Discovery was hours from launching on it final voyage to the ISS on November 5 when technicians found a hydrogen leak and later a series of long cracks on the shuttle's external fuel tank.

一开始技术人员发现有氢气泄漏，后来在外部燃料罐上发现了一些裂缝，当时是11月5日离发现号前往国际空间站的发射前的几小时，这是它的最后一次飞行。

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At 5, 500 light years distant, Cat's Paw is an emission nebula with a red color that originates from an abundance of ionized hydrogen atoms.

5500光年远处，猫爪星云是一个发射星云，红色来源于其丰富的电离状态的氢原子。

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Though the fuels are frosty, upon ignition they generate scorching steam (5, 000 degrees) and plenty of thrust: Hydrogen is 40 percent more efficient than other propellants.

虽然极寒，而在点火后此燃料可以产生炽热的蒸汽(5000度)和足够的推力：氢比其它推进器燃料的效率高出40%。

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Although this is impressive, America's Department of Energy has calculated that carbon materials will need to be able to store 6.5% of their own weight of hydrogen in order to make fuel-cell cars practical (defined as having a range of 500km, or 310 miles, between refuelling stops).

ECONOMIST: Space-age soot