[meteorite-list] NASA Crafting Bag of Tricks To Deflect Hurtling Asteroids

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:29:52 2004
Message-ID: <200309081521.IAA24771_at_zagami.jpl.nasa.gov>

http://www.al.com/news/birminghamnews/index.ssf?/base/news/1063012553228960.xml

NASA crafting bag of tricks to deflect hurtling asteroids
KENT FAULK
The Birmingham News
September 8, 2003

One day Earthlings could use lassos and lasers or
solar sails to nudge Earth-bound asteroids out of the
way, researchers say.

The ideas may seem farfetched. But the threat is
real, the technology is possible, and a few
researchers said last week that nations should begin
taking steps to defend the planet from such hits.

"We have the emerging technologies to do the job at
some point in the future," said Jonathan Campbell, a
NASA researcher at the National Space Science
Technology Center in Huntsville. "The question is, do
we have the international will."

The issue came to the forefront last week when
British astronomers were reported as giving an
asteroid about two-thirds of a mile wide a
one-in-909,000 chance of hitting the Earth in 2014.
The next day, the astronomers said that after more
observation, they had determined asteroid 2003 QQ47
had virtually no chance of hitting the Earth.

But for a day the question was there. What could be
done if an asteroid large enough to cause a global
catastrophe was headed toward Earth?

The first problem NASA researchers trying to perfect
a means of diverting incoming debris are tackling is
spotting large asteroids and comets, called Near
Earth Objects.

NASA's Near Earth Object program at the Jet
Propulsion Laboratory in California is tracking 663
large asteroids, those bigger than a half-mile in
diameter, said Paul Chodas, research scientist in
that program.

1,200 asteroids:

Researchers believe about 1,200 asteroids of that
size are in near Earth orbit, which is within 30
million miles of the planet, Chodas said. "Our goal
is to discover 90 percent of these large asteroids by
2008," he said.

Asteroids of that size could cause global climate
change and kill billions of people, Chodas said.

Odds of a collision with an asteroid that size is
small, Chodas said, since they hit just once in a
half million years on average.

Smaller asteroids, however, are more common -
possibly in the thousands or tens of thousands - and
could cause severe regional damage if they hit Earth,
researchers say.

The last significant impact was in the unpopulated
Tunguska region of Russia in 1908, a group of 10
Marshall Space Flight Center researchers noted in a
23-page paper they presented at an engineering
conference this summer. A 99-foot- to 198-foot-wide
object is believed to have struck in that area.

That paper, "Planetary Defense: Options for
Deflection of Near Earth Objects," says that if that
same object had hit Madison County, the majority of
its 250,000 or so residents would have been killed.
If it had hit a city such as New York or London,
millions would have been killed, the report says.

The group studied seven methods for deflecting or
destroying asteroids or comets on a collision path
with Earth and developed computer models for them.

One was to blast them into small pieces with a
nuclear weapon. Another was to blast a nuclear weapon
near the object and let the thrust from gases being
burned off the asteroid push it into another orbit.
And another was to tether a solar sail to slowly pull
an asteroid into a different path.

"We had a first estimate of what size and what type
comets and asteroids we could deflect with a given
system," said Rob Adams, an aerospace engineer in
Advanced Planning and Concepts at Marshall and lead
author of the paper.

Campbell, part of another group of researchers
working on the problem, has filed a NASA patent on
one idea - an inflatable laser/solar reflector that
could push asteroids into safer orbits.

That idea calls for a spacecraft to fly toward the
asteroid, and detach a smaller spacecraft. They would
be connected to each other by a tether that would
form a loop. The loop would have to spin to match the
motion of the object, then be moved over the object
and the tethers retracted to tighten the loop. A
solar reflector would be inflated. By continuously
tilting the reflector to capture sunlight, photons
from the sunlight gradually would push the asteroid
into a safer orbit.

Moon lasers:

Another idea for which Campbell plans to file a
patent would put a bank of lasers on the moon to
deflect incoming asteroids.

The debate over which method is the best continues,
but Campbell said he believes a multiple-layer
defense is needed. "I guess my answer is we should
use them all," he said.

The paper from Adams' group urges more funding for
studies in detecting and deflecting Near Earth
Objects.

"Despite the impression given by Hollywood, it is not
practical to wait until a specific threat is
identified before starting work on a mitigation
system. Systems engineering, system development and -
in some cases - technology development, will take
several years," the report says.

Chodas doesn't advocate spending money just yet to
develop a system. "I think it's worthy of study. But
I don't think it's worthy of developing a system yet
because the odds are we won't have an asteroid on a
collision course," he said.

But Chodas does support spending money to continue
sending spacecraft to asteroids to find out what they
are made of and how strong they are. "We need to know
that if we are going to try to deflect it," he said.
Received on Mon 08 Sep 2003 11:21:26 AM PDT