Pros and cons of relativistic interstellar flight.

Abstract Two technological problems must be solved before daring to interstellar flight: fuel and propulsion. The highest energy-density 'fuel' is antimatter in its solid or liquid state and this fuel is likely to be our primary choice for multi-ton relativistic rockets. High-energy ion thrusters powered by annihilation reactors promise superior performance in comparison with direct propulsion by annihilation products. However the power generator onboard can significantly enlarge the rocket dry mass thus limiting the achievable speed. Two physical factors that stand against our dream of the stars are thermodynamics and radiation hazard. Heat-disposing radiator also increases the rocket dry mass. Interstellar gas turns into oncoming flux of hard ionizing radiation at a relativistic speed of the rocket while the oncoming relativistic interstellar dust grains cause mechanical damage. Economy and psychology will play a decisive role in voting for or against the manned interstellar flights. Highlights • Technical challenges are discussed. • High-energy ion thruster is our only option. • Achievable rocket speed as a function of exhaust mass is estimated. • Limiting physical and social factors are indicated. • Robotic rocket is argued to be preferred. [ABSTRACT FROM AUTHOR]