NASA NTRS · 20140010467
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Voracek, David F.. 2014-07-05. Armstrong Research, Technology, and Engineering Accomplishments 2014. https://ntrs.nasa.gov/citations/20140010467
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While for airplanes the subject of aeroacoustics is associated with community noise, for space vehicles it is associated with vibro-acoustics and structural dynamics. Surface pressure fluctuations encountered during launch and travel through lower part of the atmosphere create intense vibro-acoustics environment for the payload, electronics, navigational equipment, and a large number of subsystems. All of these components have to be designed and tested for flight-certification. This presentation will cover all three major sources encountered in manned and unmanned space vehicles: launch acoustics, ascent acoustics and abort acoustics. Launch pads employ elaborate acoustic suppression systems to mitigate the ignition pressure waves and rocket plume generated noise during the early part of the liftoff. Recently we have used large microphone arrays to identify the noise sources during liftoff and found that the standard model by Eldred and Jones (NASA SP-8072) to be grossly inadequate. As the vehicle speeds up and reaches transonic speed in relatively denser part of the atmosphere, various shock waves and flow separation events create unsteady pressure fluctuations that can lead to high vibration environment, and occasional coupling with the structural modes, which may lead to buffet. Examples of wind tunnel tests and computational simulations to optimize the outer mold line to quantify and reduce the surface pressure fluctuations will be presented. Finally, a manned space vehicle needs to be designed for crew safety during malfunctioning of the primary rocket vehicle. This brings the subject of acoustic environment during abort. For NASAs Multi-Purpose Crew Vehicle (MPCV), abort will be performed by lighting rocket motors atop the crew module. The severe aeroacoustics environments during various abort scenarios were measured for the first time by using hot helium to simulate rocket plumes in the Ames unitary plan wind tunnels. Various considerations used for the helium simulation and the final confirmation from a flight test will be presented.
The Advanced Concepts Office (ACO) at NASA Marshall Space Flight Center (MSFC)has been performing conceptual design of launch vehicles since the Space Transportation System Program. As part of its duties ACO has been tasked with investigating the effects of known and potential threats and opportunities to a myriad of launch vehicle concepts, launch sites, and mission profiles known as the launch space. As the launch space becomes more crowded and busy with launch providers and their vehicles, the legacy method of prescribing each design discipline to a single human Subject Matter Expert (SME) has become infeasible. Rapidly changing launch, economical, and political constraints require rapid evaluation of their effects. While moving into this future of rapid response does require streamlining of data and processes, it does not however lead directly to reinventing the wheel. Flight-validated analysis tools, procedures, and lessons learned can be effectively leveraged to bring the experience from decades of government and commercial flight programs to the new paradigm. In this publication we describe the aggregation of all previous launch vehicle design efforts of ACO into an automated and integrated toolchain called menagerie. The toolchain utilizes a suite of NASA, Air Force Research Lab (AFRL), and ACO-developed tools and processes to evaluate launch vehicle concepts, mission profiles, and trades in a fraction of the time previously required.