With the SpaceX Pad Abort on peoples minds, I was wondering. How does it compare to other abort systems in terms of G load on the passengers.

SpaceX reports that their abort G load is around 4G's. That is uncomfortable, but not intolerable, and only for about 5 seconds at most. (Though the twisting and turning seen in the Pad Abort after the trunk separates and chutes deploy is probably a great carnival ride, but not a good feeling if your rocket is exploding underneath you).

The Soyuz 10 Abort is reported as being in the 14-17G range. Again, short duration, but that has to hurt.

What did Apollo, Gemini, Mercury's abort load work out too?

What does the Boeing CST-100, and SNC Dream Chaser abort loads look like?

In comparison, how about a fighter jet ejection seat, since those are sadly significantly more common.

I think the answer leads to an interesting comparison on how the load of a pusher vs a tractor LES generates.


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I can't find any performance specifications for Dream Chaser; apparently it uses its orbital maneuvering rockets for powered abort, which I would not expect to be very high acceleration. Body lift would maybe help pull it out of the booster's flight line?

CST-100 is also hard to find specs for, but it looks like it's using 4 220kN RS-88 Bantam engines in pusher configuration against 13 tons of capsule, for about 7g.

6g for Dragon v2 per Musk.

12-14g for modern fighter ejection seats.

"Over 10g" for Orion - another source said 0-800kph in 2 seconds, which is 11g average, so I would expect peak above 12g.

If I did the math right, Mercury would be about 10g at ignition, increasing to maybe 13g at cutoff.

Can't find good numbers for Apollo, but maybe around 10g.

Gemini and Vostok used ejection seats rather than an LES.

Presumably you could make either a pusher or a tractor with any degree of thrust you felt was necessary. The advantage of a tractor LES is that it's easier to throw away later in the ascent, so you carry less weight to orbit.

There are probably some situations that are survivable with a 14g escape that aren't survivable with a 6g escape, but I would not think there were many such. At ~16g you're trading off guaranteed injury against very very very unlikely death.

  • $\begingroup$ The linked NASA article never actually states that Orion would go to 15g. It only says that NASA would not approve any abort system if it went above 15g. This is in terms of a general requirement from NASA to all designs, including Dragon v2 and Orion. Nowhere does it mention the actual g load for Orion $\endgroup$
    – neelsg
    May 8, 2015 at 7:15
  • $\begingroup$ You're quite right. I'll try and find better numbers. $\endgroup$ May 8, 2015 at 16:20

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