This is an artist’s depiction of a Hyper-X research vehicle under scramjet power in free-flight following separation from its booster rocket. New research into hypersonic jets may transform space travel by making scramjet engines more reliable and efficient, leading to aircraft-like spacecraft. Credit: NASAResearchers at the University of Virginia are exploring the potential of hypersonic jets for space travel, using innovations in engine control and sensing techniques.
NASA’s B-52B launch aircraft cruises to a test range over the Pacific Ocean carrying the third and final X-43A vehicle, attached to a Pegasus rocket, on November 16, 2004. Credit: NASA / Carla ThomasThis month, however, brought some hope for potential successors to the X-plane series. Doctoral student Max Chern takes a closer look at the wind tunnel setup where University of Virginia School of Engineering and Applied Science researchers demonstrated that control of a dual-mode scramjet engine is possible with an optical sensor. Credit: Wende Whitman, UVA Engineering
UVA has several supersonic wind tunnels, including the UVA Supersonic Combustion Facility, which can simulate engine conditions for a hypersonic vehicle traveling at five times the speed of sound. Ramjets essentially “ram” air into the engine using the forward motion of the aircraft to generate the temperatures and pressures needed to burn fuel. They operate in a range of about Mach 3 to Mach 6. As the inlet at the front of the craft narrows, the internal air velocity slows down to subsonic speeds in a ramjet combustion engine. The plane itself, however, does not.
Incoming wind interacts with the inlet walls in the form of a series of shock waves known as a “shock train.” Traditionally, the leading edge of those waves, which can be destructive to the aircraft’s integrity, have been controlled by pressure sensors. The machine can adjust, for example, by relocating the position of the shock train.
No longer limited to information obtained at the engine’s walls, as pressure sensors are, the optical sensor can identify subtle changes both inside the engine and within the flow path. The tool analyzes the amount of light emitted by a source — in this case, the reacting gases within the scramjet combustor — as well as other factors, such as the flame’s location and spectral content.that are excited during combustion processes,” explained Elkowitz, one of the doctoral students.