# How to repressurize a vacuum chamber really fast?

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?

• I don't see why you would need explosive bolts, an inward-opening hatch would seem perfectly sufficient. Commented Jan 9, 2023 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. Commented Jan 9, 2023 at 16:36
• @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
Commented Jan 9, 2023 at 16:57
• The chamber doesn't seem to be too big, maybe 10m³. Repressurization within 87s can be done through a 5cm² inlet. Commented Jan 9, 2023 at 18:09
• 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
Commented Jan 10, 2023 at 1:34