英语语法分析

The propellant came from the top.

推动力来自最上面。

This saves valuable chemical propellant and extends mission lifetime.

这样既可以节省珍贵的化学燃料，又可以延长航天器的寿命。

Without those propellant burns, the station would eventually drop from orbit.

没有这些推进器的点燃，空间站最终会从轨道降落。