Until about a week ago, most observers of the space shuttle assumed that the fleet could be kept alive until its planned retirement in 2010.

But the latest mission of the shuttle Discovery, with its daily litany of stuck fuel gauges, falling foam and chipped tiles (see More falling foam puts shuttle programme in serious doubt), raises the prospect that this cannot happen. The ageing shuttle's problems may soon become so difficult to analyse and so expensive to fix that even its staunchest defenders will see that the time has come to stop throwing good money after bad.

What then? The International Space Station is at least 15 shuttle flights away from completion, and that's just counting its largest elements, the European and Japanese laboratory modules and the trusses for solar-power arrays. Several more flights are needed to haul up the experimental racks that would equip the laboratories.

The Russian Soyuz crew vehicle and Progress supply ship are each far too small to carry these large components into orbit. Europe's Automated Transfer Vehicle (ATV), a new cargo carrier scheduled to debut on an Ariane rocket next year, can deliver tons of supplies but not large sections of the station. Japan's proposed cargo carrier, called the HTV, can handle the experiment racks, but won't enter service until 2010. So abandoning the shuttle now would leave the station in its current, half-finished state.

One alternative to that would be for NASA to start work as quickly as possible on a shuttle-derived vehicle (SDV) that would replace the component of the shuttle that carries astronauts with a giant cargo pod. Such an approach is needed anyway for the proposed return to the Moon. In principle, the SDV could deliver the rest of the large pieces of the station, which astronauts, ferried to space on Russian vehicles, could assemble in orbit. In the four or five years it would be expected to take to design and build the SDV, Russian vehicles and Europe's ATV could keep the station aloft, lightly staffed and stocked.

It runs counter to the interests of Japan and Europe to watch NASA damage its reputation in further forlorn efforts to keep the shuttle in space.

Such a plan would require Europe and Japan to accept yet another major delay to the date on which their labs will enter operation. They have already stood by helplessly for years, watching NASA make essentially unilateral decisions to scale back the design according to the vagaries of US budget politics. Why should they continue to put up with this?

Well, for one thing, they may not have much choice. But it also runs counter to the interests of the Japanese and European space agencies to watch NASA — which leads most international space projects and will continue to do so for the foreseeable future — damage its reputation in further, forlorn efforts to keep the ailing shuttle in space.

The international partners could also make use of the delay to negotiate better terms for their participation in the space-station project. Michael Griffin, the latest NASA administrator, has made no secret of his low regard for the station since his appointment in April. Except for medical research on astronauts and technology tests related to the Moon–Mars programme, NASA's use of it is likely to be scaled back, so it ought to cede more laboratory time, more astronaut participation and more mission-control involvement to Europe and Japan.

Such an arrangement would assume that NASA's long-suffering international partners would relish an enhanced role in the project. Publicly, their commitment to the space station is as robust as ever. But if, in truth, they'd rather leave the project in its current state, abandon their laboratory modules, and start spending their taxpayers' money on something more useful, now is surely the time to say so. NASA could then offer something else — probably a prominent role in other cooperative projects — to compensate for reneging on its obligation to complete the US end of the deal. Either way, it's time for some plain speaking and creative thinking, not for stubbornly sticking to an obsolete plan.