This is my first post to the physics forum and I see my input is well needed. First off Fossil fuels are like fossils they are history. We cant even get into orbit with out tons of the stuff. O2 as a fuel Is just a band-aid on a larger problem. Sure it is lightweight such as hydrogen but since space is a void any depleatable resource would be inefficient and therefore useless. Nuclear Propulsion as we know it may be perfect for an underwater stay in a military submarine but that technology is to crude and still in it raw form. Maybe in the future larger spaceships or commercial space programs my investigate Nuclear Propulsion but a reactor in a spacecraft is just not a bright idea. My favorite theory would be magnetic repulsion. You see examples of that in levitation experments and high speed trains. See my theory is based on the same principle we use today in space travel. You use the majority of your fuel during takeoff, but once in orbit you only need minimum thrust to propell an object and without any external forces acting upon the vehicle the only forces acting on the craft would be magnetic repulsion. But there is more to it than that. Or is it?