Illustration of The Planetary Society's LightSail spacecraft, designed to test solar sail technology. Credit: The Planetary Society

WASHINGTON — Hoping that the third time is the charm, the Planetary Society announced Jan. 26 that it will launch a solar sail experiment in May as a secondary payload on an Atlas 5 rocket.

The Pasadena, California-based organization said that its first LightSail spacecraft, a cubesat about 30 centimeters long and weighing several kilograms, will fly in May on a United Launch Alliance Atlas 5 rocket launching from Cape Canaveral, Florida. That spacecraft will test key technologies for a second mission planned for 2016.

The Planetary Society did not disclose what Atlas mission the LightSail spacecraft will fly on, although current manifests show that an Atlas 5 is scheduled to launch May 6 from Cape Canaveral on a classified mission designated AFSPC-5. That launch is expected to carry several CubeSat secondary payloads through NASA’s Educational Launch of Nanosatellites program.

On the May flight, the LightSail spacecraft will spend four weeks undergoing tests in orbit before deploying a set of triangular sails, made of Mylar, attached to booms four meters long. Atmospheric drag from the spacecraft’s low, but unspecified, orbit will prevent the sail from generating thrust, but will allow engineers to test the sail deployment mechanism and other key systems.

“There’s an old saying in aerospace, ‘One test is worth a thousand expert opinions,’” said Bill Nye, chief executive of the Planetary Society, in a statement. “After six years of development, we’re ready at last to see how LightSail flies.”

LightSail test
The Planetary Society’s LightSail spacecraft, with its four sails deployed, undergoing tests in Sept. 2014. Credit: Justin Foley/The Planetary Society.
The Planetary Society’s LightSail spacecraft, with its four sails deployed, undergoing tests in Sept. 2014. Credit: Justin Foley/The Planetary Society.

Stellar Exploration of San Luis Obispo, California, designed the LightSail spacecraft, with final integration and testing done by Pasadena-based Ecliptic Enteprises. “We experienced several design, hardware, software, and testing issues along the way,” said Rex Ridenoure, chief executive of Ecliptic Enterprises, but added that the team working on the spacecraft “surmounted them all and succeeded in securing approval to launch.”

A second LightSail spacecraft is scheduled to launch in 2016 as a secondary payload on a SpaceX Falcon Heavy rocket. That LightSail, packaged inside a larger satellite called Prox-1 being developed at the Georgia Institute of Technology, will be deployed at an altitude of 720 kilometers. At that higher altitude, the spacecraft will be able to generate thrust as sunlight pushes against its sail.

The Planetary Society started the LightSail program in 2009 to test solar sail technology. Solar sails require no propellant, and the weak but continuous thrust provided by sunlight would allow spacecraft to accelerate to high speeds, shortening travel time for solar system exploration missions.

The organization twice previously attempted to fly solar sail technology demonstration missions. In June 2005, Cosmos 1, built by Russia’s Lavochkin Association for the Planetary Society, launched on a Volna rocket, a converted submarine-launched ballistic missile. However, the spacecraft failed to achieve orbit when the rocket’s first stage shut down early.

A July 2001 suborbital flight to test Cosmos 1 technology, also launched on a Volna, failed when the spacecraft did not separate from the rocket.


Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...