[meteorite-list] Asteroid Deflection Research Center Established at Iowa State

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 29 May 2008 14:52:25 -0700 (PDT)
Message-ID: <200805292152.OAA06548_at_zagami.jpl.nasa.gov>

http://www.scienceblog.com/cms/seeking-answers-asteroid-deflection-16559.html

Seeking answers to asteroid deflection
Science Blog
May 28, 2008

An Asteroid Deflection Research Center (ADRC) has been established on
the Iowa State campus to bring researchers from around the world to
develop asteroid deflection technologies. The center was signed into
effect in April by the Office of the Executive Vice President and Provost.

"In the early 1990s, scientists around the world initiated studies to
assess and devise methods to prevent near-Earth objects from striking
Earth," said Bong Wie, the Vance D. Coffman Chair Professor in Aerospace
Engineering and director of the center. "However, it is now 2008, and
there is no consensus on how to reliably deflect them in a timely
manner," he noted.

Wie, whose research expertise includes space vehicle dynamics and
control, modeling and control of large space structures, and solar sail
flight control system development and mission design, joined the Iowa
State faculty last August. "I am very happy that Professor Bong Wie has
joined the faculty at ISU," said Elizabeth Hoffman, executive vice
president and provost. "His work on asteroid deflection is exciting and
of great importance."

The ADRC will host an International Symposium on Asteroid Deflection
Technology in fall 2008. Scientists and engineers from NASA, the
European Space Agency, academia, and the aerospace industry will be
invited to the Iowa State campus to formulate a roadmap for developing
asteroid deflection technologies.

Despite the lack of an immediate threat from an asteroid strike,
scientific evidence suggests the importance of researching preventive
measures. Sixty-five million years ago, a six-mile-wide asteroid struck
near the Yucatan Peninsula in Mexico and created the 106-mile-diameter
Chicxulub Crater. Most scientists now believe that a global climate
change caused by this asteroid impact may have led to the dinosaur
extinction. Seventy-four million years ago, a smaller one-mile-wide
asteroid struck in central Iowa, creating the Manson Crater. Now covered
with soil, it is the largest crater in North America at more than 23
miles across.

Just 100 years ago, June 30, 1908, an asteroid or comet estimated at
100-200 feet in diameter exploded in the skies above Tunguska, Siberia.
Known as the Tunguska Event, the explosion flattened trees and killed
other vegetation over a 500,000-acre area. But if the explosion had
occurred four hours later, it would have destroyed St. Petersburg or
Moscow with an equivalent energy level of about 500 Hiroshima nuclear bombs.

The potential for such devastation has astronomers scanning the skies to
find and track asteroids that pose a danger, and it has Wie initiating
this concerted research effort now before any asteroids are discovered
heading toward Earth.

Last November, NASA reported 900 known potentially hazardous objects
(PHOs), most of which are asteroids. PHOs are defined as objects larger
than 492 feet in diameter whose trajectories bring them to within about
4.6 million miles of the Earth's orbit. NASA scientists estimate the
total population of PHOs to be around 20,000. "However," Wie said, "the
asteroid we have to worry about is the asteroid that we don't know."

"Developing technologies that can be used to prevent or mitigate threats
from asteroids while also advancing space exploration is a challenge we
accept as we work to assure a high quality of life for future
generations," said Mark J. Kushner, dean of Iowa State's College of
Engineering. "This research center serves as an excellent opportunity to
provide leadership on an issue that has worldwide implications."

According to Tom Shih, professor and chair of aerospace engineering,
"the potential for a major catastrophe created by an asteroid impacting
Earth is very real. It is a matter of when, and humankind must be
prepared for it. Our aerospace engineering department strongly supports
Professor Bong Wie's effort in establishing this center to address the
engineering and science issues of asteroid deflection."

Both high-energy nuclear explosions and low-energy non-nuclear
alternatives will be studied as deflection techniques. The nuclear
approach, which is often assessed to be 10-100 times more effective than
non-nuclear approaches as stated in NASA's 2007 report to Congress, will
be researched to verify its effectiveness and determine its practical
viability, according to Wie.

"A 20-meter (66 feet) standoff distance is often mentioned in the
literature for a maximum velocity change of a 1-kilometer (0.6 mile)
asteroid. However, we have to determine how close the nuclear explosion
must be to effectively change the orbital trajectories of asteroids of
different types, sizes, and shapes," Wie explained. "We will develop
high-fidelity physical models to reliably predict the velocity change
and fragmentation caused by a nuclear standoff explosion."

The non-nuclear alternatives include kinetic impactors and slow-pull
gravity tractors. Wie, who has previously worked on solar sail
technology as applied to asteroid deflection, will present his recent
study, "Multiple gravity tractors in halo orbits for towing a target
asteroid," at the American Institute of Aeronautics and Astronautics
Astrodynamics Specialists Conference in August. His paper has been
accepted for publication in the AIAA Journal of Guidance, Control, and
Dynamics.

The chances of having to use deflection technologies on an asteroid in
the near future are admittedly remote. Scientists estimate the frequency
of an extinction-class (6 miles in diameter or larger) object striking
Earth as once every 50-100 million years, and for a 200-foot or larger
object as once every 100-500 years.

The technologies that will be developed, including precision orbital
guidance and navigation and control, however, have other applications as
well. These may include future advanced space vehicles that will carry
astronauts to an asteroid or Mars and homeland security applications.
Received on Thu 29 May 2008 05:52:25 PM PDT


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