Velocity curves for a 1 g bare spacecraft with varying sail thicknesses. We assume the optimal case where ﹩{m}_{s}={m}_{0}﹩ and a 10 km, 100 GW DE system. The three trajectories are identical early on when they are all in the ﹩x\lt {L}_{0}﹩ regime and are completely determined by Equation (11). As each sail subsequently moves into the ﹩x\gt {L}_{0}﹩ regime, diffraction effects become important and the spacecraft quickly approaches a terminal speed. Thin sails ∼0.01 μm allow for highly relativistic travel at speeds ∼0.5c.