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

这时可以「免费」在近心点力，渐渐将心点的高。

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

重复在心点施以力，会将近心点由同步轨道内到同步轨道外。