But while higher is better from a fuel conservation perspective, there is an upper limit on how high it is safe to orbit humans for long periods.

越高耗费的燃料越少，而载人飞船能够长时间安全飞行的轨道高度就有上限。

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To counteract its orbital drag, mission controllers must use propellant in attached spacecraft to periodically loft the station to a higher orbit.

为了抵消其轨道牵引力，任务控制中心必须使用f飞船自带的推进器定期将其推进到一个更高的轨道。

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China's shrapnel, created in a higher orbit, could be around for a century to come.

中国的碎片是在更高的轨道上形成的，可能需要一个世纪才能落回来。

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Would this be enough to send any of the components to a higher orbit?

MSN: Salvaging Science from Stricken Mars Moon Probe: A Scientist's View - Technology & science - Space - Space.com | NBC News

But the elegant "Space Oddity" video, reportedly months in the making, may rocket him into a higher orbit.

CNN: Astronaut sings Bowie's 'Space Oddity' in zero gravity

Update 19 July 2011: This story has been amended to clarify that previous references to the Moon "speeding up" actually refer to it moving into a higher orbit.

BBC: Why the Moon is getting further away from Earth