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Aeronautics Ground Test and Measurement Technologies: Sensors and Diagnostic Systems for High-Speed Flows

Description:

Scope Title:

Ultrafast Response Sensors for Hypersonic Applications

Scope Description:

Ultrafast response sensors (~1 MHz or greater) to be used as probes or as surface-mounted sensors (embedded in the model surface or tunnel walls) are needed to measure output related to pressure, shear stress, temperature, velocity, mass flux, or other flow properties. Spatially and temporally resolved measurements are desired, and the physical form factor of sensing elements shall be small (submillimeter range) to mitigate spatial averaging. Low noise floor levels (minimum detectable signals) and high sensitivities are desirable to measure free-stream disturbances in ground-based facilities (to include blowdown tunnels, shock tunnels, and Ludwieg tubes) and flight. Sensors must be rugged and able to survive the harsh environment of hypersonic flow to include extreme values of temperature (>1,000 K), inertial load, and dynamic load. Sensors must demonstrate levels of electromagnetic interference (EMI) immunity necessary for flow quality measurements. Sensors shall be capable of performing in ground-based facilities or flight tests. Measurements shall be validated against accepted measurement techniques to determine accuracy and precision with preference given to approaches leading to National Institute of Standards and Technology (NIST) traceability. Sensor system needs to be fully characterized to include sensitivity along with frequency response function. 

 

The use of these measurements in quiet tunnels is critical for the study/control of instability and transition and ultimately to control the aerothermal environment of high-speed vehicle concepts. Areas of emphasis for these measurements include measurements of supersonic/hypersonic boundary layer instabilities, free-stream disturbance environments, receptivity, shock boundary layer interactions, etc. 

Expected TRL or TRL Range at completion of the Project: 4 to 6

Primary Technology Taxonomy:

  • Level 1 13 Ground, Test, and Surface Systems
  • Level 2 13.2 Test and Qualification

Desired Deliverables of Phase I and Phase II:

  • Prototype
  • Hardware

Desired Deliverables Description:

Desired deliverables for Phase I would be detailed design and analysis of proposed hardware, preliminary concept demonstration, and a proposed path to system calibration and dynamic characterization.

Desired deliverables for Phase II would be prototype hardware that has been validated through test (ground-based or flight) and also traceable metrics for hardware calibration and characterization. The prototype hardware should be ready to use in hypersonic wind tunnel testing.

State of the Art and Critical Gaps:

Currently, fully characterized ultrafast response sensors with traceability to flow parameters are lacking. This is particularly the case in the high-temperature environments of hypersonic flows. As an example, high-bandwidth (~1 MHz) pressure transducers are available commercially, but these sensors are not dynamically characterized, have significant calibration uncertainties, and are not survivable when exposed to sustained high-temperature environments. Advancement in these measurements will lead to better predictive models (e.g., in transition and turbulence modeling) for development of future hypersonic vehicles.

Relevance / Science Traceability:

The scope of this activity ties in directly with Aeronautics Research Mission Directorate (ARMD) via the Hypersonics Technology Project (HTP) by providing technology critical to the development of systems under investigation at NASA and would have applications to the wider hypersonic community to include Department of Defense (DOD) and academia. This activity is particularly relevant to the HTP emerging Technical Challenge (eTC) on boundary layer transition. Potential hardware from this solicitation will provide improved measurement capabilities that can be implemented in the experimental investigations to be incorporated as part of a new boundary layer transition TC.

References:

ARMD Strategic Implementation Plan: https://www.nasa.gov/aeroresearch/strategy

Scope Title:

Miniaturized Flow Diagnostics for High-Speed Flows

Scope Description:

Spatially resolved flow-field measurement diagnostics are sought for application in high-speed wind tunnel flows (transonic, supersonic, and hypersonic), both with and without combustion. Improved measurement capabilities are needed for velocity, temperature, density, and/or species concentrations in harsh wind tunnel environments. Molecular-based diagnostics are appropriate for multiparameter measurement approaches. Additionally, particle seeded or unseeded flow velocity measurement approaches can be proposed.  Measurement systems should be both reliable and robust and preferably would be able to be implemented in multiple wind tunnel facilities and facility types including blowdown tunnels, combustion-heated tunnels, shock tubes, shock tunnels, and arc jets. Linear or planar, spatially resolved measurement approaches are preferred for the particulate-based seeding approaches. Molecular approaches can be point based; however, linear and/or planar measurement domains are not discouraged. Ability to measure multiple parameters simultaneously is desirable. The ability to time resolve unsteady flows so that frequency spectra of the measured phenomena can be obtained is a secondary benefit, but not required. Compact/miniaturized systems that could be installed inside a wind tunnel test article with external power, fiber optic, and/or data signal connections would be very desirable. For miniaturized measurement systems, an estimate of the volumetric requirements of the measurement head should also be clearly stated along with optical access requirements. Small planar windows are preferred over large curved optical access ports, which are ultimately defined by the test application. Measurement systems should be validated against accepted standards (thermocouples, calibration flames, etc.) to determine measurement accuracy and precision. Proposals should project anticipated accuracies and precisions of the proposed measurement system(s) based on prior cited or demonstrated work. 

Expected TRL or TRL Range at completion of the Project: 4 to 7

Primary Technology Taxonomy:

  • Level 1 13 Ground, Test, and Surface Systems
  • Level 2 13.2 Test and Qualification

Desired Deliverables of Phase I and Phase II:

  • Hardware
  • Prototype

Desired Deliverables Description:

The deliverables for the Phase I research should include proof of concept of proposed idea along with a design for the comprehensive system that would be developed in Phase II, including detailed analysis of the expected performance (spatial resolution, time response, accuracy, precision, etc.). The expected deliverables at the end of the Phase II effort is a usable system to be deployed in a NASA facility and training for NASA personnel. Demonstration of the measurement system in a NASA facility would be beneficial and strongly encouraged.

State of the Art and Critical Gaps:

There are very limited technologies for measuring gas velocity, temperature, and density simultaneously. The techniques that are available are sensitive to background scattered light and tend to be point based. A planar-based technique capable of simultaneously and accurately measuring gas velocity and state variables would be a large advance in the state of the art. Another challenge is employing these optical diagnostic techniques in NASA’s large-scale wind tunnels, where there may be limited optical access or large distances from a viewing window to the test article in the tunnel. An alternative approach could be to implement miniaturized point, line, and/or planar techniques for acquiring near-surface velocity measurements that are small enough to be integrated into the test model or to be flown onboard aircraft for in-flight measurements. Single optical port (or maximum of two optical access ports) access for obtaining near-surface (boundary layer) and short-standoff (several feet) measurement capabilities would both be highly desirable.

Relevance / Science Traceability:

The target application of this technology is at NASA’s large-scale test facilities: National Transonic Facility (NTF) and Transonic Dynamics Tunnel (TDT) at Langley Research Center, the 8×6 Supersonic Wind Tunnel and 10×10 Abe Silverstein Supersonic Wind Tunnel at Glenn Research Center, and the Unitary Plan Wind Tunnels at Ames Research Center. The technology could also be applied to measure in-flow and near-wall conditions in other types of facilities like shock tubes and shock tunnels as well as conventional aeronautical testing facilities.

References:

ARMD Strategic Implementation Plan: https://www.nasa.gov/aeroresearch/strategy

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