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There was an accident during a suit test in a vacuum chamber on December 14, 1966. The suit lost pressure and

The chamber – which would normally take 30 minutes to repressurized – was blasted back to atmospheric pressure in 87 seconds.

Source

How did they blast the chamber back to atmospheric pressure in only 87 seconds? Was there an emergency hatch with explosive bolts ready for a case of need?

Uwe
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  • I don't see why you would need explosive bolts, an inward-opening hatch would seem perfectly sufficient. – Peter Green Jan 09 '23 at 16:28
  • hard to imagine why it would take 30 minutes to repressurize since there is an infinite supply of air at pressure just outside. – Woody Jan 09 '23 at 16:36
  • @PeterGreen There is a lot of force acting on an inward-opening hatch to a vacuum chamber. To open the hatch interlocks under full load may require much force without a special design and lubrication of the locks. – Uwe Jan 09 '23 at 16:52
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    @Woody For a fast repressurisation you need not only an infinite supply of air, you also need a large cross-sectional area of the air inlet. Air speed within the inlet could not be faster than sound. – Uwe Jan 09 '23 at 16:57
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    The chamber doesn't seem to be too big, maybe 10m³. Repressurization within 87s can be done through a 5cm² inlet. – asdfex Jan 09 '23 at 18:09
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    I'd guess that they did something like loosening a c-clamp on a flange connecting a pump (or some other item) to a port on the chamber, then tilted it opening a gap on one side, or just opened a valve that wasn't connected to anything at the moment. (This is how I used to it for non-critical/non-UVH/not-particularly-clean vacuum chambers) As @asdfex points out a small-sized opening is all you need, so no particularly large forces involved. The "30 minutes" may have been standard to allow clean venting from dry compressed air from a tank or through a filter, or to avoid plumbing differentials. – uhoh Jan 10 '23 at 01:34
  • There's some math for calculating flow rates through holes between atmosphere and vacuum in this answer to How could the 2018-08-30 Soyuz MS-09 / ISS leak be so slow? – uhoh Jan 10 '23 at 01:42
  • normal repressurization might have taken more factors into account - such as strain on the chamber itself or operating procedures - but in case of an emergency there should always be a method of "just opening a large valve" – tsg Jan 10 '23 at 10:42
  • @asdfex Using this https://www.tlv.com/global/TI/calculator/air-flow-rate-through-orifice.html calculator with 1 bar primary pressure, 0 bar secondary pressure, 25.2 mm diameter of the orifice with 20 °C I get 9.1 m³ per minute. But the increasing chamber pressure during repressurisation was not considered, therefore we get a shorter time than real. – Uwe Apr 28 '23 at 13:25

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