It is predicted that the Chang’e 5-T1 rocket stage will impact the Moon's far side on March 4th. The stage apparently weighs about 4 tonnes and will impact at 2.5 km/s at a shallow angle.
There's certainly plenty of energy available and it only takes a piece going at 1.7 km/s to go into orbit around the Moon. I gather that, in general, high velocity impacts even at shallow angles tend to produce circular craters simply because of the huge energy dissipated almost instaneously in a small volume. But this isn't your average space rock. Could some of the rocket break up and bounce off the surface if the angle is shallow enough? Even so, such pieces will only complete one orbit at most before crashing back into the surface. If some of the debris passed round the near side of the moon, would anyone be able to observe it (I assume the time is known fairly precisely)? Is there any situation such as collisions within the ejected debris such that something might end up in a sustained orbit around the Moon?
Perhaps there's a more general question here about how impacts can launch stuff into space. If there's debris at escape velocity, that's fine. But anything below that speed and launched from the surface has to intercept the surface again. It seems that, to get debris into orbit from an impact, there has to be some kind of interaction between the pieces of debris.
Maybe I'm starting to answer my own question here. It seems pretty unlikely that anything could go into sustained lunar orbit. Perhaps it's more likely that some debris might exceed lunar escape velocity and end up in some sort of Earth or Solar orbit?
