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Space Wars: Coming to the Sky Near You?
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Scientific American Magazine - February 18, 2008

A recent shift in U.S. military strategy and provocative actions by china
threaten to ignite a new arms race in space. But would placing weapons in
space be in anyone's national interest?

By Theresa Hitchens

"Take the high ground and hold it!" has been standard combat
doctrine for armies since ancient times. Now that people and their
machines have entered outer space, it is no surprise that generals
the world over regard Earth orbit as the key to modern warfare. But
until recently, a norm had developed against the weaponization of
space--even though there are no international treaties or laws
explicitly prohibiting nonnuclear antisatellite systems or weapons
placed in orbit. Nations mostly shunned such weapons, fearing the
possibility of destabilizing the global balance of power with a
costly arms race in space.

In war, do not launch an ascending attack head-on against the enemy
who holds the high ground. Do not engage the enemy when he makes a
descending attack from high ground. Lure him to level ground to do
battle.
--Sun Tzu, Chinese military strategist, The Art of War, circa 500
B.C.

That consensus is now in danger of unraveling. In October 2006 the
Bush administration adopted a new, rather vaguely worded National
Space Policy that asserts the right of the U.S. to conduct "space
control" and rejects "new legal regimes or other restrictions that
seek to prohibit or limit U.S. access to or use of space." Three
months later the People's Republic of China shocked the world by
shooting down one of its own aging Fengyun weather satellites, an
act that resulted in a hailstorm of dangerous orbital debris and a
deluge of international protests, not to mention a good deal of
hand-wringing in American military and political circles. The launch
was the first test of a dedicated antisatellite weapon in more than
two decades--making China only the third country, after the U.S. and
the Russian Federation, to have demonstrated such a technology. Many
observers wondered whether the test might be the first shot in an
emerging era of space warfare.

Critics maintain it is not at all clear that a nation's security
would be enhanced by developing the means to wage space war. After
all, satellites and even orbiting weapons, by their very nature, are
relatively easy to spot and easy to track, and they are likely to
remain highly vulnerable to attack no matter what defense measures
are taken. Further, developing antisatellite systems would almost
surely lead to a hugely expensive and potentially runaway arms race,
as other countries would conclude that they, too, must compete. And
even tests of the technology needed to conduct space battles--not to
mention a real battle--could generate enormous amounts of wreckage
that would continue to orbit Earth. Converging on satellites and
crewed space vehicles at speeds approaching several miles a second,
such space debris would threaten satellite-based telecommunications,
weather forecasting, precision navigation, even military command and
control, potentially sending the world's economy back to the 1950s.

"Star Wars" Redux
Since the dawn of the space age, defense planners have hatched
concepts for antisatellite and space-based weaponry--all in the
interest of exploiting the military advantages of the ultimate high
ground. Perhaps the most notable effort was President Ronald
Reagan's Strategic Defense Initiative (SDI)--derided by its critics
as "Star Wars." Yet by and large, U.S. military strategy has never
embraced such weapons.

Traditionally, space weapons have been defined as destructive
systems that operate in outer space after having been launched
directly from Earth or parked in orbit. The category includes
antisatellite weapons; laser systems that couple ground-based lasers
with airship- or satellite-mounted mirrors, which could reflect a
laser beam beyond the ground horizon; and orbital platforms that
could fire projectiles or energy beams from space. (It is important
to note that all nations would presumably avoid using a fourth kind
of antisatellite weapon, namely, a high-altitude nuclear explosion.
The electromagnetic pulse and cloud of highly charged particles
created by such a blast would likely disable or destroy nearly all
satellites and manned spacecraft in orbit [see "Nuclear Explosions
in Orbit," by Daniel G. Dupont; Scientific American, June 2004].)

But virtually no statement about space weapons goes politically
uncontested. Recently some proponents of such weapons have sought to
expand the long-held classification I just described to include two
existing technologies that depend on passage through space:
intercontinental ballistic missiles (ICBMs) and ground-based
electronic warfare systems. Their existence, or so the argument
goes, renders moot any question about whether to build space weapons
systems. By the revised definition, after all, "space weapons"
already exist. Whatever the exact meaning of the term, however, the
questions such weapons raise are hardly new to think tanks and
military-planning circles in Washington: Is it desirable, or even
feasible, to incorporate antisatellite weapons and weapons fired
from orbit into the nation's military strategy?

