Relativistic Spacecraft Propelled by Directed Energy

TL;DR

This paper presents a fully relativistic model for spacecraft propelled by directed energy, analyzing how system parameters and diffraction limit achievable speeds, and discusses photon recycling as a potential method to reach relativistic velocities.

Contribution

It provides the first fully relativistic solution for directed energy propulsion and clarifies misconceptions about causality in previous models.

Findings

Relativistic speeds are achievable with low mass spacecraft.

Diffraction limits maximum spacecraft speed.

Photon recycling may enhance propulsion efficiency.

Abstract

Achieving relativistic flight to enable extrasolar exploration is one of the dreams of humanity and the long term goal of our NASA Starlight program. We derive a fully relativistic solution for the motion of a spacecraft propelled by radiation pressure from a directed energy system. Depending on the system parameters, low mass spacecraft can achieve relativistic speeds; thereby enabling interstellar exploration. The diffraction of the directed energy system plays an important role and limits the maximum speed of the spacecraft. We consider 'photon recycling' as a possible method to achieving higher speeds. We also discuss recent claims that our previous work on this topic is incorrect and show that these claims arise from an improper treatment of causality.