Carbothermal Process summary (Rosenberg, Space 98):
CH4 reduction process: three steps.
1. Reduction of ferrous oxide and metallic silicates with methane to form CO and H2.
2. Reduction of CO with hydrogen to form CH4 and H2O.
3. Electrolysis of H2O to form H2 and ½ O2.
Reagents: CH4 and H2
Products: metal oxides, Silicon, and O2
Production numbers: 20 wt% O2 from unbeneficated regolith.
20 wt% Silicon
some varying amount of Fe metal.
The remaining wt% will be left in the form of Slag (metal oxides).
Estimated power requirements for reduction processes: ~40kW
Estimated mass for 5 mt/yr O2 production = 780kg
Scaled System to produce 500 kg O2 per year (Scale factor 1/10) (2500kg regolith mined)
Scaling from the Batch system to produce 5mt / year of O2.
We will assume for the power system here at 125 W/kg specific power. The power mass is not
included in Rosenberg’s calculations.
Products (not including slag) operating 80% of time or 7000hr/yr:
1. 500 kg O2 / year or 71g/hr
2. 200 kg Fe / year or 29g/hr
3. 460 kg Si / year or 66g/hr
NOTE: O2 is produced at ~20wt% so for 500 kg O2, 2500kg regolith is mined.
How it is scaled:
1. Assumed the Oxygen Liquefication and Storage facilities scale linearly with the
amount of O2 produced.
2. Assumed 125 W/kg for power supply
3. Assume the power requirements scale linearly.
4. The rest of the system components do not scale as their components are basically a
given mass that will not reduce.
Scaled Masses:
Power SystemRegolith Reduction Reactor (needs 2.57kW at 125 W/kg) = 20.6 kg
Water Electrolysis Reactor (needs 1.16 kW at 125 W/kg) = 9.28 kg
Oxygen Liquification Reactor (0.37 kW at 125 W/kg) = 2.96 kg
Regolith Reduction Reactor (doesn’t scale) = 52.4 kg
CO Reduction Reactor (doesn’t scale) = 75.1 kg
Water Electrolysis Unit (doesn’t scale) = 91.7 kg
O2 Liquification Unit = 393.0 / 10 = 39.3 kg
O2 Storage Unit = 167.3 / 10 = 16.7 kg
Subtotal = 308 kg
Add 20% of this total for error and other misc mass = 61.6 kg
Total Scaled Mass for 500 kg O2 system = 370 kg
Mass of system minus power = 308 – (20.6+9.28+2.96)) = 275 + 20% = 330 kg
Scaled System to produce 100 kg O2 per year (scale factor 1/50) (500kg regolith mined).
Products (not including slag) operating 80% of time or 7000 hr/yr:
1. 100 kg O2/year or 14 g/hr
2. 40 kg Fe / year
or 5.7 g/hr
3. 92 kg Si / year
or 13 g/hr
Assumptions are the same as above, masses are just changed by a factor of 1/50 in stead of
1/10.
Scaled Masses:
Power SystemRegolith Reduction Reactor (needs 0.514 kW at 125 W/kg) = 4.1 kg
Water Electrolysis Reactor (needs 0.232 kW at 125 W/kg) = 1.86 kg
Oxygen Liquification Reactor (0.074 kW at 125 W/kg) = 0.59 kg
Regolith Reduction Reactor (doesn’t scale) = 52.4 kg
CO Reduction Reactor (doesn’t scale) = 75.1 kg
Water Electrolysis Unit (doesn’t scale) = 91.7 kg
O2 Liquification Unit = 393.0 / 50 = 7.86 kg
O2 Storage Unit = 167.3 / 50 = 3.35 kg
Subtotal = 237 kg
Add 20% for error and misc mass = 47.4 kg
Total Scaled Mass for 100 kg O2 system = 284 kg
Mass of system minus power = 230+20% = 276 kg