This spy plane started when we looked at the USSR circa 1950 and literally had no better information than the German charts created during the war. We literally didn’t know the locations of many cities. Complicating things back then were old soviet maps that were deliberately inaccurate in a paper version of what we can do with GPS today.
These days, it seems like we are “needing” this plane mostly out of habit.
Consider that the SR-71 was designed 50 years ago, it is inconceivable that there hasn’t been a successor developed and flown in the last five decades.
I think the early U2 overflights found the USSR’s Baikanor Missile Launch complex by literally following a rail line. If it weren’t for advanced technical intelligence of the Soviet Union we wouldn’t have had any intelligence worthy of the name.
“These days, it seems like we are “needing” this plane mostly out of habit.”
Not really. Our Key Hole birds fly in a known orbit and you can pretty much set your watch to it. Because of that, places of interest can be easily spoofed. With an aircraft like the SR-71 it’s hard to do that because we can have over flights at anytime.