Although the end of the Cold War signaled a reduction in the likelihood of global nuclear conflict, the threat from ballistic missiles has grown steadily as sophisticated missile technology becomes available on a wider scale to countries hostile to the U.S. and its allies.

The proliferation of weapons of mass destruction, and the ballistic and cruise missiles that could deliver them, pose a direct and immediate threat to the security of the United States and its deployed military forces, allies, and friends. We have already witnessed the willingness of countries to use theater-class ballistic missiles for military purposes. Since 1980, ballistic missiles have been used in six regional conflicts. Ballistic missiles, including intercontinental and submarine launched ballistic missiles (ICBMs and SLBMs) exist in abundance around the world today.

The Airborne Laser System is designed to detect, track, target, and kill threatening missiles, whether they are short-, medium-, or long-range. The system is deployed on the front of a Boeing 747-400 freighter. (MDA photo)

The objective of the Missile Defense Agency (MDA) — formerly the Ballistic Missile Defense Agency (BMDA) — is to prevent further proliferation of these weapons and roll back the capability in potentially hostile nations where it already exists.

The United States is fielding a Ballistic Missile Defense System (BMDS) to provide such protection. The BMDS is a collection of elements and components that are integrated to achieve the best possible performance against a full range of potential threats. Formerly, some of these elements were restricted to act as independent systems. Once the U.S. withdrew from the Anti-Ballistic Missile Treaty in 2002, MDA was able to realize the benefits of integrating complementary, layered elements. The U.S. has fielded BMD assets to demonstrate missile defense technologies and provide limited defense against long-range ballistic missile attacks aimed at any of the 50 states.

Three Phases of Missile Defense

There are three phases of missile defense: the boost phase, the midcourse phase, and the terminal phase. In the boost phase, the missile is being propelled through the atmosphere into space. In the midcourse phase, the warhead separates from the missile body and proceeds through space. This phase generally lasts from 30 seconds to one minute. Finally, in the terminal phase, the warhead re-enters the atmosphere and falls to earth towards its intended target.

Boost Phase — The boost phase is the part of a missile flight path from launch until it stops accelerating under its own power. Typically, the boost phase ends at altitudes of 300 miles or less, and within the first 3 to 5 minutes of flight. During this phase, the rocket is climbing against the Earth’s gravity. Intercepting a missile in its boost phase is the ideal solution. The two types of boost defense elements are directed energy systems using high-power lasers such as the Airborne Laser, and kinetic energy interceptors.

The Airborne Laser’s role is to defend the United States, its allies, and American troops deployed around the globe by detecting, tracking, and destroying hostile ballistic missiles soon after they are launched. It is designed to detect, track, target, and kill threatening missiles, whether they are short-, medium-, or long-range. The system uses an amalgamation of technologies including deployment on a Boeing 747-400 freighter and a Chemical Oxygen Iodine Laser (COIL). The laser destroys the missile by heating its metal skin until it cracks, which causes the boosting missile to fail.

The Airborne Laser will represent the world’s first use of a directed energy weapon system in an airborne combat environment. The six-module COIL system is capable of producing a megawatt-class beam effective out to a range of several hundred kilometers. To ensure the laser beam hits its target with sufficient destructive power, the system uses adaptive optics to compensate for beam deflection and dispersion caused by atmospheric disturbance.

An Airborne Laser mission begins when one or more of its six infrared sensors detects the heat from the plume of a hostile-launched missile. One laser swings to the compass bearing indicated by the sensors and locks on to the missile to provide preliminary tracking data. The aircraft’s onboard computer system processes and refines the data, triggering the firing of a second laser that finds the missile and settles on the aim point for the high-energy laser. A third laser measures the amount of atmospheric disturbance. Finally, the COIL fires along a computer-determined path, concentrating sufficient energy on the missile’s metal skin to destroy the boosting missile.

A Standard Missile-3 (SM-3) is launched from the Aegis destroyer USS Decatur during an MDA ballistic missile flight test on June 22, 2007. Two minutes later, the SM-3 intercepted a separating ballistic missile threat target, launched from the Pacific Missile Range Facility in Kauai, Hawaii. (US Navy photo)

Kinetic energy interceptors are mobile, multi-use intercepts to destroy medium- and intermediate-range ballistic missiles, and intercontinental ballistic missiles in boost, ascent, and midcourse phases of flight. This mobile capability is used in the boost and ascent phases, where missiles are destroyed shortly after they are launched, prior to the release of their lethal payloads and countermeasures. This element is deployed close to a threat on mobile land launchers or on sea-based platforms such as surface ships or submarines.

