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Noise Measurements in the Atmosphere

Description:

TECHNOLOGY AREA(S): Air Platform

OBJECTIVE: Develop & flight-test instrumentation & diagnostics to measure pressure, temperature, density and velocity fluctuations, and particulates at 100-200kft altitude. This is sorely needed to relate ground testing to flight conditions for hypersonics.

DESCRIPTION: Today to design a hypersonic vehicle we rely mostly on ground testing due to the extremely high costs of flight testing. However, one of the major technical challenges for a successful design is knowing a-priori the unsteady and mean pressure and temperature profiles over the vehicle. These profiles affect the drag, heating and structural loads on the vehicle so a successful design hinges on knowing them accurately.

Although a lot of progress has been made to characterize the unsteadiness on flow conditions, especially on pressure and density fluctuations, achieved on both “noisy” and “quiet” hypersonics tunnels on ground testing facilities, a key link is missing. That is, we don’t have a direct comparison between what the atmosphere’s natural disturbances are (pressure, density, temperature, and velocity fluctuations) and what we are producing on our most advanced hypersonic tunnels. Therefore, we are making assumptions on how to correlate our ground testing results to actual flight conditions without thorough validations.

This project will advance the state of the art on how to measure the atmosphere’s natural disturbances by developing and flight-testing different kinds of instrumentation or diagnostics to measure pressure, temperature, density and velocity fluctuations, and particulates at 100-200kft altitude. One of the big challenges will be to have the instrumentation work at high altitude and have sampling rates of 10+kHz. The other challenge will be to accommodate enough band-with for telemetry. Sensitivity to measure fluctuations down to about 1% or less from the mean values on the variables of interest will be key. Also robustness of the instruments or diagnostics will play a critical role. The test flight platform will also be critical to the success of the program. For example, if low cost high attitude balloons could be used, it could represent a lot of savings over suborbital rockets.

At the end of the program the expectation is to have at least one flight test to prove that the instrumentation and diagnostics performed as expected and that the data is of enough quality (e.g. signal to noise ratio, sensitivity, sampling rate) that it can be used to help improve our designs of ground testing facilities and better understand the data they can produce.

PHASE I: Paper design of the instrumentation and diagnostics to be used with clear descriptions of the projected capabilities. Selection of the flight platform is also expected. Realistic costs to build and test the instruments and diagnostics on the ground is also required. As much as possible, the contractor should do bench tests to prove the feasibility of the instrumentation/diagnostic concepts.

PHASE II: Build and test on the ground the instrumentation and diagnostics designed on phase I. Verify all the specs for the instrumentation & diagnostics developed. Al least 1 iteration for fixing "bugs" encountered during testing. Finalize the design of the flight platform, how the telemetry will be handled & how the instrumentation will be integrated to the platform. Finalize the location for the flight and justify why the launch location and flight path are relevant to the objectives of the program

PHASE III DUAL USE APPLICATIONS: Fly at least once the developed instrumentation and diagnostics. Retrieve data and compare against the initial specs. Create a plan for fixing any encountered problems. Based on the flight data, develop a plan to any logical improvements on the instrumentation and diagnostics.

REFERENCES:

    • Thomas Juliano, Steven Schneider. 2012. Instability and Transition on the HIFiRE-5 in a Mach 6 Quiet Tunnel. 40th Fluid Dynamics Conference and Exhibit.

 

    • Katya Casper, Steven Beresh, John Henfling, Russell Spillers, Brian Pruett, Steven Schneider. 2012. Hypersonic Wind-Tunnel Measurements of Boundary-Layer Pressure Fluctuations. 39th AIAA Fluid Dynamics Conference.

 

    • Steven P. Schneider. (2012) Development of Hypersonic Quiet Tunnels. Journal of Spacecraft and Rockets 45:4, 641-664.

 

    • Steven Schneider. 2012. The Development of Hypersonic Quiet Tunnels. 37th AIAA Fluid Dynamics Conference and Exhibit.

 

  • Jr. John D. Anderson. 2006. Hypersonic and High-Temperature Gas Dynamics, Second Edition. AIAA Education Series.

KEYWORDS: noise measurements on the atmosphere, atmosphere unsteadiness, initial disturbances for hypersonic vehicles, hypersonic

  • TPOC-1: Ivett Leyva
  • Phone: 703-696-8478
  • Email: ivett.leyva@us.af.mil
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