Relativistic Drag Emerges for Laser-Driven Solar Sails at 0.75c
A new arXiv study shows that as a laser-driven solar sail nears relativistic speeds, Doppler shifts weaken thrust and, around 0.75c, relativistic aberration makes diffusely scattered light act as drag—reducing propulsion efficiency even though overall thrust stays positive. The model uses an idealized mirror and omits nonradiative effects like heating and interstellar gas, with real sails potentially facing material limits; advanced metamaterials could help mitigate some challenges and help stabilize the beam.