LightSail 2 proved flight by light is possible, now passes the torch to NASA

The Planetary Society’s LightSail 2 spacecraft finally went out in a blaze of glory as it reentered the Earth’s atmosphere last week on Nov17, months after it was initially expected to do so.

LightSail 2 was the first mission to successfully demonstrate solar sail technology, or flight by light, in space. Shortly after launching in the summer of 2019, the LightSail 2 mission used a 32-square-meter (244-square-foot) sail made out of mylar to raise a small CubeSat spacecraft’s orbit by 1.9 miles (3.2 km).

The Planetary Society originally expected the spacecraft to stay in orbit for less than a year, but it circled Earth for almost three and a half years. Now, the team will crunch the data from their mission and share the results with the world.

“The LightSail 2 team has a lot to do over the coming months assembling and analyzing data from the entire mission and publishing and sharing the results,” LightSail 2 program manager Bruce Betts told IE in an interview. 

The historic solar sail project has paved the way for a host of NASA missions that will fly by light, including one that just launched aboard the space agency’s Artemis I moon mission.

LightSail 2: Historic solar sail mission finally reenters Earth’s atmosphere 

LightSail 2 launched to orbit aboard a SpaceX Falcon Heavy rocket in July, 2019. The mission far outlived initial expectations, with Planetary Society CEO Bill Nye (of Bill Nye the Science Guy fame) telling IE in a February interview that LightSail 2 far exceeded his expectations.

Now, the tiny LightSail 2 spacecraft has finally burned up in Earth’s atmosphere. On Friday, November 17, the Planetary Society released a statement explaining that the toaster-sized spacecraft had succumbed to the effects of atmospheric drag.

"I feel a mixture of sadness at the loss of our spacecraft, although it was always expected, as well as pride in what we’ve accomplished,” Betts explained, “and a sense of anticipation of the coming months of analyzing data from the mission and sharing our results.”

The LightSail 2 solar sail concept was inspired, in part, by Carl Sagan, who promoted the idea on ‘The Tonight Show’ with Johnny Carson in the 1970s. Sagan was Planetary Society CEO Bill Nye’s professor at Cornell University, and the latter worked alongside numerous other Planetary Society members and crowd funders to realize Sagan’s vision. 

Betts also highlighted the community aspect of the LightSail 2 mission, which was largely crowdfunded with the participation of more than 50,000 Planetary Society members, Kickstarter backers, private citizens, foundations, and corporate partners. 

“I am proud that using a small team on a limited budget, we were able to achieve the challenging goals of the mission thanks in large part to the support of 50,000 individual donors,” he explained.  

The fruits of that collaboration came to light on August 7, 2019, when the Planetary Society announced that LightSail 2 had raised its orbit around the Earth to as high as 729 kilometers in the two weeks since it had been deployed. This means the spacecraft was able to raise its orbit by 1.9 miles (3.2 km) in total using only sunlight. 

What next for LightSail 2 and the Planetary Society?

Now that the spaceflight portion of the LightSail 2 mission is complete, the Planetary Society will work hard to compile all of its results and reveal its findings to the scientific community and the public. Even before the spacecraft’s atmospheric reentry, the organization had already passed on the baton to NASA, which has several light sail missions in the works.

“Having achieved our main goals, including demonstration of controlled solar sailing in a small spacecraft, raising the profile of solar sailing, and involving the public in space exploration, we have no plans going forward for another LightSail mission,” Betts said. 

“We have a Space Act Agreement with NASA that facilitate sharing of data and lessons learned between our team and their teams,” Betts continued. “Periodically, throughout the development and testing of our spacecraft as well as during flight, we would meet with or otherwise communicate with the relevant people on their teams, sharing information and discussing things.” 

LightSail 2’s legacy

Though light, which is made up of photon particles, doesn’t have mass, its momentum can be transferred over to a light solar sail, which can gradually lift a light CubeSat spacecraft and overcome the effects of atmospheric drag for a surprisingly long period of time, as demonstrated by the LightSail 2 mission.

The proof-of-concept mission has fueled a collaboration between the Planetary Society and NASA, with the space agency launching its first solar sail mission, NEA Scout, just last week aboard Artemis I. That mission is on course to chase down the smallest asteroid ever studied by a spacecraft.

NASA is also working on its Solar Cruiser and ACS3 missions to study the Sun and larger solar sail technologies, respectively, and several early-stage concept missions. “We look forward to the advances that will now come from NASA missions to take the next steps in solar sailing,” Betts explained, adding that the door is completely shut for another Planetary Society solar sail mission. “We do have a new completed grants program open to any topic consistent with our core enterprises, so only time will tell if solar sail-related projects get selected from the program.”

The LightSail 2 mission proved once and for all that it is possible to propel spacecraft using sunbeams. Now NASA will test the technology to its limits and chase a small asteroid in the process. One day that technology could even propel a spacecraft beyond our Solar System to intercept what some believe to be alien technology out in the far reaches of the cosmos.