In a few days, the launch window for China's Shenzhou 7 space mission will open. The mission is apparently slated for liftoff at 9:10 PM Beijing time on September 25. This flight will carry three astronauts for the first time, and include China's first spacewalk.

Zhai Zhigang has been designated as the astronaut who will carry out this historic task.

His crewmates are Liu Boming, who will don a spacesuit to assist Zhai with his spacewalk, and Jing Haipeng, who will remain inside the pressurized Descent Module of Shenzhou 7 while his colleagues are exposed to vacuum.

China surprised observers in early September with a strange series of announcements on the timing of the flight. Analysts had been expecting an October launch for months. Suddenly, the launch was brought forward in one announcement, which was then denied in a second announcement, then replaced with a new announcement that identified the new launch window.

The confusing set of messages suggested that there had been a last-minute change of plans. China has apparently decided to bring the launch forward for publicity reasons.

The mission will fit in nicely with a period of global attention on China that started with the Olympics in August, moved on to the Paralympics, and will conclude with China's national day on October 1. If the mission lifts off at the announced time, it will finish by the end of September 28. This could allow the returning astronauts to participate in national day celebrations.

But has the sudden change in the launch date produced any problems? For the overall course of the spaceflight, probably not. All the hardware was finished a long time ago, and had already been shipped to the launch site.

The fuelling and rollout of the Long March 2F rocket would need to be advanced, but this would probably be straightforward. The astronauts themselves are probably happy to find their long wait for the mission has been shortened.

This author has written extensively on the complex saga of developing China's spacesuit for the spacewalk on the flight. Amazingly, China will carry two different types of suit. A Chinese-built suit, based on the Russian Orlan spacesuit, will be worn by Zhai.

A genuine Russian Orlan suit will be worn by Liu. This plan was a big surprise, but there are solid engineering reasons behind it. China's own spacesuit is untested in flight, and a second astronaut in a reliable Russian suit will be ready to rescue the spacewalker if problems develop.

The Chinese spacesuit has been officially dubbed "Feitian", which is a reference to a type of flying god found in Chinese mythology.

At this stage, it is not clear exactly when the spacewalk will begin. Conflicting reports have appeared in China's media. Mission controllers will probably make a decision a few hours after launch, once they have assessed the condition of the crew. One option would see the spacewalk begin roughly seven and a half hours after launch.

A more recent report suggests the walk will take place on the second day of the flight. This seems more likely, as it would give the crew more time to adjust to weightlessness.

The activities of the spacewalker will be fairly modest, and mainly focused on demonstrating the dexterity and functionality of the spacesuit.

"Tightening bolts" is a phrase that has appeared more than once. A package of "solid lubrication material", probably intended for spacecraft joints, will be retrieved from outside the spacecraft and returned to Earth. Little else will be done.

This is understandable. China is taking a big step in its spaceflight activities by simply conducting a spacewalk. Complex activities should be saved for later missions, when China has more experience with spacewalking.

The spacewalk itself will probably last no longer than 40 minutes, which will allow the spacecraft to fly over the sunlit side of Earth during the spacewalk. It's worth remembering that spacewalking is a dangerous activity, and even today, experienced nations like Russia and the USA are cautious in the way they plan them.

Zhai's spacewalk will be monitored by cameras mounted on the Shenzhou spacecraft, and also by a small satellite camera that will fly beside him. This satellite will probably be thrown out of the spacecraft's hatch by one of the astronauts shortly before Zhai steps out.

Will there be other experiments on the Shenzhou 7 mission? Almost nothing has been said. Discussions of the experiments performed on the Shenzhou 6 mission in 2005 were vague, presumably to hide the real tasks being performed.

The principal experiments performed by the crew were apparently military surveillance with cameras of ground targets, turning the spaceship into a manned spy satellite. The Shenzhou 7 mission is unlikely to repeat this. The spacewalk is the principal goal and experiment of the mission. Other experiments will need to be modest in their equipment and demands on the crew.

It's possible that China will fly some more seed packages in space, which has been done repeatedly on Chinese spacecraft. Seed packages are small and require no special handling by the crew. But no announcement has been made.

It's been a long wait for this mission. China has not launched a manned space flight since the Shenzhou 6 mission of 2005. If the achievements of the flight are as promising as China hopes, it will be worth the wait to see them.

Dr Morris Jones is a Sydney-based spaceflight analyst. He is the author of "The Adventure of Mars" and "When Men Walked on the Moon". He can be contacted at morrisjonesNOSPAMhotmail.com. Replace NOSPAM with @ to send email. Dr Jones will accept media inquiries.

related report
Chinese Engineers Present New Spacesuit
Chinese spaceflight research specialists have presented a new domestically created spacesuit to be used in spacewalks by the country's astronauts, the China Daily said Thursday.

The spacesuit weighs 120 kilograms, and each model will cost about 30 million yuan ($4.4 million) to produce, the state-run paper said.

"The extravehicular spacesuit is now on board the Shenzhou VII at the Jiuquan Satellite Launch Center," the article said.

The Shenzhou VII, China's third manned spacecraft, will be launched on September 25 from northwest China with three astronauts on board.

The first spacewalk by a Chinese astronaut, to be carried out by 42-year-old fighter pilot Zhai Zhigang, will be broadcast live on national television.