On 26 September 2011, Rep. Dana Rohrabacher (R-CA) issued a press release regarding fuel depots. This included a letter to former Administrator Mike Griffin who had dismissed the notion of fuel depots and commercial launch vehicles as being a viable alternative to the Space Launch System (SLS) during Congressional testimony.
Rohrabacher noted: “When NASA proposed on-orbit fuel depots in this Administration’s original plan for human space exploration, they said this game-changing technology could make the difference between exploring space and falling short. Then the depots dropped out of the conversation, and NASA has yet to provide any supporting documents explaining the change.”
Well, despite what NASA may or may not have been telling Rep. Rohrabacher about its internal evaluations regarding the merits of alternate architectures that did not use the SLS (and those that incorporated fuel depots), the agency had actually been rather busy studying those very topics.
And guess what: the conclusions that NASA arrived at during these studies are in direct contrast to what the agency had been telling Congress, the media, and anyone else who would listen.
For the uninitiated, propellant (not fuel — one needs an oxidizer as well) depots are storage facilities on orbit that allow the accumulation of the propellant needed for deep-space missions, which is most of the payload. When the depot has enough propellant delivered to support the mission, the propellant is transferred into the earth-departure stage, and the astronauts are sent on their way. Because the propellant can go up in arbitrarily sized quantities, it enables doing lunar missions, or asteroid visits, or even missions to Mars, without having to build a large Saturn-V-like rocket (most of the payload of the Saturn V for Apollo was mission propellant).
The internal NASA study shows that tens of billions of dollars can be saved with such a mission architecture, because that is how much it will cost to develop the new launch system that Congress insists that NASA build. In addition, missions can be mounted much earlier, because the money can instead be devoted to the actual mission hardware, launched on existing or soon-to-be existing commercial rockets. The NASA study team identified several alternate architectures to the heavy-lift baseline (which doesn’t do an actual lunar or asteroid mission until almost the end of the next decade), and all of them were faster and cheaper, and what NASA would be doing if its job were to actually explore space, as opposed to provide jobs in Alabama, Florida, and Utah.