For example, Crew Dragon recently delivered two astronauts to ISS and there are at the moment 5 astronauts on board ISS. Assuming [pick your own disaster scenario] happens and all 5 astronauts had to leave the ISS and only the Crew Dragon was available, would the capsule be able to land in a similar manner as if there were only two?

Also, in this case there would be too few seats, would the astronaut left without a seat be able to hold on for dear life and still survive reentry? I think this one is based on conjecture, but I'm happy to hear anybody's thoughts.

Here's an interesting related question: If NASA's plan is to launch 4 astronauts to the ISS on CCtCAP vehicles, why design for 7?

  • $\begingroup$ Even if the Crew Dragon capsule is is capable, they would not have SpaceX space suits, which are individually custom made, and which integrate with the seats. I guess if the situation was: evacuate on Dragon or die anyway, you might get away with it anyway. $\endgroup$ – Mike H Jun 4 '20 at 23:18
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    $\begingroup$ The Dragon capsule should be equipped with enough oxygen and carbon dioxide scrubbers for life support of 5 astronauts instead of only 2. Oxygen tank size may support 7 astronauts but are tanks filled to the max for this flight? Were enough scrubber cartridges loaded? $\endgroup$ – Uwe Jun 5 '20 at 14:46
  • $\begingroup$ Maybe, in this case, it'll be wise to shelter in the Dragon while waiting for rescue rather than rushing to earth. Reentry without a suit has been done with mixed results but without a seat seems excessively hazardous. $\endgroup$ – user3528438 Jun 5 '20 at 16:16

According to the Wikipedia page, Dragon 2 has a (pressurized) return payload capacity of 3,000 kg. This is definitely enough to bring back a few extra adult humans (though you may have to remove other important payload that was initially meant to be returned to earth).

Your question however asks whether the extra astronauts would be able to hold on for dear life and still survive reentry

As @MikeH mentioned, the extra astronauts would not have custom SpaceX suits, made specifically for the seats and pressurized to ensure astronauts don't die during emergencies.

Having a suit that integrates with the seat is of course a good thing to have, and provides confort and safety, but if an emergency happens, you could be strapped tight to the seats, perhaps wearing your Sokol suit (that you would have used in the Soyuz) for extra protection, and that would suffice for reentry.

Of course this could cause problems if the capsule depressurizes during reentry as the Sokol suits are probably not compatible with the Crew Dragon, but while it takes about 35 to 40 minutes for Dragon to re-enter the Earth's atmosphere and splash down in the Atlantic Ocean, entry into the atmosphere itself where danger is the most likely only lasts a few minutes, and the atmospheric pressure after that is survivable.

Now what of the astronauts left without an actual seat?

Well, Space Shuttle contingency mission STS-400 (contingency for STS-125) would have launched with 4 astronauts and returned with the 7 from STS-125, for a total of 11 astronauts in a single orbiter. All 7 STS-125 extra passengers would have strapped in on Endeavour's lower deck, through 'lay on the floor' kind of seating.
I believe something similar would be possible to secure other astronauts in place in Dragon's payload compartment.

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    $\begingroup$ The cabin has room for four (though I’m not 100% sure that four couches are installed on this flight). $\endgroup$ – Russell Borogove Jun 5 '20 at 18:01
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    $\begingroup$ What about landing? Will the strapped-down astronaut risk injury from the landing shock? $\endgroup$ – Wayne Conrad Jun 5 '20 at 18:17
  • $\begingroup$ @WayneConrad I could not find information on Dragon splashdown speed... $\endgroup$ – Speedphoenix Jun 5 '20 at 20:04
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    $\begingroup$ @Speedphoenix I couldn't either. Might be a good question. I found that Apollo was nominally 10G, but could be more (on land instead of water, or a failed chute, or impacted the waves just the wrong way). $\endgroup$ – Wayne Conrad Jun 5 '20 at 20:41
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    $\begingroup$ @WayneConrad I posted the question (space.stackexchange.com/q/44605/29286). Also note this answer that gives the information for other spacecraft like the Shuttle space.stackexchange.com/a/25473/29286 $\endgroup$ – Speedphoenix Jun 5 '20 at 20:57

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