 µm have been demonstrated by wafer bonding on Silicon-on-Nitride-on-Insulator (SONOI) substrates. Transfer printing on silicon-on-sapphire has also enabled monolithic integration of mid-IR QCL on Si [Ref 3]. However, precise alignment limits further advance of such techniques making them less cost-effective. Direct heteroepitaxial growth of QCLs on Si would, potentially, offer a substantially lower cost, large-scale wafer-scale manufacturable approach for optoelectronic integration via growing III-V epitaxial layers on much cheaper and larger Si substrates, as the mature complementary metal oxide semiconductor (CMOS) processing on large Si wafers have proven excellent throughput and yields, thereby offering the most competitive performance and economic advantages.

Nevertheless, heteroepitaxy of III-V semiconductor alloys on Si is quite challenging due to: (a) 8% lattice mismatch between Indium Phosphide (InP) and Si; (b) 50% mismatch in thermal coefficient of expansion; and (c) the formation of antiphase boundaries and domains, which can occur during the growth of polar III-V compounds on nonpolar Si substrates. To overcome these issues, metamorphic-buffer-layers (MBLs) are generally required, which can provide a low-defect-density growth platform of same lattice constant as InP, for the subsequent growth of QCL device structures. Such approaches have been recently successful in realizing high-performance, quantum-dot, active-region diode lasers operating in the near-infrared wavelength regions (1.3-1.55 µm) on Si substrates [Ref 4]. III-V growth on patterned V-grooves alleviates the problems of antiphase domain formation and acts as a filter for dislocations and stacking faults [Ref 5]. Indium Arseide/Indium Aluminum Gallium Arsenide (InAs/InAlGaAs) quantum dots (QDs) have also shown to be effective threading-dislocation (TD) filters for InP MBLs [Ref 6]. However, there are very few studies reporting on direct growth of mid-IR QCLs on Si, in spite of the tremendous aforementioned size, performance, and cost advantages of the game-changing optoelectronic integration.

Molecular beam epitaxy-grown mid-IR QCLs, operating at low temperatures (170 K), have been demonstrated on Si substrates with 6°-miscut towards crystal orientation [111], by employing both a Germanium (Ge) buffer and a compositionally graded Aluminum Indium Arsenide (AlInAs) MBL to target the InP lattice constant [Ref 7]. MBLs, based on QD-dislocation filtering on exact (001) Si, have also been employed for the growth of QCL active regions by MOCVD [Ref 8]. Residual threading dislocation densities have been estimated to be rather high (1E8 cm² range) in both cases. The use of (001)-oriented Si substrates is key to achieving compatibility with Si-CMOS processing. Since QCLs are unipolar devices, they are expected to be insensitive to nonradiative recombination centers. However, dislocations can perturb the QCL superlattice active region and thus interfere with the coherent tunneling process. Thus, it is the objective of this project to reduce the residual-dislocation densities substantially and provide a low-surface roughness platform for the growth of high-performance, high-reliability QCLs on Si, equal with the performance specifications of 5 Watts continuous wave (CW) output at room temperature, wall-plug efficiency no less than 25%, and almost diffraction-limited beam quality with M2 < 1.5.

PHASE I: Develop a path for achieving low-defect density (< 1 x 1E7 /cm²) buffer layers on Si suitable for the growth of mid-IR QCLs. Complete the design of experiments for Phase II to establish room-temperature CW QCL operation on Si substrates. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Demonstrate room-temperature CW QCL operation on Si substrates employing direct-growth methods based on the epitaxial growth methods, and conditions, discovered in Phase I. The performance requirements of the QCL on Si substrates include 5 Watts CW output at room temperature, wall-plug efficiency no less than 25%, and almost diffraction-limited beam quality with M2 < 1.5.

PHASE III DUAL USE APPLICATIONS: Fabricate, test, and finalize the technology based on the design and demonstration results developed during Phase II. Develop a prototype using the finalized design and transition the technology with the final specifications for DoD applications in the areas of Directed Infrared Countermeasures (DIRCM), advanced chemicals sensors, and Laser Detection and Ranging (LIDAR).

The commercial sector can also benefit from this crucial, game-changing technology development of monolithic integration of QCLs with electronics on silicon substrate in the areas of detection of toxic gas environmental monitoring, non-invasive health monitoring and sensing, and industrial manufacturing processing.

REFERENCES:

1. Spott, A. et al.“Quantum cascade laser on silicon.” Optica, 3(5), 545-551. https://doi.org/10.1364/OPTICA.3.000545.
2. Spott, A. et al. “Heterogeneously integrated distributed feedback quantum cascade lasers on silicon.” Photonics, 3(2) 35. https://doi.org/10.3390/photonics3020035. 
3. Jung, S., Kirch, J., Kim, J. H., Mawst, L. J., Botez, D., & Belkin, M. A. (2017, November 20). “Quantum cascade lasers transfer-printed on silicon-on-sapphire.” Applied Physics Letters, 11(211102). https://doi.org/10.1063/1.5002157.
4. Jung, D., Herrick, R., Norman, J., Turnlund, K., Jan, C., Feng, K., Gossard, A. C., & Bowers, J. E. (2018, April). “Impact of threading dislocation density on the lifetime of InAs quantum dot lasers on Si.” Applied Physics Letters, 112(15) 153507. https://doi.org/10.1063/1.5026147.
5. Li, Q. & Lau, K. M. (2017, December). “Epitaxial growth of highly mismatched III-V materials on (001) silicon for electronics and optoelectronics.” Progress in Crystal Growth and Characterization of Materials, 63(4), 105-120. https://www.sciencedirect.com/science/article/pii/S0960897417300360?casa_token=F4B6QS3HyuEAAAAA:_KxErkUfcp6Ea__kgbmGSswbghDfcnrd1lb9nDVm6uLtBmLx_tL4p8IvK73W6Kok--u3iZKScg.
6. Shi, B., Li, Q., & Lau, K. M. (2017, April 15). “Self-organized InAs/InAlGaAs quantum dots as dislocation filters for InP films on (001) Si.” Journal of Crystal Growth, 464, 28–32. https://doi.org/10.1016/j.jcrysgro.2016.10.089.
7. Go, R. et al. (2018). “InP-based quantum cascade lasers monolithically integrated onto silicon.” Optics Express, 26(17), 22389-22393. https://doi.org/10.1364/OE.26.022389.
8. Rajeev, A. et al.(2018, October 10). “III-V superlattices on InP/Si metamorphic buffer layers for ?˜4.8 µm quantum cascade lasers.” Physica Status Solidi, 216(1). https://doi.org/10.1002/pssa.201800493.

KEYWORDS: Silicon; quantum cascade laser; QCL; monolithic integration; complementary metal oxide semiconductor; CMOS; heteroepitaxial; distributed feedback

OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR);Microelectronics;Quantum Science

TECHNOLOGY AREA(S): Electronics

OBJECTIVE: Develop a novel smart visual image recognition system that has intrinsic ultralow power consumption and system latency, and physics-based security and privacy.

DESCRIPTION: Image-based recognition in general requires a complicated technology stack, including lenses to form images, optical sensors for opto-to-electrical conversion, and computer chips to implement the necessary digital computation process. This process is serial in nature, and hence, is slow and burdened by high-power consumption. It can take as long as milliseconds, and require milliwatts of power supply, to process and recognize an image. The image that is digitized in a digital domain is also vulnerable to cyber-attacks, putting the users’ security and privacy at risk. Furthermore, as the information content of images needs to be surveilled and reconnoitered, and continues to be more complex over time, the system will soon face great challenges in system bottleneck regarding energy efficiency, system latency, and security, as the existing digital technologies are based on digital computing, because of the required sequential analog-to-digital processing, analog sensing, and digital computing.

It is the focus of this STTR topic to explore a much more promising solution to mitigate the legacy digital image recognition latency and power consumption issues via processing visual data in the optical domain at the edge. This proposed technology shifts the paradigm of conventional digital image processing by using analog instead of digital computing, and thus can merge the analog sensing and computing into a single physical hardware. In this methodology, the original images do not need to be digitized into digital domain as an intermediate pre-processing step. Instead, incident light is directly processed by a physical medium. An example is image recognition [Ref 1], and signal processing [Ref 2], using physics of wave dynamics. For example, the smart image sensors [Ref 1] have judiciously designed internal structures made of air bubbles. These bubbles scatter the incident light to perform the deep-learning-based neuromorphic computing. Without any digital processing, this passive sensor can guide the optical field to different locations depending on the identity of the object. The visual information of the scene is never converted to a digitized image, and yet the object can be identified in this unique computation process. These novel image sensors are extremely energy efficient (a fraction of a micro Watt) because the computing is performed passively without active use of energy. Combined with photovoltaic cells, in theory, it can compute without any energy consumption, and a small amount of energy will be expended upon successful image recognition and an electronic signal needs to be delivered to the optical and digital domain interface. It is also extremely fast, and has extremely low latency, because the computing is done in the optical domain. The latency is determined by the propagation time of light in the device, which is on the order of no more than hundreds of nanoseconds. Therefore, its performance metrics in terms of energy consumption and latency are projected to exceed those of conventional digital image processing and recognition by up to at least six orders of magnitude (i.e., 100,000 times improvement). Furthermore, it has the embedded intrinsic physics-based security and privacy because the coherent properties of light are exploited for image recognition. When these standalone devices are connected to system networks, cyber hackers cannot gain access to original images because such images have never been created in the digital domain in the entire computation process. Hence, this low-energy, low-latency image sensor system is well suited for the application of 24/7 persistent target recognition surveillance system for any intended targets.

In summary, these novel image recognition sensors, which use the nature of wave physics to perform passive computing that exploits the coherent properties of light, is a game changer for image recognition in the future. They could improve target recognition and identification in degraded vision environment accompanied by heavy rain, smoke, and fog. This smart image recognition sensor, coupled with analog computing capability, is an unparalleled alternative solution to traditional imaging sensor and digital computing systems, when ultralow power dissipation and system latency, and higher system security and reliability provided by analog domain, are the most critical key performance metrics of the system.

PHASE I: Develop, design, and demonstrate the feasibility of an image recognition device based on a structured optical medium. Proof of concept demonstration should reach over 90% accuracy for arbitrary monochrome images under both coherent and incoherent illumination. The computing time should be less than 10 µs. The throughput of the computing is over 100,000 pictures per second. The projected energy consumption is less than 1 mW. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Design image recognition devices for general images, including color images in the visible or multiband images in the near-infrared (near-IR). The accuracy should reach 90% for objects in ImageNet. The throughput reaches over 10 million pictures per second with computation time of 100 ns and with an energy consumption less than 0.1 mW. Experimentally demonstrate working prototype of devices to recognize barcodes, handwritten digits, and other general symbolic characters. The device size should be no larger than the current digital camera-based imaging system.

PHASE III DUAL USE APPLICATIONS: Fabricate, test, and finalize the technology based on the design and demonstration results developed during Phase II, and transition the technology with finalized specifications for DoD applications in the areas of persistent target recognition surveillance and image recognition in the future for improved target recognition and identification in degraded vision environment accompanied by heavy rain, smoke, and fog.

The commercial sector can also benefit from this crucial, game-changing technology development in the areas of high-speed image and facial recognition. Commercialize the hardware and the deep-learning-based image recognition sensor for law enforcement, marine navigation, commercial aviation enhanced vision, medical applications, and industrial manufacturing processing.

REFERENCES:

1. Khoram, E., Chen, A., Liu, D., Ying, L., Wang, Q., Yuan, M., & Yu, Z. (2019). “Nanophotonic media for artificial neural inference.” Photonics Research, 7(8), 823-827. https://doi.org/10.1364/PRJ.7.000823.
2. Hughes, T. W., Williamson, I. A., Minkov, M., & Fan, S. (2019). “Wave physics as an analog recurrent neural network.” Science advances, 5(12), eaay6946. https://doi.org/10.1126/sciadv.aay6946.

KEYWORDS: Image recognition; wave mechanics; low latency; passive computing; sensors; deep learning

OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Information Systems

OBJECTIVE: Develop a capability to collect, analyze, and predict levels of Tributyltin Oxide (TBTO) in deployed sonar domes.

DESCRIPTION: A sonar dome protects the acoustic transducers, to reduce noise and enable optimal sonar performance. Crucial to its function is that the dome does not foul. Historically, this has been done by imbuing sonar domes with Tributyltin Oxide (TBTO) during the manufacturing process. Research to prevent fouling has not developed an alternative that is qualified for the domes on surface combatants. Even when a new anti-fouling method may be identified, there will be scores of sonar domes imbued with TBTO, with decades of remaining service. A combatant is at sea for about eight years before maintenance carried out at dry dock. Conventional, off-the-shelf antifouling approaches do not work with sonar domes, because they are made of rubber.

The Naval Research Laboratory (NRL) has recently developed a rapid, non-destructive, and inexpensive method to measure TBTO (or other anti-fouling systems) in sonar domes while a ship is dry docked. This will provide, for the first time, the data necessary for a nuanced understanding of the anti-fouling efficacy, throughout its service life.

The Navy seeks technology that will enable central management of these measurements from USN sonar domes that are deployed to locations and environments around the world, together with an ontological framework to record pertinent information about the sonar dome, such as manufacturing details and service life history. It is also desired that the architecture of the proposed technology accommodate a methodology for predicting anti-fouling life and updated algorithms as data supports algorithm refinement. Development of an initial predictive algorithm could fall within the scope of this STTR topic.

The Navy seeks a centralized capability for collecting this information, populating an ontological framework with pertinent data (such as sonar dome manufacturing details and service life history) for each measurement, and predicting future TBTO levels to understand both:

1. When sonar domes will need to be replaced due to depletion of TBTO.
2. When it may be appropriate to reduce the amount of TBTO (or future anti-foulant) used in new-construction sonar domes with changes in dome material or anti-foulant.

The centralized capability will enable the Navy to minimize maintenance while also minimizing harm to the marine environment.

The framework described herein must include:

• A method to capture data from a measurement tool for utilization in a Fleet-wide physics-based model designed for modular updating manually via future re-assessment of an updated database.
• A graphical user interface (GUI) that displays tracked values of interest.

Examples of potential elements to this ontology are:

• Measured anti-foulant loading remaining in coating.
• Models of TBTO degradation as a function of time and combatant travel profile.
• Predicted remaining lifespan of sonar dome TBTO based on measurements and predicted travel profile.
• Updated physics-based model calculations.

Any additional ontological elements that would improve the model would be welcome.

The physics-based model shall also incorporate:

1. Input parameters, including service conditions, that may vary over a deployment. Variables of primary considerations are surface ocean temperature and salinity, but others may be added.
2. Capability to change the input properties, to accommodate updated material specifications and other improvements.

PHASE I: Develop a concept for a physics-based database and GUI for diffusion from a sonar dome that meets all the parameters in the Description. Demonstrate the concept is feasible through analysis, simulation, and modelling. Preliminary experimental data will be provided by NRL. The Phase I Option, if exercised, will include the initial design specifications and a capabilities description to build a prototype solution in Phase II.

PHASE II: Develop and deliver a prototype physics-based database and GUI for the TBTO collection and prediction capability. Demonstrate the prototype meets the required range of desired performance attributes given in the Description. Feasibility will be demonstrated through system performance with information from initial TBTO measurements that will be collected. Develop a Phase III commercialization plan.

PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the technology for Navy use as software to collate, analyze, and manage TBTO data collected and tested via a hardware measurement capability maintained by IWS 5.0. Demonstrate and report on performance during laboratory testing.
 

This technology can be used in a wide range of products where measurements of toxins or other material dopants of specified loadings are collected and predictions of future state are dependent on numerous variables which are not entirely dependent on one another. With the appropriate modifications, it may be used to monitor performance of commercial antifoulant systems, particularly when a new system is being adopted. The technology would be of greatest use in cases where environmental impact of a substance is of national or global concern, particularly in water / wastewater management or aquaculture settings.

REFERENCES:

1. Omae, Iwao. (2003). “Organotin Antifouling Paints and Their Alternatives.” Applied Organometallic Chemistry, Vol. 17, n2 (200302), . 81 - 105. https://www.worldcat.org/title/organotin-antifouling-paints-and-their-alternatives/oclc/4633838388.
2. Donnelly, Bradley et al. (2019) “Effects of Various Antifouling Coatings and Fouling on Marine Sonar Performance. Polymers.” Polymers Vol. 11, Issue 4, 663. https://www.mdpi.com/2073-4360/11/4/663.
3. "AN/SQQ-89(V) Undersea Warfare / Anti-Submarine Warfare Combat System." United States Navy Fact File, 24 March 2021. https://www.navy.mil/Resources/Fact-Files/Display-FactFiles/Article/2166784/ansqq-89v-undersea-warfare-anti-submarine-warfare-combat-system/.

KEYWORDS: Sonar dome; tributyltin oxide; TBTO; anti-fouling for sonar domes; ontological framework; predicting anti-fouling life; water management; wastewater management; aquaculture

OUSD (R&E) MODERNIZATION PRIORITY: Directed Energy (DE)

TECHNOLOGY AREA(S): Weapons

OBJECTIVE: Design and develop a compact and robust fiber optical isolator for kW class fiber lasers/amplifiers.

DESCRIPTION: Optical isolators transmitting light only in one direction while blocking light in the opposite direction have been extensively used to protect laser systems from the influence of the backward light. Fiber lasers have seen significant developments during the last two decades and kW class fiber lasers have been deployed in different platforms for DoD applications. This has created demand for high power compact and robust optical isolators that can be used to protect these kW class fiber lasers. Commercial free-space bulk optical isolators capable of handling optical average powers up to kW level are becoming available. However, the packaging volume, thermal resistance, reliability, and even the power handling cannot meet most DoD applications. Fiber-coupled or fiber-based optical isolators have the advantages of small format, easy operation, and high robustness while exhibiting the promise of high-power handling. Currently, the power handling capability of fiber-coupled isolators is limited to 100 W. This STTR topic seeks innovative device design, advanced Faraday material, new magnet material, and novel power polarizers that can be combined for the development of kW class fiber optical isolators. This topic supports the development of a prototype with the parameters listed below at the end of Phase II:

• Operating Wavelengths: 1µm, 1.55 µm, and 2 µm• Average Power handling: Threshold 3 kW; Objective 5 kW per amplifier
• Bandwidth: Threshold 20 nm; Objective 50 nm
• Insertion Loss: Threshold < 1 dB; Objective < 0.5 dB
• Isolation: Threshold > 30 dB; Objective > 40 dB
• Polarization extension ratio (FER) > 30 dB
• Reliability: Lifetime > 5000 hours
• Thermo Electric (TEC) or Water cooling preferred

Under the Phase II Option II, if exercised, a prototype kW class Fiber optic isolator will be delivered to a Navy lab to evaluate the performance of the system in terms of its optical isolation > 40 dB for HEL system.

