The Planetary Society will make its second attempt at solar sailing when its LightSail-1 reaches orbit. Supported by donations from its member, the LightSail project will send a series of solar sail-propelled CubeSats into space to test the technology of solar sailing.
A constant stream of photons and particles - the solar wind - stream from the Sun every second. This creates a weak, but constant, force on everything it strikes. The solar wind creates the tails of a comet as it carries away the dust and gas boiling off the comet’s core. A solar sail takes advantage of this pressure to propel spacecraft without rockets or propellant - the Sun itself is the fuel tank. The weak force of the solar wind striking the sail pushes the spacecraft away from the Sun. Compared to the crushing forces of a rocket launch, the push on a spacecraft’s solar sails are almost nothing. But almost nothing adds up. Rockets can only burn for a few seconds or minutes. Solar sails work all the time and can take you anywhere in the Solar System and beyond. The only catch is you need a very large sail and a very light spacecraft.
The Planetary Society made the world’s first solar sailing attempt in 2005 with its 100 kilogram Cosmos-1. After launch, a 600 square meter sail was supposed to unfurl and begin the mission of testing solar propulsion. Unfortunately, the submarine-launched Volna rocket malfunctioned and the Planetary Society lost its spacecraft. Five years later, the Planetary Society revived its solar sailing plans with the LightSail project. The new project adopts the smaller, lighter CubeSat-based design of Nasa’s NanoSail-D spacecraft. The 5 kilogram spacecraft will use a 32 square meter Mylar sail. Once in orbit the project’s planners will test solar sail maneuvering techniques. The next mission, LightSail-2, will use the solar wind to raise the spacecraft to a higher orbit. LightSail-3 will carry the spacecraft all the way to the Sun-Earth Lagrange 1 region where the gravitational pull from the Earth and Sun balance each other.
Nasa added LightSail-1 to its CubeSat Launch Initiative in 2011. That gives the Planetary Society’s members a free ride into space, but of course there’s a catch. The LightSail Project’s program director, Louis Friedman explained in the announcement of the Nasa award:
Our launch requirements are a bit more difficult than typical Cubesats because we want to go to a high enough altitude so that our sail will feel no atmospheric effects; being manifested on NASA’s list will help our chances greatly.
The Planetary Society is still waiting to hitch a ride on a rocket heading to the 800 kilometer orbit, but amateurs can afford to be patient.