To get somewhere in space, you’ll need engines and fuel, but maybe that won’t be the case for much longer. The Planetary Society has just reached a critical milestone in the development of its solar sail technology. The LightSail 2 spacecraft has just deployed its mylar sail in orbit, allowing it to use sunlight to move through space.

The Planetary Society advocates for space exploration under the direction of its CEO Bill “The Science Guy” Nye. While rockets accelerate much faster than a solar sail, the chemical propellants are expensive, toxic, and add considerably to the weight of a spacecraft. Solar sails produce gentle, continuous thrust from the physical force of photons hitting the sail material. The larger the sail, the more photons impart energy to the spacecraft. LightSail 2 has a total surface area of almost 30 square meters.

LightSail 2 went to space on June 25 aboard a SpaceX Falcon Heavy rocket along with numerous other missions. Since then, it has successfully extended its antenna, activated its solar panels, and now has deployed the sail. That last part was a problem for the original LightSail probe in 2015. After making it to the edge of space, communication errors and issues with the sail mechanism resulted in a less-than-perfect demonstration. However, that mission was never supposed to use the sail for propulsion — it was just a deployment test.

The partially crowdfunded LightSail 2 will use its sails to putter around in space over the coming weeks. It contains a reaction wheel that allows controllers on the ground to change the spacecraft’s orientation. By pointing the sail toward the sun at various points in its orbit, LightSail 2 will accelerate and raise its orbit little by little.

SAIL DEPLOYMENT COMPLETE! We're sailing on SUNLIGHT!!!!! pic.twitter.com/PA74NMa7Ry — Planetary Society (@exploreplanets) July 23, 2019

While solar sails have lower thrust than chemical rockets, they never run out of fuel and can accelerate constantly. Over time, they can reach respectable speeds. The Planetary Society says solar sails could be ideal for certain classes of space missions that involve long-term observations in medium-high orbits around objects in the inner solar system. In the future, powerful lasers on Earth could help accelerate solar sail craft to reach more distant targets.

LightSail 2 won’t be visiting any other planets, but it could show that this new type of propulsion is workable. The Planetary Society plans to share its technology with spacecraft developers. It will also provide details on the craft’s orbit. The shiny sail is large enough that you might be able to spot it if you look up at the right time.

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