The new National Space Policy, coupled with the Chinese test, has
brought renewed urgency to that behind-the-scenes debate. Many
American military leaders expressed alarm in the wake of the Chinese
test, worrying that in any conflict over Taiwan, China could
threaten U.S. satellites in low Earth orbit. In April 2007 Michael
Moseley, the U.S. Air Force chief of staff, compared China's
antisatellite test with the launch of Sputnik by the Soviet Union in
1957, an act that singularly intensified the arms race during the
cold war. Moseley also revealed that the Pentagon had begun
reviewing the nation's satellite defenses, explaining that outer
space was now a "contested domain."

Congressional reaction fell along predictable political lines.
Conservative "China hawks" such as Senator Jon Kyl of Arizona
immediately called for the development of antisatellite weapons and
space-based interceptors to counter Chinese capabilities. Meanwhile
more moderate politicians, including Representative Edward Markey of
Massachusetts, urged the Bush administration to begin negotiations
aimed at banning all space weapons.

International Power Plays

Perhaps of even greater concern is that several other nations,
including one of China's regional rivals, India, may feel compelled
to seek offensive as well as defensive capabilities in space. The
U.S. trade journal Defense News, for instance, quoted unidentified
Indian defense officials as stating that their country had already
begun developing its own kinetic-energy (nonexplosive, hit-to-kill)
and laser-based antisatellite weapons.

If India goes down that path, its archrival Pakistan will probably
follow suit. Like India, Pakistan has a well-developed ballistic
missile program, including medium-range missiles that could launch
an antisatellite system. Even Japan, the third major Asian power,
might join such a space race. In June 2007 the National Diet of
Japan began considering a bill backed by the current Fukuda
government that would permit the development of satellites for
"military and national security" purposes.

As for Russia, in the wake of the Chinese test President Vladimir
Putin reiterated Moscow's stance against the weaponization of space.
At the same time, though, he refused to criticize Beijing's actions
and blamed the U.S. instead. The American efforts to build a missile
defense system, Putin charged, and the increasingly aggressive
American plans for a military position in space were prompting
China's moves. Yet Russia itself, as a major spacefaring power that
has incorporated satellites into its national security structure,
would be hard-pressed to forgo entering an arms race in space.

Given the proliferation of spacefaring entities, proponents of a
robust space warfare strategy believe that arming the heavens is
inevitable and that it would be best for the U.S. to get there first
with firepower. Antisatellite and space-based weapons, they argue,
will be necessary not only to defend U.S. military and commercial
satellites but also to deny any future adversary the use of space
capabilities to enhance the performance of its forces on the
battlefield.

Yet any arms race in space would almost inevitably destabilize the
balance of power and thereby multiply the risks of global conflict.
In such headlong competition--whether in space or
elsewhere--equilibrium among the adversaries would be virtually
impossible to maintain. Even if the major powers did achieve
stability, that reality would still provide no guarantee that both
sides would perceive it to be so. The moment one side saw itself to
be slipping behind the other, the first side would be strongly
tempted to launch a preemptive strike, before things got even worse.
Ironically, the same would hold for the side that perceived itself
to have gained an advantage. Again, there would be strong temptation
to strike first, before the adversary could catch up. Finally, a
space weapons race would ratchet up the chances that a mere
technological mistake could trigger a battle. After all, in the
distant void, reliably distinguishing an intentional act from an
accidental one would be highly problematic.

Hit-to-Kill Interceptors

According to assessments by U.S. military and intelligence officials
as well as by independent experts, the Chinese probably destroyed
their weather satellite with a kinetic-energy vehicle boosted by a
two-stage medium-range ballistic missile. Technologically, launching
such direct-ascent antisatellite weapons is one of the simplest ways
to take out a satellite. About a dozen nations and consortia can
reach low Earth orbit (between roughly 100 and 2,000 kilometers, or
60 to 1,250 miles, high) with a medium-range missile; eight of those
countries can reach geostationary orbit (about 36,000 kilometers, or
22,000 miles, above Earth).

