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

这「免费」在近心点产生，渐渐将心点的高度提升。

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

重复在心点施，会将近心点由同步轨道内提升到同步轨道外。