A concept to provide low Earth orbit ( LEO ) propellant depots that could be used as way-stations for other spacecraft to stop and refuel on the way to beyond-LEO missions has proposed that waste gaseous hydrogen — an inevitable byproduct of long-term liquid hydrogen storage in the radiative heat environment of space — would be usable as a monopropellant in a solar-thermal propulsion system.

A concept to provide low Earth orbit ( LEO ) propellant depots that could be used as way-stations for other spacecraft to stop and refuel on the way to beyond-LEO missions has proposed that waste gaseous hydrogen — an inevitable byproduct of long-term liquid hydrogen storage in the radiative heat environment of space — would be usable as a monopropellant in a solar-thermal propulsion system.

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