NASA Researchers Ponder Nuclear Asteroid Deflector
Wednesday, August 08, 2007
By Paul Wagenseil
It's headed for an asteroid. It's got nuclear weapons. And it
doesn't involve Bruce Willis.
NASA scientists have proposed a spacecraft that would use atomic
blasts to deflect asteroids on collision courses with Earth.
Researchers from the Advanced Concepts Office at NASA's Marshall
Space Flight Center in Huntsville, Ala., presented the idea at the
2007 Planetary Defense Conference, held in early March in
Washington, D.C.
The asteroid deflector would be launched from low Earth orbit by an
Ares V rocket, NASA's next-generation heavy-cargo lifter, scheduled
to go into service in 2020.
As it approached the asteroid, the craft would at one-hour
intervals release six missile-like interceptors, each tipped with a
B83 one-megaton nuclear warhead.
The warheads would detonate one by one near the surface of the
asteroid, pushing it far enough off course so that it passes
comfortably wide of Earth.
Les Johnson, manager of interstellar propulsion research at the
Marshall Center, took care to point out that the asteroid deflector
is just an idea so far.
"There's no blueprints. There's no funding," he said. "At this
stage, it's just one of the many possible uses for the Ares V
vehicle."
Nevertheless, the discovery of several potentially dangerous
asteroids in recent years has prompted the space-science community
to develop what it calls Near-Earth-Object Mitigation concepts in
other words, asteroid deflectors.
Astronomers are specifically worried about 99942 Apophis, a
1,000-foot-wide asteroid discovered in 2004 that will come very
close to Earth in 2029 possibly hitting geostationary
communications satellites and might come even closer in
2036.
In June 2002, another asteroid passed within 1/3 of the distance to
the Moon, but was not discovered until three days later.
Congress in 2005 charged NASA with cataloguing and analyzing 90
percent of all near-Earth objects by 2020.
Johnson stressed that the Marshall Center's proposal was not
related to that law, which was incorporated into that year's NASA
budget.
The March presentation makes clear that nuclear-tipped interceptors
would be a last resort, best used against solid asteroids within a
short time frame before Earth impact.
A "kinetic" interceptor, which would simply smash into the
asteroid, would be better against smaller objects with a longer
time frame.
Best of all would be a solar collector, which would refocus solar
light into a beam directed against the asteroid, slowly heating the
surface to provide thrust but that would require 10 years or more
of lead time to be effective.
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