LightSail 2 has successfully deployed their solar sails as confirmed by The Planetary Society in a tweet which showed the deployment of their sails and that the spacecraft was sailing with sunlight as the propulsion source. We can now explore and wonder how solar sails will fit into humanity’s plan for space exploration.
— Planetary Society (@exploreplanets) July 24, 2019
The Planetary Society is the world’s largest non-profit space organization. LightSail 2 was their third spacecraft which launched on June 25 and has been orbiting since then, sending the pictures of Earth. The sail of LightSail 2 is a system of 4 smaller triangular sails which combine to form one large square around 32 sq. meters. After the deployment, it can be used for raising the spacecraft’s orbit and demonstrating the power and usefulness of solar sails. After receiving some telemetry from the tiny satellite, it showed the motor count to be rising and the cameras were active.
The idea of the Solar Sail is relatively simple in theory. A solar sail utilizes the momentum of the photons which reaches from the sun just like how a sailboat gains energy from the wind. The photons bounce off from the reflective surface and propel the sail as it is lightweight. Although it uses simple technology, it has great potential.
There is no resistance to the momentum due to vacuum in the space and as more and more photons bounce off, it leads to greater speeds and this can be achieved without any fuel or propulsion system. It is similar to that of a boat, the sail can be aimed at angles to direct the travel of spacecraft. If the sails are aimed at the sun, the spacecraft will directly propel away from the sun. By changing the angles it can steer and propel itself through the solar system. They keep gaining speed and momentum as they travel and can accelerate as long as photons hit the sail. It can achieve speeds which a chemical rocket could never reach, although they cannot escape the Earth’s gravitational pull on their own.
As it moves further away from the sun, fewer photons will hit the sail but the spacecraft will not slow down but the only rate of acceleration will decrease. It is aimed at long journeys where their simple yet effective system can shine. It is thought that even lasers could be pointed at the sails to increase their acceleration.
The Breakthrough Starshot aims to send a fleet of solar sails to the nearest neighbor star, Alpha Centauri. Rather than being fully dependent on the sun rays, it can be propelled by using an array of lasers. Lasers can accelerate the spacecraft to a velocity close to 60,000 km/s. At this rate, the Alpha Centauri which is 4.37 light-years away will be reached only in 20 years time. Breakthrough Starshot is a project by a Russian billionaire and LightSail is built with money raised from enthusiasts. LightSail 2 is a demonstration mission that shows how a small solar sail can raise the orbit of the spacecraft. There are many obstacles to overcome for commercial applications so that the technology is suitable to explore the Solar System.