Question

A rocket propels itself rectilinearly by emitting radiation (i.e. photons with velocity c) in the direction opposite to its motion. It continues to do so until it attains a velocity V relative to its initial rest-frame. Find the ratio of the initial to the final rest-mass of the rocket considering just the 4-momentum at the beginning and at the end of acceleration.

Answer 1

Equate energies and momenta at the beginning and at the end of the acceleration of the emitted photons.