@Mike richards
"They got a plywood model and a huge chip on their shoulder."
But it was a *really* nice plywood model.
"It must have been even more embarrassing when they realized the Soviet Union had also got a working SST and they didn't."
They went the traditional Russian way of getting the KGB to steal the design. Sadly even *they* did not get the full trickiness of the wing shape, hence the canards. Lockheed did and used chines on their SST design but I suspect they could not really explain *why* as it would have meant a *lot* of questions on the detail design of the SR71.
"Does anyone think over-land supersonic flight would have been banned if the US had an SST of their own?"
Probably not. Amaziningly enough their has been *some* work done (in the context of bullet design) on shapes which don't create a sonic boom (strictly its a double bang due to leading and trailing edge effects). *If* it works that would change *everything* but fuel economy is *critical*. The pre 1973 oil price was $3 a barrel. No that is *not* a typo.
"And I'm not sure how many passengers would have wanted to get on an all titanium Mach 3 jet - the Blackbird's tanks only seal when the airframe gets hot."
Not sure how to say this but the last book B Beaumont (Concorde test pilot) wrote before he died has some pictures of the area under the wings and fuselage. That pool of liquid is not the overflow from the in flight lavatory.
Note the speed difference between M2.3 and M3+ is *very* important. M2.3 is roughly the upper limit for high temperature use aluminium alloys (the specific one used in Concord was developed for piston heads on Rolls Royce internal combustion aero engines in the late 1930's, so it had substantial pedigree). I suspect that Concorde being an open programme in a way the SR71 was not they had staff they could devote to the tank sealing problem.
In contrast Kelly Johnson (head of Lockheed Special Projects who designed and built the SR71) was a pragmatist who went with a more stable fuel instead to get it flying sooner rather than later.