From: LARRY KLAES (ljk4@msn.com)
Date: Fri Nov 08 2002 - 06:13:18 PST
IMPACT IMPERATIVE: LASER ABLATION MAY SOON BECOME AN EFFECTIVE TOOL OF
PLANETARY PROTECTION
>From Space.com, 5 November 2002
http://space.com/businesstechnology/technology/beamed_propulsion_021105.html
By Leonard David
A micro-payload riding a shaft of light streaks for the Moon or Mars. Huge
sails are nudged outward on interstellar trajectories. A double-crosser of
an asteroid is pulsed out of harms way, saving the Earth from a messy
impact.
All benefits from on-the-spot power beaming, 21st century style. Better yet,
no need tapping your fingers waiting around for this technological
tour-de-force.
Next year, a space-deployed solar sail is to be pushed via microwave beam
broadcast from Earth - a novel experiment to test the feasibility of
beam-boosted sails.
For the first time in history, experts in the field of point-to-point power
beaming from around the world have gathered at the First International
Symposium on Beamed-Energy Propulsion, held at the University of Alabama in
Huntsville (UAH).
"Several generations of researchers are under one roof. Nothing has been
like this before. It's a special event," said UAH's Andrew Pakhomov,
co-chair and a key organizer of the meeting. "This is research once the
domain of several enthusiasts. But it has passed that initial stage. This is
a normal technological field involving researchers, engineers, as well as
prototypes and products," he told SPACE.com.
Pakhomov said researchers from nine nations and from various groups across
the United States are reporting on the progress and promise of power beaming.
Sail beaming experiment
Next year's trial run at power beaming is slated to involve The Planetary
Society's Cosmos 1 solar sail. To be launched by a Russian rocket, the sail
is to settle into a 500-mile (800-kilometer) orbit above the Earth.
Once fully deployed, the Cosmos 1 is then ready to be on the receiving end
of a microwave beam. That microwave energy will be transmitted spaceward via
a large radio dish in Goldstone, California - a powerful antenna that's part
of the Jet Propulsion Laboratory's Deep Space Network.
Louis Friedman, Executive Director of The Planetary Society and the Cosmos 1
Project Director, told SPACE.com: "If we can do the beamed power experiment
and measure its acceleration on our Cosmos 1 spacecraft, it will be a great
accomplishment for us...on the first solar sail mission to pave the way for
interstellar flight."
While the push received from the Goldstone microwave beam will be tiny
compared to the effect of solar radiation on the sail, the spacecraft's
mission is to test the feasibility of beam-boosted sails, said Greg Benford,
a professor of physics at the University of California, Irvine. His brother,
James Benford, president of Microwave Sciences, of Lafayette, California, is
keen on the experiment too.
"The significance is that this is the first demonstration of a new
propulsion method, truly 21st century, that can reach speeds far beyond the
rocket," Jim Benford said.
Lightcraft shows the way
The modern history of beamed energy propulsion, tagged BEP for short,
started in 1972, when Arthur Kantrowitz -- founder and CEO of the Avco
Everett Research Laboratory -- first popularized the idea of laser
propulsion to orbit. His research continues today as a professor at Thayer
School of Engineering at Dartmouth College in Hanover, New Hampshire.
The BEP field has evolved from a simple vision of somehow employing a remote
source to transmit energy to spacecraft in flight, into a demonstrated
propulsion technology.
In one effort, small-sized "Lightcraft" have already been shot high into the
air over White Sands, New Mexico desert. The test devices rode on blasts of
high-intensity laser light. This progress, sponsored by the Air Force
Research Laboratory and NASA, realized ever-increasing flight altitude
records. The successful tests have helped confirm the promise that useful
payloads could be delivered to low-Earth-orbit using laser propulsion.
Pakhomov points out that few advanced propulsion concepts have had
successful flight demonstration. More importantly, the field of laser
propulsion is not limited to just Earth-to-orbit launches, in the same way
as BEP is not limited to laser propulsion. A broad range of new applications
will be opened with the advancement of beamed energy propulsion research.
But there are a few catches.
Work-horse technologies
For one, the time when laser propulsion and other BEP concepts will become
mature, 'work-horse' technologies depends entirely upon expanding the
current level of BEP research and development. Furthermore, there's need to
establish high-power BEP demonstration and test facilities. On a more global
front, uniting research forces worldwide to achieve this goal is vital.
