The LightSail 2 starship will no longer fly in sunshine.
The Planetary Society’s crowdfunded solar sailing ship reentered earth atmosphere on Thursday morning (November 17) after almost 3.5 years in orbit – more than three times longer than the planned mission duration.
tea light sail 2 The team has had no communications from the spacecraft since that date, leading them to conclude that after completing 18,000 orbits and traveling about 5 million miles (8 million kilometers) around our planet, the shoebox-sized spacecraft had finally given up the ghost.
“LightSail 2 has disappeared into the sky after more than three glorious years, leaving a trail of lift with light and proving that we can defy gravity by cruising a sail in space,” said science communicator Bill Nye, CEO of The Planetary Society in one expression (opens in 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 captures stunning photos of Earth from space
LightSail 2 was the first small spacecraft to demonstrate controlled solar sailing, using photons from the Sun to adjust its orbit. (However, LightSail 2 was not the first ship of any kind to sail in space using solar sails; Japan’s Ikaros Probe did this in 2010.)
While light has no mass, its individual particles – photons – carry momentum that can be transferred to a reflective surface to give it a tiny boost.
LightSail 2 demonstrated that solar sailing is an effective and viable method of propulsion for small spacecraft, including tiny satellites known as CubeSatssaid team members.
LightSail Program Manager and Chief Scientist Bruce Betts wrote in a Planetary Society expression (opens in new tab) that de-orbiting would always be the fate of LightSail 2, though the mission’s fiery ending took longer to manifest than predicted.
The end of LightSail 2 was a drag
LightSail 2 was launched in June 2019 aboard a SpaceX falcon heavy Rocket tasked with a year-long mission to demonstrate controlled solar sailing in orbit. It began operations at an altitude of about 450 miles (720 kilometers) above Earth – slightly higher than the orbit of the International Space Station (ISS).
At this altitude, Earth’s atmosphere is still dense enough to exert slight drag on a spacecraft, and this effect eventually sealed the fate of LightSail 2.
Due to the large surface area of the vehicle’s solar wing, which measures 244 square feet (32 square meters) — about the size of a boxing ring — it experienced a greater drag effect than other spacecraft of its mass.
“Imagine throwing a rock compared to throwing a piece of paper. Atmospheric drag stops the paper much faster than the rock. In our case, LightSail 2 is the paper,” Betts wrote. “A spacecraft like the ISS is huge, but also massive, more like a rock. But even the ISS needs to be boosted higher every few weeks with drag-compensating rockets.”
During its third year of operation, demonstrating its most efficient solar sailing, LightSail 2 experienced increased atmospheric drag due to an increase in solar activity. This solar activity warmed the atmosphere, making the area LightSail 2 passed dense.
“It was the beginning of the end,” Betts wrote. “As solar activity increased even further, solar sailing could not keep up with the increased drag due to the increase in atmospheric density.”
Over the past few weeks, LightSail 2 had penetrated deeper and deeper into Earth’s atmosphere and encountered increasing resistance, which in turn dramatically increased its rate of descent.
“The spacecraft went into an increasing snowball effect: as the spacecraft deepened, the density increased, causing the spacecraft to deepen even more rapidly,” Betts wrote.
Although LightSail 2’s mission may be complete, scientific work remains to be done. The team behind the mission continues to analyze data collected from the ship, which remained operational until its last moment.
This data will also be shared with future space missions that also use solar sails, such as B. NASA’s NEA Scout, which launched on November 16 on the agency’s Artemis 1 mission, will travel with sunlight to the moon and then on to a near-Earth asteroid.
“Despite the sadness that it is over, all who worked on this project and the 50,000 individual donors who have fully funded the LightSail program should consider this a moment of pride,” Betts wrote.
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