固体燃料火箭发动机的构造更简单、分量更轻，而且相对更安全。 在固体燃料火箭发动机里，燃料和氧化剂被预先混合成稳定的液态推进剂，然后被塞满火箭发动机的燃料箱里。

Solid-fuel rockets, in which the fuel and oxidiser are pre-mixed into a stable, solid propellant and then packed inside the case of the rocket, are simpler, lighter and relatively safer.

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然而，最新的研究显示，当液体或固体表面的气泡破裂时，它们并没有简单地消失殆尽。

What the new study shows, however, is that when bubbles break open on the surface of a liquid or solid, they don't simply disappear.

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如何让固体杀菌剂到达正确的位置呢？如果杀菌剂开始流动了，问题就会变得很简单。

The problem is that to get a solid microbicide to all the right places, it is easiest if it starts off runny.

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