This novel solar sail could make it easier for NASA to stare into the sun Is diffraction

Solar power has long been wanted as a source of energy for cars throughout the world, and NASA is now one step closer to using it to explore the universe. The Diffractive Solar Sailing Project, directed by Amber Dubill of Johns Hopkins University's Applied Physics Laboratory in Laurel, Maryland, aims to enable spacecraft such as probes and satellites to sail long distances using only sunlight. This would be the first of its kind lightsail.

The project was chosen for NASA's Innovative Advanced Concepts (NIAC) program's third and final phase, which assists in the development of promising concepts for scientific, government, and commercial application. The team will receive $2 million to continue developing its system for another two years in order to establish its usefulness ahead of a future mission. Since the program began in 2012, this is the fifth project to achieve Phase III.

Solar sails, like sailboats propelled by the wind, use the pressure of sunlight to drive themselves across space, eliminating the need for rockets and fuel. However, diffractive lightsails, such as the one developed by Dunbar's team, go beyond the traditional design of reflecting lightsails. Reflective lightsails must gather and redirect solar rays, which necessitates coating them with a metal-like sheet and orienting them in the direction of the sun at all times. Because there is a continual balance between energy collection and agility, this reliance restricts navigation. Reflective sails are also huge, thin, and unstable due to their design. The technology required to stabilize and position the sails eventually causes the spaceship to slow down.

Diffractive sails aren't like other sails. Light spreads out in diverse directions when diffracted via small holes rather than reflected across large surfaces. The team uses minuscule gratings built into the surface of the diffractive sails to take use of this quality of light by scattering light to where it's required, even if the sail is at a suboptimal angle or not directly facing the sun. As a result, the spacecraft can maneuver more quickly and efficiently. Solar sails may be smaller, consume less electricity, and run at cheaper prices thanks to this design—all without compromising power.

Dubill compares the notion to genuine sails on a boat. If you wanted to steer into the wind with a reflecting sail, you'd have to shift it back and forth to get it to travel in the right direction. You could harness the power of the wind to propel you forward while also rushing straight into it if you had something similar to a diffractive sail.

“[This design] is the novel part. It’s more efficient and gets around previous lightsail issues,” Dubill says, adding that the researchers concluded that the technical effort to replace reflecting lightsails with diffractive lightsails was “well worth it” and that “the benefits far outweigh the cost.” 

During Phase III, the team will work with Dubill to strengthen the metallic substance of their solar-ray collector and conduct ground testing. She believes they're setting the framework for a constellation of lightweight diffractive lightsails carrying scientific instruments to orbit around the sun's poles in the future. While the Solar Orbiter of NASA and the European Solar Agency recently obtained high-resolution photographs of the sun, no direct images of the poles have ever been taken.

“There’s a lot about the sun that we don’t know. This technology can play a big role in monitoring the complexities of solar weather,” adds Dubill. “[Our team] has been working on this project for so long; it’s exciting to see it have this opportunity in the future of flight missions.”

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