starsails

Starsails are propulsion concepts for spacecraft that use momentum transfer from starlight or stellar particle streams to produce thrust without carrying propellant. They encompass a family of technologies designed to convert energy from stars into spacecraft acceleration, extending the idea of solar sails to a broader astrophysical context.

The most developed subtype uses photons from a star reflecting off a highly reflective, low-mass sail to impart momentum, producing continuous acceleration proportional to radiation flux and sail area. In regions closer to a star, the thrust is greater; at interstellar distances, solar radiation becomes weak, requiring very large sails or long durations.

Alternative or complementary approaches exploit stellar winds or cosmic plasma; magnetic or electrostatic sails could capture momentum from charged particles in stellar winds; plasma sails may require ultra-thin films and active control to manage collisions and erosion.

Current status: not yet fielded beyond small demonstration missions such as JAXA's IKAROS (2010) and The Planetary Society's LightSail series, which demonstrated deployment and basic thrust in near-Earth environment. Most starsail concepts remain in theoretical or experimental development, with challenges including materials durability, deployment at scale, sail pointing accuracy, and onboard energy budgets.

Impact and research: Starsails could enable long-duration, propellant-free interstellar or interstellar-proxy missions, as well as economical solar-system reconnaissance. They are typically discussed alongside solar sails, solar wind sails, and magnetic sails in propulsion literature; continued research focuses on materials science, sail architecture, and testbeds.