Suppose you build one of these things. After you get some Unobtanium to build the Dyson Cap, of course. You accelerate to 72% of the speed of light in five years. And, then the power source thingy, having used up all it’s energy, ‘evaporates’. Then a few years later, you get where you want to be. How do you stop?
it would seem that you would need to start deceleration about the time you got up to top speed. I think it’s supply of matter would come from space itself. It’s rich in hydrogen, helium, carbon and other elements. Guy named Bussard proposed collecting free hydrogen with magnetic fields to use as a fuel source.