re: Pipelauncher redux
One thing I was thinking about recently was the idea of using pipelaucher as way to provide a large space for Zero gravity for film purposes and I suppose other kinds of uses. One would probably be limited to about 10 secs of free fall and one would need to add some modifications to do this. But the limit of time in Zero gee could offset by capability of having a very large volume of space one could use.
One could make a pipelaucher specifically for this, or it could be something which gave additional use of a pipelauncher which launched rockets.