Pakhomov adds, however, that power beaming schemes and hardware needed to
turn ideas into matter-of-fact propulsion are rapidly proliferating.
One only has to look at the vetting of proposals at this week's First
International Symposium on Beamed-Energy Propulsion.
For example, consider a supersonic airbreathing laser propulsion vehicle
advocated by Korean researchers. Then there's X-ray driven micro-ships by a
Japanese team. Another suggestion by a Russian specialist is correcting
satellite orbits by laser beaming.
Arguably, one of the more bombastic thoughts presented is sidetracking
incoming objects harmful to Earth.
Titled the "Impact Imperative," the idea is to use laser ablation for
deflecting asteroids, meteoroids, and comets from smacking into the Earth.
Intelligent combination
Leader of the proposition is NASA's Jonathan Campbell, a research scientist
in the Advanced Projects Group at the Marshall Space Flight Center's new
National Space Science and Technology Center in Huntsville. An up-front
disclaimer, Campbell adds, is that the opinions expressed are not
necessarily the official position or policy of NASA.
"Preventing collisions with the Earth by hypervelocity asteroids,
meteoroids, and comets is the most important immediate space challenge
facing human civilization. This is the Impact Imperative," Campbell and
several research associates suggest.
It is clear that big and small objects hitting our planet can do serious
damage.
Can anything be done about this "fundamental existence question" facing our
civilization? The answer is a resounding yes, Campbell believes.
"By using an intelligent combination of Earth and space based sensors
coupled with a space infra-structure of high-energy laser stations and other
secondary mitigation options, we can deflect inbound asteroids, meteoroids,
and comets and prevent them from striking the Earth," Campbell will report
at the symposium.
Space interceptors
The power beaming idea is straightforward. Just irradiate the surface of an
inbound rock with sufficiently intense laser pulses so that ablation occurs.
This ablation acts as a small rocket incrementally changing the shape of the
rock's orbit around the Sun.
"We recommend that space objectives be immediately reprioritized to start us
moving quickly towards an infrastructure that will support a multiple option
defense capability," Campbell advises. "While lasers should be the primary
approach initially, all mitigation options depend on robust early warning,
detection, and tracking resources to find objects sufficiently prior to
Earth orbit passage in time to allow mitigation."
Campbell and his fellow team members envision laser and sensor stations
placed in low and high orbits around Earth, even at lunar and libration
point distances. Space interceptors would tote both laser and nuclear
ablators for close range work.
"Response options must be developed to deal with the consequences of an
impact should we move too slowly," Campbell concludes.
Ripe for serious development
>From newly fabricated ultra-tiny spacecraft thrusters to theorizing about
shoving asteroids around - power beaming research is on full-throttle.
Why now and why beamed energy?
"Because 'concentrated' energy is hard to come by in space," said Jordin
Kare of Kare Technical Consulting in San Ramon, California.
Kare, a noted researcher in power beaming, said this type of propulsion
yields several advantages.
"Chemical fuels don't provide enough oomph for lots of things we want to do,
like make single stage launchers or make fast trips to Mars. Sunlight
provides plenty of energy but it's expensive to collect and use, in both
dollars and mass. The only other choices we have for supplying energy in
space are nuclear power and beamed energy. And even if you like nuclear
power, there are situations -- like launching from the ground -- where
beamed energy is the only way to go," Kare told SPACE.com.
Kare advises keeping an eye on the power beaming field.
"Because it's ripe for serious development," Kare said. "We're a long way
from building a laser launcher -- though maybe not as long a way as many
people think -- but we could start building space power and propulsion
systems any time."
"There's lots of talk about making space flight as easy and reliable as air
travel. But we can't do it with chemical rockets -- the margins are just too
small. With beamed energy, you're not limited by what Nature lets you get
out of chemical bonds," Kare added.
At this week's symposium, Kare is presenting his own work.
"With technology we largely know how to build today, we could make a laser
orbital maneuvering system that would let us hop between orbits and go to
the Moon with ease, and even send off missions to Mars," Kare said.
"Now if we could just get the Martians to build their own laser, we'd be all set."
Copyright 2002, Space.com
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