How Missile Defense Systems Will
Work by Kevin
Bonsor
A National Missile Defense (NMD) system has been the topic
of much debate in the United States for more than half a
century. According to its supporters, such a system would
provide a sort of protective shield against a limited missile
attack. In 1999, the U.S. Congress decided that the time for
talk was over -- they passed a bill calling for the
implementation of the NMD system to defend the United States
from a growing number of countries developing long-range
missile technologies.
Photo courtesy BMDO The United States has plans to deploy a
national missile shield within the next
decade.
During the 2000 presidential campaign, George W.
Bush made it clear that his administration will strongly
back a NMD program, even at the expense of damaging
U.S.-Russian relations. Russia has protested the U.S.
government's plans for a national missile shield. Since taking
office, Bush and Secretary of Defense Donald Rumsfeld
have pushed ahead with plans to build the $30.2-billion
missile-defense system, and might have it operational as soon
as 2005.
If you've wondered how the U.S. is planning to target and
destroy enemy ballistic missiles, you'll want to read this
edition of How
Stuff WILL Work. We'll take you inside the U.S.
Defense Department's plans, and detail how NMD radar
systems and weapon interception will work.
Anticipating Attacks The NMD that is being
developed now is a toned-down version of the missile-defense
system proposed by President Reagan. Forget the lasers and
high-speed projectile weapons. The current system will not be
the impenetrable force-field that was envisioned in the
Strategic Defense Initiative (SDI). Instead, the United
States is working on a ground-based missile-defense system
that can respond to a limited missile attack. There are five
parts to this NMD system:
Upgraded Early-warning Radar (UEWR)
X-band/Ground-based Radar (XBR)
Space-based Infrared System (SBIRS)
Battle Management, Command, Control and
Communications (BMC3)
Ground-based Interceptors (GBIs)
The first part of NMD will involve detecting the launch of
enemy missiles and tracking them. Data gathered by a system of
radar and
satellites
will be sent back to personnel at the BMC3, who then will take
appropriate action. Let's take a look at the three components
that make up the detection and tracking system of NMD.
Upgraded Early-warning Radar (UEWR) - This is a
phased-array surveillance radar that can detect and
track ballistic missiles. NMD will use upgraded versions of
existing, ultra-high frequency early-warning radar. Hardware
modifications, including the replacement of existing
computers, graphic displays, communications equipment and
the radar receiver/exciter, will also be made to the EWR.
UEWRs will be used to detect and track missiles and other
projectiles during their midcourse phase, before cueing the
more precise X-Band Radar.
X-band/Ground-based Radar (XBR) - This consists
of a multi-function phased array radar that uses high
frequency and advanced radar-signal processing technology.
The XBR will track missiles as they fly closer to the United
States and assess which missiles are decoys and which are
armed with warheads. It is equipped with high-resolution
radar that allows it to accurately discriminate between
closely spaced objects. XBR radar has a 50-degree field of
view and can rotate 360 degrees to track targets. It will
transmit a radiation pattern in a narrow beam made up of
electromagnetic pulses. The radar site consists of the
X-band radar mounted on a pedestal, a control and
maintenance facility, a power generation facility and a
492-foot (150-m) protected area. The XBR site will cover
17.46 acres.
Space-based Infrared System (SBIRS) - Under
development by the Air Force, the SBIRS
satellites are on a 10-year development plan and are
expected to be added to the system three to four years after
NMD becomes operational. These satellites
will replace the current Defense Support Program (DSP)
satellites. There are three kinds of SBIRS satellites,
including four geostationary earth orbit (GEO)
satellites, two highly elliptical orbit (HEO)
satellites and an unspecified number of low earth
orbit (LEO) satellites. Eventually, there will be a
24-satellite constellation that will start tracking enemy
missiles earlier than radar, allowing for quicker response.
Image courtesy BMDO Artist's concept of SBIRS
satellite
Once radar has determined that an enemy missile has been
launched and is targeting the United States, the next phase is
to trigger one or more of the one-hundred interceptor missiles
to destroy the enemy ballistic missile before it reaches U.S.
air space. In the next section, you will learn how these
interceptors will target and destroy enemy missiles.
Shields Up! The whole idea of a NMD system
is to provide a type of shield that will guard against a light
ballistic-missile attack. Tracking enemy missiles by radar is
all well and good, but the point of the NMD system is to shoot
them down before they get to U.S. air space. This will be no
small task for the American military, and there is still much
testing to do. Let's take a look at one of the NMD's
ground-based interceptors.
Photo courtesy BMDO A payload vehicle launched from the Army's
Kwajalein Missile Range in the central Pacific Ocean
during Integrated Flight Test 5 on July 8, 2000. This
particular test was
unsuccessful.
The ground-based interceptors include two parts:
Payload Vehicle (PLV) - Flight tests have been
conducted with a PLV designed by Lockheed
Martin. It consists of the second and third stages of
retired Minuteman II boosters. The Minuteman II PLV
will later be replaced with a more advanced model for
one-site coverage of the entire United States. In addition
to the two booster stages on the PLV, there is also a
payload shroud attached to the top. The payload
shroud contains the EKV.
