As environment enthusiasts urge capitalists across the globe to take steps to combat the problems due to climate change, solar sails are quietly emerging as the future of the aerospace industry. Essentially reflective sheets that harness solar energy, solar cells save fuel and can also provide manoeuvrability to the spaceships of the future.
The concept isn’t new. Astronomer Johannes Kepler mentioned solar sails nearly 400 years ago, when he observed that it can produce force as much as the terrestrial sails that trap wind power to propel ships. Read this post to find more about solar sails and their future.
How do Solar Sails work?
Solar Sails first capture the energy from the sun’s light particles that bounce off a reflective surface. While the photons are themselves conventionally massless, they still possess relativistic mass. In other words, they possess kinetic energy by virtue of their motion. Each of the billions of photons that hits the sheets transmits energy to the reflective sheet at a small yet constant rate. These sheets are 40 to 100 times thinner than normal paper and are spread over large fields.
As per the scientists in Argonne National Laboratory, the momentum generated is enough to not just move a spacecraft but also attain very high speeds. Solar energy is a practically limitless energy source, able to provide energy for solar cells to hover at a lower cost when compared to contemporary fuel-based propulsion systems.
Why Solar Sails?
The biggest advantage of solar sails is that they feature very few moving parts. This reduces cost and improves longevity. This can also aid in reducing the space debris cloud that blankets the earth. The light weight of the sail can also help replace the heavy propellants we need for deorbiting systems. This way the payloads can be allowed extra mass or to increase the satellite’s longevity. Solar sail spacecrafts can accelerate throughout their journey, unlike conventional propellant-run rockets.
Ikaros was the first of its kind solar sailing spacecraft, which unfurled its sail by using the spinning momentum in 2010. The second upcoming project is being planned by The Planetary Society, LightSail 2. Pressure will be used to propel this spacecraft to low-Earth orbit. The third project is by the Planetary society as well. A shoe sized British satellite expected to launch in 2020 will examine a solar sail’s capability as an atmospheric brake and conclude in a fiery plunge.
The Future of Solar Sails
The primary disadvantage of using solar sails in deep space is when spaceships are placed away from the sun. The farther the sun, the fainter is the solar light and the weaker is the push. They can be used only at an altitude of 800 km or more i.e higher than the troposphere, Stratosphere, the Mesosphere, Thermosphere and 100km into the Exosphere. Temperature also limits the use of solar sails as it impacts the angle of the sail and its reflective capability.
Solar Sails on satellites have still not been put into use as the primary source for propulsion. The Japanese Aerospace Exploration Agency (JAXA) and the American Planetary Society are planning to launch missions powered solely by solar sails. The success of these missions would help other aeronautics and aerospace organisations develop the bold foresight required to shift from rudimentary use of the method to the primary energy source. With a variety of applications – ranging from asteroid scouting to deliveries to and from Mars – solar sails can become the most viable option available in coming years. The tech could also pave the way for future hybrid space engines and exhibit itself to other aerospace organisations as a more reliable fallback technology.