Energy-Based Acoustic Measurement System for Rocket Noise

Accurate estimates of the vibroacoustic loading placed on space vehicles and payloads during launch require knowledge of the rocket noise source properties. Given the extreme nature of acoustic environments near the plume, data sufficient to characterize the noise source region have been difficult to acquire. Without these data, structures may be designed to handle insufficient or excessive vibroacoustic loads, resulting in either an overbuilt structure (and extra weight), or an under-designed vibration isolation system that could result in damaged cargos. Current energy-based acoustic probe designs have limited frequency bandwidth due to physical limitations. A new set of probe designs is proposed that incorporate both a new physical probe design but also a more advanced signal processing methodology that will significantly increase the usable frequency bandwidth of the probes while reducing the manufacturing and maintenance costs of the probes. The probe system will also include the design of a complete data acquisition system capable of recording data under the harsh conditions present in typical rocket motor test firings.

Like NASA, the Air Force Space Division (AFSD) and the Aerospace Corporation perform noise measurements for community noise, on vehicle loads, and/or support structure loads assessments in support of military satellite programs, as do large rocket engine manufacturers including ATK Launch Systems (Morton-Thiokol) and UTC's Rocketdyne. Private space launch vehicle companies such as Orbital Systems Corporation, United Space Alliance, and Space Exploration Technologies are poised for growth. All of these companies will benefit from the improved technology that the energy-based probe presents. In addition, Jet engine manufacturers including Rolls-Royce (with its outdoor test facility at Stennis Space Center), UTC Pratt & Whitney, and GE Aviation perform jet engine source-noise characterization. Helicopter manufacturers Boeing, Bell, and UTC Sikorsky, as well as heavy machinery manufacturers (e.g. Caterpillar, Komatsu, John Deere) are another potential user group. As system development occurs during Phase II, alternative applications will be explored to expand the customer base.

The initial target market for the energy-based probe and data analysis tool is a core community of potential users interested in near-field rocket noise. The primary users are NASA facilities: Stennis Space Center, Marshall Space Flight Center, and Kennedy Space Center, who all perform rocket (static or lift-off) noise measurements for community noise, on vehicle loads, and/or support structure loads assessments. Our proposed system will provide a better understanding of the acoustic near-field with acoustical energy-based measures as opposed to simple pressure and intensity measures. This tool will provide a superior technical advantage over other measurements based on the ability of acoustical energy-based probes to characterize rocket noise. Once this capability is demonstrated and proved during Phase II, we fully expect energy-based measurement to be the most accurate method to characterize near-field rocket noise and as such, that NASA will require it for their noise measurement programs.

This is a mature technology (TRL 8) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

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