Exoatmospheric Kill Vehicle (EKV) - The kill
vehicle is the bullet of NMD's weapon system. This device is
intended to impact the targeted missile at a velocity of
15,000 mph (24,140 kph). The force of the collision should
destroy any ballistic missile, according to defense
officials.
The Battle Management, Command, Control and
Communications (BMC3) is the nerve center of the NMD
system. It begins tracking the threatening ballistic missile
as soon as it is launched by an enemy state. Information about
the enemy missile, including trajectory and probable impact
point, is relayed to the BMC3 from space-based sensors and
ground-based radar. In about 20 minutes after the enemy
missile is launched, an interceptor takes off. This
interceptor is programmed with information gained from the
radar.
Approximately two-and-a-half minutes after take-off, the
kill vehicle will separate from the booster. Just prior to
this separation, the kill vehicle will be given a final update
about the target. The kill vehicle will be about 1,400 miles
(2,253 km) away from its target when it separates. It will
then begin a set of maneuvers to calibrate its sensors. One
way it calibrates itself is by doing a star shot. A
star shot involves the EKV comparing itself to a constellation
that it is programmed to look for.
After the EKV is finished with calibration, it will seek
out, acquire and guide itself toward the target without any
external guidance or communications. This happens about six
minutes after takeoff. Then, the EKV draws a figurative bull's
eye on the targeted ICBM and begins a collision course. If
everything goes according to plan, the EKV will collide with
the target 120 miles (193 km) above Earth.
The process of pinpointing, aiming an interceptor at and
then killing the target with an EKV is very complex. There are
many components that have to be coordinated in real time, and
the entire procedure is completed less than 30 minutes after
the enemy missile takes off. Some critics have said that the
system is too complex to work effectively. The military has
had mixed success in testing the system.
Son of "Star Wars" The idea of a
missile-defense shield received a lot of attention about two
decades ago, when then-President Ronald Reagan proposed
his Strategic Defense Initiative (SDI). SDI called for
the deployment of space-based weapons that would shoot down
intercontinental ballistic missiles (ICBMs). Its
proposed use of lasers and spacecraft led the media and
critics to dub the system "Star Wars." While Reagan's
ambitious defense plan focused the world's attention on
missile-defense systems, the origins of such a system dates
back to the beginning of the Cold
War.
In 1946, following the discovery of a Nazi missile
program, which included plans to launch ICBMs at New York
City, the U.S. Army began to study interceptor missiles that
could destroy incoming ballistic missiles. In 1961, the Army
achieved the first successful intercept of a dummy ICBM
warhead, which led to a major push for the deployment of a
national defense shield. Six years later, the nation's first
missile-defense program, called Sentinel, was deployed.
In 1968, President Richard Nixon refocused the Sentinel
system to protect U.S. deterrent forces. The system was
renamed Safeguard. Safeguard interceptors were designed
to carry warheads to destroy re-entry vehicles of ICBMs.
Negotiations between the United States and the Soviet Union
over the proliferation of arms yielded the Anti-ballistic
Missile Treaty (ABM) of 1972. The ABM treaty banned
national missile-defense systems and was intended to prevent
the further escalation of the arms race between the two
countries. Under this treaty, the U.S. and the Soviet Union
agreed to limit missile-defense systems to two sites per
country, with no site having more than 100 interceptors. The
number of sites was reduced to one in 1974. The United States
placed its site in Grand Forks, N.D., but closed it in 1976.
The ABM treaty must be altered or rejected by the U.S. if
it is to deploy a national missile shield. During the 2000
presidential campaign, President Bush said that he would
pursue a national missile-defense system, even at the expense
of damaging foreign relations with Russia. He said that he
would work to amend the ABM treaty, but that he would push for
an American withdrawal from the treaty if he had to. Defense
secretary Rumsfeld has said that the ABM treaty is outdated
because many other nations have developed long-range missile
technology in the 30 years since it was signed.
Through the late 1970s and early 1980s, the military turned
its attention to developing a missile-defense system that did
not rely on warhead-equipped interceptors. To this end, the
U.S. Army developed a sensor and guidance system that enabled
an interceptor to collide with an enemy warhead. This
technology was demonstrated in 1984. (A year earlier,
President Reagan had announced his Strategic Defense
Initiative (SDI) in a televised national address).
Following the end of the Cold War, some suggested that
Reagan's SDI plans were no longer necessary. In 1991,
President George Bush called for a revised missile-defense
system that would use ground-based rocket interceptors. In
that same year, the world saw the first engagement of a
ballistic missile and a missile defense system during the
Persian Gulf War, when an American Patriot
missile destroyed an Iraqi Scud missile. Bush's plans
laid the groundwork for the system now being backed by his
son, George W. Bush.
In 1998, a congressional commission released the
Rumsfeld Report, which stated that several countries
would have the ability to strike the U.S. mainland within five
to 10 years. Six weeks after the report was released, North
Korea tested a three-stage missile that passed over Japan.
North Korean testing led the U.S. Congress to pass the National
Missile Defense Act of 1999, which committed the United
States to establishing a missile-defense shield. NMD is
projected to be operational by 2005.
