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 trillion 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.

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.