Tangentially related, the Space Shuttle Columbia was outfitted with modified SR-71 ejection seats for the first few flights.
Irrespective of that, the ejection seats only work for a very limited period of the shuttle's operating envelope. IIRC it's something like only the first 2 minutes of flight where the ejection seats could be used. And in most cases where you'd be able to eject, the solid rocket boosters were still firing and it was theorized that as the shuttle passed a pilot who had just ejected, the exhaust gases would ruin the parachute and/or kill an ejecting pilot anyways.
By the time the SRBs burnt out, the shuttle was too high/fast to eject.
Only the first I think, unless you're count Enterprise (which couldn't go to space.) Challenger (the second orbit-capable shuttle) never flew with less than four crew.
Incidentally, the ejection seats of questionable worth in Columbia weren't without NASA precedent; the Gemini program also used ejection seats which similarly had a pretty narrow window of usefulness at best. One of my favorite pictures ever is this shot of the Gemini capsule with both hatches open, giving a pretty clear view of how the seats would have worked: https://upload.wikimedia.org/wikipedia/commons/e/e2/Armstron...
STS-1 through STS-4 all had a crew of 2 on Columbia.
If they eject, they are essentially abandoning the rest of the crew to die. It's the antithesis of the captain going down with his ship.
Initial unpowered glide tests were the only flights where ejection was even likely survivable, and this was the reason the seats were ever installed in the first place. (Only on the first two orbiters.) Any other use was an extreme long shot.
Of course all the abort modes ended up being fairly convoluted and unsurvivable to some extent, except abort to orbit.
The "contingency" aborts were especially absurd, which depended on burning off most of the remaining fuel (which would take longer, given it would likely be used in the event of an engine failure), then orienting the shuttle into a position where the crew could attempt a midair bail out. Think about that.
RTLS was a close second, for single SSME loss in the first 4 minutes. It was a 25 minute (!) abort process that involved building up enough speed and altitude so that the shuttle could be flipped around and "put in reverse" to return to the launch site. This involved a certain amount of time at near zero horizontal velocity, so the altitude was needed to permit some time of "free fall" while reversing direction. It also put the orbiter well outside of it's survivable stress envelope, and subjected the crew to extreme g-forces. It was highly questionable that even a perfectly functioning shuttle could have executed the abort, let alone a malfunctioning one.
>Astronaut Mike Mullane referred to the RTLS abort as an "unnatural act of physics"
>John Young:"RTLS requires continuous miracles interspersed with acts of God to be successful"
These were abort modes that were considered survivable. There were another set of scenarios that were considered not survivable: LOCV for Loss of Crew and Vehicle.
It was this level of absurdity that led to the NASA culture of basically ignoring some cherry-picked risks, ultimately leading to Challenger and Columbia.
https://spaceflight.nasa.gov/shuttle/reference/shutref/sts/a...
http://www.nasa.gov/centers/johnson/pdf/383441main_contingen...
> If they eject, they are essentially abandoning the rest of the crew to die. It's the antithesis of the captain going down with his ship.
The Avro Vulcan bomber used by the RAF during the cold war had ejection seats for the pilot and co-pilot, and the 3 other crewmen had just parachutes. There were several accidents where the pilots managed to eject successfully but all the other crewmen were killed.
That's also a little different in that the crew could possibly bail before the pilots ejected, at least in theory.
Which is similar to what the shuttle plan turned to post-Challenger, except the ejection seats were already gone.
The commander and pilot were supposed to hold a bail out orientation until the rest of the crew bailed, then put it on auto pilot (assuming it was working) and bail themselves.
One in Scotland I think and Twinwoods (RAE) would have been another possibility as it was super wide and long
From memory, I think there was generally one each in Africa, GB, mainland Europe, and Azores at any given time. Along with additional sites in Bermuda and Canada (or other US East coast sites) on most post Challenger flights, which weren't specially staffed.
The interesting thing about the added sites post-Challenger, Bermuda was at an US military base. But Canada & other East coast sites were normal airports, with no training or added staff. The shuttle would have had to follow the same FAA emergency landing procedures as if it were a Cessna out-of-fuel, including contacting ATC and directly contacting local traffic at uncontrolled sites.
These were viewed as "modified RTLS" aborts, and were realistically not much more survivable than an actual RTLS.
I don't have a source saying it specifically, but I think they weren't keen on operating a shuttle where two of seven crew could survive but the other five had no chance. It must have also saved weight and space too.