The moon has a habit of de-orbiting passive satellites in low orbit because it is not a homogeneous ball. Any orbit therefore passes through different sections with different surface gravities. This appears chaotic enough that eventually the small disturbances of a lunar orbit accumulate and the orbit then intersects with the surface. I'd call this destructive.
I'm wondering two things.
- If we had very detailed maps of this gravitational field, could a super computer come up with a medium-high circular orbit that at some point "degrades" to a highly elliptical orbit with the same potential energy, which is oriented in a way to facilitate a transfer to Earth (and vice versa!)?
- Could we even gain (or lose) potential energy similar to a classical gravity-assist? Basically stealing a small fraction of the Moon's angular momentum to first park an arriving vessel in orbit and later depart the vessel again for almost free.
I'm not sure how detailed the maps are that we have of the gravitational anomalies, but I suspect they are not detailed enough for any of this. And I also wonder how long it would take for the Moon to change orbits of a craft in this way.