Originally Posted by
JamesNoBrakes
Isn't the limiting factor subsonic vs supersonic flow through the engine? Wasn't that the point of the complex inlet system, to keep subsonic flow? At some point, it has to be supersonic to go faster, which gets you into scramjet territory in terms of keeping the fuel lit.
Exactly. flow into the compressor has to be subsonic even though the aircraft is flying at supersonic speeds. Design of the spike was the answer. Slowing the inlet air to subsonic is not difficult. Doing it without a great energy loss is a problem. I had the good fortune of getting the answers on a briefing from Kelly Johnson on the SR71 while it was still the YF12. When he told us at speed the spike was producing 80% of the thrust and that the engines were merely "flow inducers" our collective jaws dropped to the floor. Johnson was a colorful guy and the Skunk Works is famous for innovation, but they seemed a little behind on dealing with the supersonic. They put the last to bed for ever. This is what may be the answer to sub space flight with an air driven engine. The Spike, can a spike design carry us to subspace.