Image: Solar sail
A space sail, as depicted in an artist’s concept at right, could power interstellar missions. NASA's Les Johnson holds one type of material that could be used to build a giant space sail.
updated 5/2/2005 1:00:25 AM ET 2005-05-02T05:00:25

Scientists working with a synthetic material 100 times thinner than a piece of paper are testing their theory that the sun can power interplanetary spacecraft. They believe that photons — particles of light — can push a giant, reflecting sail through space the way wind pushes sailboats across water.

NASA has invested about $30 million in space-sail technology, something that existed solely in science-fiction novels a decade ago. Yet the reflective solar sail could power missions to the sun and beyond within a decade.

"It's OK to breathe on it and touch it," said David Murphy, of ATK Space Systems, showing off the sail.

ATK Space Systems, based in California, is one division of a $2.4 billion company that makes rocket motors, advanced weapons systems and ammunition for the military and the Department of Homeland Security. It has about 14,000 employees at operations in 23 states.

Last year it delivered 1.2 billion rounds of small-caliber ammunition to the Army.

Testing in vacuum chamber
The Space Systems division developed the solar sail, which is being tested in the world's largest vacuum chamber at the Cleveland-based NASA Glenn Research Center's Plum Brook Station in Sandusky. It has a space environment simulation chamber 100 feet (30 meters) in diameter and 122 feet (37 meters) high.

In that chamber, Murphy displayed four silvery, triangular pieces of sail stretched over four long booms, which form a square about 70 feet (21 meters) on each side. Murphy and others want to study how the sails will deploy and operate in a vacuum under various temperatures.

"We're going to cool it down and shake it out," Murphy said.

Just in case, the fabric, which resembles Mylar plastic, has rip-stop threads to keep it from pulling apart when the chamber is closed and the air is pumped out.

"To get a lower pressure you'd have to go to space," said Edward Montgomery, an engineer from NASA's Marshall Space Flight Center in Huntsville, Ala.

The chamber has been used to test rocket components, radiators for the international space station and the crash bags that protected twin rovers when they landed on Mars last year.

The plasticlike fabric used to make the sails is a spinoff from technology used to develop spacecraft paint.

To Venus and beyond
First missions — scientific payloads of a few hundred pounds — are likely to be to the inner planets, Venus and Mercury, and to the sun. But NASA scientists think the technology is a good bet for eventually powering spacecraft to many other space destinations.

Since its fuel is free and doesn't have to be stored, a craft with solar sails would not have to slingshot around the moon or other planets for a gravity boost to reach distant destinations, as other craft do.

Craft propelled by solar sails could be launched on conventional rockets or released from space stations. In space, the force of sunlight would push the reflective sails, causing the craft to move, said NASA Marshall physicist Les Johnson.

The first sail tested in space will be about 130 feet (40 meters) on each side. Those on an actual mission could be twice as large.

While its thrust is low, it would be continuous so that the craft accelerates steadily, eventually reaching speeds of tens of thousands of miles an hour. Changing the sail's angle to the sun would allow the craft to slow down or speed up.

"Just by morphing its shape we can get it to turn," Montgomery said.

With the science worked out, Murphy said, it is now a matter of building larger sails.

"We have everything we need to do this," he said.

Copyright 2005 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.


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