Science

LightSail 2 spacecraft completes its solar sail mission in a blaze of glory

The LightSail 2 spacecraft will no longer fly on sunlight.

The Planetary Society’s crowdfunded Solar Sailing Vessel re-entered Earth’s atmosphere on Thursday morning (November 17) after nearly 3.5 years in orbit – more than three times its planned mission duration.

Since then, the LightSail 2 team has not received any communications from the spacecraft, leading them to conclude that the shoebox-sized craft has finally breathed its last after completing 18,000 orbits and about 5 million miles (8 million kilometers) around our planet.

“LightSail 2 disappeared after more than three glorious years in the sky, illuminating the ascent path with light and proving that we can defy gravity by deploying a sail in space,” said science communicator Bill Nye, CEO of the Planetary Society. in a statement (will open in a new tab). “The mission was funded by tens of thousands of members of the Planetary Society who want to advance space technology.”

RELATED: LightSail 2 takes stunning photos of Earth from space

LightSail 2 was the first small spacecraft to demonstrate controlled navigation around the solar system, using solar photons to adjust its orbit. (However, LightSail 2 was not the first ship of any type to go into space powered by solar power; the Japanese probe Ikaros did so in 2010.)

While light lacks mass, its individual particles—photons—have momentum that can be transferred to a reflective surface to give it a little push.

According to team members, LightSail 2 has shown that solar-powered sailing is an efficient and viable method of propulsion for small spacecraft, including tiny satellites known as cubesats.

LightSail program manager and chief scientist Bruce Betts wrote in a statement from the Planetary Society. (will open in a new tab) that de-orbiting would always be the fate of LightSail 2, although the fiery end of the mission took longer to manifest than anticipated.

LightSail 2 captured this image of a nearly full moon on October 24, 2021. (Image credit: Planetary Society)

The end of LightSail 2 was a burden

LightSail 2 was launched in June 2019 aboard a SpaceX Falcon Heavy rocket on a year-long mission to demonstrate controlled solar sailing in orbit. He began his work at an altitude of about 450 miles (720 kilometers) above the Earth – just above the orbit of the International Space Station (ISS).

At this altitude, the Earth’s atmosphere is still thick enough to offer little resistance to the spacecraft, and it was this effect that ultimately sealed LightSail 2’s fate.

Due to the large surface area of ​​the ship’s solar sail, which was 244 square feet (32 square meters) – the size of a boxing ring – it experienced more drag than other spacecraft of the same mass.

“Imagine that throwing a stone is comparable to throwing a sheet of paper. Atmospheric drag will stop paper much faster than stone. In our case LightSail 2 is paper,” wrote Betts. “A spacecraft like the ISS is huge, but at the same time massive, more like a stone. But even the ISS has to be rocketed every few weeks to make up for the drag.”

During its third year of operation, when it demonstrated the most efficient solar-powered sailing, LightSail 2 experienced increased atmospheric drag due to increased solar activity. This solar activity warmed the atmosphere, making the area through which LightSail 2 passed denser.

“This was the beginning of the end,” Betts wrote. “As solar activity increased further, solar-powered sailing was unable to compete with the increased drag due to increased atmospheric density.”

LightSail 2 took this image of Florida on December 24, 2021. (Image credit: Planetary Society)

Over the past few weeks, LightSail 2 has been sinking deeper and deeper into the Earth’s atmosphere, experiencing more and more resistance, which in turn has dramatically increased its rate of fall.

“The spacecraft was caught in an ever-increasing snowball effect: as the spacecraft descended lower, the density increased, causing the spacecraft to descend even faster,” Betts writes.

While the LightSail 2 mission may be completed, there is still scientific work to be done. The team behind the mission continues to analyze the data collected by the ship, which remained operational until the very last moment.

This data will also be shared with future space missions that also use solar sails, such as NASA’s NEA Scout, which launched on the agency’s Artemis 1 mission on Nov.

“Despite the sadness that this is happening, all those who worked on this project and the 50,000 individual donors who fully funded the LightSail program should take this as a moment of pride,” Betts wrote.

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