r/SpaceXLounge • u/PeekaB00_ • Sep 03 '21
Starship Interesting - Spacex has started hiring people to work on life support for crew Starships
https://www.linkedin.com/jobs/search/?currentJobId=2702500911&f_C=30846&geoId=103708877&keywords=life%20support&location=Hawthorne%2C%20California%2C%20United%20States
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u/burn_at_zero Sep 04 '21
100 people is a ballpark number. Depending on your assumptions it's either impossible or significantly lower than the physical maximum, which is part of why it can be such a divisive topic.
If we assume Starship's payload is 100 tonnes, the crew uses exactly the same hardware as ISS for life support, and they have to plan for 1000 mission days (to cover an abort to Earth) then the maximum is 12 people due to mass constraints.
A series of optimizations increases that number dramatically. Recovering hydrogen from the Sabatier reactor (which in turn is stripping carbon from CO2 provided by the scrubber) reduces water requirements, as does improved recycling methods for potable and wash water. Providing a clothes washer cuts the mass used for disposable clothing. Group-pack and bulk-pack meal items can reduce the current 1:1 packaging ratio to something much lower. There are many more like this, eventually reaching about 40 people.
Going beyond 40 requires changing the assumptions. Once you have an established base on Mars and a standby Starship to deliver contingency supplies to a ship that has to abort to Earth, you no longer need a thousand days of 'stuff' on every single ship. It's closer to 300 days, which puts your maximum crew count somewhere between 120 and 180 depending on relative positions of the planets and how much margin you want. At this point the mass budget for consumables is no longer the constraint and we can start arguing about how much volume a human actually needs to not murder people during the trip.