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In the middle of the film Gravity, Ryan Stone is drifting off to sleep in a Soyuz capsule:

and Matt Kowalski knocks on the window, opens up, climbs in, causes the air to escape, closes the hatch, takes off his helmet and starts talking. It turns out to be a dream of Ryan.

Whilst I was watching this I thought that such a sequence of events should have killed Ryan (she was not wearing a helmet at the time).

My question is actually more to do with physics. Was my assumption that she should have been killed correct?

(Thereby predicting that the sequence was not real)

closed as off-topic by AncientSwordRage Feb 19 '14 at 15:48

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    Since this is a question about real-life science, it might do better in space.se. – BESW Nov 15 '13 at 11:10
  • There are actually a lot of science holes in the whole story. I'm just wondering if this particular scene was designed to be unrealistic for the purposes of the story. – user13789 Nov 15 '13 at 11:29
  • I don't know for sure, but I strongly suspect that the external hatches on a soyuz are plug doors. They leverage the pressure differential between inside an outside to ensure they stay shut. This means they can't open the external doors without equalizing the pressure. – horatio Nov 15 '13 at 20:02
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The relevant Wikipedia article (with lots of authoritative sources cited) is Space Exposure:

A rough estimate is that a human will have about 90 seconds to be recompressed, after which death may be unavoidable. The low pressure outside the body causing rapid de-oxygenation of the blood (hypoxia) is the primary reason for unconsciousness within 14 seconds. In 1965 Jim LeBlanc lost consciousness after approx 15 seconds of being depressureised.

So it is realistic for Ryan to survive exposure to space for the depicted time, which is certainly less than 90 seconds. However, if the time without atmosphere lasted more than 15 seconds (which I am not sure it did from memory - 15 seconds is actually pretty long), she should have lost consciousness from the lack of oxygen.

Temperature would in fact have been pretty irrelevant - space is extremely cold, but there is nothing to lose heat to except via radiation, which is comparatively slow (and would not occur inside a previously heated capsule).

However, the scene also depicts uncontrolled decompression, which is very dangerous on its own:

Explosive decompression occurs at a rate swifter than that at which air can escape from the lungs, typically in less than 0.1 to 0.5 seconds. The risk of lung trauma is very high, as is the danger from any unsecured objects that can become projectiles because of the explosive force, which may be likened to a bomb detonation.

So the question is: did opening that hatch cause the air to leave the capsule in less than 0.1 to 0.5 seconds? That's way too short to time from the video. It may be possible to calculate. My intuition says that the hatch is pretty big compared to the size of the capsule, so that decompression would probably happen quickly enough to cause lethal lung trauma.

  • I was unsure what she was doing just before the hatch was opened and assumed she was decompressing the capsule in order to commit suicide, since just turning off the oxygen wouldn't have affected her that quickly. If she decompressed it enough before the hatch was opened the explosive decompression may not have been bad enough to injure her lungs. Of course, I could be totally wrong about her decompressing the capsule. – Alan Jan 30 '14 at 19:48
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    Someone uploaded the scene to YouTube: youtube.com/watch?v=f46GwvQHmOs - "Kowalski" opens the door at 0:06 seconds, and there's enough oxygen to transmit sound at around 0:45. – Plutor Feb 26 '14 at 14:13
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Yeah.

The air would have entirely been flushed out of the capsule, making Ryan gasp for oxygen and she didn't.

Plus, the temperature would have dropped to approximately 2.5K which is rather deadly.

The only way it could have been real was is Ryan had the time to put her helmet before the hatch opens. Assuming that Matt has the opportunity to reach the Soyouz. Which is hard since he's derivating in space.

EDIT : Considering the comments, I'll add that under extremely low pressure, air trapped in the lungs expands, tearing the tender gas-exchange tissues. This would have happened with a opened hatch.

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    There are differing views on how long you could survive in a vacuum. There seems to be a consensus that it wouldn't be an instant death, however opening the hatch would have caused an explosive decompression, which is another matter again. – John Rennie Nov 15 '13 at 9:54
  • Yes, the whole 'death by vacuum' has not (fortunately) been widely researched, however I was also under the impression that it may not be instant. In terms of explosive decompression, she was securely fastened in her seat. (The unsecured helmet flew out quickly) – user13789 Nov 15 '13 at 9:57
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    The lung damage may not be "that bad" if the person merely leaves their mouth open and/or exhales. Holding your breath? Bad idea. – horatio Nov 15 '13 at 19:42
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    Your claim that the temperature would drop to 2.5 K seems questionable. The radiant temperature would be whatever the temperature of the interior of the capsule was. Evaporation would have had a (severe) cooling effect. – DWin Dec 17 '13 at 17:14
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Following the wikipedia link to Soyuz 11 that 90 seconds is a little high:

According to this article cardiac arrest occurred in 40 seconds.

However what is depicted in Gravity looks like it should cause explosive decompression:

Don't watch this if your afraid of flying: