What is a solar sail?

A solar sail is a spacecraft propulsion system that uses radiation pressure from sunlight to push a spacecraft forward. It is a type of spacecraft that captures and uses the energy of photons from the sun to produce propulsion. The idea of using solar radiation pressure for propulsion was first proposed by Johannes Kepler in the seventeenth century. It was later studied and developed by various scientists and engineers.

The solar sail consists of a large, thin, reflective sail made of a material that reflects sunlight, such as Mylar or Kapton. The sail is typically stretched out by four or more booms, which keep it taut and oriented toward the sun. When sunlight reflects off the sail, it exerts a small force on the sail, known as solar radiation pressure. This force can be used to propel the spacecraft, much like a sailboat is propelled by wind.

Solar sails have the potential to provide an efficient, lightweight, and long-lasting means of propulsion for spacecraft. They can reach much higher speeds than traditional chemical rockets, and are not limited by the amount of fuel they can carry. NASA and other space agencies have tested and launched several solar sail spacecraft, including IKAROS, which was launched in 2010, and the Planetary Society's LightSail 1 and LightSail 2 missions.