In previous times, this was not regarded as a serious problem. Grafting Japan's aspirations for human spaceflight to the US shuttle program and the International Space Station had advantages. It allowed Japan, like other international partners in the station, access to an advanced project, without the need to produce an excessive amount of new hardware.

But recent events suggest that Japan will probably not remain content with these arrangements. Japan will need to change its approach to human spaceflight, and the need for an independent human spaceflight capability will become apparent.

Japan has finally made the long-overdue step of establishing a single agency to handle its spaceflight endeavours. JAXA, the new Japanese equivalent to NASA, will help to eliminate the duplication of programs and resources. But the birth of JAXA also provides an opportunity for Japan to re-examine its overall goals in space, including the launching of astronauts.

The previous division of certain spaceflight activities between different organisations such as ISAS (which specialised in tiny scientific missions) and NASDA (its larger counterpart) did not allow for the same level of synergy that could be possible now.

Irrespective of any local changes, events outside of JAXA are already producing strong influences on all of the world's human spaceflight programs. The International Space Station has been struck with so many delays and cost overruns that it would be torturous to examine then in detail. Its value is being openly questioned by members of the US government, for better or for worse.

Japan's laboratory module, Kibo, should have been launched years ago. Furthermore, the Bush administration is moving NASA in new directions, and the International Space Station does not seem to be a central element of NASA's long-term future. The USA has pledged to finish constructing the station, but it seems to have no prominent role in a spaceflight program that will focus on returning astronauts to the moon.

The recent debut of China as the world's third human spaceflight power adds more impetus for change. For the United States and Russia, our planet's traditional leaders in human spaceflight, the flight of Yang Liwei in 2003 did not produce much shock. Certainly, these nations were impressed by China's achievement, but the flight does not seem to have prompted panic, or any change in the way their space programs operate.

The reaction in Japan would seem to be less benign. Japan prides itself on its economic and technological strength, yet its recent track record in spaceflight does not compare favourably with China. Soon after China had launched Shenzhou 5, Japan lost another rocket. Rumblings in the Japanese media, and some segments of the international aerospace media, suggest that there is growing interest in developing a Japanese human spaceflight capability in the near future.

How could this be done? At the time of writing, no specific plans for a Japanese crew-carrying spacecraft have been published, and no such program has even received formal approval. But a crash program could be designed around existing Japanese space hardware, and hardware that is almost developed.

Japan's previous efforts to develop crew-carrying spacecraft have focused on winged spaceplanes. Models have been tested around the world, and research has also been conducted with France. But such a spacecraft would be complex, costly and would take a long time to develop. It would be more prudent for Japan to pursue a capsule-style design, which could produce a robust spacecraft in a modest interval.

A capsule spacecraft must be tailored to fit its launch vehicle. In this case, the only vehicle Japan could task for such a mission is the H2A. This rocket has enough lifting capacity to place a heavy vehicle into a useful low orbit. It is already operational. But H2A has the serious disadvantage of poor reliability. No engineer would declare it "man rated" on its current performance record. So any first steps in a Japanese space capsule program would need to focus on improving the safety of this rocket.

One obvious modification for man-rating H2A would be the deletion of its solid rocket boosters. Admittedly, the vehicle would suffer a serious loss in its lift capacity, but the reliability would be improved. A failure in the separation of one SRB caused the most recent failure of H2A.

In any case, solid motors are difficult to control after ignition. But H2A will require extensive tinkering and testing of all its sub-systems. Such reviews will take place for the benefit of H2A's uncrewed missions, but the possibility of human missions makes this even more important.

A reliable crew escape system, similar to the ones used on Soyuz and Shenzhou, would be essential. H2A could also benefit from fins to stabilise the aerodynamic influences of this new hardware.

Japan has dabbled in re-entry experiments, but none of these test vehicles bears any resemblance to a crew capsule. However, one Japanese spacecraft currently under development could be modified for the role.

The HTV is Japan's cargo carrier for the International Space Station. It's like a larger version of the Russian Progress spacecraft, and bears some resemblance to the European ATV spacecraft that will carry out a similar role. HTV has its own propulsion, power and navigation systems. As such, some elements could be re-used for a Japanese astronaut carrier.

The rear section of HTV is like the instrument and propulsion module on Soyuz. This segment could be re-used without much in the way of modifications. However, a pressurised module, capable of surviving launch and re-entry, would need to be added. Something resembling the descent module of Soyuz or Shenzhou could be used, but Japan could even use a conical Apollo-style capsule.

A modified HTV crew spacecraft could take more than one configuration. The crew module could sit at the front, with the central cargo module of the existing design retained. The central cargo module could be used to hold consumables for the mission. Alternatively, the crew module could sit in the middle, with the existing short, cylindrical forward module of HTV retained at the front.

In this configuration, the Japanese spacecraft could resemble Soyuz. The most basic configuration would resemble an Apollo spacecraft. Simply place the crew module atop the existing HTV instrument module, and add nothing else. This could be one way of overcoming the weight penalty of a boosterless H2A launch vehicle.

Of course, Japan may elect to design a small capsule spacecraft from scratch. But recycling existing components is a guiding principle of engineering. It saves time, money, and can also help to eliminate risk. Whatever Japan decides to do with its human spaceflight program in the next few years, it is sure to be interesting.

Dr Morris Jones is a Sydney-based correspondent. Email morrisjones NOSPAM hotmail.com Replace NOSPAM with @ to send email.

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