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

这时可以「免费」在近心产生推力，渐渐将心的高度升。

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

重复在心施以推力，会将近心由同步轨升到同步轨外。