Orion drive and related physics in Science & Spaceflight Posted February 20, 2016 4 minutes ago, SomeGuy123 said: Why bother? As your vehicle picks up speed, even if it worked, you'd very rapidly leave the range of your laser. It would be very short range because once the light intensity drops below the threshold for fusion you stop getting any thrust. I think you missed the point. I suggested a laser ground array to initially ignite the first pellet, but after that, the light from the fusion of the first pellet is supposed to ignite the next one using a parabolic mirror which doubles as the exhaust bell.