And so begins a testing time for the US space agency, Nasa, who with the final touchdown of the shuttle Atlantis lost any means to launch its own astronauts for the first time in 30 years.
The world's leading space-farer has put a brave face on a predicament it has wandered into with eyes wide open. The hiatus in US supremacy in human space-flight will be brief, officials say. While US astronauts join the queue for rides into space on the Russian Soyuz – an irony lost on no one in the industry – private companies are working flat-out to build and test new rockets to take over the bread-and-butter task of ferrying astronauts to and from the International Space Station.
The US could be stranded on Earth a while yet. Outside Nasa, some space experts predict a decade could pass before the agency can resume its own manned missions. In that time, the organisation faces an uphill struggle to maintain morale and momentum among its staff who work on human exploration of space.
The retirement of the shuttle is not the only problem that Nasa must contend with. This month, the agency learned its budget is threatened with a whopping 9% cut. Part of that includes the loss of funds for the jewel in Nasa's crown, the James Webb Space Telescope, a spectacular – albeit delayed and over budget – replacement for Hubble. It is fair to say the agency has seen brighter days.
The uncertainty that swirls around Nasa is troubling enough for its employees and contractors, but it brings to the fore a much broader issue. There is a major flaw in the single-nation leadership of space exploration we have become so used to. Even an agency of the size and pedigree of Nasa – last year it received more than $18bn (£11bn) from US taxpayers – is not insulated from bad planning or financial crises. The problem is that when hardship strikes Nasa, there are knock-on effects across the board.
There might be another way. The wavering leadership of Nasa points to the folly of over-reliance on the US and to the need to spread that leadership more widely. Taken to its extreme, we might envisage an international space agency that pools national funding, draws up shared goals and distributes contracts and responsibilities.
There are good reasons a global space agency does not exist. Those nations that have space programmes have their own agendas and want the political prestige for themselves. More practically, by learning how to send robots and humans into space, nations gain the kind of first-hand knowledge that drives competitive, high-technology industries.
But all this comes at a cost. Space exploration is piecemeal, fragile and sluggish when nations go their own way. In the half century since Yuri Gagarin's flight in 1961, we have not gone far: only the two dozen Apollo astronauts have ventured beyond low Earth orbit, a few hundred kilometres high.
There is a vast and expensive duplication of effort when space exploration is fragmented. Believe the rhetoric and the US, Russia, China, India, Japan, Iran and the European Space Agency all have tentative plans to land humans on the moon. It doesn't end there. Many of these space agencies have talked of going onwards to Mars. The phenomenal expense puts the task beyond what even a small group of nations could afford.
For all its shortcomings, an international space agency might lead to a more focused, resilient and ambitious programme of space exploration.
Some groundwork has already been done. In 2007, 14 nations signed up to a Global Exploration Strategy, a voluntary programme to share expertise and plans for the future of space exploration. There is no single programme that nations are compelled to follow, but the spirit of greater collaboration is central. Together, the combined budgets more than double what the US spends on its own space agency.
If nothing else, the $100bn International Space Station demonstrated that multiple space agencies – five in this case – can share the burden of a single goal. The next step is to relieve the US of its role as sole leader and forge broader collaborations to achieve ambitious goals more swiftly.
