> similarly airplanes stopped getting faster because we hit the point where the atmosphere starts melting you to death, and not much can be done about that. Wh

> similarly airplanes stopped getting faster because we hit the point where the atmosphere starts melting you to death, and not much can be done about that. While I agree with your point in general, have to nitpick here. Thermal protection is mostly solved problem by now (think Space Shuttles and other reentry vehicles). Commercial airplanes stopped getting faster because they hit a sweet spot between speed and fuel consumption. Military airplanes are stuck because hypersonic aerodynamics is very hard and different from subsonic/sonic/supersonic ones.