Baseline Data
The First Hard Limits
How much stuff does it take to keep a human alive in space? Here are the real numbers.
Known Baseline
Orion Capsule
NASA publishes per-day mass-balance rates for its crews. For a 4-person, 21-day Orion-class mission, the numbers come out roughly like this. This is the deepest any crewed vehicle has actually been built to go.
Crew
4
Duration
21 days
Total Mass
1,190 lb
Per Person/Day
14.2 lb
Oxygen
154 lb
That works out to 1.83 lb per person per day, across 84 person-days total. There is zero margin here for leaks or heavier breathing. See The Air Constraint.
Water
700 lb
About 8.3 lb per person per day, and that only covers drinking and food prep. Hygiene pushes it higher. Almost none of it gets recycled. Every gallon has to be launched from Earth. See The Water Equation.
Food
336 lb
About 4 lb per person per day. All pre-packaged, all shelf-stable. No cooking. No variety. No fresh food.
Projected — Unproven
Starship Concept Scale
100 crew. 180 days. You hear about this scale constantly. Nobody has ever built a life support system for it.
Crew
100
Duration
180 days
Total Mass
128+ tons
Scale Factor
215x
Oxygen
16.5 tons
That is 33,000 lb of breathable air. Without closed-loop regeneration, oxygen alone eats most of the payload budget.
Water
75 tons
150,000 lb if you recycle nothing. Even at 93% recycling, you still need 5.25 tons of water plus all the recycling hardware to process it.
Food
36 tons
72,000 lb of food. There is no way to recycle calories. Every gram has to be launched from Earth, and it takes up enormous storage volume. See The Food Ceiling.
Going from 4 crew to 100 crew is 215 times the mass.
That is a completely different kind of engineering.
Orion's consumables fit in a capsule. At Starship scale, you need an industrial life support system that nobody has built or flown. The numbers above also assume zero waste and zero equipment failure. Real hardware breaks. Real missions will weigh more.