[bigiain]

I just thought of an easier (and probably achievable) thought experiment.

Imagine a fighter jet flying circles around an airliner as it follows it along - with the fighter pilot flying at just the right radius and speed that it's accelerating at 1 gee for the turn (so they'd be "feeling" 2 gee as they pass under the airliner, and zero gee as they loop over the top of the airliner) using a helical "barrel roll" path - and at the same time "keeping up" with the airliner along it's path, so if you were sitting in the airliner looking out it'd look like the fighter was flying circles around the long axis of the fuselage.

Now imagine the fighter pilot does the same trick following the vomit comet - as it flies its parabolic arcs which gives it's occupants 20-30 secs or so of "zero gee".

https://en.wikipedia.org/wiki/Reduced-gravity_aircraft

[mhandley]

However, if you keep flying 1G after exiting that parabolic barrel roll, you're going to make a hole in the ground. The vomit comet usually does a 3G pull up afterwards. You've got to exceed 1G, either to enter the parabolic arc from level flight, or to leave it to regain level flight, or more likely, both.