Failed Intercept Shows Challenge of Hit-to-Kill Defenses

SM-3 Remains Near-Term Weapon of Choice for Midcourse Missile Defense

By HUNTER C. KEETER
Associate Editor

As the Navy and the Missile Defense Agency (MDA) prepare for the next test flight of the Aegis in the Pentagon's ballistic-missile defense program, lessons from the last flight, in which an interceptor rocket failed to destroy its target, underscore the challenges of hit-to-kill technology. Designed to destroy an incoming ballistic missile by striking it at high speed, hit-to-kill weapons rely on a team effort by radar, computers, rocket-boosters, and a kinetic warhead's guidance system to locate and intercept an elusive target. The MDA is working with the Navy, Army, and Air Force on land-, sea-, and air-based missile-defense systems, several of which rely on hit-to-kill methodology.

During a June 18 flight test called Flight Mission Five at the Pacific Missile Range Facility, Kauai, Hawaii, the MDA and the Navy launched a Standard Missile 3 (SM-3) to intercept an Aries target. It missed, according to MDA officials, because of a failure in the weapon's attitude control assembly, a part of the kinetic warhead that helps keep a target in view of the interceptor's sensors.

An investigative team found that the most likely cause "was a failure in the attitude control assembly's valve ball chamber" which caused the warhead to spin out of control, according to an Aug. 19 written statement by a Defense Department official. "The primary objective of Flight Mission Five was to characterize the SM-3 kinetic warhead's guidance, navigation, and control operation in space using an upgraded solid divert and attitude control system (SDACS). [The June 18 test] was the first flight of the upgraded SDACS."

The test was the latest step in the Pentagon's struggle of more than two decades to develop a missile defense scheme that would be affordable, effective, and able to overcome political barriers such as objections by some in Congress to placing weapons on foreign soil or in space. President Ronald Reagan's Star Wars scheme would have placed a large part of the nation's missile-defense program in space. President Bill Clinton had a variety of missile defense efforts underway, such as the Navy Theater Wide system, but at the end of his presidency deferred deployment decisions to his successor. President George W. Bush announced Dec. 17 that the Pentagon would deploy the initial elements of a missile-defense system by September 2004.

A centerpiece of the Bush plan was his decision in June 2002 to withdraw from the 1972 Anti-Ballistic Missile Treaty, which restricted the United States to two anti-missile sites and forbade deployment of a nationwide missile defense system. Withdrawal means the Pentagon now has the political flexibility to move its launchers around and can have many more launch sites.

Bush's long-term goal is to devise a multilayered defense system using an array of interceptors, sensors based in space, on land, and at sea, and a battle management scheme to make the various elements work in concert. Sea-based portions of that system, which would include the SM-3, initially would be based on the Aegis Weapons System and deployed by 2006.

The Navy enjoyed a run of three successful intercepts in tests that preceded Flight Mission Five. It was part of a planned six-flight test series under the MDA plan to deliver initial capability in 2004 against short- to intermediate-range ballistic missiles. As is true of all test shots in the ballistic-missile defense program series, Flight Mission Five was more complex than its predecessors. Subsequent tests--such as Flight Mission Six, which may occur after the first week in December--are expected to include more complex conditions. In total, nine flight missions have been planned for the Sea-Based Midcourse Defense effort, at an average cost of between $38 million and $42 million each.

The SDACS contains two pulse motors and a main motor. During Flight Mission Five, the Missile Defense Agency tested the main motor in sustained mode, plus one pulse. During Flight Mission Six, the Missile Defense Agency will limit the operation of SDACS to sustained mode only. Despite the setback of the last intercept test, observers--such as Phillip E. Coyle III, a senior advisor to the Center for Defense Information (a Washington, D.C., think-tank) and former assistant secretary of defense--have offered generally favorable assessments of the sea-based missile defense program. Coyle told Sea Power Aug. 25 that he has "been impressed with the Navy's missile-defense program. I have been impressed that the Navy has not raised unrealistic expectations, nor has it raised expectations prematurely."

The Navy last year lent to the MDA the guided-missile cruiser USS Lake Erie, one of 65 warships in U.S. service equipped with the Aegis combat system, an anti-air warfare computer system coupled with the SPY-1 radar. Since the end of the 1990s, Lake Erie has served as the test ship for a series of related air defense programs.

In addition to the Lake Erie, the Arleigh Burke-class guided-missile destroyer USS Russell participated in Flight Mission Five. Also an Aegis-equipped class, the Arleigh Burke destroyers are expected to cooperate with cruisers to form an air-defense network that is to be applied to missile-defense missions for the foreseeable future. With 66 Aegis ships set to sail world-wide--including six for Japan, four for Spain, and five for Norway--these provide a global link in the world battle space. Forty years from now, 60 percent to 70 percent of the Navy's surface combatant force will still be Aegis ships, according to Christopher D. Myers, vice president for business development with Lockheed Martin's Maritime Systems & Sensors unit.

In 2001, under a restructuring of its programs, the MDA re-named Navy Theater Wide, designating it the Sea-Based Midcourse Defense segment of the overall ballistic-missile defense effort, which includes land-based interceptors and radar as well. The midcourse defenses now in development, including the Navy's efforts, are aimed at defeating ballistic missiles during the middle portion of the flight from launch to a target.

In addition to the SM-3, interceptor rockets for midcourse defense are being developed for land-based sites at Fort Greeley, Alaska, and Vandenberg AFB, Calif. The Navy and the Missile Defense Agency have so far argued successfully before Congress that putting midcourse defensive weapons aboard ships offers the advantage of mobility and greater proximity to a ballistic-missile launch site, providing more time for a successful interception. A networked land and sea system could include 20 interceptors aboard ships and 20 on land, sharing information from various types of radar located at sea and on bases, located in Alaska or California, or at the Kwajalein Atoll Missile Testing Range in the Pacific Ocean.

According to Coyle and others, midcourse defense systems may have 20 minutes or more to accomplish the task of intercepting and destroying an incoming missile. Related efforts to stop a ballistic missile during the boost phase, or the first few seconds after launch, present even greater challenges, particularly in terms of time.

Hitting ballistic missiles during their boost phase would require an interceptor weapon that performs at more than twice the speed of current weapons such as the SM-3. According to the Navy, there remains a requirement to "develop a ship-based capability to intercept threat missiles early in the ascent phase of midcourse flight." The "ascent midcourse phase" interceptor system is to be completed by 2008 or 2010, according to MDA's stated goals. Since 1999, the United States and Japan have worked cooperatively on a research and development program to provide advanced missile technologies that could be incorporated into an ascent midcourse phase defense program.

Coyle noted, "There is still a long way to go and a lot of work to be done, specifically on developing a new missile that would be about twice as fast as anything they now have in inventory." *