Science News - September 10, 2011

The agency is also working on a much larger solar sail, 50 meters across, with hopes of launching it around 2020 to set sail for Jupiter and distant asteroids. Eventually, JAXA wants to develop novel hybrid propulsion systems, combining solar sails with ion drives to enable long trips through the solar system.

With far less money to spend than Japan, the first U. S. solar sail is far smaller, cheaper and less ambitious. Like so many projects in the solar sail world, the currently orbiting NanoSail-D was born from the ashes of much grander ideas.

NASA’s solar sail research program has waxed and waned over the years depending on funding. In the middle of the last decade, the agency conducted its biggest experiment to date, when it tested two 20-meter-by-20-meter solar sails at a research facility in Ohio. Then NASA began funneling most of its money into the Constellation program to return astronauts to the moon, and the big solar sail project foundered.

“When that ended we had a lot of
hardware and only a little budget,”
says Les Johnson, deputy manager at
the Advanced Concepts Office at the
Marshall center. “And that’s where
NanoSail-D was born.”
A few people began working on a
CubeSat-based design informally called
LunchSat, “because the only time peo-
ple had to work on it was during lunch,”
Alhorn says. But suddenly a chance to
launch arose, and the team hurriedly built
two kite-shaped sails, 3 meters on a side,
that could tuck inside a nanosatellite. The
first NanoSail-D launched in 2008 on a
Falcon 1 rocket provided by the private

LightSail, designed by the Planetary Society, measures 5. 6 meters on each side.
Once launched, it will turn 90 degrees twice every 90 minutes as it circles Earth.

company SpaceX, but the rocket never made it into orbit. A second option arose the next year, and the spare NanoSail-D launched successfully in November 2010 aboard a Minotaur rocket.

But then disaster struck. NanoSail-D
didn’t emerge and unfurl when it was sup-
posed to. Mission managers had given it
up as lost when in January the sail appar-
ently decided to deploy itself on its own
schedule. “Somehow it freed itself,” says
Alhorn. “We all have theories of what
stuck it and why it came loose, but there’s
no conclusive evidence.”
NanoSail-D unfurled itself and since
then has been orbiting Earth, the first
solar sail NASA has deployed in space.
The craft is drifting gradually lower in
altitude, and Alhorn estimates it will
burn up sometime before next January.

Ordinarily, putting a solar sail into
Earth orbit is harder than sending one to
interplanetary space, simply because the
sail has to keep readjusting its trajectory.
Although NanoSail-D has succeeded in
showing how a solar sail would deploy,
it isn’t actually controlling its position.
Because it may be tumbling along under
atmospheric drag instead of solar radia-
tion pressure, some purists insist it isn’t
a true solar sail. Alhorn is now working
on a concept for a larger sail with a novel
kind of attitude control, which sets the
sail’s orientation with panels feathered
up to 90 degrees.

Up, up and away A number of solar sail projects are planned to follow the recently launched IKAROS and NanoSail-D missions. While the more expensive missions better capture the grandeur of solar sailing, other projects are getting to space quicker with cheaper approaches.

IKAROS NanoSail-D LightSail- 1 CubeSail Cube Sail Gossamer- 1

Size 14x14 meters 3x3 meters 5.6x5.6 meters 5x5 meters 79mm x 250m 5x5 meters

Builder Japan Aerospace
Exploration
Agency
NASA The Planetary
Society
University of
Surrey/EADS Astrium
CU Aerospace/
University of Illinois
at Urbana-Champaign
German Aerospace
Center/European
Space Agency