But the real technical hurdle to making a hit-to-kill vehicle is not
launch capacity; it is the precision maneuverability and guidance
technology needed to steer the vehicle into its target. Just how
well China has mastered those techniques is unclear. Because the
weather satellite was still operating when it was destroyed, the
Chinese operators would have known its exact location at all times.

Ground-Based Lasers

The test of China's direct-ascent antisatellite device came on the
heels of press reports in September 2006 that the Chinese had also
managed to "paint," or illuminate, U.S. spy satellites with a
ground-based laser [see lower box on page 83]. Was Beijing actually
trying to "blind" or otherwise damage the satellites? No one knows,
and no consensus seems to have emerged in official Washington
circles about the Chinese intent. Perhaps China was simply testing
how well its network of low-power laser-ranging stations could track
American orbital observation platforms.

Even so, the test was provocative. Not all satellites have to be
electronically "fried" to be put out of commission. A 1997 test of
the army's MIRACL system (for midinfrared advanced chemical laser)
showed that satellites designed to collect optical images can be
temporarily disrupted--dazzled--by low-power beams. It follows that
among the satellites vulnerable to such an attack are the orbital
spies.

The U.S. and the former Soviet Union began experimenting with
laser-based antisatellite weapons in the 1970s. Engineers in both
countries have focused on the many problems of building high-power
laser systems that could reliably destroy low-flying satellites from
the ground. Such systems could be guided by "adaptive optics":
deformable mirrors that can continuously compensate for atmospheric
distortions. But tremendous amounts of energy would be needed to
feed high-power lasers, and even then the range and effectiveness of
the beams would be severely limited by dispersion, by attenuation as
they passed through smoke or clouds, and by the difficulty of
keeping the beams on-target long enough to do damage.

During the development of the SDI, the U.S. conducted several laser
experiments from Hawaii, including a test in which a beam was
bounced off a mirror mounted on a satellite. Laser experiments
continue at the Starfire Optical Range at Kirtland Air Force Base in
New Mexico. Pentagon budget documents from fiscal years 2004 through
2007 listed antisatellite operations among the goals of the Starfire
research, but that language was removed from budget documents in
fiscal year 2008 after Congress made inquiries. The Starfire system
incorporates adaptive optics that narrow the outgoing laser beam and
thus increase the density of its power. That capability is not
required for imagery or tracking, further suggesting that Starfire
could be used as a weapon.

Yet despite decades of work, battle-ready versions of
directed-energy weapons still seem far away. An air force planning
document, for instance, predicted in 2003 that a ground-based weapon
able to "propagate laser beams through the atmosphere to [stun or
kill low Earth orbit] satellites" could be available between 2015
and 2030. Given the current state of research, even those dates seem
optimistic.

Co-orbital Satellites

Recent advances in miniaturized sensors, powerful onboard computers
and efficient rocket thrusters have made a third kind of
antisatellite technology increasingly feasible: the offensive
microsatellite. One example that demonstrates the potential is the
air force's experimental satellite series (XSS) project, which is
developing microsatellites intended to conduct "autonomous proximity
operations" around larger satellites. The first two microsatellites
in the program, the XSS-10 and XSS-11, were launched in 2003 and
2005. Though ostensibly intended to inspect larger satellites, such
microsatellites could also ram target satellites or carry explosives
or directed-energy payloads such as radio-frequency jamming systems
or high-powered microwave emitters. Air force budget documents show
that the XSS effort is tied to a program called Advanced Weapons
Technology, which is dedicated to research on military laser and
microwave systems.

During the cold war the Soviet Union developed, tested and even
declared operational a co-orbital antisatellite system--a
maneuverable interceptor with an explosive payload that was launched
by missile into an orbit near a target satellite in low Earth orbit.
In effect, the device was a smart "space mine," but it was last
demonstrated in 1982 and is probably no longer working. Today such
an interceptor would likely be a microsatellite that could be parked
in an orbit that would cross the orbits of several of its potential
targets. It could then be activated on command during a close
encounter.

