FWIW I had a chance to work on an SR-71 while a DOD contractor at Otis AFB on Cape Cod, MA in 1972.
They had landed there due to an avionics problem and I was the only one with a high enough clearance in the AV shop. And even I didn’t know what they needed me for until I got out to the far end of a remote strip and there it sat. A big, black, hulking plane bathed in light from the portable light towers and reeking of fuel. And I knew instantly what it was.
Turns out that the piece of gear that was having the problem was fairly standard and I was able to repair it after a trip back to the shop.
When the AF Colonel and the two armed MP’s dropped me off back at the shop, the Colonel looked at me and said very seriously, “We were never here and you didn’t see anything.”
I said, “See what?” He just smiled, nodded, and drove off.
Fast Forward to 2010, and my wife and I were in San Francisco getting ready to take a Duck boat tour and the driver noticed the SR-71 T-shirt I was wearing, and asked why I was wearing it.
When I said I had had a chance to work on one way back when, he asked me a few questions about it, and I could tell he was kind of testing me to see if I was telling the truth.
Having answered to his satisfaction, I guess, he told me he had been a crew chief on one, so we started swapping stories.
But the most interesting thing he told me was that the SR-71 didn’t really have a known top speed. Every time the Russians would set a new record, they would just go out and open the throttles a little bit more, just enough to set a new record.
But the word was the engines would just run faster and faster until they came apart. But I guess that was never tested.
—”I said, “See what?”
A friend stationed at Okinawa took some photos of one at a distance.
He sent the film for processing and those photos and negatives did not return?
Guessing he used the Kodak mailers???
Amazing story!
Tested the engines to Mach 4 plus? Heat entry into interior of the aircraft probably the limiting factor on sustained speed.