least in nuclear terms, the world is now a much more complex
place than it was during the Cold War, when the United States
and the Soviet Union, now Russia, were the only two countries
weapons. Today, many other nations may have the ability to
launch long-range nuclear missiles.
In order to combat a potential nuclear attack, the United
States has been developing a space-based missile defense
system for the past two decades. This defense system began
under former U.S. President Ronald Reagan. His Strategic
Defense Initiative (SDI) called for the development of laser
weaponry that would orbit the earth to shoot down ballistic
missiles. There is now even talk of the United States
developing a fifth military branch, perhaps called Space
Force, that would pick up where the Air Force leaves off.
In this edition of How
Stuff Will Work, we will look at how some wars are
already being fought via satellite, and the technologies that
are being developed to fight wars in space!
The Ultimate High Ground
Preceding World War
I, it was almost a necessity for armies to secure the high
ground, by overpowering their opponent atop a hill, in order
to win battles. Getting to a higher location gave the army on
top of the hill the advantage of shooting down on the opposing
army, which had to advance up a hill with bullets raining down
on it. Historically, armies with the high ground advantage
have won more often than not.
The new high ground is space. The U.S. currently
uses space in a passive way during combat, so let's look at
space from this angle first.
In 1991, the United States and its allies used
sophisticated satellite technology to pinpoint Iraqi targets
during the Persian Gulf War. Intelligence-gathering satellites
gave the American forces an unprecedented view of the
battleground, showing every move that the Iraqi armies were
making during the war. With the vast expanse of the desert
landscape providing visibility, satellite imagery became the
main source of information on the Iraqi army during the war.
Satellites also were a valuable tool in deploying troops
during the Persian Gulf War. A constellation of satellites
orbiting Earth, known as the Global
Positioning System (GPS), was used by soldiers on the
ground to determine their bearings. These 24 satellites gave
the longitude, latitude and altitude of the U.S. soldiers
carrying handheld GPS receivers on the battlefield. The open
desert was an ideal location for using the GPS satellites,
because there were very few natural objects around to
interfere with the satellites' signals. In combination with
the imagery from the spy satellites that were tracking enemy
troops, the GPS gave the United States and its allies the
advantage of knowing exactly where to position their troops
for the greatest benefit.
The next frontier in space is much more active -- satellite
weapons systems designed to shoot down nuclear missiles.
In May 1983, Reagan proposed his Strategic Defense
Initiative (SDI), now termed Ballistic Missile
Defense, which called for laser-equipped satellites to
shoot down intercontinental ballistic missiles (ICBM). ICBMs
have a range of more than 6,000 miles (10,000 km). At that
distance, an ICBM fired from North Korea could easily reach
Honolulu or Los Angeles. Reagan's SDI, also known as "Star
Wars," was designed to provide an umbrella of protection from
such missile attacks. The SDI satellites would track a missile
from liftoff, and shoot it down with lasers before the missile
cleared the air space of the country from which it was
launched. Work on a space-based laser for Ballistic Missile
Defense is proceeding despite some international criticism.
The project has continued to receive $4 billion per year, and
recently had an extra $6.6 billion budgeted for the project
through the year 2005.
Space Weapons in Development
Space Command doesn't hide the fact that it wants to
establish U.S. supremacy in space. In its Vision for
2020 report, the Space Command points out that military
forces have always evolved to protect national interests, both
military and economic. The report suggests that space weapons
must be developed to protect U.S. satellites, and other space
vehicles, as other countries develop the ability to launch
spacecraft into space. In 1997, Assistant Secretary of the Air
Force for Space, Keith R. Hall, said, "With regard to space
dominance, we have it, we like it and we're going to keep it."
The Pentagon has said that as space enterprises begin to
gain commercial advantage, there will be those who try to take
some of the profits by attacking those space enterprises. Here
are some of the space weapons currently under development:
There are at least three
systems being developed for either space-based or ground-based
weapons. All three are a type of chemical laser that involves
the mixing of chemicals inside the weapon to create a laser
beam. While a space-based laser system is still about 20 years
from being realized, there are three lasers being considered
for it, including hydrogen fluoride (HF), deuterium fluoride
(DF) and chemical oxygen iodine (COIL).
- Chemical Lasers
- Particle Beams
- Military Space Planes
Photo courtesy TRW
Artist rendering of how a TRW designed space
laser-equipped satellite might fire a laser at a
ballistic missile from long range.
In a 1998 report titled Laser
Weapons in Space: A Critical Assessment (PDF file), Lt.
