Comment by chipsa

That said, we both know the shape of the SR-71, and the Compressor Inlet Temperature limit. The shape determines the smallest Mach angle that the entire plane fits inside, which gives a value for the maximum speed. The CIT limit gives a value for the maximum speed, which is roughly the same as the Mach angle value, at approximately Mach 3.3. To go faster, the plane would have to be skinnier, or the wing tips would poke beyond the Mach cone, and the entire tip would generate it's own set of shockwaves, which would most likely result in a sharp increase in temperature for the part outside the cone (which can be read as: the wing tips melt off).