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现在,人造卫星、宇宙飞船,已经自由自在地遨游于太空之中,并能安然返回地面。须知,没有合用的火箭燃料,这一史无前例的飞行也是不可能的。我们知道,一般的喷气发动机与火箭发动机是并不相同的。单就燃料来说,喷气发动机的工作必须依靠空气中的氧气,这至少带来两个严重后果:第一,由于越到高空空气越稀薄,相应地空气中的氧气自然也就稀少,要想得到必要的推力,通过发动机的空气量必然大得惊人,所以,随着高度的升高,喷气发动机的推力不断降低,这就限制了使用喷气发动机的飞机只能在25～30公里的高度以下工作。第二,还由于空气中的大量不参加燃料的氮气冲淡了含氧浓度,也造成对喷气发动机工作的不利条件。而火箭发动机其燃料自身便含有氧化剂,
Now, artificial satellites and spacecraft have freely travelled in space and can safely return to the ground. It is important to know that this unparalleled flight is not possible without the use of rocket fuel. We know that general jet engines and rocket engines are not the same. In the case of fuel alone, the work of a jet engine must rely on the oxygen in the air. This has at least two serious consequences. First, because the air is higher and the thinner it is, the oxygen in the air is naturally scarce. The necessary thrust, the amount of air passing through the engine is bound to be staggering, so as the altitude increases, the thrust of the jet engine continues to decrease, which limits the use of jet engines can only work under the height of 25 to 30 kilometers . Second, because the large amount of non-fuel nitrogen in the air dilutes the oxygen concentration, it also causes unfavorable conditions for jet engines. The rocket engine’s fuel itself contains oxidants.