Refueling in Low-Earth Orbit

Space explorers who need to top off the fuel tanks on the way to the moon or Mars may soon get their orbital refueling stations. NASA has put out the call for a $200 million mission to show how to store and transfer rocket propellants in space.

The idea of space gas stations has floated around – a Canadian company already has plans to launch a flying satellite gas station in 2015. But NASA's latest proposal represents a first step toward supporting future human and robotic missions to destinations such as the moon, asteroids, and Mars, rather than simply refueling satellites in Earth orbit.

NASA wants to look specifically at liquid oxygen and liquid hydrogen, which have powered the main engines of the space shuttle and several commercial rockets. Its proposal calls for "zero boil-off storage" of liquid oxygen, and at least "minimal boil-off storage" of liquid hydrogen.…

See SPACE.com for links to further info.