 Some more advanced flying saucers capable of spaceflight have been proposed, often as black projects by aeronautics companies.The Lenticular Reentry Vehicle was a secret project run by Convair for a saucer device which could carry both astronauts and nuclear weapons into orbit; the nuclear-powered system was planned in depth, but is not believed to have ever flown.More exotically, British Rail worked on plans for the British Rail "Space Vehicle" a proposed, saucer-shaped craft based on so far undiscovered technologies such as nuclear fusion and superconductivity, which was supposed to have been able to transport multiple passenger between planets, but never went beyond the patent stage.