How It Works

LightSail: The spaceship powered by light


LightSail is a citizen-funded project launched by The Planetary Society, aiming to demonstrate flight by light.

The tiny spacecraft – which is about the size of a loaf of bread – doesn’t require any fuel, and instead uses the Sun’s energy as a method of propulsion.

How it works

  • Once in space, the spacecraft’s large 32 square meter (344 square feet) sails unfold. Each sail is just 4.5 microns thick—one-fourth the thickness of an average trash bag.
  • Light made of packets of energy called photons, which have momentum, reflects off of the mirrored sails.
  • The photons’ momentum is transferred, pushing on the sail to result in small but continuous acceleration.
The LightSail spacecraft captured this image of its deployed solar sails in orbit

The first prototype was launched aboard an Atlas V rocket in May 2015, and successfully deployed its solar sail in low-Earth orbit, but wasn’t high enough to demonstrate its solar sailing capabilities. In 2016, the Space X Falcon Heavy rocket will send another LightSail spacecraft to an altitude of 720 kilometers (450 miles), high enough to escape most of the planet’s atmospheric drag and really show what ti can do.

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