We lose some of that explosion energy to things like friction, heat, engine efficiency and, most importantly, gravity.

我们失去了一些爆炸能量，比如摩擦、热量、发动机效率，以及最重要的重力。

For heat engines, efficiency is measured by the work produced for a given amount of input heat.

在热机中，效率是通过功来衡量的 该产品为一定的热量添加。

Improvements in aerodynamics, reductions in cabin weight and even improved engine efficiency means that each generation of aircraft is about 20 percent more fuel-efficient than the last.

空气动力学的进步，客舱重量减轻，甚至发动机效率的提高，结合起来，每一代飞机的燃料效率也只比上一代提高了 20% 左右。