Friday, November 4, 2011

NASA Still Studying Fuel Depots in Space


An artist's concept of an in-orbit fuel depot. Image source: NASA.

Aviation Week reports that "NASA is striving to advance orbiting fuel depot technology through a project called Cryogenic Propellant Storage and Transfer (CPST), which hopes to launch an 1,800-kg (4,000-lb.) demonstration mission in 2016."

CPST spacecraft will take about 260 kg of liquid hydrogen to orbit and evaluate techniques for keeping it cold, moving it around in microgravity and measuring its condition. Analytics Mechanics Associates Inc., Ball Aerospace, Boeing and Lockheed Martin all are working on concepts for the mission under study contracts worth $2.4 million in total.

NASA's fuel depot research is caught in the political gamesmanship between those in Congress who support the Space Launch System and those who believe a fuel depot approach would be cheaper.

The latter point to a July 2011 NASA report which "concluded it would take at least 36 Delta IV Heavy flights to deliver fuel to a space-based depot in a scenario that envisioned four lunar missions beginning in 2024," according to Aviation Week. "The study also estimated the same scenario would take at least 24 launches of the Falcon 9 Heavy proposed by Space Exploration Technologies (SpaceX), and said both would cost 'billions' less than later missions mounted on the SLS."

The Aviation Week article concludes:

But concerns about fuel boil-off in orbit remain. A paper presented by Patrick R. Chai and Alan W. Wilhite of the Georgia Institute of Technology at this year’s International Astronautical Congress estimates that depot tanks would lose about $12 million worth of propellant a month in low Earth orbit if protected only with passive insulation. But the state of the art in cryocoolers that would be needed to prevent boil-off falls short by “an order of magnitude” and would require “significant research” to meet likely requirements.

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