The Gemini hatches open outward, as can be seen in this EVA image.

enter image description here

I know this was required for the ejection seats to work, but wouldn't this also pose a risk of depressurization if the latch malfunctioned? How were the designers sure that there was no risk of this happening? Or, if there was a risk, were astronauts always strapped in in case of a rapid depressurization from a blown-out hatch?

Granted, it's only 1 atm on the hatch, but it's still a bit concerning...

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    $\begingroup$ Gus Grissom would certainly say yes. space.nss.org/… $\endgroup$ Feb 6, 2020 at 14:31
  • $\begingroup$ "the latch" And that's why in safety-critical systems, you always have at least 2 fully redundant mechanisms. A single failure should never lead to mortal danger. $\endgroup$
    – Mast
    Feb 6, 2020 at 19:47

1 Answer 1


For a number of reasons space craft and aviation closures generally have multiple latches running around the edge. This ensures a tight seal at all points around the opening, reduces the peak forces/weight and provides a degree of redundancy where failed latch/s produce an airleak rather than decompression unless multiple failures occur. The latches are generally setup so that moving them against full atmospheric pressure takes more force than the handle leverage provides, hindering accidental manual operation without first equalising pressure.

Gemini 7 was in orbit for nearly two weeks, the crew were not strapped in and space suited for the entire duration. In any case even if suited and strapped down through door failure, it would generally not be survivable since re-entry with door absent or free to move would most likely be fatal for stability or thermal reasons.

Flight model Apollo CSM also opened outwards, with an earlier 'safer' inwards/plug opening hatch being implicated in Apollo 1 fatalities.

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    $\begingroup$ Always hate when "occur" actually is a link =( $\endgroup$
    – corsiKa
    Feb 6, 2020 at 19:31
  • $\begingroup$ Thanks for explaining why outward was specifically chosen. $\endgroup$
    – IronEagle
    Feb 6, 2020 at 23:56
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    $\begingroup$ There also wasn’t any room for inward-opening hatches — as it was, any astronaut taller than Gus Grissom had the top of his helmet pressed against the inside of the hatch! $\endgroup$ Feb 7, 2020 at 15:47

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