Midcourse Phase — The midcourse phase of a ballistic missile trajectory allows the longest window of opportunity to intercept an incoming missile up to 20 minutes. This is the point where the missile has stopped thrusting so it follows a more predictable glide path. The midcourse interceptor and a variety of radars and other sensors have a longer time to track and engage the target compared to boost and terminal interceptors. Also, more than one interceptor could be launched to ensure a successful hit. A downside to the longer intercept window is the attacker has an opportunity to deploy countermeasures against a defensive system. However, the interceptor and other sensors have more time to observe and discriminate countermeasures from the warhead. The Midcourse Defense Segment has ground- and sea- based elements.

The primary elements of the Midcourse Defense Segment are Ground- Based Midcourse Defense (GMD) and Aegis Ballistic Missile Defense (Aegis BMD).

GMD uses a variety of satellites and radars to obtain information on launch warning, tracking, targeting, and discrimination, This information provides the Ground-Based Interceptor with the ability to locate, identify, and destroy the incoming ballistic missile warhead. The Ground-Based Interceptor is comprised of a booster vehicle and an exoatmospheric kill vehicle. It launches into space based on threat identification and command authority. The booster flies to a projected intercept point and releases the kill vehicle, which uses on-board sensors, with assistance from ground-based assets, to acquire the target. The kill vehicle performs final discrimination and steers itself to collide with the enemy warhead, destroying it by sheer force of impact.

The Aegis Ballistic Missile Defense is the sea-based element of the BMDS. Aegis destroyers, on BMD patrol, detect and track ICBMs and report track data to the missile defense system. This capability shares tracking data to cue other missile defense sensors and provides fire control data to GMD interceptors. Aegis cruisers and long-range surveillance and track destroyers are being equipped with the capability to intercept short- and medium-range, unitary, and separating ballistic missile threats. Engaging missiles in the ascent phase reduces the overall BMD system’s susceptibility to countermeasures.

Terminal Phase — The primary elements in the Terminal Defense Segment are Terminal High Altitude Area Defense (THAAD), PATRIOT Advanced Capability-3 (PAC-3), Arrow (a joint effort between the U.S. and Israel), and Medium Extended Air Defense System (MEADS) (a co-developmental program with Germany and Italy).

The THAAD element will provide the BMDS with rapidly deployable ground-based missile defense components that deepen, extend, and compliment the BMDS to defeat short- to intermediate-range ballistic missiles. THAAD is a land-based element that has the capability to shoot down a ballistic missile, both inside and just outside the atmosphere, using “hit-to-kill” technology (directly hitting the incoming missile to destroy it), providing regional or limited-area terminal defense. THAAD provides an effective defense against ballistic missiles carrying weapons of mass destruction by making it likely that their lethal payloads will be destroyed before reaching the ground.

THAAD consists of four principal components: truck-mounted launchers; interceptors; radars; and command, control, and battle management (C2BM). It can be air-lifted to almost anywhere in the world within hours, and all components fit inside a C-130 aircraft.

Patriot Advanced Capability-3 (PAC-3) is the most mature element of the BMDS. Now operational with the U.S. Army, this element is a land-based system built on the proven Patriot air and missile defense infrastructure. As the best defense against short-range ballistic missiles, Patriot was deployed to the Middle East as part of Operation Iraqi Freedom, where it successfully engaged all threatening ballistic missiles within its scope of operation.

In the event of an enemy launch, a single interceptor equipped with the Multiple Kill Vehicle payload will not only destroy the reentry vehicle, but all credible threat objects including countermeasures the enemy deploys to try and spoof U.S. defenses. (MDA photo)

The Arrow weapon system provides Israel with a capability to defend its borders and U.S. troops deployed in the region against short- and medium-range ballistic missiles. The system became operational in October 2000.

MEADS is cooperative effort among the United States, Germany, and Italy to develop an air and missile defense system that is mobile and transportable. It is capable of countering ballistic missiles and air-breathing threats such as aircraft, unmanned aerial vehicles, and cruise missiles, utilizing a radar with a 360° capability. MEADS’ role in ballistic missile defense is to bridge the gap between man-portable systems like the Stinger missile and the higher levels of the BMDS such as the THAAD system.

