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Protecting Hypersonic Jets at Mach 9

Former Milford high school student John Gabour is currently working on a project to help protect hypersonic aircraft, traveling at more than 7,000 mph, from the catastrophic problems caused by heat and related stresses. NASA is funding the mechanical engineering senior so he can identify new kinds of sensors to help monitor temperatures exceeding 5,000 degrees F, which build up on the leading edges of hypersonic jets. Those temperatures are hotter than the reentry temperatures that destroyed the Space Shuttle Columbia on February 1, 2003, when the vehicle disintegrated over Texas after losing some of its heat shield tiles.

NASA is funding Gabour through two fellowships that total $2,500 from the Massachusetts Space Grant Consortium. Besides helping NASA decide exactly what new sensors need to be developed for its hypersonic aircraft program, Gabour’s project is also supporting a larger grant of $100,000 from NASA’s Aerospace Mission Research Directorate. The principal investigator is Gabour’s faculty advisor, Professor Robert Hyers, with Professor Robert Gao (co-principal investigator) and post doctoral student Alaina Hanlon also part of the research team. All are from the Mechanical and Industrial Engineering Department. Gabour’s research will help pinpoint a new sensor that Dr. Hyers’ research team can conceive, build, and develop for NASA.

Through a comprehensive literature search, Gabour has been reviewing the current state-of-the-art in sensors for measuring temperature, stress, heat flux, and acceleration in these hypersonic environments. His search has identified 10 sensors of this kind currently in use on hypersonic jets.

The first part of my project is a literature search about the sensors being used on NASA’s experimental, unmanned, research aircraft, which are basically rockets,” explains Gabour. “What I’m looking at is availability of these types of sensors, and what would be a potential research subject for any aspect they need to observe. I’ve been studying a lot of articles about what’s being developed, why they’re doing it, and how they’re doing it.”

Hypersonic vehicles, such as NASA's unmanned X-43A scramjet that set a new world speed record for jet-powered aircraft of Mach 9.6 in 2004, require structures that operate at much higher temperatures for much longer periods of time than for conventional spacecraft. In addition to the high temperatures, these aircraft also experience very high static, dynamic, acoustic, and shear loads. Such extreme environments require sensors and sensory materials that are much different from those employed in conventional aircraft.

So one of the things they want to do is make the structures stronger, more reliable, and more heat resistant,” says Gabour. “These are unmanned research vehicles that are each basically a rocket about the size of a small room. The ultimate goal is a manned transport vehicle for commercial use, and also the Air Force wants a vehicle that can reach any target in the world in less than two hours.”

When completed, Gabour’s review will identify the most promising current sensors and sensory materials for instrumentation of hypersonic aircraft and single out the gaps in technology which require future development. His final report will describe the performance, manufacturing capabilities, and technological readiness of current sensors and sensory materials at high temperature. This effort will help NASA and the aviation industry decide which technologies to adopt, which to adapt and perfect, and which new sensors to develop.

Gabour’s work directly supports NASA’s Strategic Goal 3: “Develop a balanced overall program of science, exploration, and aeronautics consistent with the redirection of the human spaceflight program to focus on exploration.” It also supports Strategic Sub-Goal 3E: “Advance knowledge in the fundamental disciplines of aeronautics, and develop technologies for safer aircraft and higher capacity airspace systems.”

One possibility suggested by Gabour’s research is a new kind of fiberoptic sensor for hypersonic aircraft. The sensor would be embedded in the surface of the vehicle and indicate the temperature by the color of the material as it turns red-hot. This is one concept that Professor Hyers and his research team is considering for development as a result of Gabour’s work. As for Gabour himself, he hopes to spin-off his research for NASA into a career in aeronautics.

“I would like eventually to become an aeronautical design engineer,” says Gabour. “I’ve always marveled at the way airplanes are designed. I’m a pilot myself, so I’m always looking at how I could make propulsion more efficient, or how I could reduce the drag on certain components.” (January 2009)