Solar Sails Hit Photon Drag at 75% of Light Speed as Relativity Cuts Laser Thrust
Updated
Updated · ScienceDaily · Sep 2
Solar Sails Hit Photon Drag at 75% of Light Speed as Relativity Cuts Laser Thrust
1 articles · Updated · ScienceDaily · Sep 2
Summary
A new arXiv study finds laser-driven solar sails begin suffering drag at about 75% of light speed, when diffusely scattered photons start pushing against the craft instead of helping accelerate it.
Relativistic Doppler shift already weakens thrust as the sail speeds away from the laser, and light aberration then redirects scattered radiation forward, creating an opposing force that sharply reduces propulsion efficiency.
The total force remains positive because direct incident light and specular reflection still push the sail forward, but the paper says continued acceleration becomes much less effective at relativistic speeds.
The model uses an idealized mirror and excludes interstellar gas, dust, spacetime curvature and thermal limits, leaving open whether advanced metamaterials or photonic crystals could mitigate or exploit the effect in future interstellar probes.