NASA solar sail tech is ready – now who's up to use it in a mission?

Ready for cruising: successful deployment leaves the ball in the scientists' court

NASA says its latest take on solar sail technology is ready for proposals for it to be flown on science missions.

The announcement comes after a quarter of the sail was unfurled, demonstrating that the deployment technology works as expected. The system is now at Technology Readiness Level (TRL) 6, meaning it is an option for scientists considering space missions.

Solar sails resided in the realm of science fiction for decades. According to NASA, Les Johnson, a technologist at the NASA Marshall Space Flight Center, was "riveted" by Jerry Pournelle and Larry Niven's 1974 novel The Mote in God's Eye, which features a spacecraft propelled by a solar sail.

Johnson has since spent a good chunk of his career – the last 25 years or so at Marshall – involved in developing the technology. Now that it's reached TRL 6, the solar sail is fit for inclusion in mission proposals.

"What's next is for scientists to propose the use of solar sails in their missions. We've met our goal and demonstrated that we're ready to be flown," said Johnson.

Solar sails have been successfully demonstrated in space before. The JAXA IKAROS mission showed that the technology worked during a five-year mission that ended in 2015. However, the IKAROS solar sail, which measured 2,110 square feet when unfurled, was considerably smaller than the fully deployed 17,780 square feet of Johnson's sail.

Johnson told The Register that whereas IKAROS was primarily a deployment-only demonstration, the "Solar Cruiser is designed to provide much more thrust [and] enable precision navigation through space from deployment to a specific location (be it a planet, moon, asteroid, or location in deep space.)"

He also noted that approaches had been made concerning the use of the technology in potential upcoming missions, but he could not share more due to the competitive nature of the proposals.

Other examples of solar sail technology demonstrators include NASA's NanoSail-D, which was lost in the failure of a SpaceX Falcon 1 vehicle. A ground spare, NanoSail-D2, was subsequently launched in 2010. More recently, the Planetary Society launched its LightSail spacecraft, and the final incarnation – LightSail-2 – was launched in 2019.

Solar sails work using the radiation pressure of sunlight on large surfaces. While lacking the immediate bang of chemical propulsion, a sufficiently large sail could produce propulsion comparable to the electric engines favored by modern uncrewed space missions.

There is a lot to be said for the technology. It doesn't require any fuel, and the cumulative effect of a low level of thrust (compared to chemically powered engines) over a long period is very attractive to mission planners.

In the NASA post, Johnson explained: "Once you get away from Earth's gravity and into space, what is important is efficiency and enough thrust to travel from one position to another."

"A solar sail achieves that by reflecting sunlight – the greater the size of the sail, the greater thrust it can provide."

Missions that would see the most significant immediate benefit from the technology would involve spacecraft venturing close to the Sun to take advantage of the enhanced thrust a solar sail would receive.

Johnson also spoke of using space-based lasers, aiming their beams at solar sail-equipped spacecraft to venture beyond the solar system.

El Reg fears that we might be a good few years away from realizing that particular concept. ®

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