SAILING TO MARS

ASEE Prism, Nov 2004 by Craft, Lucille

SPACE

TOKYO-Japan advanced one step for science in August with the world's first successful space deployment of a "solar sail," an ultra-thin mirrored sheet that scientists hope will pave the way to interplanetary travel. Called "a spacecraft without a rocket engine," by the Japanese Institute of Space Astronautical Science (ISAS), which successfully launched two large solar sails, the metallic sheets are propelled by reflecting light particles from the sun, accelerating as exposure time to the sun increases. First dreamed up in 1924, these nonfuel, continuously accelerating space sails are the only feasible method of traveling among the planets. They are much slower than conventional, heavy, and expensive rocket-fueled spacecraft.

The stuff of science fiction became reality after ISAS launched a compact S-310 rocket from Uchinoura Space Center in Kagoshima on the southern Japanese island of Kyushu. The spacecraft was outfitted with two types of sails, each 7.5 micrometers thick. The first to be deployed, shaped like a four-leaf clover, was unfurled 100 seconds after liftoff at an altitude of almost 76 miles. After it was jettisoned, a fanshaped version was unfolded at an altitude of 105 miles and 230 seconds after liftoff. The flight ended 400 seconds later, when the rocket splashed down in the Pacific Ocean.

U.S. and European scientists have space sail projects of their own. The difficulty up to now has been finding a material with the requisite lightness and durability. -LUCILLE CRAFT