Catching sunbeams (Image: The Planetary Society)

Hoist the solar sail! A small spacecraft designed to test technology that derives thrust from sunlight is finally fully operational. LightSail, operated by the non-profit Planetary Society in Pasadena, California, has been dogged with problems since its launch last month, but this weekend mission managers made contact with the craft and unfurled its 32-square-metre sail.

Solar sails offer a potentially cheap way of exploring the solar system, but few have been tested in orbit. They work by reflecting photons from the sun, providing a small thrust in the opposite direction. The force from each reflected photon is tiny, but a large enough sail can build up significant momentum.

The LightSail mission got off to a bad start when its computer crashed shortly after launch, but it rebooted a week later and engineers were able to make contact and deploy its solar panels, which feed power to the sail deployment systems. A few days later, LightSail again fell silent, seemingly due to issues with its battery, forcing another reboot.


On Saturday the Planetary Society made contact with LightSail again, and issued the command to unfurl the sail. On Sunday the craft sent back data confirming the sail deployed successfully.

This version of LightSail can’t gain enough thrust from the sun to overcome the drag of the atmosphere at its current altitude, so it will fall back to Earth in the next few days. But the technical difficulties it encountered will inform the launch of a second version of the spacecraft, bound for a higher orbit next year.