The benefits of liquid oxygen (LOX) propellant depots in Low Earth Orbit (LEO) are becoming increasingly apparent, as evidenced by investments from NASA and aerospace contractors in fuel storage and transfer technologies. But LOX fuel is still launched from Earth at a cost of 22kg of launch propellant for every kilogram put in orbit. The Space Gas Station (SGS) concept aims to eliminate this inefficiency by capturing oxygen in space.

Initially, the SGS would capture and store the Oxygen found in LEO at 300km altitude. The collection and storage of the Oxygen alone would significantly reduce the fuel load as it makes up nearly 90% of the propellant mass. Ultimately, the SGS is intended to operate at altitudes of 800–900km within the ionosphere, utilizing highly inflatable magnetic focusing coils to capture hydrogen and oxygen ions, which would then be stored as water ice.

For operations at 300km, a magnetic cusp dipole configuration is employed to capture and direct oxygen ions into a gridded ion accelerator, akin to an ion engine. By leveraging the ambient O ions, the complications and losses associated with ionization are eliminated. The focusing fields are below a milli-Tesla, requiring less than 1.2kWe to power.

As the captured neutral Oxygen flow exerts a drag force of just 0.12N onto the 5m radius conical collector, the structural requirements for the collector are minimal. A thin membrane supported by stays, similar to an umbrella, can serve as the collector and be retracted for a much smaller footprint at launch. Likewise, the magnetic cusp coils and tethers can be readily compacted for launch. The coils are self-inflating and maintain position by magnetic forces when deployed.

Comprehensive scaling studies have been conducted to optimize operating parameters and establish a nominal mass budget for the SGS of 100kg. Analyses of mechanical, thermal, and electrical subsystems support the feasibility of the concept, including considerations for launch deployment and inflation. As a next step, a subscale experimental demonstration is planned for LEO.

Potential applications include supporting a human mission to Mars with sufficient time to mature the technology and process the necessary LOX fuel. The SGS could generate propellant for both the entry vehicle’s reaction control system, requiring 5 tonnes of LOX, and the Mars Ascent Vehicle, which needs 30 tonnes. Preliminary analysis indicates that each SGS spacecraft can harvest up to 2 tonnes of O₂, so that deploying multiple units could readily satisfy mission requirements. Utilizing LOX for landing and ascent enables greatly increased payload capacities. The successful implementation of the SGS would markedly reduce costs and enhance capabilities for deep space missions reliant on LOX propellant, such as sample-return missions. While the advantages of In Situ Resource Utilization are clear, ISRU approaches on distant planetary bodies face significant challenges due to hostile environments and the need for autonomous mining, chemical processing, and storage operations. The SGS presents a simpler, more accessible and maintainable solution in LEO. It can also be employed for both the outbound and return portions of the mission.