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In The Martian, why did the hab explode, the night when Mark's crops died?

marked as duplicate by FuzzyBoots, Jason Baker, Rand al'Thor, DVK-on-Ahch-To, The Fallen Oct 27 '15 at 17:41

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  • Too many depress/repress events, IIRC; basic fatigue of the Hab material in the airlock. Don't have the text of the book handy to confirm, though. – John Bode Oct 27 '15 at 17:19
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The HAB was designed to last for 31 days. Mark Watney was there for way more than that. In the book is describes how part of the fabric around the airlock had a defect. It wasn't enough to do anything bad initially, but Mark's repeated use of Airlock 1 (which was the most convenient) and the extended mission time resulted in that defect eventually causing a small hole, which resulted in explosive decompression of the HAB.

Airlock 1 was closest to the rvoer charging station, so the astronaut preferred it to the other two. When pressurized, the airlock expanded slightly; when depressurized, it shrunk. Every time the astronaut used the airlock, the strain on the AL102 relaxed, then tightened anew. Pulling, stressing, weakening, stretching. - LOG ENTRY: SOL 118

AIRLOCK 1 SLOWLY depressurized to 0.006 atmospheres. Watney, wearing an EVA suit, stood inside it waiting for the cycle to complete. He had done it literally hundreds of times. Any apprehension he may have had on Sol 1 was long gone. Now it was merely a boring chore before exiting to the surface.
As the depressurization continued, the Hab's atmosphere compressed the airlock, and AL102 stretched for the last time.
On Sol 119, the Hab breached. - LOG ENTRY: SOL 119

In the movie they don't explain this. However, after the airlock blows and Watney regains communication with NASA, you see a NASA official say "We think overuse of airlock 1 caused the breach."

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