Extra oxygen from breathing when lighting up the hydrazine?
When he first tries to light up hydrazine in the greenhouse in order to obtain water, The Martian Mark Watney blows up the contraption. Later, he reasons this was due to the extra oxygen he exhaled.
But the oxygen level of the air in the dome must've been around 20%, and the oxygen in human exhaled air is around 15%. Why would there be significantly more oxygen around the ignition apparatus (which was at an arm's length above Mark)?
Best Answer
Disclaimer: Answer according to the book, not sure if it is the same in the movie.
The whole process happens in two steps:
- Burning the hydrogen directly as it is produced from the hydrazine in the normal 20% oxygen atmosphere. Mark does this until he notices that not all hydrogen is burned and the concentration in the hab atmosphere gets up to 60% hydrogen.
- Then he tricks the hab into lowering the oxygen level to 1% so the hydrogen can't ignite and uses a small oxygen tank to burn small amounts of hydrogen at a time. During this process his exhaled air increases the oxygen level until all remaining hydrogen ignites at once. Luckily this happens while the resulting explosion is small enough for Mark and the hab to survive it.
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What happens when Mark is trying to burn on the oxygen in the hab?
After a good night of sleep, Mark comes up with a plan. First, he'll remove all of the oxygen from the Hab to eliminate the possibility of a giant explosion. Next, he'll slowly release some O2 and slowly burn off the hydrogen in "controlled bursts" (5.10).What was the fuel Watney used to make hydrogen?
Watney takes the risk of creating his own water by using his oxygenator (a device that creates oxygen from carbon dioxide), extracting hydrogen from the crew's unused hydrazine fuel (from the MDV, or Mars Descent Vehicle), and burning them to create the extra water he needs to nourish his potatoes.Lighting up oxygen
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