Environmental Testing of a Fully Automated Carbothermal Reactor for Lunar Oxygen Production

Oxygen comprises the majority of propellant mass required for ascent from the lunar surface and for in-space chemical propulsion. Using in-situ resource utilization (ISRU) technologies to produce oxygen on the moon enables a robust lunar economy through a dramatic reduction in lunar launch costs. In the Summer of 2024 Sierra Space completed thermal vacuum (TVAC) testing of a flight-like Carbothermal Oxygen Production Reactor (COPR) through a NASA Tipping Point program. The COPR reactor uses a mass efficient, scalable architecture optimized for a lunar technology demonstration mission. Concentrated solar energy is directly applied to the lunar regolith simulant. The insulating material properties of the regolith isolate the corrosive molten material from the reactor walls and other hardware. This approach allows for a completely passive thermal control system where high temperature (~1800°C) carbothermal processing is performed without requiring exotic materials or complex cooling systems. The reactor also includes an end-to-end automated solid material handling system capable of metering the lunar regolith simulant from a supply hopper into a pressurized volume, weighing it, distributing it into the carbothermal reactor, and removing the reduced metallic slag. Sierra Space demonstrated repeated use of the automated material handling, gas handling and carbothermal reduction processing systems inside NASA JSC’s “dirty” TVAC chamber while at the relevant lunar topographical, vacuum, and temperature conditions. This testing matured key hardware to Technology Readiness Level (TRL) 6. Oxygen extraction and performance measurements were taken by the NASA KSC Mass Spectrometer Observing Lunar Operations (MSOLO) team using a commercial version of their flight instrument. Oxygen extraction energy efficiency and production yield from regolith exceeded the program goals. The COPR system will be integrated with a flight forward solar concentrator, optical shutter, gas analysis system, avionics, and software as a part of the NASA CaRD program integrated testing in Summer 2025.