NASA trade studies compare life-support hardware with Equivalent System Mass (ESM): every non-mass resource a spacecraft spends — volume, power, heat rejection, crew time — is converted into an equivalent kilogram penalty via literature equivalency factors, so architectures with very different engineering can be ranked on one scale:
ESM = M_hw + M_consumables(t)
+ V·VEF + P·PEF + Q·CEF + CT·CTEF
M_consumables(t) = rate_kg/crew-day · (1 − closure) · crew · days
VEF ≈ 250 kg/m³ PEF ≈ 240 kg/kW
CEF ≈ 180 kg/kW CTEF ≈ 0.05 kg/crew-hr
Three real architectures are compared: an expendable system (stored O₂/water, LiOH CO₂ scrubbing — light hardware, but consumables scale with crew and duration), an ISS-style physicochemical-regenerative loop (CDRA + Sabatier + OGA + water recovery — heavier, power-hungry, but far lower resupply), and a bioregenerative system (algae/plant bioreactors — heaviest and most power-hungry, but nearly closed-loop).
- Mission duration — the plotted curves already span 0–3650 days; the slider only moves the vertical marker and the live readouts, so you can see today's number against the whole trend at once.
- Crew size — scales hardware, volume, power, cooling and crew-time roughly linearly, since a bigger crew needs a bigger loop.
- Recycling efficiency — the water/O₂/CO₂ closure fraction achieved by the two regenerative architectures; pushing it up shrinks their consumable-mass slope and pulls the breakeven day (where they beat the expendable system) earlier.
The takeaway mirrors real ECLSS engineering: expendable systems win on very short missions, but every regenerative architecture eventually crosses over and wins on long-duration ones — exactly when depends on how efficiently it recycles.