After edging out the Soviets and winning the race to land a human on the moon in 1969, the United States has enjoyed more than four decades unchallenged as the world's dominant force in space. The launch on Thursday of the first stage of a new Chinese space station could be seen as the beginnings of a shift in that power.

That China has joined the US and Russia as the third nation with the capability of a permanent crewed presence in space is not, in itself, a significant challenge to American supremacy. Nasa launched its first habitable research laboratory, Skylab, in 1973, and even if China's Tiangong-1 remains safely in orbit after its arrival, it is still likely to be at least another year before its astronauts are able to make any kind of extended-duration stay.

The wider concern of those who follow the US space programme is the converse trajectories the two nations appear to be taking in support of their ambitions in space.

China, which has invested millions of dollars in recent years into a burgeoning space programme, now has a flagship piece of hardware already off the launchpad. Nasa currently has no manned launch capability of its own for crewed vehicles following the retirement of the space shuttle fleet this summer.

It is a situation that rankles with prominent figures in the US space community, among them Neil Armstrong, the first man on the moon, who last week lambasted the American programme as an embarrassment that could soon be eclipsed by the achievements of other nations.

"For a country that did so much for so long to achieve a leadership position in space exploration and exploitation, this is viewed by many as lamentably embarrassing and unacceptable," he told a congressional hearing on the future of space flight. "Nasa leaders enthusiastically assured the American people that the agency was embarking on a new age of discovery. But the termination of the shuttle, the cancellation of existing rocket and spacecraft programmes, the lay-off of thousands of aerospace workers [and] the outlook for American space activity through the next decade is difficult to reconcile with agency assertions."

Nasa did, earlier this month, announce its vision of a future spacecraft, the Space Launch System, which will be the most powerful rocket ever built and is designed to carry astronauts farther into space than ever before. Its cost, estimated in leaked Nasa calculations at more than $62bn over the next 15 years, could yet prove a barrier and the first unmanned test flights are not scheduled until 2017.