One of the first tasks of the spacewalker on Saturday will be to retrieve solid lubricants fixed on the surface of the orbital module.
They will be used for scientific studies when Shenzhou VII returns to Earth.
Among the 80 samples from four different kinds of lubricants the astronaut will retrieve will be molybdenum disulfide, the most widely used substance for space applications.
"In space projects, lubricants are very important, because all parts of the spacecraft rely on them to operate," Zhang Shuguang, a professor with Beijing University of Aeronautics & Astronautics, said.
Even the air system in the extravehicular spacesuit needs a special lubricant to make it work, she said.
But containing lubricants in low-pressured space environments has been a problem, since conventional liquid lubricants are mostly unstable and could cause contamination during their degradation, chief of Shenzhou VII's solid lubricant sub-system, Liu Weimin, said.
Unqualified or polluted lubricants could cause big problems in space, Zhang Chunhui, director of the R&D department of Sinopec, said.
It was reported that polluted lubricants caused problems in the launch of an Ariane rocket in Europe in the 1990s, he said.
"It is because radiation in space can change the molecular structure of a lubricant, making it dysfunctional, while the dramatic temperature changes in space can make some lubricants freeze or burn," Zhang Chunhui, said.
All this information is vital for space projects, he said.
"The lubricant used in the extravehicular spacesuit's breathing system must not pollute the air that the astronaut breathes," Zhang Chunhui said.
He said supported by more than 400 research staff at Sinopec's four labs, the company has improved its lubricants by making them "purer with lower volatility".
China is now one of the few countries that can develop and manufacture space lubricants. Sinopec is the country's only space lubricant supplier.
The environmental effects on solid lubricants in space are very important to know, not the least, it will help develop new materials for space applications.
Shenzhou VII's solid lubricant experiment is similar to that of the US space shuttle Atlantis in 1992, Gu Yidong, chief designer of the Shenzhou VII project's space applications system, said.
Gu said results from the study could be beneficial to other industries.
"In the automotive industry, for example, high-performance lubricants could save about 2 percent of fuel, or 20 billion ($2.9 billion) to 30 billion yuan each year," he said.
Source: China Daily
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