Quote:
Originally Posted by gunnut
I know air intakes are needed to keep combustion going. I just want to know exactly why variables are needed and what fighters have them.
SR-71 is kind of special. I know it has movable cones to keep the shockwave just outside the intake (I think). It also cruises on ram jets. Something not many other planes run on.
Here's a tangent. The B-70 has wings that can bend down to capture the shockwave it generates when it exceeds the speed of sound. It almost surfs the shockwave to maintain the mach 3 cruising speed. Does it have variable inlets as well?
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Gunnut, the B-70 had variable engine inlet ramps. Think the system was called the Air Induction Control System. (AICS). It did the same thing any variable inlet system does, slow the air flow down to subsonic speeds, automatically.
The outboard sections of the wings drooped down to 65* above M1.4 to capture shockwaves which generated additional LIFT.
The B-70 had the best lift/drag ratio of any aircraft ever built, utilised "compression lift" and basically rode it`s own shockwave at high speeds. This "Compression lift" configuration produces 30% more lift in the flying prototypes than the wing/body area alone could produce. You get compression lift by directing the shock outwards towards the down-turned wings, the conical shaped under-body was designed to do that.
If this method wasn`t used, the wing area would have to be huge, with the obvious penalty of increased drag, lower speed.