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June 1, 2018
U.S. Missile Defense Programs at a Glance

Wade Boese

President George W. Bush announced December 17, 2002, that the United States would field initial elements of a limited national missile defense system by September 2004.

The United States has researched and worked on the development of missile defenses to counter ballistic missiles for more than five decades. Bush’s declaration marks the second time that the United States has moved to deploy a system against long-range missiles following negotiation of the 1972 Anti-Ballistic Missile Treaty, from which the United States withdrew June 13, 2002. The first effort, Safeguard, was shut down within a few months of being declared operational in October 1975. Under Safeguard, the United States deployed missile interceptors in North Dakota to protect an ICBM field.

The Bush administration inherited seven main missile defense programs, including the strategic ground-based interceptor system, and two related satellite programs from the Clinton administration. For the most part, despite increased spending the Bush administration has not been able to accelerate the various programs’ development. A sea-based system has also been canceled, and another system, the space-based laser, has been dramatically scaled back to a general research program.

The following factfile provides a brief look at each major U.S. missile defense program. It contains information on what type of ballistic missile each defense is intended to counter. Also included are Pentagon estimates on when each defense may have an initial, rudimentary capability as well as when it may be fully operational.

Ballistic Missile Basics

Ballistic missiles are classified by the maximum distance that they can travel, which is a function of how powerful the missile’s engines (rockets) are and the weight of the missile’s warhead. To add more distance to a missile’s range, rockets are stacked on top of each other in a configuration referred to as staging. There are four general classifications of ballistic missiles:

  • Short-range ballistic missiles, with a range less than 1,000 kilometers (approximately 620 miles)
  • Medium-range ballistic missiles, with a range of 1,000–
    3,000 kilometers (approximately 620-1,860 miles)
  • Intermediate-range ballistic missiles, with a range of 3,000–5,500 kilometers (approximately 1,860-3,410 miles)
  • Intercontinental ballistic missiles (ICBMs), with a range of more than 5,500 kilometers

Short- and medium-range ballistic missiles are referred to as theater ballistic missiles, whereas ICBMs, or long-range ballistic missiles, are described as strategic ballistic missiles. The ABM Treaty prohibited the development of nationwide strategic defenses but permitted development of theater missile defenses.

All ballistic missiles have three stages of flight:

  • The boost phase begins at launch and lasts until the rocket engines stop firing and pushing the missile away from Earth. Depending on the missile, this stage lasts between three and five minutes. During much of this time, the missile is traveling relatively slowly, although toward the end of this stage an ICBM can reach speeds of more than 24,000 kilometers per hour. The missile stays in one piece during this stage.
  • The midcourse phase begins after the rockets finish firing and the missile is on a ballistic course toward its target. This is the longest stage of a missile’s flight, lasting up to 20 minutes for ICBMs. During the early part of the midcourse stage, the missile is still ascending toward its apogee, while during the latter part it is descending toward Earth. It is during this stage that the missile’s warhead, as well as any decoys, separate from the delivery vehicle.
  • The terminal phase begins when the missile’s warhead re-enters the Earth’s atmosphere, and it continues until impact or detonation. This stage takes less than a minute for a strategic warhead, which can be traveling at speeds greater than 3,200 kilometers per hour.

Short- and medium-range ballistic missiles may or may not exit the atmosphere. They also may stay in one piece instead of deploying a separating warhead, and are less likely to employ countermeasures that could accompany an ICBM.