PHASE I: Develop a concept that uses the Faraday material, magnet material, and polarizers for a best-performance optical isolator construction that can be used for kW class fiber lasers. Demonstrate the power handling scalability of the new isolator material and device. The isolator concepts will be designed to meet the performance capabilities identified in the Description section. Demonstrate the feasibility of the concept to meet the parameters listed in the Description through modeling, simulation, and analysis.

The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build a prototype solution in Phase II.

PHASE II: Develop and deliver a prototype based on the results of Phase I, supporting the parameters listed in the description. Optimize the design and development of the Phase I kW class optical isolator to a prototype compact and robust fiber optical isolators for kW class fiber lasers.

Deliver a prototype kW class Fiber optic isolator to a Navy lab to evaluate the performance of the system in terms of its optical isolation > 40 dB for HEL system as described in the Phase II SOW. Any test data collected at Navy facilities shall be Government use only.

PHASE III DUAL USE APPLICATIONS: Transition of kW class Fiber optic isolator to Navy use for the purpose of HEL technology integration at 1 to 2 µm MW class laser. Identify the final kW class fiber isolator product and describe how the company will support transition to Phase III. Ultimately, the HEL system will be deployed in a submarine or other Navy platform advancing future Navy warfighting capabilities.

Fiber optical isolators with high power handling capability can be used in various HEL laser systems for DoD and industrial applications such as welding, cutting, soldering, marking, cleaning, and material processing.

REFERENCES:

1. Khazanov, E.A. “Slab-based Faraday isolators and Faraday mirrors for 10-kW average laser power”, Applied Optics, Vol. 43, Issue 9, 1907 (2004).
2. Snetkov, I.L.; Voitovich, A.V.; Palashov, O.V. and Khazanov, E.A. “Review of Faraday isolators for kilowatt average power lasers,” IEEE Journal of Quantum Electronics, Vol. 50, Issue 6, 434 (2014).
3. Turner, E.H. and Stolen, R.H. “Fiber Faraday circulator or isolator”, Optics Letters, Vol. 6, Issue 7, 322 (1981).
4. Sun, L. et al. “Compact all-fiber optical Faraday components using 65-wt%-terbium-doped fiber with a record Verdet constant of -32 rad/(Tm)”, Optics Express, Vol. 18, Issue 12, 12191 (2010).
5. Sun, L. et al., “All-fiber optical isolator based on Faraday rotation in highly terbium-doped fiber”, Optics Letters, Vol. 35, Issue 5, 706 (2010).

KEYWORDS: Optical isolator; fiber isolator; kW class fiber lasers; Faraday rotator; magneto-optical material; polarizer

OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Electronics

OBJECTIVE: Develop test equipment to measure electrical properties related to shipboard environmental factors that affect creepage and clearance in Medium Voltage (MV) Naval electrical power systems.

DESCRIPTION: Naval electrical power systems and associated high power combat systems are increasingly employing Medium Voltage (MV) power in the range of 1 to 35 kiloVolt (kV) AC or DC. Creepage and clearance requirements are a major driver in power density of MV equipment. Clearance is the shortest “air” distance between two exposed conductors while creepage is the distance along insulation surfaces between two exposed conductors. Setting these values too conservatively results in excessively large equipment; setting them too low results in equipment failure due to flashover. MVDC requirements have not yet been established, and the appropriateness of the MVAC requirements is not known. MVAC requirements are based on terrestrial commercial standards which have never been validated to apply to the marine environment. Naval ships have experienced arcing fault flashovers that have caused significant amounts of damage and lost operational time.

The most significant factor for establishing safe clearance distances is the electrical properties of the air, which is affected by pollutants, salts, and other air contaminants. The air in different spaces onboard ship is certain to have varying electrical properties.

Similarly, the most significant factor for establishing safe creepage distances is the electrical properties of the surface contaminants on insulators, which will vary significantly throughout the ship. Currently, there are no Navy or commercial products that are designed to measure creepage or clearance within a naval ship environment.

The Navy seeks a portable testing apparatus to measure the electrical properties of air and surface contaminants onboard a naval ship at a threshold level of 20kV and objective of 35kV. A method is also needed to use these measurements as Objective Quality Evidence (OQE) for developing safe creepage and clearance requirements for inclusion in applicable equipment specifications and military standards. The portable testing apparatus measurements shall be accurate and repeatable enough to enable the Navy to employ the method to establish the creepage and clearance requirements.

The Navy anticipates using multiple test apparatuses to create an initial survey of shipboard spaces over an extended period of time in operational conditions and industrial conditions. Following initial surveys, the Navy intends to employ the test apparatus in both prognostic and forensic procedures to understand the shipboard environment in specific ships.

PHASE I: Provide a concept design for an apparatus that measures the electrical properties of air and surface contaminants onboard a naval vessel. Provide evidence, either through experimentation or simulation, that the concept design is feasible. Also provide a method to use measurements from the apparatus as Objective Quality Evidence (OQE) for developing safe creepage and clearance requirements for inclusion in applicable equipment specifications and military standards. The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build a prototype apparatus in Phase II.

PHASE II: Provide, demonstrate, and deliver an initial prototype apparatus that measures the electrical properties of air and surface contaminants onboard a naval vessel. Demonstrate the method to use measurements from the prototype apparatus as OQE for developing safe creepage and clearance requirements for inclusion in applicable equipment specifications and military standards. Based on feedback from demonstrations of the initial prototype apparatus, incorporate improvements in the apparatus design and produce two additional prototype apparatuses. Demonstrate these two prototypes function as intended and deliver to the U.S. Government.

PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the technology to Navy use. Update the prototype design to a final production configuration and develop supporting training documentation. The Government anticipates using multiple test apparatuses to create an initial survey of shipboard spaces over an extended period of time in operational conditions and industrial conditions. Following initial surveys, the Government intends to employ the test apparatus in both prognostic and forensic procedures to understand the shipboard environment in specific ships.

This device should also prove useful in both the naval and commercial marine sectors to ensure the air and surface contaminants onboard ship are not more severe than for contaminants the shipboard equipment was designed for.

REFERENCES:

1. Damle, Tushar; Park, Chanyeop; Ding, Jeffrey; Cheetham, Peter; Bosworth, Matthew; Steurer, Mischa; Cuzner, Robert and Graber, Lukas. “Experimental setup to evaluate creepage distance requirements for shipboard power systems.” 2019 IEEE Electric Ship Technologies Symposium, Arlington VA, August 14-16, 2019. https://ieeexplore.ieee.org/abstract/document/8847827.
2. Kaaiye, Sharif F. and Nyamupangedengu, Cuthbert. “Comparative study of AC and DC inclined plane tests on silicone rubber (SiR) insulation.” The Institution of Engineering and Technology, 20 April 2017. https://www.researchgate.net/publication/316518121_A_Comparative_Study_of_AC_and_DC_Inclined_Plane_Tests_on_Silicone_Rubber_SiR_Insulation. 
3. “IEEE Recommended Practice for 1 kV to 35 kV Medium-Voltage DC Power Systems on Ships.” IEEE Industry Applications Society and IEEE Power Electronics Society, IEEE Std 1709-2018, 27 September 2018. https://ieeexplore.ieee.org/document/8569023.

KEYWORDS: Creepage; Clearance; Air Contamination Electrical Properties; Surface Contamination Electrical Properties; Medium Voltage; MV; MVAC; MVDC; Flashover

OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Ground / Sea Vehicles

OBJECTIVE: Develop a hardened data module that can withstand blast effects from detonation of underwater explosives while preserving accumulated mission essential data from Unmanned Undersea Vehicles (UUV) and Remotely Operated Vehicles (ROV) systems.

DESCRIPTION: The Maritime Expeditionary MCM Unmanned Undersea Vehicle (MEMUUV) and Maritime Expeditionary Standoff Response (MESR) systems provide Navy Expeditionary forces with specialized UUV and ROV systems that deploy for search, detection, localization, neutralization and disposal of naval mines and underwater improvised explosive devices (IEDs). Mines and IEDs are often detonated by acoustic and magnetic noise from ships and subsurface platforms in the vicinity and by UUVs and ROVs conducting time-intensive mine and IED clearance operations in undersea environments. Although UUV and ROV platforms are not deployed as expendable platforms, they are susceptible to and not sufficiently hardened against inadvertent arming and detonation of a mine or IED while performing clearance missions. The blast effects from an inadvertent detonation may result in loss of essential mission data accumulated during hours of UUV/ROV operations. Mission data collected during a single, 20-hour sortie may result in an accumulation of up to 10 terabytes of data. Wireless data transfer bandwidth limitations for expeditionary platforms (typically between 5 kilobits per second up to 150 megabits per second) preclude real-time data exfiltration from the platforms; most mission essential information must be downloaded post-mission.

This STTR topic seeks to develop a compact, survivable “black box” mission module to collect mission data prior to a detonation. The solution must preserve the data and allow system operators to retrieve the data post-detonation. Data preservation can occur either by retrieval of the module or via secure wireless data transfer following an underwater explosive detonation event occurring within 10 meters of a 2500-pound TNT-equivalent net explosive weight (NEW) object on the seabed in up to 300 meters of water depth, which could result in total loss of a UUV or ROV platform. The module must have interface capabilities to facilitate recovery or autonomous data transfer and must be designed to protect the module and information from recovery by adversaries.

Aircraft flight recorders are not suitable in size, nor in the types of mission data they collect as a survivable mission module for undersea platforms; however, the basic concept is the same. There are currently no known solutions for preservation of mission essential data from UUV missions. Mission data collected on objects in the water column and on the seabed, including accumulated geo-referenced imagery up to the point where a mine explosion which destroys or incapacitates a UUV, is important for time constrained clearance operations. Proposed concepts must be compact for integration into small, volume-constrained UUV and ROV systems without adversely impacting trim, balance, or hydrodynamic performance of the platform. Size, weight and power (SWaP) constraints will vary depending on design concept. A self-contained module should not exceed 20 cubic inches in volume (e.g., a ~1 inch diameter x 6 inches long cylinder). Weight/mass should enable a neutrally buoyant solution in seawater. For a completely self-contained hardware solution mounted externally to a platform, a neutrally buoyant, hydrodynamic form factor must be sufficiently small and streamlined as not to add drag or impact platform endurance while maneuvering. Additionally, concepts must be powered independently. Power endurance requirements vary based on the concept for data retrieval; however, proposed solutions should have sufficient power and longevity to enable recovery while also being able to erase data if not recovered. If lithium chemistry batteries are proposed as a component of the independent power system design, solutions should incorporate batteries which have previously been certified for Navy shipboard use, storage and transportation in accordance with NAVSEA Instruction 9310.1, or should include evaluation of battery safety suitability within the scope of the proposed concept validation. To align for successful future transition following a successful demonstration, concepts should consider hardware and software solutions that will either satisfy or be easily adaptable to satisfy cyber security compliance for DoD/Navy use in accordance with DoD Instruction 8500.1 and Department of the Navy Cyber Security Policy compliance (SECNAVINST 5239.3C of 2 May 16).

Testing of the key performance parameters and key system attributes will be performed in a relevant environment to verify that the task objectives were met. To demonstrate some aspects of the technical performance (e.g., survivability of large explosive charges), modeling and simulation coupled with technical analysis is deemed an acceptable approach.

PHASE I: Develop an innovative concept for a blast-survivable mission data module that meets the design constraints listed in the description. Establish feasibility by modeling and simulation, analysis, and/or laboratory experimentation, as appropriate.

The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build a prototype solution in Phase II.

PHASE II: Develop and deliver a prototype of the survivable data module compatible for demonstration and characterization of key performance parameters, key system attributes, and objectives. Conduct testing of the key performance parameters and key system attributes in a relevant environment to verify that the task objectives were met. To demonstrate some aspects of the technical performance (e.g., survivability of large explosive charges), consider modeling and simulation coupled with technical analysis. Based on lessons learned in Phase II through the prototype demonstration, a substantially complete design of the data module should be completed and delivered that would be expected to pass Navy qualification testing.

PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the technology to Navy use through system integration and qualification testing of a survivable mission data module. The final survivable minefield mission data module product will need to conform to all specifications and requirements. A full-scale prototype will be operationally tested at sea and certified by the Navy.

Innovative concepts offer a broader opportunity for use of a “black box” solution across many military activities collecting and transporting high value sensitive data, on autonomous subsurface and surface platforms, at risk of being destroyed in the course of their mission.

REFERENCES:

1. Keevin, Thomas and Hempen, Gregory. “The Environmental Effects of Underwater Explosives with Methods to Mitigate Impacts.” Army Corps of Engineers, St Louis District, August 1997. https://denix.osd.mil/nr/otherconservationtopics/coastalandoceanresources/marine-mammals/the-environmental-effects-of-underwater-explosions-with-methods-to-mitigate-impacts/. 
2. Secretary of the Navy Innovation Awards; “The Expeditionary MCM (ExMCM) Company: The Newest Capability in U.S. Navy Explosive Ordnance Disposal (EOD) Community.” July 2017. https://www.secnav.navy.mil/innovation/Documents/2017/07/ExMCM.pdf.
3. Secretary of the Navy Instruction 5239.3C dated 2 May 2016. (Department of the Navy Cyber Security Policy).
4. NAVSEA Instruction 9310.1B dated 13 Jun 1991 (Naval Lithium Battery Safety Program).

KEYWORDS: Mine Countermeasures; Survivability; Unmanned Undersea Vehicles; Remotely Operated Vehicles; Mines; Improvised Explosive Devices.

OUSD (R&E) MODERNIZATION PRIORITY: Directed Energy (DE)

TECHNOLOGY AREA(S): Sensors

OBJECTIVE: Develop a capability that enables reliable emission of high power, single lateral mode, long wave infrared laser beams from Indium Phosphide-based solid state waveguides.

DESCRIPTION: Infrared (IR) photonic integrated circuits, especially those incorporating solid state laser diodes operating in the long wave infrared (LWIR) band, often employ the Indium Phosphide (InP) III-V semiconductor system. Optical signals are transmitted in solid state waveguides fabricated directly in epilayers grown on the InP substrate, which are usually designed for light propagation in a single lateral mode. In many applications, the optical power may be emitted to free space at an edge facet or from some other surface. However, the emitted power is sometimes quite high and the maximum power density at the center of the beam can be exceedingly intense. Furthermore, the efficient extraction of optical power from the facet is typically aided by the deposition of an anti-reflection (AR) coating that minimizes the reflection of light back into the waveguide.

Current InP-based waveguides operating in the 9-11 µm spectral band are susceptible to optical damage at the AR-coated output facet, which limits the maximum continuous wave or average power that can be emitted to less than 2 W. This limitation severely constrains the usefulness of technologies that could otherwise enable higher levels of integration, such as beam combining by an arrayed waveguide grating (AWG). Therefore, the Navy needs an LWIR InP-based waveguide and output coupling technology that reliably increases the maximum power that can be emitted to at least 10 W.

The goal is to demonstrate damage-free operation in both the waveguide and at the output interface over long term operation. Propagation in the waveguide shall be in a single lateral mode and the transmission at the output surface should be at least 90%. The output should be in a nearly diffraction-limited beam with maximum M2 factor of 2.0 (M2 defined according to ISO Standard 11146). The output interface is considered to be to the atmosphere, at sea-level.

Methods for injecting optical power into the waveguide for testing are not a subject of this effort. However, accurate measurement of the output coupling efficiency is expected. In addition, the ability to vary the transmitted power, incrementally or continuously, in order to “test to failure” is highly desirable. Prototype solutions may be demonstrated at any wavelength (or combination of multiple wavelengths) between 9 and 11 µm. However, test wavelengths should be chosen for maximum atmospheric transmission in order to minimize uncertainties in testing and all prototypes should be tested at the same wavelengths. While testing at all wavelengths across the LWIR band is not required, the solution should be suitable for applications that combine multiple LWIR wavelengths spanning the entire upper LWIR band (8-14 µm) in the same beam. Solutions that are “tuned” to specific wavelengths or narrow bands are unacceptable.

Potential solutions may include improvements in ridge geometry, improved AR coatings with lower absorption in the LWIR, tapering of the waveguide along one or both axes, improved heat dissipation at the output surface, surface-emitting (versus edge-emitting) geometries, or other solutions employing innovative architectures and materials. However, acceptable solutions must be capable of fabrication through normal integrated circuit manufacturing processes and work flow. The objective is to develop a technology that can be incorporated into multiple photonic integrated circuit designs. Therefore, coatings and bonding processes are acceptable but solutions that require the addition of “off-chip” elements or require labor-intensive “touch time” assembly are unacceptable. Assembly steps that are performed solely to incorporate diagnostic elements or are performed for fixturing or calibration and do not form a part of the actual technical solution are acceptable. For example, process and assembly steps required to inject optical power into the device for demonstration and testing are not considered to be part of the solution.

As this effort is assumed to be necessarily iterative in nature, it is expected that multiple prototype devices will be produced during its course. In addition, a staged approach in which prototypes capable of 5 W output are first demonstrated and then extensively tested over long term cyclical operation (a minimum of 100 hours of operation with 50 on-off cycles) to assess cumulative damage effects is highly desirable. Testing will be performed in a laboratory environment provided by the proposer. At the end of the effort, the five best performing prototype devices (which have not been “tested to failure”) shall be delivered to the Naval Research Laboratory (NRL). Any specialized equipment (e.g., power sources, test equipment and test fixtures, calibration standards, etc.) specifically built or acquired for testing of the devices, along with test data on the devices, shall also be delivered to NRL.

