Diffractive solar sails / NASA-supported concept; materials and mission-design research

Steering a spacecraft by bending sunlight

Sunlight carries momentum. Redirect it with a sufficiently light sail and the repeated tiny pushes can alter a spacecraft's motion. A diffractive solar sail adds an optical twist: microscopic gratings in a thin film would steer the light, giving engineers another way to control the direction of that push.

A conventional reflective sail changes its orientation to change its thrust. The diffractive concept aims to produce a useful sideways force while keeping the sail facing the Sun. Researchers have also explored switchable optical elements, which could change how light is redirected. The proposed benefit is more freedom to navigate while continuing to collect sunlight, rather than relying entirely on turning a huge sheet.

One proposed destination is an orbit passing over the Sun's poles, a demanding journey for conventional propulsion. A constellation there could study the solar corona and magnetic fields from valuable new viewpoints. NASA selected the project for a third phase of concept development in 2022, following earlier material tests and navigation studies. The work supports a possible future demonstration, not an already flying fleet. Its appeal is simple: the same light scientists want to study could help carry their instruments into position.