Costs – and NASA's reputation for going over budget on large programmes – are major hurdles the agency will have to overcome to send people back to the Moon, say outside experts.
NASA administrator Michael Griffin unveiled the agency's scheme to return humans to the Moon on Monday. It involves building on existing space shuttle technology and proven methods of landing people on the Moon, drawn from the Apollo programme.
A reusable capsule will be fitted atop a longer shuttle rocket booster to send a four-person crew into space. Separately, a heavy-lift launcher will deliver other elements of the Moon-bound ship into orbit. All of this is supposed to be developed and tested before the project's first lunar landing in 2018.
Griffin says the mission could cost at least $104 billion. He says the agency would adopt a pay-as-you-go approach and would not need to drastically increase its budget, now at about $16 billion per year. But critics are unconvinced.
Currently, NASA's share of the federal budget is about 0.7%. During the Apollo era, NASA took up as much as 4% of the US budget.
NASA has been widely criticised for its accounting practices – especially in its human spaceflight programme. "Given the funding shortfalls in the space shuttle programme, there is simply no credible way to accelerate the development of a Crew Exploration Vehicle unless the NASA budget increases more than has been anticipated," says Congressman Sherwood Boehlert, chairman of the US House Science Committee.
"Whether such an increase is a good idea in the context of overall federal spending at this time is something neither Congress nor the Administration has yet determined," he adds.
It’s rocket science
"I don't think this plan will succeed," says Alex Roland, a history professor at Duke University in Durham, North Carolina, US. "It's plausible in a certain way because they have taken things from Apollo and the shuttle that were reasonably successful and good. Who knows whether or not you can quickly and cheaply cobble those together into a workable system?"
But others defend the plan, arguing the agency needs to move beyond its current Earth-orbiting shuttle and space station programmes. "It's obvious there's a rocket scientist running NASA again," says Elliot Pulham, president and chief executive officer of the Space Foundation, a non-profit space advocacy group. "I wish I was still young enough to go."
But even the spirit of exploration is not enough to convince everyone to spend billions on the project. As Roland put it: "I think this whole enterprise of trying to put people on the Moon and then put people on Mars begs the question: what for?"