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  3. Aristotle believed that the heavens were perfect. If they ever were, they are no longer. The skies above Earth are now littered

Aristotle believed that the heavens were perfect. If they ever were, they are no longer. The skies above Earth are now littered

admin2011-03-11  17
问题     Aristotle believed that the heavens were perfect. If they ever were, they are no longer. The skies above Earth are now littered with the debris (残骸) of dead satellites, bits of old rockets and the odd tool dropped by a spacewalking astronaut. Such is the extent of the detritus that the first accidental collision between two satellites has already taken place. It happened in February 2009, when a defunct (废弃的) Russian Cosmos smashed into a functioning American Iridium, destroying both and creating even more space junk.
    To stop this sort of thing happening again Vaios Lappas of the University of Surrey, in England, has designed a system that will remove satellites from orbit at the end of their useful lives--and as a bonus will scour part of the sky clean as it does so. Dr. Lappas’s satellite-removal system employs a solar sail. As light from the sun hits the sail, it imparts a minuscule but continuous acceleration. When a satellite is first launched, the sail is angled in a way that causes this acceleration to keep the satellite in orbit. (Orbits gradually decay as a result of collisions with the small number of air molecules found even at altitudes normally classified as "outer space". )
    Solar sails have yet to be used widely to propel spacecraft in this way--several earlier versions came unstuck when the sails failed to unfurl properly-but doing so is not a novel idea in principle The novelty Dr. Lappas envisages is to change the angle of the sail when the satellite has become defunct. Instead of keeping the derelict craft in orbit, it will, over the course of a couple of years, drag it into the atmosphere and thus to a fiery end. Not only that, but the sail will also act like a handkerchief, mopping up microscopic orbital detritus such as flecks of paint from previous launches. A fleck of paint may not sound dangerous, but if travelling at 27 000kph (17 000mph), as it would be in orbit, it could easily penetrate an astronaut’s spacesuit.
    A prototype of Dr. Lappas’s design, called CubeSail, will be launched late next year. It weighs just 3kg and, when folded up, measures 30cm (12 inches) by 10era by 10era. Once unfurled, however, the sail will have an area of 25 square metres. If this prototype, which is paid for by EADS, a European aerospace company, proves successful, solar sails might be added to many future satellites. That would enable them to be removed rapidly from orbit when they became useless and would restore to the skies some measure of Aristotelian perfection.
If the CubeSail turns to be practical, the design will ______.
选项 A、be granted a patent to reward Dr. Lappas
B、make our skies return to be perfect
C、be still useless to remove the satellites from orbit
D、be applied to all the future satellites
答案B
解析 本题考查立方体太阳能帆板模型试用成功的实际意义。文章最后提到，这些卫星使命完成时，可以迅速从轨道中清除，天空就会慢慢回归亚里士多德时期的完美无瑕。由此可见该设计的最终目的还是为了使天空更洁净，所以[B]为正确答案。[A]文章没有提及。文中最后一句提到当这些卫星没有用途时，它们就会被迅速从轨道中清除，而不是对清除卫星没作用，[C]是对该意思的误解。文中倒数第二句提到，该模型一经试用成功就会应用于很多未来发射的卫星，并没有说应用于所有卫星，所以[D]也不正确。  
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