Space Habitat Water Recovery System

Distillation Drum Controls

Feed rate (wastewater in) 1.2 L/hr

Drum speed 450 RPM

Cabin/boiler pressure 30 kPa

Max concentration factor 6.0×

System Readouts

⚠ Drum below ~2g — phase separation degraded, product carrying entrained brine

Water recovery

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Specific energy

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Boiling point

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Concentration factor

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Potable water made

0.0 L

Drum g-force

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How it works

A real closed-loop habitat's Water Recovery System does not just boil wastewater — that would spend roughly 2260 kJ per kilogram of water evaporated (its latent heat). Instead a Vapor Compression Distillation (VCD) drum spins the wastewater into a thin liquid film against its wall using centrifugal force (needed because there is no buoyancy-driven boiling in microgravity), boils it under vacuum at low temperature, then mechanically re-compresses the vapor and condenses it against the still-boiling liquid — reusing almost all of that latent heat as the actual boiler heat source.

Boiling point at pressure P (Clausius–Clapeyron):
  1/T(P) = 1/T_ref − (R / L)·ln(P / P_ref)
  T_ref = 373.15 K, P_ref = 101.325 kPa, L = 2260 kJ/kg, R = 0.4615 kJ/(kg·K)

Specific energy (compressor + vacuum pump only, latent heat is recycled):
  E = c_p,vapor · ΔT_transfer / η_comp  +  k_vac · ln(P_ref / P)

Concentration factor & recovery:
  CF = feed processed / brine remaining
  recovery R = 1 − 1/CF   (bounded by the CF limit before scaling risk forces a canister purge)

Feed rate — how fast wastewater (urine + humidity condensate) enters the drum; sets how quickly particles move through the loop.
Drum speed — the RPM of the centrifuge. Real ISS-style units need roughly 2–3 g at the drum wall for the liquid film to separate cleanly from the vapor; drop below that and liquid gets entrained into the vapor stream, degrading recovery and product quality.
Cabin/boiler pressure — a deeper vacuum lowers the boiling point (Clausius–Clapeyron above) but costs more vacuum-pump energy, so specific energy is a trade-off, not monotonic in one direction.
Max concentration factor — how far the brine is allowed to concentrate before mineral scaling risks clogging the drum; hit the limit and the canister purges, resetting the concentrate.

Real hardware (ISS's UPA/WPA and the newer Brine Processor Assembly) pushes overall water recovery from wastewater into the high-80s to mid-90s percent — this model uses the same governing relationships at a simplified, visually-legible scale.

Wastewater feed Vapor / condensate Potable product Concentrated brine

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