Japan's Solar Sail Is the Toast of Space Science

NEW YORK ? Researchers from around the world are celebrating what they're calling a new dawn for spaceflight following the success of a Japanese craft propelled by a solar sail.

The Japan Aerospace Exploration Agency spacecraft Ikaros, which launched in May alongside the Venus-bound orbiter Akatsuki, is the first vehicle to have deployed a solar sail and successfully rode the sunlight in deep space.

Ikaros mission scientists and other researchers are discussing the state of solar sail propulsion this week at the second International Symposium on Solar Sailing at the New York City College of Technology in Brooklyn. The three-day symposium began Tuesday.

"It should have begun with a famous New York ticker-tape parade for our colleagues from Japan who took us to this reality," said Louis Friedman, co-founder of the Planetary Society, in Pasadena, Calif., which has attempted to use solar sails and is preparing for another mission.

Ikaros' solar sail, which was unfurled in June, has done more than just harness the power of the photons striking its reflective surface. It has generated electricity from the thin film solar cells embedded in its membrane, a demonstration of a possible power source for future spacecraft.

A future space sail mission potentially could use that power source to create a hybrid propulsion method that combines sailing with an ion-propulsion engine powered by embedded solar cells, researchers said.

The Japan Aerospace Exploration Agency, or JAXA, sees Ikaros as a stepping-stone for a future solar sail mission to Jupiter and the asteroids, according to JAXA program manager Junichiro Kawaguchi. That mission could fly around 2019 or 2020, he added.

Ikaros also briefly demonstrated a new attitude control system that relies upon sunlight alone to navigate, rather than using up fuel in thrusters to change direction.

The new system differs from merely tilting the sail to change the sunlight angle and pressure. Liquid crystal devices mounted on the edges of the sail use very low amounts of electricity to turn on or off. The "on" setting leads to specular (or mirror-like) reflection that redirects sunlight in one focused direction, while the "off" setting leads to more-diffuse reflection that bounces sunlight off in all directions.

The different reflections created unequal forces of sunlight on the sail edges and allowed Ikaros handlers to demonstrate attitude control over the course of almost 24 hours, said Ryu Funase of the JAXA Space Exploration Center.

As Ikaros heads toward Venus, JAXA officials hope it eventually reaches the far side of the sun.

• Japan Aims for Venus, Part 2
• World's First Solar Sail Photographed in Deep Space
• How Do Solar Sails Work?