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

这时可以「免费」产生推力，渐渐将的高度提升。

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

施以推力，会将由同步轨道内提升到同步轨道外。