Propellant depot

An orbital propellant depot is a cache of propellant that is placed in orbit around Earth or another body to allow spacecraft or the transfer stage of the spacecraft to be fueled in space. It is one of the types of space resource depot that have been proposed for enabling infrastructure-based exploration. Many different depot concepts exist depending on the type of fuel to be supplied or its location. In-space fuel depots are not necessarily located near or at a space station.