You know, I've thought about this whole thing before. The problem with faster-than-light travel (or lightspeed travel) is that when an object of mass m approaches the speed of light, its mass increases to infinity as does the required energy to reach or maintain that speed. But why does an object need to reach that speed at all? According to the theory of relativity, as an object approaches the speed of light, time effectively slows around it. Take for example the old example of an astronaut who travels near the speed of light for a year and returns to earth to find all his friends in retirement homes. If that's the case, traveling slower than the speed of light technically results in faster-than-light travel times, right? I suppose this method would dramatically reduce the energy expenditure though. I'd be curious to know what "causes" that bubble to form.