Ground-Based Midcourse Defense

Program & Key Elements
  • The key element of the ground-based midcourse defense is a ground-based missile interceptor consisting of a powerful multistage booster and an exoatmospheric kill vehicle (EKV), which separates from the booster in space and seeks out its target through radar updates and use of its onboard visual and infrared sensors.
  • The EKV destroys its target by colliding with it. This process is referred to as hit-to-kill.
Designed to Counter
  • The projected system’s goal is to intercept strategic ballistic missile warheads in the midcourse stage.
  • To date, the system has had five successful intercept attempts in eight developmental tests.
  • After four straight successes, the system failed to hit its target in the most recent test December 11, 2002. Another intercept attempt is not planned until at least late 2003 following the selection of a multistage booster.
  • The development of the multistage booster is more than two years behind schedule. Early Pentagon testing plans called for the booster to be integrated into an actual intercept attempt during the first few months of 2001, but that will not occur until at least late 2003. Two companies are currently working on separate booster models, both of which will be flight-tested twice in the summer of 2003. MDA may keep both or select one of the boosters for use in future intercept testing.
  • Lieutenant General Ronald Kadish, director of the Pentagon’s Missile Defense Agency, declared October 31, 2002, that “[o]ne of my greatest disappointments has been not being able to produce a booster for this ground-based system.”
  • The Pentagon is currently planning to deploy six missile interceptors, which are to incorporate the new booster, at Fort Greely, Alaska, and four more interceptors at Vandenberg Air Force Base, California, by September 2004. Another 10 interceptors are to be deployed at Fort Greely during 2005.
  • There are no plans to fire interceptors from Fort Greely for testing purposes.
  • Clinton’s missile defense plans called for deployment of 20 missile interceptors in Alaska by 2005.
  • The interceptors under the Clinton plan were to have been supported by a land-based X-band radar, but the Bush administration announced plans August 31, 2002, to develop a sea-based X-band radar instead.
  • Pentagon plans call for the new radar, which will be put on a mobile sea platform, to be completed by September 2005.
  • Bush’s plans also call for the missile interceptors to be supported by an upgraded, although less capable, early-warning radar on Shemya Island at the western tip of the Aleutian Islands chain. This radar, known as the Cobra Dane radar, will only be able to track missiles fired from the direction of Asia because the radar is fixed to face northwest.

Aegis Ballistic Missile Defense (BMD)

(Referred to as Navy Theater Wide by the Clinton administration)

Program & Key Elements
  • The key elements of the proposed sea-based defense are a ship-based missile (Standard Missile-3, or SM-3) and the Aegis combat system, an advanced system that can detect and track more than 100 targets simultaneously while directing a ship’s weapons to counter incoming air, surface, and submarine threats.
  • The SM-3 is a hit-to-kill missile comprised of a three-stage booster with a kill vehicle.
  • Two Pentagon reports have declared that the Aegis combat system, particularly its radar, is not capable of supporting a strategic missile defense mission.
  • The SM-3 is also considered too slow to intercept a strategic ballistic missile.
Designed to Counter
  • Initially, the Aegis BMD is geared toward defending against short-, medium-, and intermediate-range ballistic missiles during their midcourse stage with an emphasis on the ascent phase.
  • Eventually, the Pentagon wants the defense to be capable of countering strategic ballistic missiles, possi-bly in the boost phase.
  • A senior Pentagon official announced May 2, 2002, that the Pentagon would also explore whether the system can be adapted to counter short- and medium-range ballistic missiles in their terminal stage.
  • In a January 25, 2002, test, the system intercepted a target for the first time, but the flight paths of the interceptor and target had been plotted in such a way that an intercept was expected. A second test in June, which was described as “identical” to the first, also succeeded.
  • The third and latest test, which took place on November 21, 2002, also resulted in the target being destroyed. In this test, the target was still ascending, whereas in the previous two tests it was descending.
  • The target used in the three intercept tests is not reflective of what the system is expected to engage in a real-world situation. The target used is larger and slower-moving than what the defense is expected to counter.
  • Clinton administration plans called for five intercept tests to be completed by September 2002, but the Pentagon has only conducted three so far.
  • As part of its initial missile defense capability, the Bush administration announced December 17, 2002, that it will try to deploy up to 20 sea-based interceptors on three ships during 2004 and 2005. Another 15 ships are to receive upgraded radars to improve their missile tracking capabilities.
  • Kadish estimated in July 2001 that testing the system against long-range ballistic missiles could begin in 2007 or 2008.

Airborne Laser (ABL)

Program & Key Elements
  • The key element of the proposed ABL system is a modified Boeing 747 plane equipped with a chemical oxygen-iodine laser.
  • The laser beam is produced by a chemical reaction.
Designed to Counter
  • Although the Pentagon originally aimed to field the ABL against theater ballistic missiles, the Pentagon now contends the ABL may have an inherent capability against strategic ballistic missiles as well.
  • The expanded ABL objective is to shoot down all ranges of ballistic missiles in their boost phase.
  • The first ABL test plane made its inaugural flight on July 18, 2002. The plane was not equipped with the laser, which is still under development.
  • The first attempt to intercept a ballistic missile target is supposed to occur in late 2004 or mid-2005. But Kadish indicated in April 2003 that the estimated heavy weight of the laser is proving troublesome and could delay the program. Kadish added, “We are right on the edge of making this very revolutionary technology either prove itself or fail. And we just don’t know the answer to that question yet.”
  • The Clinton administration planned for the first ABL intercept attempt to take place in 2003.
  • The Pentagon said in 2002 that it wanted to have one ABL available for emergency use in 2004 and two or three ABL aircraft operational between 2006 and 2008. At this time, the earliest an ABL will be available for any use is 2005.

