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Theoretical study finds light aberration creates drag on solar sails at 75% light speed

Researchers calculate that relativistic effects reduce propulsion efficiency for laser-driven interstellar probes approaching relativistic velocities.

Updated Sep 2, 2026 · 15:18 UTC1 reports

The short version

  • A research paper by Harbin Institute of Technology scientists finds that laser-pushed solar sails encounter a radiative drag effect once they reach roughly 75% of the speed of light.
  • The phenomenon is caused by relativistic light aberration, which redirects diffusely scattered photons forward and exerts an opposing force on the craft.
  • Coupled with Doppler redshift, this effect reduces overall propulsion efficiency, though the net force from the laser remains positive.
  • The theoretical model relies on idealized mirrors, leaving practical material limits and interstellar dust collisions to be resolved by future engineering.

Key facts

  • Harbin Institute of Technology researchers Chao Shen and Jiaze Li published a theoretical paper on arXiv examining the radiative dynamics of relativistic lightsails.[ScienceDaily]
  • The study calculates that at approximately 75% of light speed, relativistic light aberration causes diffusely scattered photons to be emitted forward relative to a stationary observer, generating an opposing drag force.[ScienceDaily]
  • A progressive Doppler shift decreases the incoming light frequency as the sail accelerates away from the laser beam, lowering thrust efficiency.[ScienceDaily]
  • The net force on the lightsail remains forward-directed because incident light and specular reflection still outweigh the drag caused by diffuse scattering.[ScienceDaily]

What remains uncertain

  • The research models the solar sail as an idealized mirror and does not account for real-world material thermal limits, laser-induced melting, or collisions with interstellar gas and dust.[ScienceDaily]
  • It remains untested whether proposed advanced metamaterials and photonic crystals can effectively stabilize trajectories or leverage aberration effects in actual flight conditions.[ScienceDaily]

Sources