I don't have a massive problem engineering wise from the layout. I agree that for some scenarios that configuration makes sense. In terms of precession. Doesn't really come I to it. What it isn't like is the movie starship enterprise. It doesn't zip I to orbit and go from warp 9 to orbit in no time at all. Starting and stopping the rotating section would be done over a long time period. You don't really make aggressive turns in space. The trajectory is for the most part a section of an elongated solar orbit. Ion engines make sense in terms of energy source. If you use nuclear what you have is electrical energy. The other option would be a nuclear drive, but we don't really have one yet so may void the idea of using current tech" Really the problem is money rather than technology. I am sure a ship that can travel as fast as this one, and is as big as this o e would end up looking quite different to this concept. However that is not really the issue. The issue is money.