Speaking of the SR71 we use to live about 45 miles from AFB 42 at Palmdale Airport where Lockheed made all the SR71, they kept what they called the house bird at Edwards AFB, about fifteen miles to the northeast.
We went over to Edwards AFB several times on their open house days, one of the Lockheed employees acting as the spokepeson for the SR71 made a comment on one visit about the SR71 growing 14 inches longer at cruising speeds above 63,000 Ft due to air friction heat on the skin At that altitude or higher it is common to see -65 F outside air temps
Lots of information shared with the public after those planes where retired
My wife uncle help design parts on that airplane back in the day of slide rules
Lockheed and other military contractors did a lot of Department of Defense work that developed products we still don't know about, especially from 1981 to 1989