CO2 Reduction Reactor Cross-Section: Sabatier vs Bosch (2D)

Reactor Architecture

CO2 + 4H2 → CH4 + 2H2O

Crew size 4

Mission duration 400 d

Bed temperature 350 °C

Live Readouts

H2 recycling loop closure

50%

fraction of reactor H2 self-regenerated by electrolysis of product water

Mission resupply mass

— kg

makeup H2 over full mission

Carbon bed fill

0 bed swaps so far

How it works

Both reactors close the ECLSS oxygen loop by turning metabolic CO2 back into water that an electrolysis unit (OGA) splits into O2 and H2. They differ in what happens to the hydrogen and carbon:

Sabatier:  CO2 + 4H2 → CH4 + 2H2O   (Ni catalyst, ~300-400°C)
             → CH4 vented overboard, carries away 4 H atoms
             → electrolysis of 2H2O returns only 2 mol H2
             → net 2 mol H2 / mol CO2 must be resupplied

Bosch:     CO2 + 2H2 → C(s) + 2H2O  (Fe catalyst, ~600-650°C)
             → all reacted H ends up in H2O, fully recycled
             → net H2 makeup = 0 (closed loop)
             → solid carbon instead accumulates on the bed
                and must eventually be swapped out

Metabolic CO2 production is taken as 1.04 kg/person/day. Bed temperature sets a Gaussian conversion-efficiency curve peaked near each catalyst's real operating window (Ni ≈ 350°C, Fe ≈ 650°C) — the small chart under the reactor cross-section plots that curve live and marks where your slider sits on it. Drifting off that window lets unconverted CO2/H2 pass straight through the bed, visible in the flow.

Resupply mass (Sabatier) = net H2 deficit (g/day) × mission days, since the vented methane permanently removes hydrogen the crew must replace.
Resupply mass (Bosch) = number of catalyst-bed swaps × 8 kg cartridge, where a swap triggers once accumulated solid carbon reaches a 5 kg bed capacity.
Drag inside the reactor view to rotate it about its long axis and tilt the viewing angle — the packed catalyst bed and flowing gas are real 3D-style radial positions projected to 2D, not a flat side view.

drag to rotate / tilt

CO2 in H2 in CH4 (vented) H2O (recycled) solid carbon

⚠ Bed swapped — capacity reached