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Thermally Functional UAV Coating


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 statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with section 3.5 of the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. OBJECTIVE: Research and develop an innovative, low ESOH risk coating for infrared (IR) and thermal management of a UAV. Demonstrate this IR-functional coating on a UAV in a relevant environment. DESCRIPTION: In multi-domain operations, Unmanned Aerial Vehicles (UAV) widely operate as an extension of the Warfighter and squad, enabling much better situational awareness. UAVs are also used commercially for transporting loads, monitoring networks, and many other civilian applications. More widespread infrared (IR) imaging capabilities among adversaries means that it is increasingly easy to identify UAVs during operation, reducing their effectiveness and compromising the mission. Due to both increased use of UAVs and increased access to IR imaging capabilities by adversaries, there is a strong and emerging need for coatings to protect UAVs from detection by reducing the expected maximum range to image. However, many of the available coatings that could protect the UAVs from detection, especially in the IR/ visible (optical) ranges, contain materials that are toxic and bad for the environment; e.g., isocyanates. Nature has enabled sophisticated color schemes in the animal kingdom, including bright and dark tones for camouflage. Bio-inspired materials have been extensively researched in the academia, and bio-inspired coatings fabricated with the ability to mask signature, and even regulate temperature, as Nature does. Simultaneously, bio-inspired materials and biomaterials are being explored in synthetic biology, enabling US manufacturing to be simpler, more environmentally friendly, use less toxic materials, and be less dependent on rare materials imported from few foreign nations. The DoD and Army must bring more environmentally friendly and less toxic materials into its supply chain, and is required to make surface coating products and processes that are more Environment, Safety, and Occupational Health (ESOH) sustainable. The goal of this topic is to develop an innovative coating with infrared functionality – managing both signature and thermal properties/temperature – for a small UAV that accompanies the Warfighter and is capable of reconnaissance missions. “Infrared functionality” includes passive (and active, i.e. actuated heat release port, etc) temperature control. Emissions must be controlled in the longwave IR (LWIR) or thermal IR, as specified quantitatively below. While the visible, near-infrared, and short-wave (SWIR) infrared are not a focus of this Topic, a coating that is successful for both military and commercial applications must also manage optical properties (e.g., reflectivity and absorption) in these spectral ranges. Batteries, operating as hot as 60°C, and motors, will contribute hotspots to a UAV’s thermal image. UAVs can be observed at distances ~ 100m with IR cameras [1], even when not visually observable. Advanced gimballed, large detection systems could image UAVs at shorter range. Bio-inspired materials, like bio-pigments, exhibit strong IR scattering and high refractive indices, and could strongly affect IR images of a passive coating [2]; these materials have been introduced into fibers. Coatings could be smooth and paint-like, or on fibers and/or textile-like material (i.e. [3]), possibly adding IR functionality, but they must be robust to withstand continuous flights at the rated velocity of the UAV, through different weather conditions. Coatings must have lower ESOH risk than traditional DoD paints, which can no longer contain materials like hexavalent chromium. Polyethylene is an example of one environmentally-interesting material, proposed for thermal and color management [4]. PHASE I: Conduct a feasibility study by identifying, through early stage experiments and modeling (not just modeling), a coating that can be used to trap heat inside a UAV that is conformal, paint-like, and does not have significant ESOH risk for use by operators and manufacturers; for example, a bio-inspired material with backwards infrared scattering centers. Deliver coated samples of representative UAV body elements (wings, battery encasements, motor hubs, etc.) with experimental results demonstrating IR absorption/reflection properties that indicate potential range reduction for LWIR camera-based detection/imaging below 100m. Model potential performance improvements relevant to increased operating temperature for UAV, and possibly LWIR imaging degradation. Model weight of coating for an entire UAV and any effects on aerodynamics of the UAV. Document results of experiments and modelling in a report. PHASE II: Building on Phase I work, in Year 1 of Phase II: demonstrate a prototype, consisting of a fully coated UAV using a coating with low ESOH risk, and demonstrate in a lab environment the coating’s effect on LWIR imaging (using a LWIR camera) of the UAV, degrading images taken at more than 100 m. Also in Year 1, demonstrate improvement to operating temperature range (e.g., any thermal management improvements). In Year 2, include in the prototype a way to mitigate temperature swings of the UAV; e.g., release heat if internal temperature becomes too high; for example, opening a heat exhaust port (“heat valve”) at the back of the UAV temporarily to reduce heat load inside the UAV. In Year 2, the 100 m maximum LWIR range must be improved, any leakage of elevated UAV body temperature into the SWIR range considered, and some temperature control demonstrated. Ideally in Year 2, conduct a toxicological assessment of any new materials used in the coating, with Army Public Health Command. Report ESOH impact and weight of the optimized coating, including potential new heat valve, and demonstrate minimal effects on aerodynamics of UAV and plan for mitigating any heat build-up in warmer environments. Demonstrate coating is as resilient to environmental conditions (temperature, humidity, rain, etc) as uncoated UAV body elements, or report on the reduction in operating ranges for these properties, ideally in a relevant environment (the full system must be demonstrated at least in a laboratory environment). Deliver full prototype of coated UAV to the government. Document results of experiments and modelling in reports for both Year 1 and Year 2. Comment in the reports about the tradeoffs of using a low ESOH-risk passive coating vs. active approaches to avoid detection like use of scattering agents in a released gas. PHASE III DUAL USE APPLICATIONS: Scale the technology demonstrated in Phase II up to a level that produces a full system that could be used in an operationally relevant environment for the Army. Demonstrate reduced IR signature and improved operating temperature range in this environment. Dual use potential for coating comes in two principle areas (1) its use for IR concealment and (2) its use for thermal regulation. (1) Coated UAVs could be marketed to law enforcement (police, department of homeland security, etc.) for its ability to provide UAV concealment to improve surveillance applications. Licensing to or partnering with existing UAV manufacturers in this commercial space would be ideal. (2) Coated UAVs and coatings could also be marketed to widespread commercial applications (agriculture, delivery services, photography, cinematography, hobbyists) on the basis of improving thermal regulation of the UAV in cold environments. Many users face issues from temperatures being too cold for batteries of flight computers to operate normally, reducing mission and flight times. REFERENCES: 1. Night-time Detection of UAVs Using Theral Infrared Camera; Andrasi; Radisic; Mustra; Ivosevic; Vol. 28; 2017; 183-190;; 2. Natural light-scattering nanoparticles enable visible through short-wave infrared color modulation in cephalopods Adv. Opt. Mat. Kumar A. et. al; 6 1701369 2018. , with reference to peer-reviewed publication; 3. Crye Precision; Compact Alpine Overwhites Product Detail;; 4. Lozano L. M. et. al. Optical engineering of polymer materials and composites for simultaneous color and thermal management Opt. Mat. Exp. 9 2019 KEYWORDS: Unmanned aerial vehicles (UAVs), Unmanned vehicles (UXVs), Thermal Management, IR Concealment, Bio-pigment Coatings, Bio-manufacturing
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