Advanced Technologies

The Advanced Technology program is responsible for identifying and developing new technologies to improve BMDS capabilities. The program leads a national effort to develop algorithms for improved target discrimination, sensor data fusion, and battle management capabilities. Advanced Technology serves as the focal point for identification and evaluation of advanced concepts with applicability to the system. For those technologies selected for development, Advanced Technology promotes their integration into the system. Technology areas for advanced development include active and passive sensors, directed energy systems (lasers), interceptors, portable energy sources, advanced decision and discrimination algorithms, fuels, and materials research.

Advanced Technology also conducts the Technology Applications Program to assist businesses in the commercialization of developed technologies through product development, partnerships, and private funding to improve a product’s technological maturity, while sharing cost and risk. The Deputy for Advanced Technology acts as the primary coordinator for the Missile Defense Agency’s Science and Technology (S&T) activities within the Department of Defense and allied nations. MDA is developing a laser radar (Ladar) that will be integrated with a passive electro-optical sensor so that target acquisition, tracking, and discrimination functions can be performed from an interceptor platform. Extensions of this technology may apply to airborne and space-based surveillance and tracking.

The Advanced Discriminating Ladar Technology (ADLT) program is developing a range-resolved Doppler imaging (RRDI) Ladar to improve the target-tracking and selection capability for long-range targets that cannot be resolved by passive optical sensors. The ADLT program improves 3D tracking of objects within the field-of-view; improves correlation accuracy of detected objects with data in an uplinked target object map; improves resolution of closely spaced objects; and improves onboard discrimination of targets based on size and motion.

The Early Launch Detection and Tracking (ELDT) technology detects threat missiles quickly after launch to track missiles during the boost and ascent phases, and to determine the missile type. All-weather surveillance and tracking sensors are used to improve the timeliness and reliability of cues provided to other sensors and engagement systems within the BMD system. Radio frequency concepts may use over-the-horizon- radar techniques or the scattered signals from indigenous transmitters. Electro-optical concepts exploit inherent signal characteristics that separate the signature of the boosting missile from background clutter.

Through the High-Altitude Airship (HAA) Advanced Concept Technology Demonstration (ACTD), the MDA will design and produce a lighter-than-air, high-altitude airship prototype. The HAA ACTD will demonstrate the feasibility and potential military utility of an unmanned, untethered, gas-filled, solar-powered airship. The current HAA design is a non-rigid, super-pressure airship. It is expected to be 150' in diameter by 500' long. Its total volume will be 5.6 × 106 cubic feet. The airship will be controlled by four electrically powered, vectored propulsion pods. A solar-powered regenerative battery-based power system with thin-film photovoltaics on the hull surface will provide power generation. The payload bay will be externally mounted and provide for multiple payloads with a weight of up to 4,000 pounds.

It has potential use as a sensor, communications, and/or weapons platform, and acts as a demonstrator for future high-altitude airships. Its utility as a mobile, retaskable, high-altitude, geostationary, long-endurance platform will span from communications and weather/ environmental monitoring to short- and long-range missile warning, surveillance, and target acquisition.

Multiple Kill Vehicle

The Multiple Kill Vehicle (MKV) system allows more than one kill vehicle to be launched from a single booster. The system consists of a carrier vehicle with onboard sensors and a number of small, simple kill vehicles that can be independently targeted against objects in a threat cluster. The integrated payload is designed to fit on existing and planned interceptor boosters.

The MKV mission is to negate medium and intercontinental ballistic missiles equipped with multiple warheads and/or decoys in midcourse attack phase with a single engaging interceptor missile. The MKV payload intercepts the threat clusters with kill vehicles launched from a single carrier vehicle. Using data from existing and planned ground-based, sea-based, air, and space-based sensors, the BMDS interceptors equipped with MKV payloads are capable of attacking and negating the potentially large number of inbound warheads in multiple threat clusters. Therefore, the MKV capability dramatically alters the battle space in favor of the United States, its allies, and friends.

At the system level, MKV will intercept multiple midcourse targets from one defensive interceptor booster and will be fully integrated with the BMDS. The carrier vehicle will assign kill-vehicle- to-target and manage the kill vehicle engagements; the carrier vehicle will fly and navigate to the carrier vehicle’s assigned target intercept areas, identify the target, select a target aim-point, home-in on the target, and destroy the target.

MDA continues its research and development program to improve and upgrade existing capabilities. In 2008, MDA will work to add more networked, forward-deployed sensors, and increasingly capable interceptors at sea and on land.

For more information on the Missile Defense Agency (MDA), visit

Defense Tech Briefs Magazine

This article first appeared in the December, 2007 issue of Defense Tech Briefs Magazine.

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