Interstellar travels aboard radiation-powered rockets

TL;DR

This paper models high-velocity interstellar travel using radiation-powered rockets and light sails within general relativity, highlighting the immense energy requirements and relativistic effects experienced during such journeys.

Contribution

It applies Kinnersley's solution to analyze relativistic kinematics and celestial deformation for radiation rockets, providing new insights into energy costs and relativistic phenomena in interstellar travel.

Findings

A Proxima Centauri flyby with a laser sail requires about one day of 1 GW energy.

Sending a 100-ton rocket to the nearest star needs over 15 times current global energy production.

Relativistic aberration and Doppler effects differ from special relativity predictions at high velocities.

Abstract

We model accelerated trips at high-velocity aboard light sails (beam-powered propulsion in general) and radiation rockets (thrust by anisotropic emission of radiation) in terms of Kinnersley's solution of general relativity and its associated geodesics. The analysis of radiation rockets relativistic kinematics shows that the true problem of interstellar travel is not really the amount of propellant, nor the duration of the trip but rather its tremendous energy cost. Indeed, a flyby of Proxima Centauri with an ultralight gram-scale laser sail would require the energy produced by a 1 GW power plant during about one day, while more than 15 times the current world energy production would be required for sending a 100 tons radiation rocket to the nearest star system. The deformation of the local celestial sphere aboard radiation rockets is obtained through the null geodesics of Kinnersley's spacetime in the Hamiltonian formulation. It is shown how relativistic aberration and Doppler effect for the accelerated traveller differ from their description in special relativity for motion at constant velocity. We also show how our results could interestingly be extended to extremely luminous events like the large amount of gravitational waves emitted by binary black hole mergers.