PHASE I: Develop a concept for a high-power LWIR InP-based waveguide technology with transmission, out-coupling, and power-handling characteristics that meet the objectives stated in the Description. Define the architecture and materials required for the concept, and demonstrate its feasibility for meeting the Navy need. Feasibility shall be demonstrated by a combination of analysis, modelling, and simulation. Identify key manufacturing steps and challenges. Define the test configuration, including the method for injecting and measuring the power introduced to the waveguide. The Phase I Option, if exercised, will include formulation of the device specification, test specifications, interface requirements, and the manufacturing requirements necessary to build and evaluate device prototypes in Phase II.

PHASE II: Develop and deliver a prototype high-power LWIR InP-based waveguide transmission and out-coupling technology based on the concept, analysis, architecture, and specifications resulting from Phase I. Demonstrate that the prototype waveguides operate without damage as detailed in the Description. Demonstrate the technology through production and testing of prototypes in a laboratory environment provided by the proposer. It is expected that multiple prototypes will be produced during execution of this Phase as the design process is assumed to be necessarily iterative in nature. At the conclusion of Phase II, five samples employing the best-performing prototype solution (or solutions) shall be delivered to the Naval Research Laboratory, along with complete test data and any specialized equipment needed to replicate testing.

PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the technology for Government use. Identify specific manufacturing steps and processes that require further development, mature those steps and processes, establish a hardware configuration baseline, create production-level documentation, and insert the technology into specific semiconductor fabrication processes. Assist the government in integrating the technology into specific photonic integrated circuit designs meeting requirements supplied by the government and transitioning those designs into production.

Commercial, and scientific applications include use in laser spectroscopy for remote detection of chemicals and explosive compounds, and free-space optical communications (backhaul networks).

REFERENCES:

1. Hitaka, M., et al. “Stacked quantum cascade laser and detector structure for a monolithic mid-infrared sensing device.” Applied Physics Letters, Vol. 115, Issue 16, October 2019. https://aip.scitation.org/doi/full/10.1063/1.5123307.
2. Sin, Y., et al. “Catastrophic Degradation in Quantum Cascade Lasers Emitting at 8.4 µm.” 2014 IEEE Photonics Society Summer Topical Meeting Series, Montreal, 14-16 July 2014. https://ieeexplore.ieee.org/document/6902994.
3. Phillips, Mark C., et al. “Standoff detection of chemical plumes from high explosive open detonations using a swept-wavelength external cavity quantum cascade laser.” Journal of Applied Physics 128, Issue 16, 27 July 2020. https://aip.scitation.org/doi/abs/10.1063/5.0023228.
4. Johnson, Stephen, et al. “High-speed free space optical communications based on quantum cascade lasers and type-II superlattice detectors.” Proceedings of the SPIE, Quantum Sensing and Nano Electronics and Photonics XVII: 11288, San Francisco, 2-6 February 2020. https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11288/1128814/High-speed-free-space-optical-communications-based-on-quantum-cascade/10.1117/12.2548348.short.

KEYWORDS: Long Wave Infrared; Anti-Reflection Coating; Beam Combining; Indium Phosphide; Solid State Waveguides; Photonic Integrated Circuits.

OUSD (R&E) MODERNIZATION PRIORITY: Directed Energy (DE)

TECHNOLOGY AREA(S): Sensors

OBJECTIVE: Develop an array of visible to near-infrared (VNIR) lasers with integral (on-chip) wavelength beam combining for a single, high quality output beam.

DESCRIPTION: Many threats to surface ships employ imagers and detectors operating in the visible to near-infrared (VNIR) band. These include lethal threats as well as aircraft and unmanned aerial systems performing routine surveillance. To combat these threats, shipboard countermeasures are needed and, for the most sophisticated threats, lasers are the fundamental component of the electro-optic (EO) countermeasure suite. For compactness and simplified power and control circuitry, semiconductor lasers are a highly attractive solution. However, in order to achieve the output powers required, multiple individual laser diodes must be combined in a laser “module” with a single output. This solution also provides spectral coverage across the wavelength band (or a specified portion of the band) as laser diodes of different wavelengths are combined ? a highly desirable feature for countermeasure applications. However, the architecture presents a considerable cost in manufacturing as the exacting tolerances required result in high component costs and the assembly process is highly labor-intensive. The assembly cost of the laser diode combiner typically accounts for as much as half the cost of the finished laser module.

Other possible laser sources are either bulky, even more expensive, or have other undesirable characteristics such as multi-mode operation. For example, some high brightness semiconductor lasers require an additional pump source or other free-space optics which increases size and cost. Other solutions involve frequency doubling to produce single wavelength output that would still have to be combined with the output from other lasers to achieve spectral coverage. Currently, there is no off-the-shelf laser source that can produce any significant power (> 1.5 W) across the VNIR waveband at an affordable price and in a sufficiently compact form factor.

The Navy needs compact and affordable laser sources in the VNIR band, specifically the wavelengths covering 0.5 through 0.85 microns. In this context, a “laser source” is understood as being distinct from a simple laser, in that the laser source combines the output of multiple individual lasers into a single output beam. In the case of the laser module described above, this is done through the assembly, integration, and alignment of multiple individual laser diodes with external optical components that perform the beam combining. However, it may also be done by integration of the combining optics directly on the same semiconductor substrate that contains the laser diodes, creating a photonic integrated circuit that is effectively a miniature laser “module” on a chip. With the exception of packaging and alignment of the output optics, this “on-chip” combining eliminates almost all of the assembly steps required for the discrete-component laser module. And while the cost of semiconductor fabrication increases, the overall cost of the resulting laser source can be significantly reduced, provided the technical challenges of on-chip combining in the VNIR can be overcome.

The goal of this topic is to demonstrate a laser source operating in the VNIR and designed for optimum size, weight, and power (SWaP), while also reducing the cost (SWaP-C). The source should be a laser array integrated on the same chip and combined into a single output, which is considered to be the key technical achievement of the effort. The minimum required continuous wave (CW) output power is 1.5 W, and the power should be distributed in at least six spectral lines. More lines are desirable, and increasing the number of integrated lasers represents an acceptable way of scaling to the required power output. The source should cover the entire VNIR band, with at least 20% of the total output power appearing in each of the sub-bands: 0.5-0.6 microns, 0.6-0.7 microns, and 0.7-0.85 microns. The output should also be placed at spectral lines corresponding to wavelengths of maximum atmospheric transmission. While the maximum number of discrete laser diodes that can be integrated on a single chip is fundamentally limited by die size and beam-combining losses, nothing about the chosen architecture should preclude further power scaling by external (off-chip) combining of multiple integrated laser arrays. In particular, the combined beam output from the chip should be of high quality, with M2 less than 2.0 and with 1.5 as a goal (note that M2 is defined by ISO Standard 11146 for this effort).

The solution must demonstrate the laser source as a packaged prototype laser module. Of fundamental importance is low SWaP, with a size goal of less than 20 cubic inches for the entire laser module and a weight goal of less than one pound. In this context, the “laser module” comprises the integrated on-chip combined laser array (which is the laser source), the mount (including thermal stack-up), the optics required for transmitting the output beam, and the packaging (including electrical and coolant connectors), but does not include the mounting hardware or power supplies. External optics for shaping the beam are acceptable, so long as they fit within the specified total module volume. Although the prototype module produced during Phase II need not be environmentally hardened, it must be contained within a closed package rather than an open breadboard.

The laser module prototype is intended for laboratory demonstration and limited outdoor range testing. However, for ease of use and in order to inform future system concepts, the laser module will be integrated with a closed-loop cooler, power supplies, and control circuitry to form a system demonstrator prototype. The system demonstrator will accept normal 60 Hz 120 V prime power and employ air cooling (convective or forced). The system demonstrator also need not be environmentally hardened, but should be capable of operation in ambient temperatures ranging from 40 to 90°F. Other than electrical prime power, the demonstrator should be self-contained and no larger than 300 cubic inches, including the laser module. The total weight of the demonstrator is not restricted. While the laser module is an integral part of the demonstrator, it should be removable to accommodate the possibility of substituting different laser modules in the future (for example, modules emitting with different spectral line placement). As a benchmark, the demonstrator prototype should be designed to meet a cost goal of $10,000 per unit when manufactured in a volume of 1,000. At the conclusion of the effort, the demonstrator unit will be delivered to the Naval Research Laboratory.

PHASE I: Develop a concept for a compact high-power integrated VNIR laser source that meets the objectives stated in the Description. Define the laser source architecture and demonstrate the feasibility of the concept in meeting the parameters of the Description. Feasibility shall be demonstrated by a combination of analysis, modelling, and simulation. The cost estimate for the concept shall be obtained by analyzing the key manufacturing steps and processes, their maturity and availability within the industry, the cost and availability of key components, and by comparison to the manufacture of similar items. The Phase I Option, if exercised, will include the laser source specification, the laser demonstrator system specification, test specifications, interface requirements, and capabilities description necessary to build and evaluate the full system demonstrator prototype in Phase II.

PHASE II: Develop and deliver a prototype compact high-power integrated VNIR laser source based on the results in Phase I. The integrated laser source (within the laser system demonstrator) shall be demonstrated by producing and testing a prototype (or multiple prototypes) in a laboratory environment. Multiple prototypes (or partial prototypes) may be produced as the design process is assumed to be necessarily iterative in nature. However, at the conclusion of Phase II, the final (best performing) prototype laser source, integrated with the system demonstrator, shall be delivered to the Naval Research Laboratory along with complete test data, a final manufacturing analysis, and final production cost estimate.

PHASE III DUAL USE APPLICATIONS: Assist the Navy in transitioning the technology for Government use. Specific manufacturing steps and processes that require development will be identified. Iterative testing will establish a hardware configuration baseline, produce production level documentation, and transition the laser source into production. Assist the Government in incorporating the integrated laser source into next higher assemblies and deployable systems.

Law enforcement, commercial, and scientific applications include use of VNIR lasers as sources for laser spectroscopy in detection of hazardous materials and chemical substances. The technology should also find application in the telecommunications sector as sources for wavelength multiplexed communications.

REFERENCES:

1. Zhao, Yunsong and Zhu, Lin. "On-Chip Coherent Combining of Angled-Grating Broad-Area Diode Lasers.” Optics Express, Vol. 20, Issue 6, 2012, pp. 6375-6384. https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-20-6-6375&id=229737.
2. Pauli, M. et al. “Power Scaling and System Improvements to Increase Practicality of QCL-Based Laser Systems.” Proceedings of the SPIE 10926, 27 June 2019. https://doi.org/10.1117/12.2508710.
3. Chang, Hsu-Hao, et al. “Integrated Hybrid Silicon Triplexer.” Optics Express, Vol. 18, Issue 23, 2010, pp. 23891-23899. https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-18-23-23891&id=206982.
4. Latkowski, S., et al. “Monolithically Integrated Laser Sources for Applications Beyond Telecommunications.” Proceedings of the SPIE, Physics and Simulation of Optoelectronic Devices XXVIII, 11274N, 2 March 2020. https://spie.org/Publications/Proceedings/Paper/10.1117/12.2552784?origin_id=x4325&start_volume_number=11200.

KEYWORDS: VNIR Lasers; Near-Infrared; Laser Source; Semiconductor Lasers; Beam Combining; Laser Diodes.

OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Materials / Processes

OBJECTIVE: Develop additive manufacturing (AM) processes to produce high performance copper-based components and materials.

DESCRIPTION: Additive manufacturing (AM) has matured rapidly over the past decade and is currently a viable manufacturing process in many industries. This is especially true in the production of polymer parts. AM not only allows production of specialized components in small quantities, but it also makes possible the creation of devices and materials that cannot be otherwise produced by traditional means. Additive manufacturing of metals has also matured rapidly; however, the utility of metal AM has not been realized as fully as for polymer processes. This is especially true in the defense electronics and defense systems industries.

To a large extent, AM has been seen as a tool for the production of solid models (rapid prototyping), on-demand manufacturing, and in the fabrication of complete parts where traditional fabrication techniques would require the joining of multiple components. However, the full potential of AM lies in the fabrication of parts and materials that cannot be realized by any other means. This is already being exploited in polymer AM processes where the material constituents can be changed “on the fly” during the fabrication process to achieve gradations in material properties that create specific performance characteristics. For example, the current state of the art for polymer-based materials allows the dielectric constant of a part to be varied throughout the part using advanced additive techniques.

In defense electronics, stringent requirements place unparalleled demands on materials selection and performance, which directly increases cost. Mechanical and especially thermo-mechanical properties of metals used in high performance radio frequency (RF) and laser systems are a primary concern during design and material selection. These metals typically serve as mechanical supports and heat transfer paths for high power electronics. In other applications they serve directly as RF circuit components (such as connectors, transmission lines, waveguides, and antenna elements). Modern vacuum electronics use metal and ceramic construction exclusively, with material purity and performance being of paramount concern.

The Navy has a compelling interest in developing components and materials that increase the overall performance of high-power sensor (radar and electronic warfare) and weapon systems. Specifically, for this topic, this means developing AM processes for copper and copper-based materials and structural elements (at very small scales) that provide performance characteristics exceeding what can be obtained through traditional manufacturing processes. “Copper-based materials” include both copper alloys and metal matrix composites (including hybrid composites) where the primary metal constituent is copper. For structural (three-dimensional vice planar) elements, the interior dimensions of WR-10 waveguide (0.100 X 0.050 inches) serve as the benchmark for the feature size and aspect ratio desired. That is, RF circuit components are assumed to require this level of resolution and cooling channels should achieve these dimensions (or smaller) to be useful.

There are two key aspects to this STTR topic: (1) the demonstration of three-dimensional structures with fine (high aspect ratio) features, tight tolerances and smooth surfaces, and (2) the development of innovative materials. Either may be selected and addressed, both may be addressed separately, or both may be addressed in combination. For the demonstration of three-dimensional structures, a 10X improvement in feature aspect ratio, tolerance, and surface roughness over the current state of the art is the goal. The objective is to demonstrate through the production and testing of prototypes the ability of the innovative process (or combination of processes) to deliver parts that cannot be manufactured by traditional (non-AM) means. And while either new structures or new materials may be addressed under this effort, innovative AM processes and techniques that demonstrate multiple benefits and utility for wide application are most desirable.

Of particular interest to the Navy are materials and components for thermal management of high power electronic modules. These may be solid heat spreaders or small cooling structures (base plates) incorporating small channels for liquid cooling. Along these lines, thin oscillating heat pipes (OHPs) are an area that embodies multiple technical challenges of particular interest (for example, feature size, tolerance, finish, and affordability). Typically, these components find their most challenging application in transmit and receive (T/R) modules incorporating high power monolithic microwave integrated circuit (MMIC) amplifiers and in high power laser modules incorporating large numbers of solid-state laser diodes. In these cases, differences in the coefficient of thermal expansion (CTE) between the device being cooled and the module structural elements create significant design challenges. Therefore, materials that show superior heat transfer and CTE matching performance through the gradation of material constituents and properties are of great interest. Likewise, innovative structures or composites that provide built-in strain relief as well as superior thermal performance are also of interest. In either approach, AM solutions that provide comparable performance (to the current state of the art) while reducing overall cost (target of 50%) through the elimination of other components or assembly steps are also desired.

Another particularly challenging application of interest is the fabrication of components for vacuum electron devices (VEDs), especially high frequency (>28 GHz) amplifiers such as traveling wave tubes (TWTs). The metal components used in fabrication of a TWT are, by nature, three dimensional with large aspect ratios, require demanding mechanical tolerances, and exhibit high standards of finish and metallurgical quality. Copper is widely used in all VEDs for its good electrical and thermal conductivity properties and for the vacuum properties copper exhibits when produced in its high purity grade. However, copper is relatively soft, deforms and melts at relatively low temperatures, and can be difficult to machine. Consequently, VED fabrication typically includes the joining of copper to other metals and ceramics through brazing and, to a lesser extent, welding. So, AM processes that produce superior copper parts for VED fabrication are also of great interest. This includes processes that improve mechanical and heat transfer performance, improve the joining of parts, and reduce cost by the elimination of traditional machining steps. Again, this may be done through the development of innovative structures or innovative copper-based materials (or combinations of both).

The Navy seeks to develop an AM capability that benefits the RF and electro-optical electronics industry and not to produce any particular part. The solution is assumed to include the development of new AM hardware, feedstock, tooling, design methodologies, and fabrication steps. It also includes the identification of, development of, refinement of, and application of measurement techniques for use both as in-process checks and for use post-fabrication to assess the efficacy of the new capability. Copper is chosen because of its relevance to the electronics industry and because of the particular challenges it presents to AM. Prototype devices and structures should be selected to demonstrate the innovative AM capability. These prototypes should be “real” components that demonstrate relevance to the electronics industry, not just material samples (“blanks”) for testing. Prototype components and devices should demonstrate utility and performance that cannot be achieved through manufacturing by traditional means. Otherwise, the selection of prototypes is not restricted and the examples cited above are not exhaustive. It should also be noted that the overall solution may include traditional treatment techniques such as annealing, chemical polishing, and hot isostatic pressing. However, solutions that require extensive “clean-up” machining are not considered sufficiently additive in nature and will not be considered. Processes that use traditionally fabricated parts or stock as foundations for further fabrication of AM structures and materials are acceptable.

PHASE I: Propose a concept for additive manufacturing of high performance copper and copper-based materials that meets the objectives stated in the Description. The concept shall include specific prototypes by which the proposed AM process technology will be demonstrated. These prototypes will subsequently be produced and used (in Phase II) to verify, by testing and analysis, the efficacy of the proposed AM concept. During Phase I, feasibility of the concept shall be demonstrated by a combination of analysis, modelling, simulation, and evaluation of proposed process steps against established manufacturing methods. The Phase I Option, if exercised, will include the initial process specifications, AM equipment requirements, test specifications, and capabilities description to build a prototype additive manufacturing facility in Phase II.