In 2005 the air force described a program that would provide
"localized" space "situational awareness" and "anomaly
characterization" for friendly host satellites in geostationary
orbit. The program is dubbed ANGELS (for autonomous nanosatellite
guardian for evaluating local space), and the budget line believed
to represent it focuses on acquiring "high value space asset
defensive capabilities," including a "warning sensor for detection
of a direct ascent or co-orbital vehicle." It is clear that such
guardian nanosatellites could also serve as offensive weapons if
they were maneuvered close to enemy satellites.

And the list goes on. A "parasitic satellite" would shadow or even
attach itself to a target in geostationary orbit. Farsat, which was
mentioned in an appendix to the [Donald] Rumsfeld Space Commission
report in 2001, "would be placed in a 'storage' orbit (perhaps with
many microsatellites housed inside) relatively far from its target
but ready to be maneuvered in for a kill."

Finally, the air force proposed some time ago a space-based
radio-frequency weapon system, which "would be a constellation of
satellites containing high-power radio-frequency transmitters that
possess the capability to disrupt/destroy/disable a wide variety of
electronics and national-level command and control systems."

Air force planning documents from 2003 envisioned that such a
technology would emerge after 2015. But outside experts think that
orbital radio-frequency and microwave weapons are technically
feasible today and could be deployed in the relatively near future.

Space Bombers

Though not by definition a space weapon, the Pentagon's Common Aero
Vehicle/Hypersonic Technology Vehicle (often called CAV) enters into
this discussion because, like an ICBM, it would travel through space
to strike Earth-bound targets. An unpowered but highly maneuverable
hypersonic glide vehicle, the CAV would be deployed from a future
hypersonic space plane, swoop down into the atmosphere from orbit
and drop conventional bombs on ground targets. Congress recently
began funding the project but, to avoid stoking a potential arms
race in space, has prohibited any work to place weapons on the CAV.
Although engineers are making steady progress on the key
technologies for the CAV program, both the vehicle and its space
plane mothership are still likely decades off.

Some of the congressional sensitivity to the design of the CAV may
have arisen from another, much more controversial space weapons
concept with parallel goals: hypervelocity rod bundles that would be
dropped to Earth from orbital platforms. For decades air force
planners have been thinking about placing weapons in orbit that
could strike terrestrial targets, particularly buried, "hardened"
bunkers and caches of weapons of mass destruction. Commonly called
"rods from God," the bundles would be made up of large tungsten
rods, each as long as six meters (20 feet) and 30 centimeters (12
inches) across. Each rod would be hurled downward from an orbiting
spacecraft and guided to its target at tremendous speed.

Both high costs and the laws of physics, however, challenge their
feasibility. Ensuring that the projectiles do not burn up or deform
from reentry friction while sustaining a precise, nearly vertical
flight path would be extremely difficult. Calculations indicate that
the nonexplosive rods would probably be no more effective than more
conventional munitions. Furthermore, the expense of lofting the
heavy projectiles into orbit would be exorbitant. Thus, despite
continued interest in them, rods from God seem to fall into the
realm of science fiction.

Obstacles to Space Weapons

What, then, is holding the U.S. (and other nations) back from a
full-bore pursuit of space weapons? The countervailing pressures are
threefold: political opposition, technological challenges and high
costs.

The American body politic is deeply divided over the wisdom of
making space warfare a part of the national military strategy. The
risks are manifold. I remarked earlier on the general instabilities
of an arms race, but there is a further issue of stability among the
nuclear powers. Early-warning and spy satellites have traditionally
played a crucial role in reducing fears of a surprise nuclear
attack. But if antisatellite weapons disabled those eyes-in-the-sky,
the resulting uncertainty and distrust could rapidly lead to
catastrophe.