Theater High Altitude Area Defense (THAAD)

Program & Key Elements
  • THAAD’s main components are a missile comprised of a single rocket booster with a separating kill-vehicle that seeks out its target with the help of a specifically designed THAAD radar.
  • The THAAD kill vehicle is hit-to-kill.
  • THAAD missiles are fired from a truck-mounted launcher.
Designed to Counter
  • THAAD’s mission is to intercept short- and medium-range ballistic missiles at the end of their midcourse stage and in the terminal stage. Intercepts could take place inside or outside the atmosphere.
  • The system had two successful intercept attempts in the summer of 1999 after experiencing six test failures between April 1995 and March 1999.
  • The THAAD missile is currently being redesigned.
  • THAAD flight tests are scheduled to resume in 2004. Intercept attempts against threat-representative targets are set for 2006.
  • Current Pentagon plans call for THAAD testing through at least 2008, although the Pentagon also envisions deploying THAAD interceptors sometime between 2006 and 2008.

Patriot Advanced Capability-3 (PAC-3)

Program & Key Elements

  • PAC-3 consists of a one-piece, hit-to-kill missile interceptor fired from a mobile launching station, which can carry 16 PAC-3 missiles.
  • The missile is guided by an independent radar that sends its tracking data to the missile through a mobile engagement control station.

Designed to Counter

  • PAC-3 is designed to defend against short- and medium-range ballistic missiles in their terminal stage at lower altitudes than the THAAD system.


  • During earlier developmental testing, the system struck nine out of 10 targets.
  • In four, more difficult operational tests between February and May 2002 that involved multiple interceptors and targets, seven PAC-3s were to be fired at five targets. Of the seven PAC-3s, two destroyed their targets, one hit but did not destroy its target, one missed its target, and three others did not launch.
  • PAC-3s destroyed two Iraqi short-range ballistic missiles in the latest conflict and reportedly shot down a U.S. fighter jet.


  • By the end of 2002, more than 50 PAC-3s had been delivered to the U.S. Army for deployment.
  • Kadish projected in March 2003 that about 350 PAC-3s should be available for use by the end of 2005.

Space Tracking and Surveillance System (STSS)

(Previously referred to as Space-Based Infrared System-low (SBIRS-low))

Program & Key Elements
  • STSS will initially comprise two satellites, but the constellation could expand to as many as 30 satellites.
Designed to Counter
  • STSS satellites are expected to support U.S. missile defense systems by providing tracking data on missiles during their entire flight.
  • The two STSS satellites are to be launched in fiscal year 2007. The SBIRS-low program had called for the first launch of a satellite a year earlier.
  • The first next-generation STSS satellite is to be launched in 2011.
  • Two satellites would provide little, if any, operational capability. The Pentagon estimates that at least 18 satellites would need to be deployed to provide coverage of key regions of concern. Worldwide coverage could require up to 30 satellites.

Space-Based Infrared System-high (SBIRS-high)

Program & Key Elements
  • SBIRS-high will be comprised of four satellites in geosynchronous orbit and sensors on two host satellites in a highly elliptical orbit.
Designed to Counter
  • SBIRS-high’s primary objective is to provide early warning of global ballistic missile launches.
  • A geosynchronous satellite launch was set for fiscal year 2005, but it is now slated for October 2006.
  • The first payload for the two satellites in a highly elliptical orbit was supposed to be delivered in early 2003, but a U.S. Air Force spokesperson said in May 2003 that the payload “encountered issues during final testing” and that it is now scheduled for delivery later in the summer.
  • The first geosynchronous satellite is to provide an initial operational capability in fiscal year 2007. The operation of multiple satellites is supposed to be tested in fiscal year 2009.