焦炭，煤气和汽油是更加有效地利用煤和石油的第二级燃料的范例。
The gas and petrol are examples of secondary fuels by which coal and oil may be more effectively used.
介绍了某型号运载火箭二级燃料箱后底顶盖成形方法改进及工艺试验过程。
The paper introduces the shaping method improvement and technological trial course of bottom cap of certain model of carrier rocket's fuel tank.
火箭又长又细，上部有点粗，因为它的第二级比固体燃料火箭发动机驱动的第一级要厚。
The rocket is long and slender, and fatter on top because its second stage is thicker than its solid rocket motor-powered first stage.
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