This graph shows LightSail’s average altitude with time (shown in blue).Illustration: The Planetary Society
As the spacecraft got lower, the atmospheric density increased very rapidly, resulting in atmospheric drag. LightSail smashed into atmospheric particles as it traveled at speeds reaching 20,000 miles per hour (32000 km / hr), causing the spacecraft to slow down. “Our case is more extreme than most spacecraft because the area of our sail is very large compared to the mass of the spacecraft,” the Planetary Society wrote in a statement. “Imagine throwing a rock compared to throwing a piece of paper. Atmospheric drag will stop the paper much faster than the rock. ”
Ironically, the Sun also worked against LightSail 2. When the Sun is more active, it heats Earth’s upper atmosphere, causing it to expand into higher altitudes. At the start of the mission, the Sun was going through some downtime as part of its 11-year cycle, but our host star recently revved up its activity for its solar maximum period. This has caused the atmosphere to be denser at higher altitudes, even reaching the spacecraft, causing LightSail 2 to drag downwards.
The third factor leading to LightSail’s demise is more human than cosmic. The mission suffered Communication glitches due to faulty equipment at the ground station. During times of communication drop-off, the team was unable to send data to the spacecraft, causing its sailing to suffer, albeit slightly.
Although LightSail 2 will soon meet its fiery death, the spacecraft’s legacy will still live on. The orbiter has inspired several other missions, including NASA’s NEA Scout mission to a near-Earth asteroid (scheduled for launch in August), NASA’s Advanced Composite Solar Sail System to test out sail boom material in Earth orbit (scheduled for launch sometime mid-2022)and NASA’s Solar Cruiser (scheduled for a 2025 launch). The era of the solar sail, it would seem, is quickly approaching.
More: LightSail 2, Pushed by Sunlight, Raises Its Orbit by 10,500 Feet in Just Two Weeks