scramjet
A supersonic combustion ramjet engine that
operates – in fact, can only operate – at hypersonic
(greater than Mach 5) speeds. Like its comparatively slower ramjet counterpart,
the scramjet has engines with a simple mechanical design and no moving parts.
However, scramjet combustion occurs at supersonic air speeds in the engine.
Rather than using a rotating compressor like a turbojet engine, the forward
velocity and vehicle aerodynamic design compress air into the engine. There,
fuel, usually hydrogen, is injected and the expanding hot gases from combustion
accelerate the exhaust air and create thrust. Experimental scramjets include
NASA's X-43A and a DARPA (Defense Advanced
Research Projects Agency) scale model that can be fired from a special gun.
The later achieved the first-ever free flight of a scramjet in September
2001 when it was gun-launched at Mach 7, then used its scramjet engine to
travel 80 m in just over 30 milliseconds.
Related category
• AERODYNAMICS
AND AERONAUTICS
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