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The first four STS missions were flown by Columbia with two pilots and had ejection seats as an option. These seats were eventually disabled (by STS 5) and removed (by STS-61-C). They could only be used to about Mach 4, in the first 1/5th of the Shuttle's powered ascent.

From researching I found that this was accomplished through ejection panels on the top of the Shuttle's cabin, using the same powered seats at the SR-71.

Diagram of ejection panels for seats

Source: http://www.collectspace.com/

The Buran seems to have also had ejection seats installed, but never flew with them. Their seats seem to be designed to take the pilots 500 meters from the rocket itself.

However, with the gimbled direction of the SSME's firing, and the two extremely powerful solid rockets on the Shuttle stack, would being outside the craft have been even survivable at that close a proximity? Has any analysis on a best case/worst case scenario for these ejection seats ever been done?

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The seats were ineffective above 80K feet on ascent due to the expansion of the SRB plumes - if you ejected after that, you would pass through the plumes making a bad day worse. A call was made at that point "Negative Seats". [Note that the reference cites a thermal limit on the faceplate - I remember it was the plumes - who are you going to believe, me or a former Flight Director and Space Shuttle Program Manager?]

There was a "speed limit" on ejection during entry above which the crewmember would be going too fast to thermally survive the entry. Sadly I don't remember what that point was.

So, the ejection seats were usable only for a short time during ascent, and a short time during entry. Worth it? At the time it was thought yes, due to the fact that no un-crewed test flights were made.

FWIW, here's a picture from the STS-3 training era in the Shuttle Mission Simulator showing what the cockpit looked like then with the ejection seats with the large "rails" that connected the deck to the overhead. Jack Lousma in the commander's seat and Gordon Fullerton is in the pilot's seat; I believe the lady is Mrs. Fullerton.

enter image description here

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  • $\begingroup$ Is it correct that after some point in the launch, abort options become available in which the orbiter separates from the remainder of the stack and glides either to a runway somewhere or worst-case ditches at sea? If so, would those options open up at or before "negative seats", and could safe ejection be accomplished while the vehicle was on the pad? $\endgroup$
    – Anthony X
    Commented May 8, 2017 at 16:34
  • $\begingroup$ Negative seats happened whilst still on the SRBs so there was no separation option at that time. Good question about use on the pad. I would guess that would work but I can't back that up. $\endgroup$
    – Organic Marble
    Commented May 9, 2017 at 10:50
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    $\begingroup$ Seems to me like the seats would be almost more about escape on landing approach. $\endgroup$
    – ikrase
    Commented Jan 25, 2020 at 8:18

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