A review of interstellar rocketry fundamentals.
To reach even the nearest stars in a human lifetime requires a ship speed that is a substantial fraction of the speed of light.  This means an enormous kinetic energy investment in the ship and suggests that maximizing the efficiency may be more important than minimizing the mass ratio.  This paper develops the pertinent relativistic rocket equations and finds the conditions for high kinematic efficiency.  Using the limiting efficiency of 100%, the minimum energy needed for one-way and for round trip voyages, and to explore all "good" suns out to a given distance, using pre-fueled rockets, is determined.  Savings due to refueling the rocket (and reloading propellant) at the destination and in flight are both somewhat greater than 2:1.
Oliver
B M
BM
NASA Ames Research Center, Moffett Field, CA 94035, USA.
D008433:Mathematics; D008962:Models, Theoretical; D013026:Space Flight / Q000191:economics / Q000295:instrumentation*; D018531:Spacecraft / Q000191:economics / Q000295:instrumentation*