Yay! The Planetary Society's Lightsail 2 has deployed it's solar sail. Now to see how it performs.
On July 23rd, a tiny spacecraft in orbit around Earth unfurled a thin sheet of mylar that’s the area of a boxing ring. The result is a reflective sail that rides not on wind, but on light from the Sun to propel the vehicle through space.
Over the course of the next month, LightSail 2 will perform something of a dance in orbit, twisting its sail back and forth to ride on sunlight. As it approaches the Sun, the spacecraft will keep its sail edge on toward the light. Then, once it’s directly in front of the Sun, it will twist and face the sail toward the Sun. “It’ll work very much like a sailboat, where you push, twist, and pack into the ‘wind,’” Nye said. “And then you twist and take advantage of sailing ‘downwind.’” If all goes well, the sunlight will push on LightSail 2, and the spacecraft’s orbit will rise slightly as it whips around the Earth.
Eventually, this orbit raising will lead to the spacecraft’s demise. LightSail 2 will only be able to raise its orbit on one side of the Earth, and each time the orbit gets higher on that side, the orbit gets lower on the other. In about a year, LightSail 2 will pass close enough to Earth that it will be dragged into the planet’s atmosphere, burning up during its descent.

However, its fiery demise won’t be a tragedy since LightSail 2 is only intended to prove that this type of in-space propulsion can work. If it manages to do that, The Planetary Society plans to share its solar sail technique with other spacecraft developers that are looking for innovative ways to maneuver vehicles through space. A solar sail could be used for something as simple as maintaining a spacecraft’s position in orbit, or it could be amplified for something as complex as sending cargo to Mars.
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