Monday, October 24, 2011

NASA Considers In-Orbit Fuel Depots


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

I wrote on October 19 about reports that NASA may have buried a favorable fuel depot study because of political pressure to build the Space Launch System.

But The New York Times reported on October 22 that NASA hasn't given up on fuel depots after all, as part of a broader strategy that includes the SLS.

Next month, engineers will meet at NASA headquarters in Washington to discuss how propellant depots could be used to reach farther into space and make possible more ambitious missions using the heavy-lift rocket that NASA is planning to build. The discussions grow out of a six-month NASA study of propellant depots, completed in July.

However, the space agency has rejected the study’s most radical conclusion: that NASA could forgo the heavy-lift and use existing smaller rockets, combined with fuel depots, to reach its targets more quickly and less expensively. Those targets, for the next two decades at least, include a return to the moon or a visit to an asteroid. (A trip to Mars is unlikely until at least the 2030s.)

“This study highlights some interesting benefits of depots, but it is too singularly focused,” William H. Gerstenmaier, the associate administrator for NASA’s human exploration and operations directorate, said in a statement. “NASA is actively studying depots and how they can be used with other proposed elements to provide the lowest cost, sustainable exploration plan.”

Under the plan outlined in the document, the propellant depot would be launched first, and then other rockets would carry fuel to the depot before a spacecraft arrived to fill up. That would increase the complexity for an asteroid mission — 11 to 17 launchings instead of four — but could get NASA astronauts to an asteroid by 2024, the study said. The total budget needed for the project from 2012 through 2030 would be $60 billion to $86 billion, the study said.

By contrast, a study last year that designed an asteroid mission around a heavy-lift rocket estimated that it would cost $143 billion and that the trip could not happen until 2029. The earlier study briefly considered propellant depots but quickly dismissed them.

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