Solar Sailing

The Challenges Ahead

The Planetary Society hoped to demonstrate the technology with its Cosmos 1 mission in 2005. "Cosmos 1 was a fully developed solar sail spacecraft intended to fly only under the influence of solar pressure for control of the spacecraft's orbit," says Friedman, now the director of the Planetary Society.

"If all had gone as planned, the US-based Planetary Society, working with Russia, would have been the first to fly a fully functional, though performance-limited, solar sail in space," says Johnson. "It would have been the first spin-stabilized, free-flying solar sail to fly in space." Cosmos 1, however, was lost when the launch vehicle failed.

Meanwhile, NASA has also continued to dabble in solar sailing. Between 2001 and 2005, the Agency developed two different 20-meter solar sails (fabricated by ATK Space Systems and L'Garde, Inc., respectively) and tested them on the ground in vacuum conditions. "These sail designs are robust enough for deployment in a one atmosphere, one gravity environment and are scalable to much larger solar sails - perhaps as much as 150 meters on one side. A NASA flight test is possible by the year 2010."

Edward E. Montgomery's team from the Marshall Space Flight Center has been working in cooperation with Elwood Agasid's Ames team toward deploying the NanoSail-D solar sail (pictured), which was launched on a SpaceX Falcon 1 rocket, from Omelek Island in the Pacific Ocean on August 2. Unfortunately, that launch vehicle too failed when the second stage separated from the first. Before the mission, Montgomery stated: "Our primary objective is to demonstrate successful deployment of a lightweight solar sail structure in low Earth orbit." They hoped to measure two types of pressure as NanoSail-D circled Earth: (1) aerodynamic drag from the wispy top of Earth’s atmosphere and (2) the pressure of sunlight.

And what of Cosmos 2? The mission is a privately funded project, a partnership of The Planetary Society and Cosmos Studios. Work has begun at the Russian Space Research Institute on some Cosmos 2 spacecraft hardware. They are also studying possible launch configurations on a reliable launch vehicle.

Interstellar Flight

If successful, Cosmos 2 and its successors could profoundly affect the future of science and exploration missions.

"Success would be huge for the future of space exploration," says Montgomery.

"Solar sailing is the only means known to achieve practical interstellar flight," says Friedman. "It is our hope that the first solar sail flight will spur the development of solar sail technology so that this dream can be made real."

Each effort is a stepping stone, in the great visionary Carl Sagan's words, along "the shore of the cosmic ocean," leading us closer to sailing among the stars. Future attempts will surely take us the rest of the way.

"'Twas all so pretty a sail it seemed
As if it could not be,
And some folks thought 'twas a dream they'd dreamed
Of sailing that beautiful sea."
- Eugene Field

For more information

The History of Solar Sailing, by Louis Friedman
http://www.planetary.org/solarsailcd/friedman.htm

News and technical details of solar sailing
http://wiki.solarsails.info/index.php?title=Solar_Sailing