ASTROPHYSICS
Physicists Bob Forward and Rob Hoyt believe they've found a way to keep satellites and astronauts safe from space junk. The two Seattle scientists have invented the Terminator Tether, a long, thin aluminum wire designed to yank a satellite from orbit and allow it to burn up in the atmosphere. Currently, the only way to pull a satellite out of orbit is to fire up its thrusters and propel it toward Earth - a method that doesn't work if a satellite has run out of fuel.
The Terminator Tether doesn't burn fuel; it drags against Earth's electromagnetic field. One end of the tether is tied to the satellite while the other end swings free. As the 3-mile-long wire whips through the magnetic field, it induces a current that opposes the motion of the satellite, knocking it downward. When the satellite hits the atmosphere, it burns and - poof! - terminates.
NASA has given Forward and Hoyt's company, Tethers Unlimited, $2 million for development, plus another $500,000 to study tether-based propulsion systems. In June 2001, NASA will test an electrodynamic tether of its own design as proof of concept.
The two scientists are already convinced that the Terminator Tether is a wonderfully elegant and cost-effective way to ditch a dead satellite. The device weighs only 22 pounds, and it's cheap (by NASA's standards - about $200,000) and easy to manufacture. "The fuel needed to take a satellite out of orbit adds up to 30 percent of its weight," says Forward. "The Terminator Tether is only 1 percent."
Not everyone is sold on the tether concept, however. This is because satellites don't always disintegrate when they hit the atmosphere. In 1979, Skylab ended up raining bolts over western Australia as it crashed to Earth.
"The current legal opinion is that if you try to take something down, then you are responsible if it hits somebody," says Forward. "But if you leave it up there to fall down by itself, it's an act of God."
But Forward and Hoyt believe that simply ignoring the accumulation of space junk is no longer an option. Satellite company Loral is scheduled to launch 80 communications satellites beginning late next year, most of which will have to be replaced within 10 years. Space trash is growing exponentially - collisions beget debris, which beget more collisions - polluting ever larger swaths of space.
MUST READ
The 38th Parallel Port
Flipping the Optical Switch
The Hit Charade
Ask Dr. Bob
Adventures in Mind Control
The New Pod People
People
Jargon Watch
The CPU Cure
Eyes of Truth
IM Not a Crook
Pulling Down Serious Gs
Raw Data