PHASE II: Develop and demonstrate a prototype facility for AM of high performance copper-based components and materials. In this context, “facility” refers to the combination of equipment, tooling, and process steps required to demonstrate the end-to-end additive manufacturing capability provided by the proposer, not the actual physical facility. Demonstration of the AM process (or multiple processes) shall be accomplished by fabrication and evaluation of the prototype components and materials identified during Phase I. Multiple prototype components and samples are expected during execution of this Phase as the process development is assumed to be necessarily iterative in nature. However, at the conclusion of Phase II, at least one example of each proposed prototype component or material sample shall be delivered to the Government with no fewer than five total prototype samples delivered overall. Test data shall also be delivered with each prototype sample delivered.

PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the technology for Government use. Identify specific products and material formulations appropriate to the new AM processes and, in conjunction with the broader industry, develop specific production flows and process parameters to either market finished copper-based AM products or transition the technology to produce them in quantity.

The technology resulting from this effort is anticipated to have broad commercial application in the electronics industry as well as niche application to the broader industry for applications such as heat exchangers and thermal management components for electrical power conversion.

REFERENCES:

1. Horn, Timothy J. and Gamzina, Diana. “ASM Handbook, Volume 24, Additive Manufacturing Processes.” ASM International, Cleveland, Ohio, 2020, pp. 388-418. https://dl.asminternational.org/handbooks/book/119/chapter-abstract/2350563/Additive-Manufacturing-of-Copper-and-Copper-Alloy.
2. Jordan, Nicholas M., et al. “Additively Manufactured High Power Microwave Anodes." IEEE Transactions on Plasma Science, Vol. 44, August 2016, pp. 1258-1264. https://ieeexplore.ieee.org/document/7479563.

KEYWORDS: Copper Alloys; Metal Matrix Composites; Thermal Management; Heat Spreaders; Oscillating Heat Pipes; Vacuum Electron Devices

OUSD (R&E) MODERNIZATION PRIORITY: Artificial Intelligence (AI)/Machine Learning (ML);Hypersonics

TECHNOLOGY AREA(S): Air Platforms;Weapons

OBJECTIVE: Formulate, implement, and validate data-driven turbulence models for Reynolds Averaged Navier-Stokes (RANS) closure applicable to hypersonic flows with favorable pressure gradients, adverse pressure gradients, shock wave/turbulent boundary layer interaction (STBLI), and high heat flux.

DESCRIPTION: Hypersonic weapons are exposed to harsh operating environments requiring careful calculation of turbulent boundary layers to accurately estimate heat transfer and design thermal protection systems. Given the wide range of altitudes and velocities hypersonic vehicles operate in, the Navy requires a flexible modeling approach. However, direct numerical simulation data, let alone flight test or even wind tunnel experimental data, is expensive to develop and covers only very specific flight profiles. Faster, cheaper modeling approaches are needed to enable design for entire mission profiles. Modeling approaches, such as RANS equations that are well established for incompressible flow, provide inconsistent results, deviating by more than 50% from data when modeling relevant hypersonic flows, especially for STBLI [Refs 2, 3]. The principal problem lies in the models used to determine Reynolds Shear Stresses and turbulent heat flux required to close the RANS equations; existing methods are inadequate for hypersonic flow.

Over the last decade, improvements have been made in the development of data-driven techniques to close the RANS equations. Application of machine learning (ML) provides a powerful extension to empirical and semi-empirical methods common for developing and tuning closure models. ML allows application of much larger data sets with higher accuracy, removing some of the need for assumptions in traditional closures. These approaches typically use available Direct Numerical Simulations (DNS) or Large Eddy Simulations (LES) data sets to train ML models that can then be used on flows for which no high fidelity, scale-resolved results are available. Wang et al. [Ref 4] have improved on legacy RANS closures in square ducts with varying Reynolds number and flows with massive separation with varying Reynolds number and varying geometry. Wang et al. [Ref 5] extended the technique to hypersonic flat plate turbulent boundary layers and obtained substantial improvements over RANS on Mach 8 flow, even using only Mach 2 DNS results; even better results were obtained from an aggregate of Mach 6 and Mach 2 models. Wang’s [Ref 5] results point to the potential applicability of data-driven approaches to improve RANS modeling for more generalized hypersonic flow fields. Not only have these approaches been able to provide more accurate modeling, they also can be used to quantify uncertainty [Ref 1]. Uncertainty quantification is especially important for ML and other empirical approaches, which can experience losses in accuracy away from design conditions.

These data-driven applications are, however, not straightforward. Developing these models requires addressing such problems as defining input and output flow field variables for ML that have physical significance, are normalized, and have Galilean invariance [Ref 6]. Additionally, ML on DNS data cannot be used to simply replace terms in the RANS models, as ill-conditioning of the RANS equations and errors in mean flow quantities will result [Ref 1]. ML approaches are commonly used to predict discrepancies between RANS and DNS data [Refs 1, 4, 5] to train the model to predict the discrepancies between RANS calculations and DNS data throughout the flow field, but how this information is used to improve predictions of quantities of interest (such as heat transfer or separation region location) varies. These discrepancies can be used to adjust existing closure models [Ref 1], adjust model parameters [Ref 10], or to correct Reynolds Stress terms [Refs 4, 5]. Added to this is the general difficulty of ML in determining the scope of applicability of results, amplified in studying hypersonic flow by variations in Mach number, Reynolds number, flow geometry, and shock geometry that can substantially change the character of flow.

Data driven approaches offer great potential for improving the speed and accuracy of existing hypersonic turbulence models, but product development must take into account the facts that (1) ML corrections to RANS models apply only to a range of flight profiles and vehicle geometries, (2) we must know when a particular ML model loses accuracy due to a change in flow configuration, and (3) ML models can be developed using a wide range of training sets with different choices as to which ML approach (i.e., random forest, neural network, etc.) and different approaches to using the model data to obtain quantities of interest.

PHASE I: Formulate and assess methodologies to improve RANS turbulence models for hypersonic flows using data driven approaches. Specifically, we are seeking a proof of concept for an add-on compatible with existing CFD codes. Significant improvements in the prediction of heat transfer, skin-friction and pressure in attached and separated hypersonic flows are required. Validation against relevant hypersonic experimental data and DNS will be a key consideration towards successful phase transition. The analysis must show that the proposed methodology improves agreement with existing datasets over a wide range of relevant flow conditions. Develop a Phase II plan.

PHASE II: Expand the capabilities and flow configurations of the add-on developed in Phase I. Emphasis should be placed on expanding the models to a wider range of flow geometries, Mach numbers, Reynolds numbers, wall temperature ratios and flight enthalpies. For instance, add ML models based on different training datasets and a variety of data-driven approaches to provide improved accuracy for different flow regimes. Generation of new DNS training datasets can be performed as needed to eliminate gaps in existing datasets. Inclusion of boundary layer transition effects (i.e., length and shape of the transition region and heat transfer overshoot) are needed to increase the applicably of RANS to flow with laminar, transitional and fully turbulent regions. Any new features should be assessed for accuracy.

PHASE III DUAL USE APPLICATIONS: Automate user choice in specific model and flow parameters. Apply uncertainty estimation methods such as those surveyed in Ref 1 to determine which of the expanded training sets, ML models, and closure methods (i.e., Reynolds Stress estimation, coefficients, closure models) will provide the best result for the particular flow profile under consideration, taking into account factors such as geometry, Mach number, Reynolds number, and target quantities of interest (i.e., separation region location and size, heat transfer, etc.). Provide an automated, flexible means of assessing turbulent boundary layers, especially in STBLI without requiring dedicated knowledge and experienced judgment needed to determine the ideal data and model for different flow problems. As with Phase II, specific details of breadth of flows that automation is applicable to and depth of accuracy and detail available, is left to assessment of market need and available developmental resources.

REFERENCES:

1. Duraisamy, Kathik et al. “Turbulence Modeling in the Age of Data.” Annual Review of Fluid Mechanics, vol. 51, 2019, pp. 1-23. https://arxiv.org/pdf/1804.00183.pdf. 
2. Holden, Michael et al. “Comparisons of Experimental and Computational Results from “Blind” Turbulent Shock Wave Interaction Study Over Cone Flare and Hollow Cylinder Flare Configurations.” AIAA Aviation Conference, Atlanta, GA, 2014. https://cubrc.org/_iassets/docs/6_Wadhams_AIAA_Atlanta_SWTBI.pdf. 
3. Georgiadis, Nicholas J. et al. “Status of Turbulence Modeling for Hypersonic Propulsion Flowpaths., NASA/TM-2012-217277. https://ntrs.nasa.gov/api/citations/20120008521/downloads/20120008521.pdf?attachment=true.
4. Wang, Jian-Xun et al. “A Physics Informed Machine Learning Approach for Reconstructing Reynolds Stress Modeling Discrepancies based on DNS Data.” Physical Review of Fluids, March 2017. https://arxiv.org/pdf/1606.07987.pdf.
5. Wange, Jian-Xun et. al. “Prediction of Reynolds Stress in High Mach Number Turbulent Boundary Layers using Physics Informed Machine Learning.” Theoretical and Computational Fluid Dynamics, Vol 33, 2019, pp. 1-29. https://arxiv.org/abs/1808.07752.
6. Wu, J.L. et al. “Physics- Informed Machine Learning Approach for Augmenting Turbulence Models—A Comprehensive Approach.” Physical Review Fluids, Vol 3, 2018. https://arxiv.org/pdf/1801.02762.pdf.
7. Zhang, Chao et al. “Direct Numerical Simulation Database for Supersonic and Hypersonic Turbulent Boundary Layers.” AIAA Journal, Vol 56, No. 11, 2018. https://arc.aiaa.org/doi/pdfplus/10.2514/1.J057296.
8. Duraismy, Karthik et al. “Augmentation of Turbulence Models Using Field Inversion and Machine Learning.” AIAA SciTech Forum, 55th Aerospace Sciences Meeting, Grapevine Texas, Jan 2017. https://deepblue.lib.umich.edu/bitstream/handle/2027.42/143032/6.2017-0993.pdf?isAllowed=y&sequence=1.
9. Gnoffo, Peter et al. “Uncertainty Assessments of 2D and Axisymmetric Hypersonic Shock Wave- Turbulent Boundary Layer Interaction Simulations at Compression Corners.” 42nd AIAA Thermophysics Conference, 27-30 June 2011, Honolulu, Hawaii. https://arc.aiaa.org/doi/pdf/10.2514/6.2011-3142. 
10. Durbin, Paul. “Some Recent Developments in Turbulence Closure Modeling.” Annual Review of Fluid Mechanics, Vol. 50, 2018, pp. 77-103. https://www.annualreviews.org/doi/abs/10.1146/annurev-fluid-122316-045020. 

KEYWORDS: Turbulence modeling; data-driven; machine learning; ML; hypersonics; boundary layers; Reynolds-averaged Navier–Stokes equations; RANS; Direct Numerical Simulations; DNS; Large Eddy Simulations; LES

OUSD (R&E) MODERNIZATION PRIORITY: Artificial Intelligence (AI)/Machine Learning (ML);General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Biomedical;Human Systems;Materials / Processes

OBJECTIVE: Develop a digital design tool for personal protective equipment (PPE) that allows for rapid exploration of the entire design space.

DESCRIPTION: Developing high-performing, detailed designs of PPE require a thorough examination of conceptual designs and experimental testing. Testing numerous designs is costly and time consuming, both of which contribute to delayed product development and deployment. Moreover, traditional non-biofidelic physical human surrogates limit the translation from testing to the actual response of the warfighter in theater. To facilitate faster and rational design decisions, modeling and simulation utilizing biofidelic human body models can streamline the design process. However, even current state-of-the-art models can still be

time consuming to develop, modify, and analyze. New digital technology that allows for rapid design exploration to couple with state-of-the-art models is needed in order to leverage the advantages of computational modeling. PPE design parameters (e.g., fit, form, weight, material) can be extensively probed on digital human models with accurate injury risk analysis prior to the first physical prototype.

PHASE I: Conceive of and clearly articulate a feasible formulation for a digital design tool for PPE using digital engineering principles used by the DoD. A complete plan for the PPE digital design tool should be developed and the methods of creation for this tool should be fully explained. A methodology for a future approach to validation of the PPE design tool should be presented including how the tool would reduce system design costs, how the tool would allow novel designs to be explored, and how the design tool would specify the characteristics of the PPE under development. Develop a Phase II plan.

PHASE II: Build a functional prototype PPE development tool with a Graphical User Interface (GUI) and the required related environment. Integrate the prototype PPE software tool with a human digital twin that is created in the physics-based solvers, LS-Dyna and FEBio finite element software packages. Create a functional system using both the PPE development tool and the human digital twin with two novel PPE designs that demonstrate the ability to estimate injury risk for any given PPE design as well as the characteristics of the PPE itself (e.g., coverage, dimensions, material). Conduct a cost savings analysis to compare the PPE design tool to more traditional design methods for creating novel PPE items to demonstrate the value of the design tool to reduce acquisition costs.

PHASE III DUAL USE APPLICATIONS: Build and deploy a functional PPE design tool at a Navy organization, preferably within the Naval aviation realm. Verify and validate the ability of the PPE design tool to produce protective gear that are functional, achievable with currently available materials and material handling processes, and provide the protection and injury risk reduction as predicted by the design tool during in silico design processes.

Develop a plan for the sustainment and improvement of the design software tool over time so that the tool does not become outdated or irrelevant due to advances in injury risk prediction, human body modeling, personal protective equipment fundamentals; development of new protective materials, system optimization methodologies, application of AI/ML, or technological advances in related technologies and supporting data sets such as constitutive properties of biological tissues and materials used in PPE systems. Address how the PPE design software tool can address the requirements for military and dual-use PPE, especially body armor, helmets, sensory system protection (e.g., goggles, wearable noise abatement systems), bomb suits, as well as civilian PPE systems such as hard hats, football helmets, and PPE for manufacturing facilities. Software tool can be formulated to be sustained and improved over time to remain functional. Commercialization must include DoD applications and may include non-DoD applications.

REFERENCES:

1. Zimmerman P.; Gilbert, T. and Salvatore, F. “Digital engineering transformation across the Department of Defense.” The Journal of Defense Modeling and Simulation: Applications, Methodology, Technology, 16(4), 2017, pp. 325-338. https://journals.sagepub.com/doi/abs/10.1177/1548512917747050?journalCode=dmsa.
2. Olivares, G. and Yadav, V. “Mass transit bus-vehicle compatibility evaluation during frontal and rear collisions.” Proc 20th Int Technical Conf Enhanced Safety of Vehicles, 2007. Paper number 07-0477. https://www-esv.nhtsa.dot.gov/Proceedings/20/07-0477-O.pdf.
3. Bredbenner, T.L.; Eliason, T.D.; Francis, W.L.; McFarland, J.M.; Merkle, A.C. and Nicolella, D.P. “Development and validation of a statistical shape modeling-based finite element model of the cervical spine under low-level multiple direction loading conditions.” Frontiers in Bioengineering and Biotechnology, 2: 58, 2014. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4245926/.
4. Michalski, A.S.; Amin, S.; Cheung, A.M.; Cody, D.D.; Keyak, J.H.; Lang, T.F.; Nicolella, D,P,; Orwoll, E.S.; Boyd, S.K. and Sibonga, J.D. “Hip load capacity cut-points for Astronaut Skeletal Health NASA Finite Element Strength Task Group Recommendations.” npj | Microgravity, 2019, 5: 6. https://www.nature.com/articles/s41526-019-0066-3.pdf.
5. Olivares, Gerardo. “Integrated Occupant Safety for Urban Air Transport Emergency Landing Applications.” 8th Biennial Autonomous VTOL Technical Meeting and 6th Annual Electric VTOL Symposium. Mesa, AZ USA. https://www.researchgate.net/publication/330764309_Integrated_Occupant_Safety_for_Urban_Air_Transport_Emergency_Landing_Applications (Note: Full text of article available upon request from author.)
6. Goertz, A,; Viano, D. and Yang, K.H. “Effects of Personal Protective Equipment on Seated Occupant Spine Loads in Under-Body Blast: a Finite Element Human Body Modeling Analysis.” Human Factors and Mechanical Engineering for Defense and Safety, Vol 5, Issue 1, January 6, 2021. https://www.mysciencework.com/publication/show/effects-personal-protective-equipment-seated-occupant-spine-loads-underbody-blast-finite-element-human-body-modeling-an-1f165f4e?search=1.

KEYWORDS: digital engineering; personal protective equipment; PPE; body armor design; helmet design; systems engineering; structural analysis; injury risk reduction; human digital twin; risk analysis; verification and validation models; design models; manufacturing

OUSD (R&E) MODERNIZATION PRIORITY: Artificial Intelligence (AI)/Machine Learning (ML);Autonomy;Microelectronics

TECHNOLOGY AREA(S): Electronics;Materials / Processes;Sensors

OBJECTIVE: Develop an innovative, wide-area synthetic skin that utilizes advances in machine perception to enhance the sensory capabilities of the device or system to which the skin is applied and for enhanced investigative capabilities in low-visibility, undersea environments.

DESCRIPTION: A key characteristic of a high-performing synthetic sensory skin is the ability to remain fully operational when stretched, deformed, or used in undersea operations conducted in harsh environments. There are technical risks associated with the implementation of synthetic skins with human-like sensory capability such as manufacturability, resiliency, sensors, and data processing. This STTR topic seeks to develop innovative, wide-area, synthetic sensory skin technologies that address these risks. Solutions should provide high-functioning synthetic sensory skin that augments operations in low-access, low-visibility environments as well as in missions requiring teleoperations of critical systems.

PHASE I: Conduct a proof-of-concept study, culminating in a design package and a demonstrable simulation and/or laboratory experiment, that proves the feasibility of achieving the desired synthetic sensory skin requirements. Produce a detailed report summarizing simulation and/or testing results, a presentation of the initial design, and plans for prototyping the synthetic skin in Phase II.

