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Orbital junk threatens space station

作者:舜航    发布时间:2019-02-27 02:19:03    

By Vincent Kiernan Washington DC RUSSIA’s contributions to the planned International Space Station will be so poorly shielded against impacts with orbital debris that they could jeopardise the entire project and put astronauts’ lives at risk. Additional shielding should be added to these segments, says a report from the US National Academy of Sciences. The first components of the space station will be launched next year. A series of modules will then be bolted on until construction is completed in 2002. The surface area of the finished station will total some 11 000 square metres. This will provide a huge target for orbiting space junk, including the debris of old satellites and rockets. NASA plans to use ground-based radars to detect large chunks of debris and manoeuvre the station out of their way. The craft will be protected against small fragments by aluminium shielding. But computer models of the bombardment that the station is likely to receive suggest that the Russian-built components would probably be penetrated by debris at least twice during the station’s 15-year life, says the academy committee. An accident of this type would almost certainly render the station useless. The structure could even break apart, killing astronauts. Russia is to provide a service module with living and working areas for the station’s crew, a cargo block with docking ports, a power-generating platform, escape pods to evacuate astronauts in an emergency and three research modules. The vulnerability of this hardware is “a major problem”, says the academy committee, which studied the issue at NASA’s request. The committee was chaired by George Cleghorn, formerly chief engineer for the satellite manufacturer TRW Space and Technology Group in Redondo Beach, California. He says that when the US wooed Russia as a partner in the station, it agreed to incorporate components that had already been designed for Russia’s own use. But the components were not designed to NASA’s standards for durability against debris. By contrast, says Cleghorn, hardware from other partners, such as Japan and the European Space Agency, was designed from scratch, and NASA was able to impose stricter standards. Nicholas Johnson, an expert on orbital debris at NASA’s Johnson Space Center in Houston, says that the Soviet and Russian space programmes never tried to shield their orbiting space stations from space junk. One reason is that orbital debris is relatively rare at the 400-kilometre altitude at which Soviet and Russian space stations, all based on the same design, have orbited. “They have 25 years’ worth of experience with one basic tin can, and they’ve never had a problem,” says Johnson. But the International Space Station will fly at an altitude of 350 kilometres,

 

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