By Adam Mann of Nature magazine

NASA should be revitalized "not just with dollars, but with clear aims and a larger purpose," US President Barack Obama said last April, after cancelling the previous administration's under-resourced Constellation programme of rockets and capsules for human space flight. But 12 months later, money and clarity are in short supply at the agency, which finds itself hamstrung by a budget showdown and buffeted by conflicting messages from Obama and the US Congress about the next steps in human space flight (see 'Space wars').

This week may finally bring some relief on the fiscal front -- if Congress manages to pass a 2011 budget, now more than six months overdue. That would free NASA from its lingering 2010 budget requirements, which have prevented it from starting new projects or from terminating funding for Constellation. But a larger debate remains unresolved over what rockets to build to replace the venerable space shuttle, due to make its penultimate flight on 29 April.

"I've spent over 40 years closely observing the US space programme and I've never seen it as confused as it is now," says John Logsdon, former director of the Space Policy Institute at George Washington University in Washington DC. "It's simply a mess."

The goal of the Bush-era Constellation programme was to develop rockets and capsules that could both replace the shuttle and take astronauts beyond low-Earth orbit to the Moon and, ultimately, to Mars. In cancelling it, Obama called for increased spending on new rocket technologies for voyages beyond Earth's orbit, extended the end date of the International Space Station (ISS) from 2015 to 2020, and invested in private space-flight companies to ferry crew and supplies to low-Earth orbit.

The plan failed to impress Congress, particularly those members representing regions that benefit from the federal dollars NASA contracts bring. It "has spawned thousands of lost jobs" and "cast fear and doubt" throughout the space-flight industry, said Ralph Hall (Republican, Texas), chairman of the House Committee on Science, Space, and Technology, during a House subcommittee hearing on human space exploration on 30 March. Other legislators caution that Obama's proposal to buy space transportation services from private contractors is an invitation to delay and possibly disaster.

In September 2010, Congress offered up a proposal to resurrect parts of Constellation under another name. In an authorization bill -- which provided direction but no money -- it told NASA to produce a multi-purpose crew vehicle (MPCV) and a heavy-lift launch system with similar specifications to those of Constellation's Orion crew capsule and Ares V rocket. The new rocket, to launch by 2016, would have to be capable of taking astronauts beyond low-Earth orbit. The bill calls for NASA to maintain as many contracts from Constellation as possible to avoid the US$2.5 billion in termination fees that Obama's plan would have triggered. The plan's overall budget comes in about $1 billion lower than projected for Constellation.

Obama signed the bill into law in October, but the debate is far from settled. In its 2012 budget request, the administration allocates $850 million towards aggressively promoting the development of commercial space transportation -- 70% more than Congress authorized. And although Obama's request includes $2.81 billion for work on the MPCV and heavy-launch vehicle, it does not specify a target date for the launch of the rocket, or what vehicle might carry the MPCV in the interim.

The Obama administration and Congress also differ on what size the heavy-lift rocket should be. The authorization act says it must be capable of delivering 130 tonnes into orbit, 4.5 times more than the shuttle. Last month, NASA administrator Charles Bolden told reporters that he does not think that the 130-tonne lift capability is necessary for at least a decade, when the president's plan calls for manned missions beyond low-Earth orbit. Doug Cooke, NASA's associate administrator for exploration systems, expanded on this during the House subcommittee hearing, saying that NASA officials plan to develop a vehicle with an initial capability of 70-100 tonnes, which would allow the agency to launch it by 2016 or soon after.

Meanwhile, funding remains in limbo. The previous Congress failed to pass a budget for this year, and November's midterm elections swept a Republican majority into the House of Representatives that is bent on making drastic cuts to government spending. With the two parties deadlocked over the 2011 budget, members have had to opt for a series of short-term measures that maintain 2010 programmes and funding levels. Constellation continues to be funded, delaying work on any new initiative.

Some argue that the roughly $250 million spent on Constellation in the current fiscal year has not been wasted. For example, on 21 March, Lockheed Martin Space Systems, based in Denver, Colorado, unveiled a new simulation centre where engineers will try out docking manoeuvres with the programme's Orion crew capsule. The capsule meets most requirements from the authorization bill and all indications are that it will be selected as the MPCV, says Larry Price, deputy programme manager for Orion. Continuing Constellation's contracts in this way is in NASA's best interests, he says. "As you can imagine, it would have been hugely inefficient to stop something, redistribute the labour force, and start it over again -- especially if it's exactly the same," he says.

Even if NASA finally achieves the clarity Obama promised a year ago, it faces many years with no way to send people into space. The last time the agency had a similar gap -- between the end of the Apollo programme in 1975 and the first shuttle launch in 1981 -- it knew what was to come next. The shuttle programme had been announced three years before Apollo's conclusion.

The current situation is much worse, said James Maser, chairman of the corporate membership committee at the American Institute of Aeronautics and Astronautics, during the House subcommittee hearing. "We simply do not know what is next," he said.

This article is reprinted with permission from Nature magazine. It was originally published on April 5, 2011.