MISSILES: Last Line of Defense

DN Staff

April 24, 1995

10 Min Read
MISSILES: Last Line of Defense

Desert Storm and the war between Iran and Iraq demonstrated decisively that short-range and intermediate-range ballistic missiles and cruise missiles now occupy a prominent place in the armories of combatants. Ballistic and cruise-missile deployments will surely increase around the world during the next ten years. To deal with these emerging threats, the Ballistic Missile Defense Organization (BMDO) at the Department of Defense (DOD) has established a core Theater Missile Defense (TMD) program.

Three anti-missile systems comprise the TMD core program. They are: the Patriot Advanced Capability-3 (PAC-3); the AEGIS/Standard Missile-2 Block IVA (SM-2 Blk IVA); and the Theater High Altitude Area Defense (THAAD) system. According to the 1994 National Defense Authorization Act, the United States will develop these advanced theater missile defense systems for deployment, while continuing to comply with the 1972 ABM treaty.

All the TMD core programs will require considerable research and engineering work. In the near term, the enhanced Patriot Advanced Capability-2 (PAC-2), the AN/TPS-59 Radar, and the HAWK weapon system will provide an endoatomospheric defense against short-range ballistic missiles and cruise missiles.

Army TMD doctrine now calls for a defensive system that uses Patriot missiles and THAAD to create a two-layer defense in a theater of operations. During fiscal year 1998, the Army's 88 Patriot firing batteries will begin upgrading to the PAC-3 configuration. THAAD will go into service early in the next decade. Also, the THAAD program will develop a functional prototype system at the end of its Demonstration/Validation stage in 1997. According to BMDO, the prototype, called a User Operation Evaluation System (UOES), could be deployed to a combat theater.

The U.S. Navy intends to modify its AEGIS system to make the system effective against theater ballistic missiles (TBM). Called the Sea Based Area TBMD program, the Navy effort requires combat system modifications for AEGIS and the Standard Missile-2. Today, the AEGIS system uses the Standard Missile for air defense. After modification, the Standard missile will carry out what's called lower-tier (endoatmospheric) theater-wide intercepts. If contractors meet their schedules, a UOES prototype of the modified AEGIS system will be available in 1997.

Modifications to the HAWK weapon system and the TPS-59 radar will provide a TMD capability for the U.S. Marine Corps. Technical development and operational testing of the upgraded HAWK and TPS-59 will occur in fiscal year 1996, with the first operational units equipped late that year.

Modifications to the TPS-59 will allow detection of tactical ballistic missiles at ranges to 400 nautical miles and altitudes to 500,000 ft. A system called an Air Defense Communications Platform will provide a communications interface between the radar and the HAWK system. Under current plans, the USMC will retain one active duty HAWK battalion. It will consist of three batteries, each equipped with 12 launchers. Each launcher can carry three missiles. There will be a reserve HAWK battalion consisting of two batteries, each with eight launchers.

"We've improved the HAWK warhead and fuse, and incorporated software changes to provide greater capabilities against short-range tactical ballistic missiles," says Gail Hayes of Raytheon Corp. "Several countries have requested this upgrade, and we anticipate that others will as well."

New interceptors. There are two aspects to the enhanced-capability Patriot TMD system: A new, highly lethal hit-to-kill interceptor and an improved radar. Last year, after extensive tests, the Army selected the Extended Range Interceptor (ERINT) as the missile to be used for the PAC-3 program.

When the Patriot's radar detects a target, track information goes to a Fire Solution computer that calculates a predicted target acquisition point. It then electronically loads those coordinates into the missile. The interceptor flies to the acquisition point, acquires target update information from the ground-based radar, turns on its active seeker, and relies on its onboard systems to find the target.

Developed by the Loral Vought Div. of Loral Corp., Dallas, TX, ERINT/PAC-3 carries an on-board active Ka-band (GHz) seeker. Aerodynamic control vanes and impulse attitude control thrusters maneuver the missile for a hit-to-kill intercept. Honeywell Corp., Clearwater, FL, is responsible for the vehicle's inertial measurement unit, Rockwell International, Anaheim, CA for the millimeter-wave active radar seeker, Atlantic Research Corp. of Gainesville, VA, for the solid rocket motor and attitude control motors, and Lucas Aerospace, Aurora, OH for the aerodynamic maneuvering system.

ERINT represents the end product of some 30 years of work on non-nuclear anti-ballistic missiles. Engineers at the old Vought Corp., and then LTV Corp., developed the guidance concepts used in ERINT. Their work resulted in a project called FLAGE which, in 1987, demonstrated that hit-to-kill technology could work.

The PAC-3 is a hit-to-kill weapon designed to intercept tactical ballistic missiles at mid-endoatmospheric altitudes. Weighing 701 lbs (318 kg) at launch and 10 inches (255 mm) in diameter, the 16-ft (5.01m) long missile is inertially guided by aerodynamic fins toward a predicted impact point. In the terminal flight phase, the active, on-board radar seeker acquires the target and provides instantaneous data to the on-board guidance processor. The processor then calculates the endgame guidance commands that steer the missile to its target.

Two factors give the missile the agility it needs to close on a target: its small size and a set of attitude control motors located near the vehicle's nose. The PAC-3 fires these thrusters in flight to steer itself into the target. Loral Vought's Line Of Sight Antitank system (Design News 4-20-92) also employs this attitude control system.

PAC-3 will employ a lethality enhancer to improve its performance envelope against cruise missiles and high-performance aircraft. The lethality enhancer consists of a ring of tungsten fragments deployed pyrotechnically just before target intercept. It's located just aft of the PAC 3's attitude control motor module.