Col. William H. Possel of the U.S. Air Force compared the
workings of the hydrogen fluoride laser system to the
way a rocket
engine works. Atomic fluorine reacts with molecular
hydrogen to produce excited hydrogen fluoride molecules. This
reaction creates a wavelength between 2.7 and 2.9 microns. At
that wavelength, the hydrogen fluoride laser beam would be
soaked up by the Earth's atmosphere, meaning that it is most
likely to be used in space-to-space combat as part of the
Space-Based Laser program. The Ballistic Missile Defense
Organization has already demonstrated a hydrogen fluoride
laser with megawatt power in a simulated space environment.
Another laser, similar to the hydrogen fluoride system, is
the deuterium fluoride laser system. Instead of using
molecular hydrogen, deuterium is used to react with atomic
fluoride. Because deuterium atoms have more mass than hydrogen
atoms, this laser has a longer wavelength, about 3.5 microns,
and can transmit better through the atmosphere. In 1980, TRW
demonstrated a deuterium fluoride laser, called the
Mid-Infrared Advanced Chemical Laser (MIRACL), that can
produce more than one megawatt of power. This type of laser
system was used in tests to shoot down a rocket at the
White Sands Missile Range in 1996.
The third type of chemical laser that might be used in
ballistic missile defense is the chemical oxygen iodine
laser (COIL), which made its debut in 1978. In this laser
system, a reaction generated between chlorine and hydrogen
peroxide excites oxygen atoms, which transfer their energy to
iodine atoms. This transfer of energy causes the iodine atoms
to become excited, creating a laser with a wavelength of about
1.3 microns, smaller than either of the two previously
mentioned lasers. This smaller wavelength means that smaller
optics could be used to develop a space-based lasing system.
In 1996, TRW tested a COIL laser that produced a beam with
hundreds of kilowatts of power that lasted several seconds.
Right now, this is the most promising of the spaced-based
lasers in development.
One of the problems with space-based lasers is that they
would have to be fixed to a moving satellite as they tried to
hit another moving object moving at thousands of miles per
hour. Imagine trying to shoot a bird from aboard a supersonic
jet. The laser and the object it is trying to hit will likely
be traveling at different speeds, making it an almost
impossible shot. This is why the U.S. Department of Defense is
also considering a particle beam weapon, which would be
able to fire beams of subatomic particles, at near the speed
of light, at a military target. If a beam could be fired at
those speeds, it would, for all intents and purposes, freeze
the targeted object.
A particle beam weapon would be able to generate power many
times more destructive than any laser in development. Such a
weapon would essentially be composed of two parts: a power
source and an accelerating tunnel. If a functional particle
beam weapon could be built, it would use its power source to
accelerate electrons, protons or hydrogen atoms through the
tunnel, which would focus these charged particles into a beam
that would be fired at the target.
The "bolts" of energy fired from the particle beam weapon
would enter into the target's materials, passing the energy
onto the atoms that compose the target. This impact would be
like a cue ball striking a racked group of billiard balls on a
pool table. The rapid increase in the target object's
temperature would cause the object to explode in a matter of
seconds following impact.
The major obstacle in developing a functional particle beam
weapon has been creating a power source that is light enough
to put into space, but that can produce millions of electron
volts of power and tens of megawatts of beam power. A
conventional power station would be able to meet those power
demands, but it is far too large to put into orbit. So far,
scientists have not been able to develop a suitable
lightweight power source that can meet those power demands.
A third space weapon in
development is the military space plane. A joint
venture between NASA and the Air Force is trying to develop a
space plane labeled the X-33. While President Clinton line
item vetoed the Air Force portion of the military space plane
in 1998, NASA has continued development of the space plane for
non-military reasons. If the Air Force were to rejoin the
development of the space plane at a later date, it could use
the vehicle to control space both offensively and defensively.
Photo courtesy NASA
The X-33 space plane may be used for military
combat in space.
Currently, there are many international agreements that
have prohibited the deployment of such weapons into space. One
such agreement is the Outer Space Treaty of 1967, which
covers outer space, the Moon, and other celestial bodies. The
one loop hole in this treaty is that it doesn't say anything
about the area just above Earth, where most satellites are in
orbit. However, the treaty does prohibit placing nuclear
weapons, or other weapons of mass destruction, into Earth's
orbit. But the question is, are lasers and particle beams
weapons of mass destruction? The treaty further prohibits the
construction of military bases and fortifications on any
celestial body, including the Moon.
In November, 1999, 138 United Nations members voted to
reaffirm the Outer Space Treaty. Only the United States and
Israel abstained from the vote. Based on that vote, which
upheld the ban on weapons in space, it would seem that space
weapons will remain grounded for the time being. So, for now,
thoughts of Death Star-like weapons and X-Wing fighters,
battling it out thousands of miles into space, will have to be
put on hold.
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