A project to develop an innovative solar sail has advanced to the final leg of a NASA research program. Phase three of the Innovative Advanced Concepts program (NIAC) will allow researchers to continue exploring and developing a diffractive solar sail for two years with a funding award of $2 million, reports George Dvorsky for Gizmodo. This award could push the solar sail concept, a long-simmering field of research for space exploration only used a handful of times, towards far wider use.
"As we venture farther out into the cosmos than ever before, we'll need innovative, cutting-edge technologies to drive our missions," NASA administrator Bill Nelson says in a statement. "The NASA Innovative Advanced Concepts program helps to unlock visionary ideas—like novel solar sails—and bring them closer to reality."
In a similar way that a regular sail on a boat uses wind to create motion, solar sails work by using the pressure exerted by sunlight to move through space. When photons of light bounce off the mirror-like surface, their momentum pushes the sail forward in a manner that allows a craft not to use any fuel. Current refractive solar sail designs are large, thin and often limited in what directions they can travel. However, a diffractive solar sail, which uses small grates embedded into thin films, could be smaller, more versatile and steerable, closer in maneuverability to a fuel-powered ship.
The concept of a diffractive solar sail was first selected for NIAC Phase 1 and Phase 2 status in 2019. During those phases and their trials, a team tested several sail materials and developed navigation and control schemes for a potential diffractive lightsail mission to orbit the Sun’s poles, a statement explains. Both phases also had space weathering experiments that tested the sail’s ability to survive the harsh ultraviolet exposure of space, according to a NASA statement from 2019. During phase 3, researchers will optimize the sail material and perform ground tests to prepare for the conceptual solar mission.
Solar sails have a relatively short and checkered history. The nonprofit research organization The Planetary Society attempted to launch the Cosmos 1 probe in 2005 to orbit around Earth, but it didn’t even leave the planet due to a rocket failure. The government of India launched small solar sail-powered missions as accessories on communication satellites in 1992 and 2003. The Japanese Exploration Space Agency (JAXA) successfully launched the IKAROS spacecraft, deployed with a solar sail, in 2010, to study Venus and the Sun. Since then, NASA and the Planetary Society have both launched successful solar sail-powered crafts into low-earth orbit.
“Diffractive solar sailing is a modern take on the decades old vision of lightsails,” says Amber Dubill, a mechanical engineer at Johns Hopkins University who will lead the third phase, in a NASA statement. “While this technology can improve a multitude of mission architectures, it is poised to highly impact the heliophysics community’s need for unique solar observation capabilities.”