PHASE II: Finalize design details through Preliminary and Critical Design Reviews, provide a manufacturability analysis, and develop and demonstrate the prototype synthetic skin in a relevant environment.

PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the technology to a program of record for operational use. Potential medical applications include telemedicine, where it could enable a medical clinician to replicate the physical contact they have when they evaluate a patient in person, and as a covering for prosthetic limbs. Another commercial application includes using it to enable robots to work more safely around humans.

REFERENCES:

1. Majidi, C. “Soft Robotics: A Perspective—Current Trends and Prospects for the Future.” Soft Robotics, Vol. 1, Issue 1, 2013. https://www.liebertpub.com/doi/10.1089/soro.2013.0001.
2. Technical University of Munich (TUM). “Biologically-Inspired Skin Improves Robots' Sensory Abilities.” Science Daily, October 10, 2019. https://www.sciencedaily.com/releases/2019/10/191010125623.htm.
3. Dahiya, R.; Manjakkal, I.; Burdet, E. and Hayward, V. “Large-Area Soft e-Skin: The Challenges Beyond Sensor Designs.” Proceedings of the IEEE. Vol. 107, No. 10, October 2019. https://www.cim.mcgill.ca/~haptic/pub/RD-ET-AL-PIEEE-19.pdf.

KEYWORDS: artificial intelligence; perception; underwater; robotics; synthetic skin; bio-inspired; materials; microelectronics; sensors

OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR);Hypersonics;Space

TECHNOLOGY AREA(S): Air Platforms;Materials / Processes;Space Platforms

OBJECTIVE: Enhance and optimize oxidation resistance and thermal, mechanical, and physical properties of ceramic matrix composites (CMCs) through computational-directed and validated design and the addition of additive(s) to the CMC.

DESCRIPTION: The service life of ultra-high temperature materials such as CMCs in gas turbine engines or hypersonic applications is dependent on a complex combination of temperature-stress- environment- time conditions. Maximizing thermal transport to avoid local hot spots on leading edges of reusable hypersonic structures and optimizing tensile strength require a thorough understanding of CMC phenomena. Additives such as nanoparticles and micron-sized chopped fibers have been reported to reduce localized mechanically and thermally-induced stresses thereby increasing overall strength and toughness. Informed design will enhance interphase coatings and reduce CMC porosity. Modeling strength and deformation processes of CMCs as a function of CMC structure and additive load will lead to fabrications processes that maximize CMC component strength.

PHASE I: Using Integrated Computational Materials Engineering (ICME) functionalities, establish models to predict the effect of composition on phase stability and key properties in ceramic matrices such as thermomechanical and thermochemical behavior with and without the application of additives as a function of temperature. The ICME effort needs to be combined with experimental approaches to generate requisite information for model validation. Develop a process for applying novel additives to CMC fibers. Evaluate the oxidation resistance and creep resistance of SiC CMC fibers with and without the addition of novel additives as a function of temperature up to 2000oC, if possible. Develop a Phase II plan.

PHASE II: Apply validated models, developed in Phase I, to the synthesis of advanced matrices and coatings, initially as monolithic materials and later in sub-systems and complete EBC/CMC systems. In coordination with an appropriate original equipment manufacturer (OEM), establish and execute a test plan that will provide sufficient data for preliminary assessment of design allowables for critical and relevant design requirements. These requirements will be developed in conjunction with an OEM and ONR. Test samples will be manufactured with different testing geometries (necessitated by uniformity and testing hardware requirements) for determination of thermal and mechanical property data, including: density, hardness, thermal conductivity, thermal expansion, tensile strength, modulus, creep, and creep rupture, and vibrational and dynamic fatigue.

Test conditions shall include controlled stress, temperature, and time under environmental conditions, including simulated turbine engine by-products of combustion gases with and without sodium sulfate and water present. By the end of the Phase II, ensure that data will be available to initiate constituent modeling of modified CMCs with lifetime predictions of oxidation resistance and thermal-mechanical-creep performance up to 100 hours. Also ensure that thermal-mechanical-creep tests will reach up to 1000 hours at 2000°C or more.

PHASE III DUAL USE APPLICATIONS: Adoption of models/optimized matrix by an OEM for further maturation to manufacture robust self-healing matrix CMC components that can operate in complex environments with less maintenance, lower overall life cycle cost, and improved operational capabilities. Coordinate with an engine OEM on work toward further maturation of the knowledge and/or process to fabricate CMC engine components for military and commercial platforms or show how the CMCs with additives can perform at temperature exceeding 2000°C.

REFERENCES:

1. DeCarlo, J.A. and van Roode, M. "Ceramic Composite Development for Gas Turbines Engine Hot Section Components." ASME Turbo Expo 2006, Power for Land, Sea and Air, May 8-11, 2006, Barcelona, Spain. Paper GT2006-90151. https://asmedigitalcollection.asme.org/GT/proceedings-abstract/GT2006/42371/221/314649.
2. Padture, N.P. "Environmental Degradation of High-Temperature Protective Coatings for Ceramic Matrix Composites in Gas Turbine Engines." Nature: npj Materials Degradation, v. 3, p.11, 2019. https://www.nature.com/articles/s41529-019-0075-4.
3. "US Hypersonic Initiatives Require Accelerated Efforts of the Materials Research Community." MRS Bulletin, Vol. 46, March 2021. https://link.springer.com/content/pdf/10.1557/s43577-021-00050-2.pdf.
4. Lauten, F.S. and Schulberg, M.T. “Composite Materials for Leading Edges of Enhanced Common Aero Vehicles and Hypersonic Cruise Vehicles.” Physical Sciences Inc., 2006.
5. Evans, A.G.; Zok, F.W.; McMeeking, R.M. and Du, Z.Z. "Models of high temperature, environmentally assisted embrittlement in ceramic-matrix composites." Journal of the American Ceramic Society, Vol. 79, Issue 9, September 1996, pp. 2345-2352. https://ceramics.onlinelibrary.wiley.com/doi/10.1111/j.1151-2916.1996.tb08982.x.

KEYWORDS: Ceramic Matrix Composite; CMC; gas turbines; hypersonics; nanoparticles; ultra-high temperatures; oxidation resistance; metal carbines

OUSD (R&E) MODERNIZATION PRIORITY: Artificial Intelligence (AI)/Machine Learning (ML);Autonomy

TECHNOLOGY AREA(S): Information Systems;Sensors

OBJECTIVE: Develop inexpensive Lidar-like 3D imaging sensors that have high depth and lateral resolution, have a large field-of view for reliable object detection, respond in real time, and work at medium to long ranges in indoor and outdoor environments.

DESCRIPTION: 3D scene understanding (i.e., 3D scene segmentation and parsing, depth estimation, object detection and recognition) are essential components in a vision system. 3D sensors similar to Microsoft Kinect are inexpensive and high resolution but have limited range outdoors, thus not suited for many robotics applications. Lidars have long range and high depth accuracy, but are very expensive; for example, those used in self-driving cars are typically several times more expensive than other car components. Another drawback of current Lidars is their small “vertical” field-of-view, which results in limited vertical resolution and accuracy in object detection because Lidars (even the more expensive ones) have at most 64 scan lines, which could fail to detect small objects even at medium range distances.

The goal of this STTR topic is to develop inexpensive, high-resolution, high-accuracy 3D imaging sensors for wide use on a variety of large and small ground and aerial robotic platforms that can work in dynamic environments under different conditions. ONR expects recent promising advances along a number of directions including machine learning-based algorithms for improved depth estimation with stereo cameras [Refs 2, 5], active illumination technologies [Ref 1], and optimal time-of-flight coding [Ref 3], etc., open new approaches to building hybrid systems that combine optical cameras and laser ranging for developing such 3D imaging sensors. Combining these advances (ML-based stereo imaging, utilizing active illumination for 3D imaging, and novel time-of-flight coding for improved range estimation) requires innovative approaches.

PHASE I: Design the system architecture including sensors and computing hardware, and processing and inference algorithms for building inexpensive, high-resolution, accurate, 3D imaging sensors. Since these sensors are intended for use on various UGVs and UAVs deployed in dynamic and cluttered environments, the design should consider tradeoff estimates among size, weight, and power (SWAP), as well as resolution, detection accuracy, operating range, frame rate, and cost. Develop a breadboard version to demonstrate the feasibility of the design. Develop a Phase II plan.

PHASE II: Perform experiments in a variety of situations and refine the system. Goals for Phase II are: (a) the system should have a field-of-view and resolution comparable to optical cameras; (b) Demonstrate the system’s capability for human detection. Normal vision can detect humans up to a distance of about 300m in daylight. At nighttime, typical headlights illuminate the road up to a distance of about 60m [Ref 4]. The minimum detection range should be the aforementioned distances in daylight and nighttime. (c) Develop a compact prototype imaging system that is small, lightweight, and low power, suitable for portability by personnel and small autonomous platforms (UxVs).

PHASE III DUAL USE APPLICATIONS: Perform additional experiments in a variety of situations and further refine the system for transition and commercialization. Ensure that the real-time imaging system is operable in real-world dynamic environments, thus extending the imaging to handle real-time acquisition, that is, at least 30 fps. This technology could be used in the commercial sector for self-driving cars, and in surveillance and navigation on any land or air vehicle.

REFERENCES:

1. Achar, Supreeth et al. “Epipolar Time-of-Flight Imaging.” ACM Transactions on Graphics, Vol. 36, No. 4, Article 37, July 2017. https://dl.acm.org/doi/pdf/10.1145/3072959.3073686.
2. Garg, D. et al. “Wasserstein Distances for Stereo Disparity Estimation.” 34th Conference on Neural Information Processing Systems (NeurIPS 2020), Vancouver, Canada. https://arxiv.org/pdf/2007.03085.pdf.
3. Gupta, M. et al. “What are Optimal Coding Functions for Time-of-Flight Imaging?” ACM Transactions on Graphics, Vol. 37, No. 2, Article 13, February 2018. https://dl.acm.org/doi/pdf/10.1145/3152155.
4. Farber, Gene. “Seeing with Headlamps.” NHTSA Workshop on Headlamp Safety Metrics, Washington, DC, July 13, 2004. https://pdf4pro.com/view/seeing-with-headlights-4b1377.html. 
5. Wang, Yan et al. “Pseudo-LiDAR From Visual Depth Estimation: Bridging the Gap in 3D Object Detection for Autonomous Driving.” CVPR 2019. https://arxiv.org/pdf/1812.07179.pdf.

KEYWORDS: Lidar-like 3D imaging sensor; hybrid imaging; high-resolution sensor with large field of vision; FOV; outdoor imaging; indoor imaging

OUSD (R&E) MODERNIZATION PRIORITY: Networked C3

TECHNOLOGY AREA(S): Battlespace Environments;Electronics;Ground / Sea Vehicles

OBJECTIVE: Develop a low-cost inertially stabilized mechanism for motion compensation on antenna beam pointing and tracking aboard buoys and small crafts subject to winds, waves, and vehicle motion. Capability goals include low Size/Weight/Power (SWAP), high fault tolerance, and ability for customization and integration with representative antennas.

DESCRIPTION: Current small radio implementations for sensor exfil, telemetry, and data-on-the move lack the performance capabilities to connect small unmanned platforms to communication gateways separated by extended communication link ranges. Recent advances in antenna structures have proven significant increases in gain performance, thereby enabling link closure at farther ranges without increased transmit power. However, advanced inertial measurement electronics and algorithms are needed that can provide fine beam pointing, acquisition, tracking, stabilization (PATS) accuracy required in various environments. It is paramount this innovative solution has low cost, low size/weight/power (SWAP), high fault tolerance, ability for customization, and easy integration into different antenna configurations.

PHASE I: System engineering and trade study for phased array antenna motion-compensating electronics that consists of (i) industrial-grade low-cost commercial off-the-shelf (COTS) IMU/GPS, and (ii) signal processing of incoming IMU data to provide RF beam steering corrections at a rate 100 Hz or higher. Develop varied designs for acquisition, beam pointing and tracking accuracy and performance as a function of electronics/sensor cost, power consumption and size, taking into consideration the requirements for antenna beam width and PATS loss. Develop a case study with detailed design and architecture for integrating the beam correction to a representative phased array antenna up to sea state 4, or for land-based vehicle, on the move. Modeling and simulation results that captures and visualize real-time environmental dynamics and perturbations and their impact on maintaining the RF link stability is highly desirable. Propose solutions for identified gaps and performance improvements. Develop Phase II plans.

Produce knowledge-based deliverables: (1) technical trades and systems engineering addressing cost-size-weight-power and beam PATS loss; (2) architectural designs of stabilized antenna with integrated pointing/tracking in a few frequency bands of interest; and (3) down select prototype design to targeted small radio and antenna systems offering highest value-benefit for Naval stakeholders.

PHASE II: Develop working experimental prototypes based on initial architectural designs delivered in Phase I. Demonstrate the capabilities of developed prototypes in a relevant lab environment up to TRL 4/5. Continue additional integration and tests activities to elevate and achieve TRL 6 during the option Phase, if exercised.

Knowledge-based deliverables: Finalized targeted prototype design.

Hardware & Software deliverables: Prototype system(s) capable of being lab tested up to TRL 4/5. Over-the air limited range test desirable.

Metrics: Objective Size (< 10 cu. in.), weight (< 8 oz), and power (< 1 W); Low cost; Good Pitch/roll/heading accuracy at refresh rate up to 100 Hz; PATS loss < 3 dB for data link at maximum range

The Phase II Option, if exercised, will include the following deliverables and metrics: Integrated system(s) with local at-sea TRL 6 demonstrations of range and stabilization performance.

PHASE III DUAL USE APPLICATIONS: Develop and refine the final design based on Phase II. Include varied stress testing (extended temperature range, vibration, etc.). Demonstrate autonomous communication capabilities at extended ranges over various sea state environments.

Deliverables: Fully integrated systems on which to conduct rigorous testing with variable beam widths for robust autonomy, stabilization up to sea state 4 and on-the-move platforms, including SATCOM applications.

Private sector commercial potential includes autonomous observation systems, remote monitoring, ocean Internet-of-Things (IOT), and oil and gas exploration.

REFERENCES:

1. Smith, I.S.; Chaffer, E.A. and Walker, C. “Recent Developments in a Large Inflatable Antenna.” IEEE Aerospace Conference, 3-10 March 2018, Big Sky, MT. https://ieeexplore.ieee.org/document/8396633.
2. Ganti, S.R. and Kim, Y. “Design of Low-Cost On-Board Auto-tracking Antenna for Small UAS.” 12th Intl Conference on Information Technology – New Generations, 13-15 April 2015, Las Vegas, NV. https://ieeexplore.ieee.org/document/7113485.
3. Hoflinger, F. et.al. “A Wireless Micro Inertial measurement Unit (IMU).” 2012 IEEE International Instrumentation and Measurement Technology Conference, Vol. 62, No.9, May 2012. https://ieeexplore.ieee.org/document/6229271.

KEYWORDS: Phased array beam stabilization; Inflatable Antenna; Autonomous Communication

OUSD (R&E) MODERNIZATION PRIORITY: Artificial Intelligence (AI)/Machine Learning (ML);General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Sensors;Weapons

OBJECTIVE: Develop techniques to enable high resolution optical ranging in underwater environments that rely on the encoding and decoding of the optical phase and/or the temporal signature of a blue-green laser source while providing accurate range measurements of underwater objects.

DESCRIPTION: Laser-based techniques offer the potential of providing range measurements with high speed and accuracy. When such techniques are used in the underwater environment, they must overcome the challenges of optical absorption and scattering in water. Blue-green wavelengths minimize absorption, but scattering distributes the optical signal in both time and space and reduces range accuracy. Techniques which reduce the contribution of scattered light to the range measurement can enhance optical ranging in challenging underwater environments. The challenge is to develop solutions that provide accurate range measurements (less than 5cm error) with processing speeds that are compatible with a moving underwater platform. Current techniques use time-encoded optical waveforms and subsequent time-resolved detection to discriminate between scattered and unscattered light. Such techniques involve hardware that is not compatible with small platforms and/or have insufficient dynamic range to operate in challenging underwater environments.

PHASE I: Provide model and/or low fidelity proof of concept results for a proposed optical ranging solution. The results should demonstrate how the proposed approach improves optical ranging in underwater environments. Develop a Phase II plan.

PHASE II: Develop a ruggedized hardware prototype that can be operated in relevant laboratory and/or in-situ environments. The prototype should fit within a 10 to 30 inch diameter cylindrical underwater vehicle, and there should be a path to meet the size, weight, and power requirements of a small unmanned underwater platform. Results from the prototype testing should demonstrate improved optical ranging in challenging underwater environments.

PHASE III DUAL USE APPLICATIONS: Work with the Government to transition the prototype hardware to a specific platform meeting that platform’s size, weight, and power limitations. Dual use opportunities include unmanned underwater vehicle (UUV) surveying (pipeline inspection) and automotive light detection and ranging (LIDAR).

REFERENCES:

1. Lee, R.W.; Laux, A. and Mullen, L.J. “Hybrid technique for enhanced optical ranging in turbid water environments.” Optical Engineering, Vol. 53, No. 5, 2014. https://www.spiedigitallibrary.org/journals/optical-engineering/volume-53/issue-5/051404/Hybrid-technique-for-enhanced-optical-ranging-in-turbid-water-environments/10.1117/1.OE.53.5.051404.short?SSO=1.
2. Jantzi, A.; Jemison, W.; Laux, A.; Mullen, L. and Cochcenour, B. “Enhanced underwater ranging using an optical vortex.” Optics Express, vol. 26, no. 3, Feb 5, 2018, pp. 2668-2674. https://pubmed.ncbi.nlm.nih.gov/29401804/.

KEYWORDS: laser ranging; underwater ranging; scattering; optical vortex; turbid; time of flight; LIDAR; undersea weapon; mine detection, mine countermeasure; underwater sensor

OUSD (R&E) MODERNIZATION PRIORITY: Biotechnology;General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Ground / Sea Vehicles;Materials / Processes

OBJECTIVE: Develop next-generation STEM Education aquatic robotics kits that employ soft, flexible, and waterproof materials and designs that will become widely accessible to students at various education levels (grades K-12); and support the workforce demands of a technically savvy and innovative current Naval enterprise.

