To be honest I had always a lot of thoughts about this how Rama would be filled with air.... I mean it spins, but how Ramas filled it with air? Central Sea was one of sources, but water wasn't possible there before whole Rama being filled with air. So my thinking was always, air enters in the center, goes in all directions, hits surface which is 750 km/h... so ~40% of speed of molecules... how much it "slows down" Rama? Would there be needed some additional force to spin it? How long it would take to "calm down", and build gradient of oxygen/air in Rama...

Always was thinking about writting some simulation for it, but it was always "someday" ;-)

Conservation of angular momentum. Once everything is in it, and it's spun up, it won't stop.