NASA's new solar sail design bends light to propel spacecraft efficiently

NASA's new solar sail design bends light to propel spacecraft efficiently
An artist's impression of the new Diffractive Solar Sail
An artist's impression of the new Diffractive Solar Sail
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An artist's impression of the new Diffractive Solar Sail
An artist's impression of the new Diffractive Solar Sail

NASA has selected a fascinating new project for further development, known as the Diffractive Solar Sail. By bending light before it hits the sail, this device could propel spacecraft more efficiently than conventional propulsion technologies.

In the age of chemical rockets and ion thrusters, it seems rather quaint to unfurl a giant sail and coast through the cosmos, but that could be a viable method of propulsion. Solar sails propel spacecraft by tapping into the pressure exerted by sunlight, as photons bounce off the surface. That force is quite small, but with a big enough surface area, light enough materials and plenty of patience, it can build up to drive and steer a spacecraft.

The idea has been discussed for decades, and even tested in space multiple times, starting with Japan’s IKAROS space yacht in 2010. More recently, the Planetary Society’s LightSail 2 demonstrated how sunlight could be used to alter the orbit of a spacecraft using a solar sail.

The technology still has room for improvement, however – solar sails generate the most thrust when the sunlight is hitting them straight on, which limits the direction they can travel and how well they can maneuver. The new Diffractive Solar Sail concept is designed to improve the efficiency of harvested sunlight.

As the name suggests, the tech is based on the phenomenon of diffraction. Essentially, as light waves pass through a small gap, they begin to spread out in a fan shape on the other side of the barrier. To tap into that, the Diffractive Solar Sail would be made with small gratings embedded in thin films, spreading out the sunlight that hits them. The end result is a more efficient and maneuverable spacecraft.

The project team says that this technology would allow spacecraft to reach places that others haven’t been able to. For example, they suggest that a constellation of them could be placed into orbit around the Sun’s poles to improve forecasts of space weather.

The Diffractive Solar Sail project has been selected as part of Phase III of the NASA Innovative Advanced Concepts (NIAC) program. The team will get to work optimizing the material of the sail itself, and perform ground tests to prepare the design for future space missions.

“As we venture farther out into the cosmos than ever before, we’ll need innovative, cutting-edge technologies to drive our missions," said NASA Administrator Bill Nelson. "The NASA Innovative Advanced Concepts program helps to unlock visionary ideas – like novel solar sails – and bring them closer to reality.”

Source: NASA

so... the sunlight still TOUCHES some part of the Solar Sail then. what an entirely misleading title, this is nothing more than advancing different forms of fiber optics. and here I thought we might actually have been bending the light before contact with like maybe some kind of charged field or something, pathetic_meme.bmp.
Not much detail on the theory. Maybe it allows more photons to exit perpendicular to the sail. The more of an angle away from the sun, the greater the increase in efficiency over plain reflection, but the sail is still much less efficient, since it intercepts fewer photons, but is also much heavier, due to the second layer of material. I certainly don't see why this is likely to be a really worthwhile investment.
“As we venture farther out into the cosmos..." we'll encounter less and less light !
Ralf Biernacki
@ARF: Technically, diffraction bends wavefronts that pass through a *gap*; so yes, bending without touching. The touching comes later. Creepy_Wonka_meme.jpg