DESCRIPTION: Recent research has shown that students are most challenged to use critical thinking skills when tasked to build around a specific application with specific design criteria [Ref 1]. Therefore, this STTR topic seeks the development of a STEM education toolkit that addresses a specific Naval application (aquatic soft robots) relevant for building the critical skills for future Naval technologies. Building aquatic robots from flexible materials requires a multidisciplinary skill set centered on math, physics, biology, and materials design, all which are valuable to nurture the expertise of the future Naval workforce [Ref 2]. The principles that would be achieved through this aquatic soft robotics toolset would modernize current robotic programs and offer students new and innovative skill sets (manufacturing, material science, mechanical, design and human-robot cooperation) by advancing the state of the art. The toolset should serve educational purposes as well as provide competition and engagement opportunities for building an evolving and growing community.

PHASE I: Demonstrate feasibility through scientifically sound design of a robotic kit that is built using flexible materials that are waterproof. Focus should be on physical concepts such as forces, motion, and friction; and robotics concepts such as actuation, pneumatics and controls; and how all of these can relate to biology. Attention must be paid to the educational instructions, guides, and design in addition to the robotic design. The kit should be adaptable for lesson plans, workshops, home, and school use. Consider educational value through thoughtful design and application of educational principles for each age group. Develop a Phase II plan.

PHASE II: Develop, demonstrate and validate the underwater soft robot prototype educational kit based on the Phase I design concept. Test and evaluate the prototype using meaningful metrics with the appropriate target student populations (as cited in the Description). Develop educational instructions and guides. Ensure that the kit is adaptable for lesson plans, workshops, and home and in-school use. Feasibility of the educational value should be considered through thoughtful design and application of educational principles for each age group.

PHASE III DUAL USE APPLICATIONS: Transition prototype to a partner in the educational sector.

REFERENCES:

1. Holland, D.P.; Walsh, C. and Bennett, G.J. “An assessment of student needs in project-based mechanical design courses.” 2013 ASEE Annual Conference & Exposition, Atlanta, Georgia. Paper #7038. https://biodesign.seas.harvard.edu/files/biodesignlab/files/2013_-_holland_-_an_assessment_of_student_needs_in_project-based_mechanical_design_courses.pdf.
2. Calabria, M.F. “Move Like a Shark, Vanish Like a Squid: The Navy Must Invest in Biomimetics to Sustain Dominance on the High Seas.” Proceedings USNI, Vol. 147/7/1,421. https://www.usni.org/magazines/proceedings/2021/july/move-shark-vanish-squid.

KEYWORDS: Science Technology Engineering Mathematics Education; STEM; Robotics; Soft materials; Aquatic; Biomimetic; Bioinspired

OUSD (R&E) MODERNIZATION PRIORITY: Artificial Intelligence (AI)/Machine Learning (ML);Space

TECHNOLOGY AREA(S): Battlespace Environments;Information Systems

OBJECTIVE: Develop novel software algorithms to characterize vertical thermodynamic profiles in the lowest 2-3 km of the atmosphere, leveraging satellite-based environmental monitoring (SBEM) data that combines information from at least 2 of the following observing methods: optical, infrared, microwave, radio occultation.

DESCRIPTION: While characterization of the marine atmospheric boundary layer (MABL) environment is fundamental for Naval operations (e.g., directed energy, C4ISR, and communication applications), there is a lack of sufficient data in areas of interest to analyze and predict tactical scale environmental conditions. Current satellite data methods to measure MABL thermodynamics have limitations based on physical observing characteristics, such as horizontal resolution, vertical resolution, refractivity, or temporal refresh. With the proliferation of broader environmental data availability and smallsat platforms, there exists the potential to improve vertical profiles of temperature, water vapor, and/or refractivity in the boundary layer by combining data from two or more observed mediums. Innovation is sought to develop the theory, algorithm, and software to demonstrate, verify, and validate such a satellite data fusion technique. This development will result in valuable knowledge and technology advances beyond DoD specific applications for the entire meteorological analysis and forecasting community.

PHASE I: Determine and demonstrate the technical capability to leverage at least two different environmental satellite remote sensing observation types (including, but not exclusive to, optical channels, infrared channels, microwave imagers, microwave sounders, radio occultation, synthetic aperture radar, etc.) to add value to current single source atmospheric profiling techniques. Identify those factors that will contribute to enhanced understanding of the MABL compared to conventional methods using historical meteorological data from available defense, civil, research, international partner, and/or commercial data streams. Develop a final summary report, including literature review and overall conclusions/recommendations, to be presented at the end of this Phase. Develop a Phase II plan.

PHASE II: Expand technical development and validation of a robust prototype system for retrieval of MABL thermodynamics in a variety of maritime environments. Given feeds of meteorological satellite information, the algorithm should produce near-real time estimates of temperature, water vapor, refractivity at a higher spatial resolution than conventional satellite retrievals, on the order of 250 m vertical and 10 km horizontal. This prototype software should be capable of interoperating alongside conventional satellite algorithms in a similar computing environment, including both a stand-alone server for single algorithmic demonstration and high performance computing cluster for parallelization of near-real time satellite feeds. Demonstration during a government meteorological field event will be coordinated to provide additional verification and validation opportunities. Characterization of data quality and uncertainty will also be necessary to support potential for data assimilation into numerical modeling systems. It is anticipated that the prototype software will be expanded, or in a position to be expanded, to other satellite platforms and/or sensing methods at the conclusion of Phase II efforts, such demonstration/research sensors being demonstrated in near-realtime by NASA. Delivery of a prototype software package and final verification report is expected at the end of this Phase.

PHASE III DUAL USE APPLICATIONS: This development will result in valuable knowledge and technology advances for the entire meteorological analysis and forecasting community. Naval applications will immediately benefit from a significant increase in environmental data and prediction availability/quality where the Navy operates. Other civil and commercial applications will benefit from enhanced data streams for broad blue-water maritime applications, improved predictability in numerical weather prediction, and increased cross-over between civil and commercial satellite remote sensing activities. Specifically, environmental characterization and prediction efforts by NOAA will be improved by augmenting meteorological analysis and data assimilation with new observations. Commercial meteorological entities will be able to add value with targeted local enhancement to atmospheric characterization and forecasting by leveraging such data and techniques. This effort has the potential to fill a data gap in all aspects of meteorological analysis as well as provide a proof of concept for additional data fusion opportunities.

REFERENCES:

1. Healy, S.B. and Eyre, J.R. “Retrieving temperature, water vapour and surface pressure information from refractive-index profiles derived by radio occultation: A simulation study.” Quarterly Journal of the Royal Meteorological Society, Vol. 126, Issue 566, pp. 1661-1683. https://doi.org/10.1002/qj.49712656606.
2. Blackwell, W.J.; Leslie, R. Vincent; Pieper, Michael L. and Samra, Jenna E. "All-weather hyperspectral atmospheric sounding." Lincoln Laboratory Journal, Vol. 18, No. 2, 2010, pp. 28-46. https://www.ll.mit.edu/sites/default/files/page/doc/2018-05/18_2_2_Blackwell.pdf.
3. Lindsey, Daniel T.; Grasso, Louie; Dostalek, John F. and Kerkmann. Jochen. "Use of the GOES-R Split-Window Difference to Diagnose Deepening Low-Level Water Vapor." Journal of Applied Meteorology and Climatology 53, 8, 2014. https://journals.ametsoc.org/view/journals/apme/53/8/jamc-d-14-0010.1.xml?tab_body=pdf.
4. Sun, B.; Reale, A.; Tilley, F.H.; Pettey, M.E.; Nalli, N.R. and Barnet, C.D. "Assessment of NUCAPS S-NPP CrIS/ATMS Sounding Products Using Reference and Conventional Radiosonde Observations." IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, vol. 10, no. 6, June 2017, pp. 2499-2509. doi: 10.1109/JSTARS.2017.2670504.

KEYWORDS: Meteorology; Boundary Layer; Sounding; Profile; Satellite; Remote Sensing; Algorithm; Temperature; Water Vapor; Refractivity

OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Battlespace Environments;Electronics;Sensors

OBJECTIVE: Develop techniques to exploit ship structural vibrations appearing as micro-Doppler signatures in remote Inverse Synthetic Aperture Radar (ISAR) imagery for the purposes of improved vessel classification.

DESCRIPTION: Significant advancements have been made in the automated classification of ships at long ranges using feature extraction from ISAR imagery. The most capable of these seek to classify a particular ship to the fine naval class level. While physical dimensions of major structural elements of the ship provide the primary classification clues, other micro-Doppler based signatures such as those associated with rotating antennas can provide important additional information to support separation among similar ship classes [Ref 1]. This STTR topic seeks to expand the scope of signatures further. Ship structural vibrations may be another important signature to improve overall classification performance. The sources of structural vibrations are generally understood; however whether they are reliably exploitable for classification clues is unanswered.

Multiple authors have shown that radar-sensed micro-Doppler can be used to remotely monitor the vibration of buildings and bridges [Refs 2, 3]. The vibrations generated by an automobile or truck engine has shown to be detectable by radar micro-Doppler signals returned from the surface of the vehicle [Ref 4]. In principle, ship hull and superstructure vibrations primarily driven by propulsion systems should be similarly detectable. Essential to such a technique is the ability to sense the small-scale vibrations of the vessels while they are in motion [Ref 5]. The exploitation of the vessel hull and superstructure vibrations remotely using legacy Navy airborne maritime surveillance radar systems is desired. In addition to single channel monostatic operation, consideration should be given to interferometric and multi-static techniques. If the vibrations are exploitable at long range by these radar systems, they may provide a hull class specific classification feature that in combination with other features will improve overall classification performance. The signatures may also provide information comparable to a fingerprint if it is found that the spectral characteristics are hull specific.

PHASE I: Utilizing open-source ship hull and superstructure vibration measurements such as those described in [Ref 6] or simulated data, analyze the feasibility of remote micro-Doppler sensing by x-band maritime surveillance radar systems. Single channel monostatic, multi-channel interferometric, and multi-static operation should be considered. An initial assessment of signal processing approaches should be completed. Develop a Phase II plan.

PHASE II: Develop and demonstrate a ship vibration micro-Doppler exploitation mode using collected field data supplied by the Navy sponsor. Assess the performance as a function of range, dwell time, and illumination geometry. Develop mode design and tactical utilization recommendations for radar systems identified by the Navy sponsor.

PHASE III DUAL USE APPLICATIONS: Complete development, perform final testing, and integrate and transition the final solution to naval airborne radar systems either through the radar system OEM or through third party radar mode developers. The technology developed from this STTR topic is applicable to Coast Guard Missions.

REFERENCES:

1. Chen, V.C. et al. “Analysis of micro-Doppler signatures.” IEE Proceedings-Radar Sonar Navigation, Vol. 150, No. 4, August 2003. http://www.geo.uzh.ch/microsite/rsl-documents/research/SARlab/GMTILiterature/Ver09/PDF/CLHW03.pdf.
2. Luzi, G. et al. “Radar Interferometry for Monitoring the Vibration Characteristics of Buildings and Civil Structures: Recent Case Studies in Spain.” Centre Tecnòlogic de Telecomunicaciòns de Catalunya (CTTC/CERCA), Geomatics Division, Avinguda Gauss, 7, E-08860 Castelldefels (Barcelona), Spain. https://www.mdpi.com/1424-8220/17/4/669/htm.
3. Luzi, G. et al. “The Interferometric Use of Radar Sensors for the Urban Monitoring of Structural Vibrations and Surface Displacements.” IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Vol. 9, Issue 8, August 2016. https://ieeexplore.ieee.org/document/7493683.
4. Chen, V.C. et al. “Micro-Doppler Effect in Radar: Phenomenon, Model, and Simulation Study.” IEEE Transactions on Aerospace and Electronic Systems, Vol. 42, No. 1, January 2006. http://www.geo.uzh.ch/microsite/rsl-documents/research/SARlab/GMTILiterature/Ver09/PDF/CLHW06.pdf.
5. Rodenbeck, C. et al. “Vibrometry and Sound Reproduction of Acoustic Sources on Moving Platforms Using Millimeter Wave Pulse-Doppler Radar.” IEEE Access (Volume 8), 04 February 2020, pp. 27676-27686. https://ieeexplore.ieee.org/document/8981984.
6. Weintz, Brett. “Ship vibration.” Brabon Engineering Services, 15 June 2021. https://brabon.org/tech-notes/ship-vibration/.

KEYWORDS: Inverse Synthetic Aperture Radar; ISAR; Synthetic Aperture Radar; SAR; ship classification; hull and superstructure vibration; radar

OUSD (R&E) MODERNIZATION PRIORITY: Artificial Intelligence (AI)/Machine Learning (ML);Autonomy;Microelectronics

TECHNOLOGY AREA(S): Electronics;Ground / Sea Vehicles;Materials / Processes

OBJECTIVE: Develop a device to bring the benefits of machine health and usage monitoring to a broad spectrum of Navy and Marine Corps assets, especially those of lower value that cannot afford full-up Health, Usage, and Monitoring System (HUMS) systems by developing powerful, inexpensive processing hardware at a target price of less than $100.00 per node.

DESCRIPTION: Lower cost USN/USMC platforms (especially land systems) cannot afford conventional HUMS sensors/processors typically priced at over $1,000.00 per node. Direct sensing of relevant features and the extraction of "actionable" information may be accomplished by purpose-built signal processing hardware. On-chip integration of neural networks (trained offline) holds the promise for self-contained smart sensors that are both extremely powerful and affordable for all platforms. This capability is vital for those platforms deployed and operating at (or beyond) the tactical edge. Very high risk with extremely high payoff is possible if successful. The envisioned device (or family of devices) is expected to be self-contained in a rugged package able to be permanently installed on vehicle components.

This STTR topic seeks innovation in the development of onboard analytics (e.g., neural networks) that operate at the component level and are able to detect and identify anomalous signatures. State of the art is to attach sensors to the component and wire them to conventional signal conditioning hardware in data acquisition components. Digital Signal Processing (DSP) and other computations are done to convert the raw sensor values into information on centralized processors. Some sensors are directly connected to serial buses on the platform with analog-to-digital (A/D) inside the sensor package. The intent is to push the processing into the sensor package, leveraging integration of neural networks and other Artificial Intelligence/Machine Learning (AI/ML) tools at the chip scale to combine the data acquisition and health determination into a single, low-cost device.

PHASE I: Define and develop a concept for a compact device able to monitor, detect, and identify symptoms of failure on typical rotating mechanical equipment. Vibration, temperature, and electrical current signature are typical measurands of interest. The device should be inobtrusive in size and rugged to the ground vehicle’s under-hood environment. Approximately 1 cubic inch volume and less than $100 unit cost. The intent is for the device to be self-contained conducting measurement, analysis, and communications within the package. Ideally it should be environmentally powered or contain energy storage capable of design operation for 1 to 3 years. It should support wired (e.g., CAN bus) or wireless (e.g., IEEE 1451) communications. Perform modeling and simulation to provide an initial assessment of the concept and exercise alternatives. Develop a Phase II plan.

PHASE II: Develop a Phase II prototype for evaluation based on the results of Phase I. The prototype will be evaluated to determine its capability to meet the performance goals defined in the Phase II Statement of Work (SOW) and the Naval need for detection and diagnosis of typical faults in military ground vehicles. In production, the device will be a part of an integrated system of similar devices monitoring different symptoms of faults on a single machine, other similar devices on other machines, and additional control system parametric data captured from existing onboard buses or traditional sensors. The intent is to detect early stage faults at a component level and merge the information to understand the impact of the faults on the mission capability of the platform. Conduct further evaluation of the feasibility of the prototype to evolve into a hardened device capable of surviving in the target environment, meeting required cost targets, and performing the necessary analytics. The device should support other third party analytics as well as provide native analytic capability. A family of devices with different processing, memory, and sensing capacity for different applications is anticipated. Testing will be performed on laboratory equipment at the proposer's facility to demonstrate performance. Cybersecurity is a key attribute; “cyber-invisible” is the goal. Formal approval is not to be sought during Phase II, but the design must consider the cyber environment from the outset and incorporate the ability to be properly secured when produced.

PHASE III DUAL USE APPLICATIONS: The technology developed in this effort is intended to comprise a part of an onboard, health monitoring and processing system providing Autonomic Readiness Management (ARM) applicable to all types of naval vehicles. The ARV acquisition program is an ideal target for a rapid maturation and integration into the production process. The FFG-62 Mission Readiness Support System (MRSS) is another acquisition program with need for CBM+ and ARM to which this device could apply.

Commercial uses of the device are everywhere. Interest in condition monitoring for all classes of vehicles is high and lack of an affordable implementation has limited the deployment of the capability. The device developed here is an inherent member of the Internet of Things (IoT) and could be adapted to a variety of applications beyond condition monitoring for vehicles. The fundamental capability to measure, monitor, detect, and project are capabilities that have broad applications across the IoT.

Specific commercial industries/markets that could use and benefit from the technology include: commercial trucking, heavy construction equipment, manufacturing, aircraft and related equipment, commercial maritime, and infrastructure monitoring (e.g., bridges, locks, damns).

REFERENCES:

1. Liobe, J.; Fiscella, M.; Moule, E.; Balon, M.; Bocko, M. and Ignjatovic, Z. “DS Sentry: an acquisition ASIC for smart, micro-power sensing applications.” Proceedings Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XVI, Vol. 8017, 2011, p. 80170H. https://www.spiedigitallibrary.org/conference-proceedings-of-spie/8017/80170H/DS-Sentry--an-acquisition-ASIC-for-smart-micro-power/10.1117/12.884253.short?SSO=1.
2. Liobe, J.; Ignjatovic, Z. and Bocko, M. “Ultra-low overhead signal acquisition circuit for capacitive and piezoelectric sensors.” 2008 51st Midwest Symposium on Circuits and Systems, August 2008, pp. 33-36. https://ieeexplore.ieee.org/document/4616729.
3. Japkowicz, N.; Myers, C. and Gluck, M. "A novelty detection approach to classification." IJCAI'95: Proceedings of the 14th International Joint Conference on Artificial Intelligence, Volume 1, August 1995, pp. 518–523. https://dl.acm.org/doi/10.5555/1625855.1625923.

