If a space explorer needed to eject an inert object from a cylindrical airlock that was roughly barrel shaped (length >> diameter) at maximum velocity, would they be better suited to position the object at either end or somewhere in the middle, before opening?

In the hopes of exposing the underlying physics, I propose to assume that the hatch is able to open pretty much instantaneously, but other considerations would be interesting.

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    $\begingroup$ You can be 100% sure that the airlock won't open until it has cycled all the air inside it. Opening vacuum onto vacuum, your position inside it will be irrelevant. Is this an actual space exploration question, or perhaps something more suited to worldbuilding stack exchange. $\endgroup$ Commented Feb 14, 2019 at 11:20
  • $\begingroup$ What does "either orifice or otherwise" mean? What orifices? $\endgroup$ Commented Feb 14, 2019 at 12:53
  • $\begingroup$ @Diego Sanchez - of course you are right, this would not be the normal operation of an airlock. Perhaps this is too hypothetical for SESE, but its not science fiction. Surely NASA looks at all sorts of uncontrolled decompression scenarios. $\endgroup$ Commented Feb 14, 2019 at 15:02
  • $\begingroup$ @Organic Marble - meaning at the inner or outer hatch of the airlock or somewhere in between. I revised the wording. $\endgroup$ Commented Feb 14, 2019 at 15:03
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    $\begingroup$ I'm voting to close this as off topic - it should be on Worldbuilding - it doesn't work here because it is based on inaccurate assumptions around how airlocks work. $\endgroup$
    – Rory Alsop
    Commented Feb 15, 2019 at 11:23

1 Answer 1


You can't open an airlock hatch to vacuum until the pressure inside is essentially zero. The hatch opens inward and is held closed by tons of force if there is any appreciable delta pressure.

Airlocks are designed for safety and reliability, not circus stunts.

  • $\begingroup$ I wonder if you could add to your answer. I modified the question to eliminate some implausibility. I assume that the decompression is similar to that of a bullet in a gun barrel and you would want the projectile to be nearer the outer hatch, in front of the expanding gas. $\endgroup$ Commented Feb 15, 2019 at 2:52

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