What if a docking accident leaves the spacecraft depressurized and unable to re-pressurize. The hatch may be jammed/ punctured or a window blown. In such a scenario, the astronauts would have their pressure suits on. They would be unable to dock, or abort & return to earth.

They could only survive if they could do an emergency EVA to the station's airlock.

Do the Dragon or Starliner pressure suits have that functionality? Could they shut off and detach the umbilical and use a small emergency air tank like divers have? They are not EVA suits, so they lack insulation and other features, but one would imagine they would be adequate for the few minutes it would take to save life.

  • $\begingroup$ Another situation comes to mind where the spacecraft is depressurized but still able to dock. They would need for the ISS to be able to depressurize their side of the docking hatch. The astronauts in the ship would still have to detach their umbilicals and have a few minutes of oxygen to be able to come through and close the hatch. They just wouldn't have to go outside. $\endgroup$ Mar 7, 2019 at 6:02

2 Answers 2


Sure, but I doubt there are any plans to do so. There were, however, plans to do this using the Apollo suits that landed on the Moon. It isn't super well known, but one of the last steps before launching from the Moon was to open the hatch, dump out as much junk as could be done, including the life support packs for the EVA suits. Of course, they were still wearing their suits. They had about 5 minutes of life support in them. They connected these suits to the LM ECS for the final dumping of the portable life support systems (PLSS) at the end of the mission. In theory, they could do a number of very short EVAs, in the event of something requiring them to do so after they ditched their PLSS. It was never done, but theoretically it could have been done.

I assume that pressure suits used inside of a spacecraft could be used much the same way. There's probably contingency procedures to do some of this stuff with them, but they aren't probably specifically rehearsed.


An air tank would not help for a suit filled with pure oxygen. The suit is a closed loop breathing system, a carbon dioxide scrubber is more important than an oxygen tank. But the exhaled gas shouled be forced through the scrubber.

Remember Apollo 13 when it was necessary to use the CM's scrubber canisters in the LM.

If the suit is disconnected from the umbilicals and no scrubber is present, pressure inside the suit would not drop due to oxygen consumption as inhaled oxygen is replaced by exhaled carbon dioxide. If the partial pressure of carbon dioxide is too high the astronaut may loose consciousness and even die.

The exhaled carbon dioxide could accumulate within the helmet, but some few minutes should be possible, about 5 minutes.

But the suit may converted to an open loop breathing system. The oxygen from the emergency oxygen tank should be inhaled directly. The exhaled gas should be vented from the suit without mixing with the inhaled gas. Then no carbon dioxide scrubber is necessary, but the gases for inhalation and exhalation should be separated by a breathing mask within the helmet. A lot of exhaled and vented oxygen mixed with a little carbon dioxide would be wasted.

  • $\begingroup$ I guess I stated my question too simplistically. Yes of course whatever "mini backpack" they used would have to accommodate CO2 either with a scrubber or open vent system. Probably electricity also. I imagine they would close a valve to the umbilical, detach the umbilical, attach a small pack in it's place and then have some about of time, 15 minutes or so, of survival to get into the ISS or another spacecraft. Obviously it could be done. My question is has anyone done it? I think it very likely that whatever causes a depressurization might be impossible to fix by someone strapped in a couch. $\endgroup$ Mar 7, 2019 at 13:26
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    $\begingroup$ I think in a depressurization event most crewed capsules in the near future would be pressing the big red button and deorbiting within a few orbits or immediately depending on air supply and how stable the ship is. $\endgroup$
    – Saiboogu
    Apr 6, 2019 at 18:49

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