KEYWORDS: Condition-based maintenance; CBM; Internet of Things; IoT; neural network chips; wireless sensors; integrated processing; anomaly detection

TECH FOCUS AREAS: Directed Energy

TECHNOLOGY AREAS: Sensors; Electronics; Battlespace

OBJECTIVE: The objective of this project is to develop and demonstrate key components that would help make sodium-beacon or Rayleigh-beacon adaptive optics practical for military, ground-to-space imaging applications.  Current commercial laser systems used to produce sodium and Rayleigh beacons were developed for astronomical applications. These commercial lasers are not suited for smaller military telescopes, which are typically installed in locations with much worse turbulence, when compared to astronomical telescopes.  The objective is to develop these laser components and demonstrate them on-sky, in conditions that are representative of typical sites for ground-based observations of earth-orbiting satellites. These components could be demonstrated on government, university, or civilian telescopes.

DESCRIPTION: AFRL supports the US Space Force in researching and developing effective, affordable techniques to identify, track, and characterize satellites in earth orbit. Radar, although it is expensive to build and operate, works for satellites in low-earth orbit. However, because of the distances involved, only a few specialized ground-based radars are capable of tracking satellites in geosynchronous orbit.  Compared to ground-to-space radars, ground-based optical telescopes are less expensive to build and operate; in addition, they work well for satellites in all orbits. However, atmospheric turbulence limits the resolution and effectiveness of ground-based optical telescopes.   Laser-beacon adaptive optics is an established technique to overcome the effects of atmospheric turbulence.

However, there remain significant challenges to improving the utility and effectiveness of laser beacon adaptive optics for military applications.   There are two main types of laser beacons used in adaptive optics, Rayleigh beacons and sodium beacons. Rayleigh beacons are formed by scattering light from molecules of nitrogen and oxygen lower in the atmosphere; typical altitudes range from 10 km to 20 km. Pulsed lasers are typically used for Rayleigh beacons so that the light may be sampled from a particular altitude by using a technique called range gating. Because Rayleigh scattering is much stronger for shorter wavelengths of light, common wavelengths for Rayleigh beacons are 355 nm and 532 nm.  

Because Rayleigh beacons rely on scattering from air molecules, they are limited to relatively low altitudes where the density of air molecules is higher. Light from the beacon traverses a cone of air above the telescope, with the beacon at the apex of the cone and the telescope pupil at the base of the cone. If a Rayleigh beacon is used for a larger telescope, the cylindrical column of air above the telescope will not be well sampled. Because of this cone effect, Rayleigh beacons are suitable only for smaller telescopes of up to 2 m in diameter.    Sodium beacons are formed from scattering light from a layer of ionic sodium that is centered at an altitude of 90 km above the ground. Because of their high altitude, sodium beacons sample a much larger cone of air when compared to Rayleigh beacons. So, they are better suited for use with large telescopes. 

Lasers for bright Rayleigh and sodium beacons are large and heavy; they are difficult to mount on typical military telescopes, which tend to be much smaller than astronomical telescopes.   In addition, military telescopes are typically deployed to locations where the atmospheric turbulence is much worse than locations for astronomical observatories. To make matters worse, when a ground-based telescope tracks a satellite in low-earth orbit, it must slew quickly across the sky. This, in effect, creates a situation that is equivalent to a strong wind blowing across the aperture of the telescope. The combination of these two factors means a laser beacon for military purposes must be much brighter than a laser beacon for astronomy. 

Another factor to consider is the risk that laser beacons pose to the safe operation of aircraft. Visible laser beacons are not eye-safe, thus considerable effort is necessary to avoid blinding aircraft pilots. Ultra-violet lasers are not transmitted by aircraft windscreens, but the silver mirror coatings typically used in telescopes do not reflect ultra-violet wavelengths well. Furthermore, the quantum efficiency of typical wave-front sensor cameras is low at ultra-violet wavelengths.  Thus, AFRL is seeking development of key components that would help to make sodium-beacon or Rayleigh-beacon adaptive optics practical for military ground-to-space imaging applications. These components are listed below.

• On-telescope (side- or center-launched) Rayleigh beacon laser (ultra-violet and visible)

• Ultra-violet (eye-safe) laser beacon

• Uplink compensation of laser beacon to reduce beacon size

• Polychromatic laser beacon for sensing tilt and high-order aberrations

• Laser-beacon (Rayleigh and sodium) simulator for laboratory bench-top testing

• Hybrid Rayleigh-sodium beacon adaptive optics

• Tilt anisoplanatism compensation

• Electronic camera shutter or low-radio-frequency-interference Pockels cell for gating Rayleigh beacon return • Using adaptive optics telemetry in near-real-time for improving laser-beacon imaging and detection of closely spaced objects

• Advanced wave-front sensors and cameras for laser beacon adaptive optics

PHASE I: Phase I deliverables include a report that describes thoroughly concepts, analyses, and simulations for laser beacon components that are suitable for military ground-to-space imaging applications. These analyses and simulations must show that the proposed components are effective and affordable. The report should describe the components at a level suitable for a conceptual design review. (See the references section for the contents of a conceptual design review.)   The report shall include a plan for demonstrating the laser components on-sky, in conditions that are representative of typical sites for ground-based observations of earth-orbiting satellites.

PHASE II: Phase II deliverables include a detailed design of laser beacon components suitable for military ground-to-space imaging applications. This design must illustrate the proposed components are effective and affordable. The design documents should describe the components at a level suitable for preliminary and critical design reviews. (See the references section for the contents of preliminary and critical design reviews.)  

The report shall include a detailed plan for demonstrating the laser components on-sky, in conditions representative of typical sites for ground-based observations of earth-orbiting satellites.  As cost and schedule constraints allow, a prototype component shall be built, tested, and demonstrated on-sky at government, university, or civilian observatory.

PHASE III DUAL USE APPLICATIONS: A Phase III effort would require identifying a suitable transition partner, which could be a government program office, a government contractor or other commercial entity, or a civilian astronomical observatory.

NOTES: The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the proposed tasks intended for accomplishment by the FN(s) in accordance with section 5.4.c.(8) of the Announcement and within the AF Component-specific instructions. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. Please direct questions to the Air Force SBIR/STTR Help Desk: usaf.team@afsbirsttr.us  

REFERENCES:

1. Laser beacons or laser guide stars https://en.wikipedia.org/wiki/Laser_guide_star;

2. Conceptual Design Review https://en.wikipedia.org/wiki/Engineering_design_processConcept_Generation

KEYWORDS: laser beacon; laser guide star; Rayleigh beacon; polychromatic beacon; adaptive optics; tilt anisoplanatism; wave-front sensor; electronic shutter

TECH FOCUS AREAS: Directed Energy

TECHNOLOGY AREAS: Space Platform

OBJECTIVE: This topic's outcome will be ability to create a telescope mirror not requiring much/any figuring to be usable for observing space objects.

DESCRIPTION: Efforts will aim to develop techniques/technologies to allow 3D printing at nanometer scales to produce parabolic/spherical mirrors requiring little to no figuring or modification. Visible light is in the range of 400 - 700 nm and typical figuring of astronomical telescopes is to the wavelength/10 or better.

Achieving this level of figuring with a 3D printer will require either the ability to print at the nanometer scale, or some technique to get the nanometer figure at a larger print scale. The Air Force is looking for a solution eventually providing the ability to mass produce custom size/shape mirrors for use in telescopes supporting Space Domain Awareness at reduced costs and at lighter weights to improve performance.

PHASE I: Investigate the capabilities of various Additive Manufacturing devices and techniques for micrometer-to-nanometer-scale accuracies.  Research how those capabilities could be improved to provide required accuracy to 3D print a quality mirror. Research various printing materials providing the strength required for a size-able mirror to retain its shape when used in a telescope. Investigate techniques to make the process scalable; being able to 3D print a meter-class mirror for a telescope could provide additional opportunities for successful technology transition.

PHASE II: The contractor will demonstrate the ability to 3D print a high-quality mirror that can be used for astronomical purposes by printing an 8-inch mirror with an approximate focal length of 840mm (F/4 focal ratio) and a surface figure of wavelength/10 (./10). The mirror will be assembled into a Newtonian telescope design to demonstrate its ability to hold its shape in actual use. The contractor will, in the course of this phase also demonstrate the tradeoffs of time to print vs. the quality of the printed mirror (./4 vs. ./10 figuring). The contractor should make contact with telescope manufacturers during this phase to garner interest in their technique/potential products. The resulting telescope will be provided to the Space Force for evaluation under normal operations.

PHASE III DUAL USE APPLICATIONS: The contractor will demonstrate the scalability of the technology/techniques to a twenty-inch mirror with wavelength/10 figure.

For dual use potential: Recently there has been a shortage of commercial, hobbyist telescopes due to supply issues from non-indigenous manufacturers. This capability could relieve this shortage.

REFERENCES:

1. https://3dprint.com/238521/nanofabrica-micron-resolution-3d-printing-platform/
2. https://www.energy.gov/science/bes/articles/how-3d-print-nanoscale
3. https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.202001675?af=R
4. https://www.researchgate.net/publication/341454859_3D_Printing_of_Micrometer-Sized_Transparent_Ceramics_with_On-Demand_Optical-Gain_Properties

KEYWORDS: Additive Manufacturing; Telescope Mirrors; 3D Printing; Astronomical Mirrors; Nanometer scale

TECH FOCUS AREAS: Autonomy

TECHNOLOGY AREAS: Space Platform

OBJECTIVE: Research and develop algorithms applied distributed satellite autonomy for clustered satellite systems as well as leveraging multi-perspective observations and measurements.

DESCRIPTION: Academic circles have investigated the topic of distributed collaborative control and autonomy for decades and recent applications to UAV’s, warehouse servicers, ground robotics and more are increasingly available. More specifically, the topic of distributed collaborative autonomy applies to the situation where a group of agents share their information to achieve a common task.

However, there exist numerous challenges of applying this work to the space domain that may not be seen in terrestrial domains, in particular, communication networks between satellites and/or ground stations are dynamic and are, in general, low bandwidth and throughput, contain significant latencies.  Limited computational hardware requires lightweight algorithms to compute correct collaboration tasks, manage scalability and fuse agents’ sensor measurements. 

Moreover, space is growing increasingly congested and contested, for which the resiliency of the space domain must be assured.  The objective of this STTR is to address the resiliency of the space domain through autonomous mission distribution of satellite systems. More specifically, the Offeror will research, develop and test lightweight distributed satellite autonomy of heterogeneous sensors and consider the impact of multi-perspective sensor fusion into the autonomous architecture. The capabilities of this software and algorithm-based approach will enhance the future of the space domain architecture. Offerors are encouraged to work with prime contractors to facilitate technology transition. Offerors should clearly indicate in their proposals what Government furnished property or information are required to conduct this effort.

PHASE I: Conduct a comprehensive comparative assessment and trade-off study of distributed autonomy architectures, algorithms and techniques that are computationally efficient and with low communication throughput requirements.

PHASE II: Design, implement, integrate and test the most promising and effective instantiation of the distributed autonomy algorithms in an AFRL/RV Laboratory Environment. Conduct analysis and simulations to demonstrate the effectiveness and resilience of the algorithms. Assess the implementation overhead of the candidate techniques and conduct through trade-off studies.

PHASE III DUAL USE APPLICATIONS: Develop flight ready software for implementation into future AFRL or other Government flight missions and laboratory experiments.

NOTES: The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the proposed tasks intended for accomplishment by the FN(s) in accordance with section 5.4.c.(8) of the Announcement and within the AF Component-specific instructions. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. Please direct questions to the Air Force SBIR/STTR Help Desk: usaf.team@afsbirsttr.us

REFERENCES:

1. C. Araguz, E. Bou-Balust, E. Alarcon, “Applying autonomy to distrusted satellite systems: Trends, challenges and future prospects,” Systems Engineering, 21:5, 401-416, Sept. 2018 ;

2. D. Selva, A. Golkar, O. Korobova, I. L. i Cruz, P. Collopy, and O. L. de Weck, “Distributed Earth Satellite Systems: What Is Needed to Move Forward?” Journal of Aerospace Information Systems 14:8, 412-438 2017; 

3. S. A. Szklany, J. L. Crassidis and S.S. Blackman, "Centralized and Decentralized Space Object Estimation and Data Association with Pattern Recognition", John L. Junkins Symposium, College Station, TX, May 2018.

KEYWORDS: Distributed Satellite Autonomy; Autonomy; Sensor-Fusion

TECH FOCUS AREAS: General Warfighting Requirements (GWR)

TECHNOLOGY AREAS: Space Platform

OBJECTIVE: Currently, for USSF satellites there is a team of >5 SMEs furiously monitoring the state of a satellite's health. Fault classification software plus already existing fault detection software would remove the need for constant monitoring. This would not only allow the operators to focus on the congested and contested manner of space but also mitigate faults in a satellite quickly and effectively.

DESCRIPTION:  For an operator to mitigate a satellite fault quickly and effectively, the fault's cause must be understood. This requirement is due to the fact many faults have similar effects on the satellite but completely different causes. For instance, a solar Coronal Mass Ejection (CME) looks similar to a developer’s bug in the software and various types of cyber-attacks. All of these faults might require completely different mitigation steps. For a CME, one way to fix the satellite is a restart after the event, the developer’s code fix should be uploaded, and the cyber-attack could require a variety of responses depending on the attacker and the severity of the attack. These events also might not exist in the same dataset if they exist at all [1,2]. Therefore, this classification must also work for unknown unknown events so that it can be prepared to interact with the dynamic environment of space.  

This topic's objective is to develop algorithms and code classifying a detected fault. The contractor will be given different satellite datasets either simulated or real on which to train. A separate dataset will be provided to prove out the algorithm.

PHASE I: In Phase I, selected companies will conduct a comprehensive comparative assessment with trade-offs of various classification algorithms and approaches.  Implementation complexity of candidate techniques and conduct trade-offs will be assessed with respect to impact on SWAP-C and operational suitability. Deliverables of this should include a trade study and appropriate analysis reporting.

PHASE II: If selected for Phase II, companies will design, implement, integrate, and test the most promising and effective algorithm with ground software to classify detected satellite faults in near real time.  Deliverables will include any relevant reporting analysis and software developed where appropriate.

PHASE III DUAL USE APPLICATIONS: In cooperative efforts with one or more satellite software manufacturers and military satellite system developers, Phase III efforts would integrate the proposed algorithms with satellite software; demonstrate the algorithm running on board a satellite; and evaluate transition opportunities for utilization in approved Government civilian applications.

NOTES: The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the proposed tasks intended for accomplishment by the FN(s) in accordance with section 5.4.c.(8) of the Announcement and within the AF Component-specific instructions. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. Please direct questions to the Air Force SBIR/STTR Help Desk: usaf.team@afsbirsttr.us

REFERENCES:

1. Trevor Hastie, Robert Tibshirani, and Jerome Friedman. The Elements of Statistical Learning.Springer, New York, NY, 2001.;

2. D. T. Magill. Optimal adaptive estimation of sampled stochastic processes. IEEE Transactions on Systems, Man and Cybernetics, AC-10:434–439, October 1965.

KEYWORDS: Satellite Faults; fault classification

TECH FOCUS AREAS: Artificial Intelligence/Machine Learning

TECHNOLOGY AREAS: Information Systems; Air Platform

OBJECTIVE: This topic's objective is to develop analysis techniques via application of machine learning, artificial intelligence and/or other advanced data analysis techniques to evaluate and characterize large amounts of trajectory data generated for stores released from an internal cavity weapons bay. The goal would be to utilize such techniques to identify and subsequently exploit potential linkages between flow conditions in the cavity at and after the time of release with the disparity of the store trajectories observed due to variation in release time.

DESCRIPTION: A large dataset consisting of approximately 100 cases is currently being generated via high-fidelity CFD simulating the trajectories of small, light-weight stores being released from internal weapons bays (cavities) at high speeds. The simulation in this dataset primarily consists of the store configuration being held in carriage for some period of time and then released using a prescribed ejector profile, with the release time being the only variation in the simulations. It has been shown that the time of release of the store has a significant impact on its subsequent trajectory due to the unsteady flow-field in the cavity. The existing CFD dataset consists of high-frequency integrated force/moment components acting on the store, two-dimensional flow-field representations at various spanwise locations and heights in the cavity, and pressure time histories at various positions on the cavity walls/ceiling and the store prior to release as well as during the trajectory.

Additional data could also be collected during subsequent simulations as needed to develop appropriate analysis techniques. This rich data set will be provided as a training set in order to use various AI/ML or other analysis techniques to attempt to determine if there is some predictable cavity flow-field and/or force/moment state either 1) at the time of release and/or 2) after release while the store is traversing the cavity, shear layer and/or free-stream that leads to specific trajectory states. Of particular interest are the states associated with “bad” releases, defined as the distance between the store center of gravity and aircraft hardware not monotonically increasing or the store entering the free stream with high rates of pitch and/or yaw.

PHASE I: Phase I efforts will determine the scientific and technical merit and feasibility of application of AI, ML and/or advanced analysis techniques to determine root causes for a specified store to reach a particular state when released from an internal store configuration. High-fidelity, unsteady CFD of 6DOF trajectories generated for a particular store released at various times will be provided as GFE.

Tangible outcomes for the Phase I effort would be the demonstration of a practical process to relate particular states of the cavity to specific trajectory behaviors. The envisioned main deliverable for Phase I would be a report documenting the process with sufficient detail to allow evaluation by the government and example(s) of its application on the dataset provided. Identification of the overall plan to mature the concepts into a useable tool along with plans to generate additional data needed to support development/expansion of method to additional configurations should also be reported.

