My understanding was that the specific requirement was for a launch into polar orbit (southbound from Vandenberg AFB, just north of Los Angeles) and then a landing ~90 minutes later at Vandenberg, clearly to snatch something out of orbit.

Since the earth is rotating under the orbital plane of the shuttle, this requires a large amount of cross-range maneuverability on reentry so it could land back in California rather than ~22.5 degrees west of Vandenberg in the pacific ocean, and this required large wings.

I don't believe it's known for certain outside of classified circles what was to be brought back. One theory was that it was to snatch a Soviet spy satellite out of orbit, but it's entirely possible given the timelines that the classified requirement was to pull a film cartridge from a US spy satellite in polar orbit and return it quickly to earth for processing.

Unfortunately there would be no way for the USSR to know that they weren't going there to nuke Moscow from the south where there weren't any radars looking. I'm not sure if that was ever seriously considered on the US side but my sense is that the eventual realization that there was no way for the USSR to know and trust that is part of what stopped the shuttle from ever launching from there.

> I don't believe it's known for certain outside of classified circles what was to be brought back.

Given that many details of the keyhole program were recently declassified [1], is there any chance we'll get to know the true nature of the shuttle program? (And if so, when might it happen?)

[1] (a decade ago) https://en.wikipedia.org/wiki/KH-9_Hexagon