"Since the PAC-3 missile entered engineering and manufacturing development last October, we've been working to prepare the missile for full-scale production," says Sid Wells, vice president-air defense programs at Loral Vought. "We believe the missile is ideal for application to other missile defense systems because of its light weight, high performance, and ability to interface with different fire-control systems." In fact, Loral Vought believes the ERINT missile could provide theater ballistic missile defense aboard ships, and could be used with the HAWK system.

The ERINT missile will go through Developmental Test and Evaluation (DT&E) and flight tests using PAC-3 missile flight test software. DT&E will run from this year through 1998.

Radar upgrades will enhance the Patriot system. Benefits include: increased target detection range, positive target identification, more secure engagement of targets with small radar cross-sections, increased target-handling capability, and enhanced system survivability. Raytheon Corporation of Lexington, MA, will perform these upgrades.

Anchors aweigh. To enable the Navy's AEGIS system to destroy tactical ballistic missiles, SPY-1 radar computer programs and equipment will be modified to allow search at higher elevations and longer ranges. Doing so will allow the system to detect the missiles and track them.

Onboard a vessel carrying the modified AEGIS, the weapon control system will predict intercept points, fire missiles, and provide a data uplink to the missile as it flies out to attack the enemy's ballistic missile. AEGIS displays and all systems involved in attacking missiles will be updated to display missile tracks and to interface with off-ship sensors and other combat-system elements.

Now under development, the new SM-2 Block IVA missile will use an IR seeker to reduce miss distance. A new fuse will help ensure that the missile destroys its target. In addition to fighting ballistic missiles, the SM-2 Block IVA will retain its ability to combat aircraft and antiship cruise missiles.

Test and evaluation for sea-based TBMD includes early missile-hardware flight tests, IR seeker wind-tunnel and sled testing, and warhead development. Early testing at sea of prototype software and land-based development of AEGIS software and hardware will also take place. Sea tests will include multiple engagements, electronic countermeasures and other activities designed to test the system's robustness, according to BMDO.

Low-rate production of the new missile will begin in 1997. By the year 2000, some 90 missiles should be available to the Navy. The BMDO says that 35 missiles will be purchased for use with the Navy's UOES to deal with any potential contingencies. Early flight tests will begin this year-first at White Sands Missile Range, New Mexico, and then on an operational AEGIS ship. As of now, the DOD believes the first AEGIS theater missile defense system will enter service with the fleet in 1999.

At long range. The Army's THAAD system involves two programs aimed at solving separate, but closely linked, technical problems. They are the THAAD weapon system and the ground-based radar needed to direct the interceptor.

These elements will combine to engage targets at high altitudes and distances of more than 100 miles from the incoming missile's intended target. This long-range-intercept capability will minimize damage caused by debris generated above the target. Also, intercept will occur at a high enough altitude to ensure safe diffusion of chemical weapons. The THAAD system will receive cueing data from U.S. space-based sensors.

As for the interceptor, it's a single-stage, solid-fuel vehicle. The booster employs a thrust-vectoring nozzle to help stabilize and guide the missile, as well as a divert and attitude-control system. THAAD's booster provides initial thrust and acceleration. It also helps stabilize the vehicle by deploying a conical metal "flare" rather than fins. The flare deploys when the vehicle clears the Patriot-type launch canister. After several minutes of flight, the kill vehicle separates from the booster and maneuvers to the target.

Ground-based radar provides a predicted target intercept point and guidance data to the missile before launch. Able to receive in-flight data updates, the THAAD missile generates its terminal guidance data via a gimbal-mounted infrared seeker looking through a side-mounted, uncooled window. A shroud protects the seeker window prior to terminal homing, and separates from the missile as it closes in on the target.

Lockheed Missiles & Space Co. of Sunnyvale, CA, serves as prime contractor on THAAD. United Technologies Chemical Systems Div., San Jose, CA, has responsibility for the solid rocket booster motor, Rocketdyne Div. of Rockwell International in Canoga Park, CA, the kill-vehicle divert and attitude control system, Loral Infrared & Imaging Systems of Lexington, MA, the kill vehicle's infrared seeker, and Honeywell Space Systems Group Clearwater, FL, the missile avionics and navigation system.

Like the PAC-3, the THAAD missile is a hit-to-kill weapon. Unlike the PAC-3, it can perform intercepts either in the atmosphere (endoatmospheric intercept) or in space (exoatmospheric intercept).

THAAD's ground-based radar consists of five major elements: a single-faced, mobile, phased-array radar operating in the X-band (5200 to 11,000 MHz), and separate power generation, system cooling, equipment control, and operations control units.

The THAAD flight test program began last year at White Sands Missile Range. "The next major event in the program will be our first attempted intercept at White Sands this summer-and we expect a success," says Lockheed spokesman Eric DeRitis. Two test flights will precede the intercept. The first test flight of the full THAAD prototype is scheduled to take place before the end of June. System tests that are scheduled to follow the flight will demonstrate, in a step-by-step fashion, improved performance capability by the integrated missile, launcher, radar and C 3 I systems.

Defense authorities agree that U.S. military forces need some means of defeating tactical ballistic missiles. Leaving aside the non-technical (i.e. political) issues, interceptors of the sort described here represent a viable near-term method of accomplishing that objective.

Building the missiles, radar and support equipment for these systems will require spending billions of dollars. Clearly, the contracts can provide employment opportunities for many engineers and skilled workers employed by prime contractors and subcontractors.

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