Spaceflight Now: Breaking News

NASA charts course to 'sail' toward the stars
Posted: May 15, 2000

  Solar sail
An artist's concept of a space sail. Photo: NASA/MSFC
NASA is setting sail for the stars -- literally. NASA's Marshall Space Flight Center in Huntsville, Ala., is developing space sails technology to power a mission beyond our solar system.

"This will be humankind's first planned venture outside our solar system," said Les Johnson, manager of Interstellar Propulsion Research at the Marshall Center. "This is a stretch goal that is among the most audacious things we've ever undertaken."

The interstellar probe will travel over 23 billion miles -- 250 astronomical units -- beyond the edge of the solar system. The distance from Earth to the Sun, 93 million miles, is one astronomical unit. For perspective, if the distance from Earth to the Sun equaled one foot, Earth would be a mere 6 inches from Mars, 38 feet from Pluto, 250 feet from the boundaries of the solar system, and a colossal 51 miles from the nearest star system, Alpha Centauri.

This first step beyond our solar system en route to the stars has an estimated trip time of 15 years.

Proposed for launch in a 2010 time frame, an interstellar probe -- or precursor mission, as it's often called -- will be powered by the fastest spacecraft ever flown. Zooming toward the stars at 58 miles per second, it will cover the distance from New York to Los Angeles in less than a minute. It's more than 10 times faster than the Space Shuttle's on-orbit speed of 5 miles per second.

Traveling five times faster than Voyager -- a spacecraft launched in 1977 to explore our solar system's outer limits -- an interstellar probe launched in 2010 would pass Voyager in 2018, going as far in eight years as Voyager will have journeyed in 41 years.

Sail material
Les Johnson, manager of Interstellar Propulsion Research at NASA's Marshall Space Flight Center holds a rigid, lightweight, carbon fiber material that could be used to build a giant space sail. Photo: NASA/MSFC
Johnson says transportation is quite possibly the toughest challenge with interstellar missions because they have to go so far, so fast. "The difficulty is that rockets need so much fuel that they can't push their own weight into interstellar space. The best option appears to be space sails, which require no fuel," he said.

Thin, reflective sails could be propelled through space by sunlight, microwave beams or laser beams -- just as the wind pushes sailboats on Earth. Rays of light from the Sun would provide tremendous momentum to the gigantic structure. The sail will be the largest spacecraft ever built, spanning 440 yards -- twice the diameter of the Louisiana Superdome.

"Nothing this big has ever been deployed in space. We think we know how to do it, but we're in the beginning phases of turning a concept into a real design," Johnson said.

Researchers are optimistic about recent breakthroughs with strong, lightweight composite materials. A leading candidate for sails is a carbon fiber material whose density is less than one-tenth ounce per square yard -- the equivalent of flattening one raisin to the point that it covers a square yard. In space the material would unfurl like a fan when it's deployed from an expendable rocket.

The Marshall Center is leading NASA's transportation research for interstellar probes. Engineers at Marshall are conducting laboratory experiments to evaluate and characterize materials for space sails. Materials will be exposed to harsh conditions in a simulated space environment to test their performance and durability in extremely hot and cold temperatures. The emphasis of the current research effort is on the interstellar precursor missions designed to set the stage for missions to other star systems later this century.

Marshall is partnering with NASA's Jet Propulsion Laboratory in Pasadena, Calif. The Jet Propulsion Laboratory has overall responsibility for NASA's interstellar missions and the Marshall Center is responsible for developing transportation systems for the missions. Marshall's effort is part of its Advanced Space Transportation Program, NASA's core technology program for all space transportation. The Advanced Space Transportation Program is pushing technologies that will dramatically increase the safety and reliability and reduce the cost of space transportation.