[SES1066]

Especially when you consider its design age of the late 1950s with first flight in 1962 (A-12 predecessor). Mystery is, with its retirement, what is replacing it? My current guess is that ever so mysterious USAF unmanned shuttle-like Boeing X37B, which spends months in orbit, is part of it. No where near as glamorous but probably quite effective!

[Portcall24]

First flight as OXCART from Area 51. Yes. There really was secret stuff at Area 51.

[No Truce With Kings]

“Mystery is, with its retirement, what is replacing it?”

Actually, the answer is a combination of unmanned drones and low-altitude mini-satellites. It is hard to stop UAVs, and even if you shoot one down, they are so cheap that it does not matter. Perhaps something like the Lockheed Martin RQ-170 Sentinel for areas with layered air defense, but I would bet Global Hawks fill a lot of the missions originally done by the SR-71.

For areas that are too hot for that, the military has a bunch of small mini-satellites that us a low orbit (100 to 130 nmi). These weigh less than 50 pounds (probably less than 10 pounds in some cases) and can be launched on very small boosters.

Not as hot or glamorous as the Blackbird, but reconnaissance is best done by inconspicuous vehicles.

[Crusher138]

Mystery is, with its retirement, what is replacing it?

If I told you, I'd have to kill you.

Seriously.