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The Shenzhou 7 spacecraft is scheduled to be launched on September 25 evening. The highlight of its mission will be the first spacewalk by a Chinese astronaut. It also marks the first time that the spacecraft will carry its maximum capacity of three astronauts. The Shenzhou 7 will release a small satellite to monitor the operation of the spacecraft itself and the course of the spacewalk. During the mission, new satellite communications technology will be tried out as well.
The blastoff of Shenzhou 7 will be televised live in the foyer of the Hong Kong Space Museum from 8pm to 9pm on September 25 when the public will be able to witness this important moment.
The Space Museum will also hold an exhibition, entitled "Shenzhou 7 - China's First Spacewalk", from tomorrow (September 24) to December 31 in the foyer of the museum. Visitors will be able to learn more about the Shenzhou 7 and the history of the Chinese manned space programme through exhibition panels, photos and models of the Shenzhou spacecraft and launching vehicle featured in the exhibition.
A spacewalk is a complicated task. An astronaut cannot proceed to walk in space immediately after putting on a spacesuit without adequate preparation. The first problem to tackle is pressure. Inside the spacesuit, the pressure is only 0.3 to 0.4 atmospheres, and the gas is pure oxygen. Therefore, an astronaut has to breathe pure oxygen inside the spacecraft for a certain period of time to remove the nitrogen in his body. Otherwise, the nitrogen inside his body will turn into bubbles, resulting in decompression sickness.
The spacesuits worn by the astronauts of Shenzhou 5 and 6 were designed for use inside a spacecraft, and weighed only 10 kg each. However, the astronauts of Shenzhou 7, who will venture outside the spacecraft, must wear a spacesuit specially designed for extra-vehicular activity, which weighs over 100 kg. Such a spacesuit gives an astronaut the same protection as Earth's atmosphere provides to all creatures on its surface: oxygen supply, carbon dioxide removal, radiation protection, temperature control and pressurisation.
During blastoff, the three astronauts of Shenzhou 7 will stay in the returning module. When the spacewalk is about to take place, one of them will remain in this module, and the other two will enter the airlock module modified from the orbit module. These two astronauts will wear two different models of spacesuits for the spacewalk, namely, the imported Russian Orlan-M spacesuit and the Feitian (Flying) spacesuit developed by China. They will start breathing pure oxygen for the removal of nitrogen in their bodies. Pressure in the airlock module will be lowered until the module turns into a vacuum completely. As the air pressure inside and outside the module becomes identical, the module hatch will ready to open. One of the two astronauts will exit the spacecraft, making use of the handrails installed around the airlock module to aid his bodily movements. Staying inside the airlock module, the other astronaut will play a supportive role such as launching rescue operations in case of accidents.
A spacewalk refers to the activities of astronauts that take place outside a spacecraft, or extra-vehicular activities. Working in the weightless environment in space is different from working on Earth. Take loosening bolts for example. If an astronaut tries to loosen a bolt by turning a wrench counterclockwise, the bolt will not come loose. Instead, the astronaut's body will turn in the opposite direction - clockwise - if his body is not restrained. To adapt to such conditions, astronauts undergo special underwater training in a pool. With appropriate lead counterweights, his weight balances with his buoyancy in the water. If an astronaut is neutrally buoyant underwater and tries to loosen a bolt, he will get the same reaction and his body will move in the opposite direction to any force he exerts. This explains why practising underwater is good preparation for a spacewalk.
Following the spacewalk of Shenzhou 7, China will launch an unmanned spacecraft, Shenzhou 8, which will be the target of docking another unmanned spacecraft, Shenzhou 9, which paves the way for the docking mission to be carried out by the manned Shenzhou 10 spacecraft.
To tie in with the "Shenzhou 7 - China's First Spacewalk" exhibition, a lecture "Chinese Aerospace Technology: The Past and Future" by the Curator of the Space Museum, Mr Chan Ki-hung, will be held at 3pm on October 4 at the Lecture Hall of the Space Museum. It will be conducted in Cantonese. Mr Chan will introduce the development, characteristics, achievements and future of the Chinese aerospace programme, and the significance of aerospace programmes in science.
The Space Museum is located at 10 Salisbury Road, Tsim Sha Tsui. It opens from 1pm to 9pm on Mondays, Wednesday to Friday and 10am to 9pm on Saturdays, Sundays and public holidays. It is closed on Tuesdays (except public holidays).
Admission is free for the exhibition and the talk on Shenzhou 7.
For further information, please call 2721 0226 or visit the museum's website at http://hk.space.museum/.
Ends/Tuesday, September 23, 2008
Issued at HKT 15:06
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