Comet capture and conversion into a space craft might enable fusion rocket craft to obtain gamma factors close to 2 commensurate with velocities on the order of 0.867 C. A billion metric ton comet that was almost pure hydrogen ice might permit an M0/M1 ratio of 100,000 which when substituted into the relativistic rocket equation Delta V = C Tanh [(Isp/C) ln (M0/M1)] where Isp is expressed in units of C and is assumed to be equal to a maximum of 0.119 C for fusion fuel, obtains a velocity close to 0.867 C: All this with a payload of 10,000 metric tons.
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