Now thrust could be generated (for “free” again) at periapsis, progressively increasing the altitude of apoapsis.

这时可以「免费」在近产生推力，渐渐将远的高度提升。

The repeated thrust applications at apoapsis would raise periapsis from inside to outside the stationary orbit.

重复在远以推力，会将近由同步轨道内提升到同步轨道外。