Why were ridiculously fast planes like the SR-71 built, and why hasn’t it speed record been broken for 50 years?
In: Engineering
For the “why hasn’t something faster been built”:
There’s no need for anything as fast or faster. Flying at M3.2 requires Ramjet engines, custom fuel that won’t spontaneously ignite when the aircraft gets hot and a shit ton of maintenance time on the ground.
Theoretically, a Ramjet engine is good up to Mach 5 at which point the intake temperature exceeds the working temp of all known materials. The SR-71 showed that even getting 2/3 of the way there requires buckets of money, R&D and maintenance, so we’re pretty much at the limits of that technology.
The next step up requires a new generation of engines, either a Scramjet (Supersonic Combustion Ramjet) being developed by NASA on the X43-A) or the Sabre engine being developed by a British company. Shit like this takes a looooong time to develop and test, when I was studying aerospace engineering in the late 80s I wrote a paper on the design and development of both engines. They’ve only started testing them in the last few years!
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