I was doing some internet research on the idea of using nuclear reactors for cargo ships, and a couple of sites I found discussed the possibility of building fast cargo ships (> 30 knots) that would run on nuclear power so that they wouldn't face the economic difficulties with fuel price. E.g. http://onlinepubs.trb.org/onlinepubs/archive/marineboard/fall08/cushing.pdf" [Broken]'s an example of a conventional ~30 knot design that ran into trouble because of fuel costs. I was wondering, suppose we did switch to nuclear powered cargo ships in the future (maybe when oil runs out), would one expect to see a general across the board decrease in ocean shipping times as a result? I understand the uranium is a very small part of the cost of a nuclear vessel (http://nuclearinfo.net/Nuclearpower/WebHomeAvailabilityOfUsableUranium" (thousands of dollars a day in fuel costs with oil). Are the speeds of modern cargo ships limited mainly by fuel/energy costs, or other factors like the cost of equipping them with more powerful engines?