PHASE II: Further develop the approach to demonstrate its ability to identify conditions in the cavity (including the shear layer) related to trajectories. This identification should be probabilistic in nature, where certain flow features and/or force/moment states produce, bad trajectories are observed to exist in some statistically significant number of cases.

Extension of approach to data from other stores and/or other cavity configurations would be encouraged. Tangible outcomes and expected deliverables for the Phase II effort would include stand-alone software that would take in high-fidelity unsteady CFD data and produce output that could identify release points or flow states/flow-field features associated with problematic trajectories. A stretch goal would be the inclusion of surrogate modeling of key cavity environmental features that would permit reduced order evaluation of configurations beyond the training data set.

PHASE III DUAL USE APPLICATIONS: Phase III efforts will focus on transitioning the developed technology to a working commercial or warfighter software/processes. Solutions developed will be immediately relevant to precision airdrop, cargo and weapons release, among a whole range of commercial and military applications. If a viable approach to identify conditions associated with bad trajectories are identified, this would allow potential flow-control solutions to be investigated to "fix" these conditions and diminish problematic releases. They would be in a position to supply future software/processes to the Air Force, and other DoD components to facilitate future weapons bay designs that would improve separation characteristics.

NOTES: The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the proposed tasks intended for accomplishment by the FN(s) in accordance with section 5.4.c.(8) of the Announcement and within the AF Component-specific instructions. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. Please direct questions to the Air Force SBIR/STTR Help Desk: usaf.team@afsbirsttr.us

REFERENCES:

1. Brunton, S. L., Noack, B. and Koumoutsakos, P., "Machine Learning for Fluid Mechanics", Annual Review of Fluid Mechanics, Vol. 52, pp 477-508, 2020 (doi:10.1146/annurev-fluid-010719-060214);
2. Sun et al., "Resolvent Analysis of Compressible Laminar and Turbulent Cavity Flow", AIAA Journal, Vol .58, No. 3, pp. 1046-1055,(doi:10.251.4/J058663)

KEYWORDS: Artifical Intelligence; Machine Learning; Store Separation; Cavity; Computational Fluid Dynamics; Six-Degree-of-Freedom Trajectories

TECH FOCUS AREAS: Microelectronics

TECHNOLOGY AREAS: Sensors

OBJECTIVE: This topic seeks to develop infrared focal plane arrays (FPAs) directly onto silicon readout integrated circuitry without hybridization, operating at 2 um or longer, and using GeSn or GeSiSn absorbing layers.

DESCRIPTION:  Conventional short- and mid-wave infrared (SWIR and MWIR) detectors based on III-V (i.e., GaInSb) or II-VI (i.e., HgCdTe) materials are relatively expensive and incompatible with silicon-based readout integrated circuitry (ROIC), requiring hybridization (typically in bump bonding) which is very expensive. Technologies based on Si and SiGe are pervasive for electronic applications, but indirect energy gaps prevent their use as the active elements in optoelectronic devices. Recent progress in the material system of Group-IV alloys containing Sn (GeSiSn and GeSn) and the potential of a direct energy gap for certain compositions promises significant optical performance which is compatible with and will allow for direct integration with Si complementary metal-oxide-semiconductor (CMOS) device processing. Extremely high-quality thin films and initial proof-of-concept emitters and detectors have been demonstrated on Ge substrates but corresponding films on Si substrates suffer from high defect levels due to the lattice mismatch of high Sn content GeSiSn and GeSn alloys necessary for direct energy gap devices. The use of one or more buffer layers (e.g., a Ge virtual substrate alone or with GeSn overlayers) on Si have been used to reduce such defects but impede device integration.  Therefore, development of easily integrated emitters and detectors on Si substrates are critical for mass production of optoelectronic devices using standard CMOS production equipment and large diameter Si wafers.   A number of patterned deposition techniques have been developed for other heteroepitaxy systems (e.g. GaN on SiC or Al2O3 substrates), including nanopillars, template growth, epitaxial overgrowth, and planarization to reduce structural defects such as dislocations.  Therefore, it should be feasible to use similar approaches or develop novel ones to synthesize high quality GeSiSn or GeSn films directly on Si ROICs without the need for hybridization.  Such layers could be used to fabricate integrated FPAs operating in the SWIR or MWIR spectral regions.  Thus, if successful, this technology could be rapidly scaled and industrialized to produce low cost, large format imagers.

PHASE I: Demonstrate the feasibility of novel techniques for growth of GeSiSn and/or GeSn films directly on Si substrates. Design device structures incorporating barriers for dark current reduction, including single and complementary barrier architectures that minimize optical and electrical crosstalk between devices.  All devices should be vertical to facilitate mating to either a commercially available readout integrated circuit (ROIC) or a fanout for testing purposes. Provide experimental evidence for improved material performance of device quality epitaxial films grown on Si substrates, improved infrared absorption, and narrower X-ray rocking curves compared to typical films synthesized on traditional vacuum deposited buffer layers. Deliver a GeSiSn or GeSn film on 2" silicon wafer or larger with a minimum of 500 nm thickness for material characterization, as well as a processed variable area device die for photodetector testing.

PHASE II: Companies selected for Phase II will fabricate and characterize integrated focal plane array (FPA) detectors operating within the spectral range of 2 - 5 um on Si readout intectrated circuits (ROICs).  The external quantum efficiency (EQE) of the devices should be greater than 20% from 1.1 to more than 2.0 um and the dark current density should be less than 1 uA per sq. cm at temperatures of 200 K or greater. Deliver a silicon fanout (minimum 32 x 32, <50 um pitch) using direct deposition to verify dark current density and EQE. Deliver full FPAs for array level testing.

PHASE III DUAL USE APPLICATIONS: In Phase III, the device quality GeSiSn and/or GeSn films will be used to make infrared device structures as required by military and commercial customers including those who manufacture integrated circuits and IR optical detectors.

NOTES: The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the proposed tasks intended for accomplishment by the FN(s) in accordance with section 5.4.c.(8) of the Announcement and within the AF Component-specific instructions. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. Please direct questions to the Air Force SBIR/STTR Help Desk: usaf.team@afsbirsttr.us

REFERENCES:

1. C.-H. Tsai, K.-C. Lin, C.-Y. Cheng, K.-C. Lee, H. H. Cheng, G.-E. Chang, “GeSn lateral p-i-n waveguide photodetectors for mid-infrared integrated photonics”, Opt. Lett. 46, 864 (2021);

2. H. Kumar and R. Basu, “Effects of Defects on the Performance of Si-Based GeSn/Ge Mid-Infrared Phototransistors”, IEEE Sensors J.  21, 5975 (2021);

3. H. Tran, T. Pham, J. Margetis, Y. Zhou, W. Dou, P. C. Grant, J. M. Grant, S. Al-Kabi, G. Sun, R. A. Soref, J. Tolle, Y.-H. Zhang, W. Du, B. Li, M. Mortazavi, S.-Q. Yu, “Si-Based GeSn Photodetectors toward Mid-Infrared Imaging Applications”, ACS Photonics 6, 2807 (2019);

4. C. Chang, H. Li, C.-T. Ku, S.-G. Yang, H. H. Cheng, J. Hendrickson, R. A. Soref, G. Sun, “Ge0.975Sn0.025 320 x 256 imager chip for 1.6-1.9 um infrared vision, Appl. Opt. 55, 10170 (2016);

5. Matthew Coppinger, John Hart, Nupur Bhargava, Sangcheol Kim, and James Kolodzey, “Photoconductivity of germanium tin alloys grown by molecular beam epitaxy”, Appl. Phys. Lett. 102, 141101 (2013);

6. R. Roucka, J. Mathews, C. Weng, R. Beeler, J. Tolle, J. Menendez, and J. Kouvetakis, “High-performance near-IR photodiodes: a novel chemistry-based approach to Ge and Ge–Sn devices integrated on silicon,” IEEE J. Quantum Electronics 47, 213 (2011);

7. J. Taraci, S. Zollner, M. R. McCartney, J. Menendez, M. A. Santana-Aranda, D. J. Smith, A. Haaland, A.V. Tutukin, G. Gundersen, G. Wolf, and J. Kouvetakis, “Synthesis of silicon-based infrared semiconductors in the Ge-Sn system using molecular chemistry methods,” J. Am. Chem. Soc. 123, 10980 (2001)

KEYWORDS: GeSiSn; GeSn; silicon; germanium; silicon-germanium-tin; Buffer layers; Molecular Beam Epitaxy; MBE; CVD; chemical vapor deposition; epitaxial lateral overgrowth (ELO); detectors; Group IV photonics; silicon photonics; optoelectronic devices; device fabrication; growth; heterostructures; radiative recombination; quantum efficiency; semiconductor characterization; infrared; focal plane arrays (FPA)

OUSD (R&E) MODERNIZATION PRIORITY: Artificial intelligence/machine learning

TECHNOLOGY AREA(S): Information systems, modeling and simulation technology

OBJECTIVE: Develop a single neural network that learns representations at multiple spatial and semantic scales and that may be applied to different geospatial tasks, such as land cover segmentation, object detection, key-point matching, and few-shot/fine-grained/long-tailed classification.

DESCRIPTION: NGA is interested in a single, hierarchical network that learns representations at multiple spatial and semantic scales and can improve the performance of all aspects common to differing geospatial computer vision pipelines.

Existing representation learning techniques are often tailored to a specific task such as semantic segmentation, classification, object detection, or key-point matching. As a result, the trained feature extractors are focused on learning global image-level features, object-level features, or local interest-point features but do not work well at extracting all such feature types at varying scales. This problem is compounded when introducing data that differs fundamentally in format, such as images with more or fewer bands than the data that the feature extractor was trained on.

Recent advancements in representation learning and generalizability show promise that such a one-network solution may be on the horizon. CNN feature extractors for object detection have used feature pyramid networks for several years, which are architected to extract features at different scales [1]. Self-supervised learning has now matched, or exceeded, the transferability of supervised techniques and has demonstrated promising performance on diverse downstream tasks requiring learning different feature types and scales [2, 3]. Transformers, which have earned the state-of-the-art (SoTA) in a variety of vision benchmarks, have shown ability to work across mid-sized and small image scales when pre-trained on large datasets, show parity with SoTA in self-supervised vision tasks, and have been successfully applied to remote sensing [4, 5, 6]. Moreover, the attention layers in a Pre-Trained Frozen Transformer are generalizable across a wide variety of data types and tasks—for example, from language to vision [7].

PHASE I: Develop a neural network architecture that learns representations at multiple spatial and semantic scales and a pre-training methodology on publicly available satellite imagery and/or Government furnished WorldView-3 imagery. Self-supervised pre-training is preferred. Using the same pre-trained network backbone, demonstrate near-parity with SoTA on two different satellite imagery computer vision benchmark tasks requiring either different resolution imagery or different feature scales. Proposers are expected to identify which benchmarks they will target in the proposal.

PHASE II: Extend Phase I results to 4+ computer vision benchmarks using 3+ different image resolutions and/or feature scales. Develop techniques to use the same pre-trained backbone with 4-16 band imagery and demonstrate parity with SoTA on at least two associated benchmarks. Collaborate with NGA’s SAFFIRE program for testing and evaluation on classified imagery, and provide code and support for integration.

Deliverables include a comprehensive report on the architecture, training scheme, and benchmark performance delivered to NGA at the conclusion of Phase I, Phase II midpoint, and Phase II conclusion; at least two papers submitted to academic journals or conferences by the conclusion of Phase II; all data procured, curated, and/or labeled during the period of performance; and delivery without restriction (or open-sourcing) of code. Proposing teams are expected to have a strong and ongoing academic publication track record on related research topics.

PHASE III DUAL USE APPLICATIONS: A single neural network that learns representations at multiple spatial and semantic scales has the potential to apply broadly to diverse machine learning tasks across Government and industry. For example, such technology could improve performance in all aspects of geospatial computer vision, as well as diverse fields such as facial recognition, self-driving cars, and robotics.

REFERENCES:

1. Lin TY., et al. “Feature pyramid networks for object detection,” 2017 IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 10.1109/CVPR.2017.106.
2. Xiao, T., Wang, X., Efros, A., Darrell, T., “What should not be contrastive in contrastive learning,” 9th International Conference on Learning Representations, ICLR 2021, Virtual Event, Austria, 3-7 May  2021. OpenReview.net 2021.
3. Xiao, T., Reed, C., Wang, X., Keutzer, K., Darrell, T., “Region similarity representation learning,” arXiv preprint, arXiv:2103.12902v2.
4. Dosovitskiy A., et al. “An image is worth 16x16 words: Transformers for image recognition at scale,” 9th International Conference on Learning Representations, ICLR 2021, Virtual Event, Austria, 3-7 May 2021. OpenReview.net 2021.
5. Caron M., et al. “Emerging properties in self-supervised vision transformers,” arXiv preprint arXiv:2104.14294 (2021).
6. Bazi Y., et al. “Vision transformers for remote sensing image classification,” Remote Sens. 2021, 13(3), 516; https://doi.org/10.3390/rs13030516.
7. Lu, K., Grover, A., Abbeel, P., Mordatch, I., “Pretrained transformers as universal computation engines,” arXiv preprint, arXiv:2103.05247.
8. Bingyi, C., Araujo, A., and Sim, J. “Unifying deep local and global features for image search.” European Conference on Computer Vision. Springer, Cham, 2020, https://link.springer.com/chapter/10.1007/978-3-030-58565-5_43.
9. Yurun, T., et al. “HyNet: Learning local descriptor with hybrid similarity measure and triplet loss.” arXiv preprint, arXiv:2006.10202 (2020).
10. Zhuoqian, Y., Dan, T., and Yang, Y. “Multi-temporal remote sensing image registration using deep convolutional features.” IEEE Access 6 (2018): 38544-38555.

KEYWORDS: Artificial intelligence, deep learning, machine learning, representation learning, computer vision, remote sensing

OUSD (R&E) MODERNIZATION PRIORITY: Artificial intelligence/machine learning, statistical forecasting

TECHNOLOGY AREA(S): Information systems, modeling and simulation technology

OBJECTIVE: Develop computer models to forecast risk to US critical infrastructure from a range of potential climate futures. During Phase I, research will be restricted to modeling past and forecasting future wildfire potential in a chosen area containing critical infrastructure.

DESCRIPTION: NGA provides GEOINT to support national policy makers and other federal and local agencies on matters of environmental security such as humanitarian and disaster relief efforts. Much of this GEOINT provides tactical intelligence, such as complementing the picture on the ground with near real time GEOINT to build a comprehensive awareness of the operating environment (e.g., [1]). Because of the increasing incidence and severity of natural disasters correlated with climate change [2], NGA requires the capability to forecast such events, particularly in areas where critical infrastructure is present, which would allow decision makers time to implement mitigation strategies beforehand.

Currently, fire intelligence analysts compile climate and drought forecasts, regional fuel conditions, and satellite and mapping imagery into short-term and seasonal forecasts for broad regions [3]. However, these existing forecasting methods are unable to make fine-grained distinctions in at-risk areas based on small-scale variations in land use, land use change, vegetation, and, moreover, proximity to critical infrastructure.

In recent years, both the volume and resolution of commercial and publicly available satellite imagery relevant to wildfire forecasting has massively increased. Together with recent improvements in machine learning, this imagery may be used to produce high-resolution GEOINT products relevant to wildfire conditions; for example, land use change, soil moisture, and normalized difference vegetation index [4,5]. Alternative phenomenologies such as SAR and lidar may be applied to monitor conditions and changes in forest health. Additionally, new applications of machine learning have produced much more robust risk assessment modeling in a variety of fields, including fire risk [6].

PHASE I: Identify two geographic areas containing US critical infrastructure, one of which that has experienced wildfire-related damage or destruction. Complete a forensic analysis of wildfire risk based on historical remote sensing data from these areas to identify predictive variables. Suggest potential mitigation strategies that would decrease risk. Using identified predictive variables, develop a computer model that forecasts wildfire risks monthly and/or seasonally and suggests mitigation strategies. The forensic analysis and methodology used to model and forecast shall be provided to NGA and (optionally) submitted to an academic journal or conference.

PHASE II: Extend Phase I results to at least two other natural disaster types relating to environmental security of critical infrastructure (e.g., flooding, permafrost melting). Extend analysis to 6+ geographic areas per natural disaster type containing US critical infrastructure on at least two different continents. Extend duration of forecasting capability (seasonal+) and compute statistically valid uncertainty and error estimates.

PHASE III DUAL USE APPLICATIONS: Accurately forecasting environmental security risks and suggesting mitigations would have immense and broad applications. Analysts across a variety of Government and commercial sectors could utilize these forecasts to improve risk understanding and suggest mitigation strategies that could potentially prevent costly repercussions of natural disasters.

REFERENCES:

1. Lopez, T., “DOD extends 'Firefly,' related 'FireGuard' support to extinguish wildfires,” U.S. Department of Defense News, https://www.defense.gov/News/News-Stories/Article/Article/2768197/dod-extends-firefly-related-fireguard-support-to-extinguish-wildfires/. Accessed Sept 24, 2012.
2. “Climate and land use change,” USGS FAQ, www.usgs.gov/faq/climate-and-land-use-change. Accessed 24 September 2012.
3. “Fire forecasting,” USDA Science and Technology, Fire Science, www.fs.usda.gov/science-technology/fire/forecasting. Accessed 24 September 2012.
4. Khan. S., Alarabi. L., and Basalamah. S., “Deep hybrid network for land cover semantic segmentation in high-spatial resolution satellite images,” Information 2021, 12, 230. doi.org/10.3390/info12060230.
5. Babaeian, E., et al. “A new optical remote sensing technique for high-resolution mapping of soil moisture,” Frontiers In Big Data, 5 November 2019, doi.org/10.3389/fdata.2019.00037.
6. Lee, J., Lin, Y., and Madaio, M. (2018). A Longitudinal Evaluation of a Deployed Fire Risk Model. Presented at the AI for Social Good Workshop at the Neural Information Processing System Conference. (NeurIPS 2018).

KEYWORDS: Environmental security, climate, fire, forecasting, remote sensing, computer vision, machine learning, deep learning