Sailing in space
The Planetary Society
LightSail 2 has set sail on the solar breeze. Over the past few days, the spacecraft has demonstrated controlled solar sailing in orbit around Earth for the first time.
The small spacecraft was developed by the Planetary Society, a space advocacy group led by the US science communicator Bill Nye. It was launched aboard a SpaceX Falcon Heavy rocket on 25 June and unfurled its sails from their boxes on 23 July.
The Planetary Society announced late yesterday that operators had raised the spacecraft’s orbit by about 1.7 kilometres, completing its main mission of demonstrating that solar sails work and can be used to steer.
“Today we declare mission success – we are going to a higher orbital altitude, without rocket fuel, just from the push of sunlight,” Nye said. “We can sail on sunlight.”
Solar sails are propelled by photons from the sun. As the photons bounce off a lightweight, mirrored sail, they give it a small amount of energy that pushes it forward, like wind in a sail on the sea.
LightSail 2’s sails are thinner than a human hair and their total surface area is 32 square metres. Each photon imparts a minuscule amount of energy to the sails, but over time the momentum adds up and the spacecraft continually accelerates.
Friction from Earth’s atmosphere will eventually slow LightSail 2 down until it falls toward the ground and burns up in the air. “LightSail 2 will fly for another almost a year, and we are gonna learn a lot about controlling the spacecraft and the performance of the sails in the coming months,” Nye said.
That will help future light sails, which may be able to propel small spacecraft to other worlds in the solar system, and perhaps even beyond. They do not require heavy chemical fuel like traditional spacecraft, so in theory they can accelerate to an appreciable fraction of the speed of light, especially if they are propelled by powerful lasers instead of sunlight.