One of the most serious technological challenges posed by space
weapons is the proliferation of space debris, to which I alluded
earlier. According to investigators at the air force, NASA and
Celestrak (an independent space-monitoring Web site), the Chinese
antisatellite test left more than 2,000 pieces of junk,
baseball-size and larger, orbiting the globe in a cloud that lies
between about 200 kilometers (125 miles) and 4,000 kilometers (2,500
miles) above Earth's surface. Perhaps another 150,000 objects that
are a centimeter (half an inch) across and larger were released.
High orbital velocities make even tiny pieces of space junk
dangerous to spacecraft of all kinds. And ground stations cannot
reliably monitor or track objects smaller than about five
centimeters (two inches) across in low Earth orbit (around a meter
in geostationary orbit), a capability that might enable satellites
to maneuver out of the way. To avoid being damaged by the Chinese
space debris, in fact, two U.S. satellites had to alter course. Any
shooting war in space would raise the specter of a polluted space
environment no longer navigable by Earth-orbiting satellites.

Basing weapons in orbit also presents difficult technical obstacles.
They would be just as vulnerable as satellites are to all kinds of
outside agents: space debris, projectiles, electromagnetic signals,
even natural micrometeoroids. Shielding space weapons against such
threats would also be impractical, mostly because shielding is bulky
and adds mass, thereby greatly increasing launch costs. Orbital
weapons would be mostly autonomous mechanisms, which would make
operational errors and failures likely. The paths of objects in
orbit are relatively easy to predict, which would make hiding large
weapons problematic. And because satellites in low Earth orbit are
overhead for only a few minutes at a time, keeping one of them
constantly in range would require many weapons.

Finally, getting into space and operating there is extremely
expensive: between $2,000 and $10,000 a pound to reach low Earth
orbit and between $15,000 and $20,000 a pound for geostationary
orbit. Each space-based weapon would require replacement every seven
to 15 years, and in-orbit repairs would not be cheap, either.

Alternatives to Space Warfare

Given the risks of space warfare to national and international
security, as well as the technical and financial hurdles that must
be overcome, it would seem only prudent for spacefaring nations to
find ways to prevent an arms race in space. The U.S. focus has been
to reduce the vulnerability of its satellite fleet and explore
alternatives to its dependence on satellite services. Most other
space-capable countries are instead seeking multilateral diplomatic
and legal measures. The options range from treaties that would ban
antisatellite and space-based weapons to voluntary measures that
would help build transparency and mutual confidence.

The Bush administration has adamantly opposed any form of
negotiations regarding space weapons. Opponents of multilateral
space weapons agreements contend that others (particularly China)
will sign up but build secret arsenals at the same time, because
such treaty violations cannot be detected. They argue further that
the U.S. cannot sit idly as potential adversaries gain spaceborne
resources that could enhance their terrestrial combat capabilities.

Proponents of international treaties counter that failure to
negotiate such agreements entails real opportunity costs. An arms
race in space may end up compromising the security of all nations,
including that of the U.S., while it stretches the economic
capacities of the competitors to the breaking point. And whereas
many advocates of a space weapons ban concede that it will be
difficult to construct a fully verifiable treaty--because space
technology can be used for both military and civilian
ends--effective treaties already exist that do not require strict
verification. A good example is the Biological Weapons Convention.
Certainly a prohibition on the testing and use (as opposed to the
deployment) of the most dangerous class of near-term space
weapons--destructive (as opposed to jamming) antisatellite
systems--would be easily verifiable, because earthbound observers
can readily detect orbital debris. Furthermore, any party to a
treaty would know that all its space launches would be tracked from
the ground, and any suspicious object in orbit would promptly be
labeled as such. The international outcry that would ensue from such
overt treaty violations could deter would-be violators.

Since the mid-1990s, however, progress on establishing a new
multilateral space regime has lagged. The U.S. has blocked efforts
at the United Nations Conference on Disarmament in Geneva to begin
negotiations on a treaty to ban space weapons. China, meanwhile, has
refused to accept anything less. Hence, intermediate measures such
as voluntary confidence-building, space traffic control or a code of
responsible conduct for spacefaring nations have remained stalled.

Space warfare is not inevitable. But the recent policy shift in the
U.S. and China's provocative actions have highlighted the fact that
the world is approaching a crossroads. Countries must come to grips
with their strong self-interest in preventing the testing and use of
orbital weapons. The nations of Earth must soon decide whether it is
possible to sustain the predominantly peaceful human space
exploration that has already lasted half a century. The likely
alternative would be unacceptable to all.