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.

When presidential candidate Barack Obama first mentioned his stance on space policy, he spoke of the NASA budget as a perfect offset for additional education spending. Later, when he realized that he had to win Florida, he changed his tune. But it came as little surprise to those of us watching this issue that the first NASA budget he submitted to Congress effectively dismantled the nation’s human spaceflight program. And it should come as no surprise to us now that, despite his signature on the NASA Authorization Act of 2011 and subsequent appropriations legislation to provide funding for the nation’s next steps in space, the administration continues to flaunt congressional intent and law, refusing to move forward on any sequel to the space shuttle.