Commentary | Propellant Depots Instead of Heavy Lift?
Considerable recent attention has been devoted to the possible use of orbiting fuel depots for human exploration beyond Earth orbit. In this concept, large propellant tanks are placed in a suitable low Earth orbit (LEO), to be filled by multiple launches of medium-payload-class vehicles, i.e., a few tens rather than a hundred or more metric tons of payload capacity. These depots are then used to refuel upper stages, which arrive empty in LEO after launch from Earth, after which they are launched outward to the Moon or beyond.