pathology_doc
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Here is my call - Air-breathing hypersonic-cruising aircraft, particularly passenger aircraft, will never be a thing (possibly outside of "black" research/military applications).
The two critical difficulties are keeping the engines lit and stopping the aircraft from melting, for hours on end. The SR-71 required a lot of compromises just to be able to sustain Mach 3 (taking off leaking like a sieve, struggling to slow down to the speed of its jet tanker and then racing to accelerate to a speed where expansion would stop the fuel from leaking out) and that was a two-place military aircraft that didn't have to recoup costs. Mach 5-plus is much worse.
Right now, and I predict for the foreseeable future, I suspect it is actually a technically easier (and in the long term possibly less expensive) proposition to go directly to space with rocket power and suffer the relatively brief indignity of re-entry heat.
Needless to say, I would be very pleased to be proved wrong in my lifetime!
The two critical difficulties are keeping the engines lit and stopping the aircraft from melting, for hours on end. The SR-71 required a lot of compromises just to be able to sustain Mach 3 (taking off leaking like a sieve, struggling to slow down to the speed of its jet tanker and then racing to accelerate to a speed where expansion would stop the fuel from leaking out) and that was a two-place military aircraft that didn't have to recoup costs. Mach 5-plus is much worse.
Right now, and I predict for the foreseeable future, I suspect it is actually a technically easier (and in the long term possibly less expensive) proposition to go directly to space with rocket power and suffer the relatively brief indignity of re-entry heat.
Needless to say, I would be very pleased to be proved wrong in my lifetime!
