From this came the requirement for an interim ballistic missile defense system that could be operational in just a few years. Luckily for the Gulf War Coalition, this became the famous Patriot Advanced Capability Two (PAC2) surface-to-air missile that dueled the Iraqi Scuds in the skies over the Middle East. PAC-2, however, was hardly the answer to the Iraqi Scud threat, much less to that of more advanced ballistic missile systems around the world. This is why the Army is preparing to deploy the new PAC3 interceptor, which has a greater hit-to-kill capability, as well as greater range, in 1999. But there are only a handful of Patriot units available for deployment (the U.S. Army has just four Patriot battalions), and the defensive "footprint" for PAC-3 is relatively small. With ballistic missiles proliferating at an alarming rate, deployed U.S. forces are going to need more and better defense to operate successfully in an expeditionary environment.
The Ballistic Missile Threat
In assessing the need for theater ballistic missile defense (TBMD) systems, it is important to understand the different classes of ballistic missiles. Table 1 shows the basic missile types. Of the five categories, the submarine-launched and intercontinental types are of little interest to our fielded forces. The remaining three classes, however, pose a growing threat, and systems to defend against them are not covered by treaty. This means that TBMD systems capable of engaging so-called theater ballistic missiles (short-range [SRBMs], medium-range [MRBMs], and intermediate-range [IRBMs]) are legal and can be developed and deployed without restriction.
So far, the most commonly used class of ballistic missile has been the SRBM, which includes the family of Scud-based systems. These are the "entry-level" missiles for countries intent on acquiring a basic SRBM capability. As shown in Table 2, however, Scud-based systems are hardly the only threat. All of the SRBMs in Table 2 are equipped with high-explosive warheads, although "special" payloads (nuclear, chemical, and biological) also can be fitted. As illustrated in Table 3, the well-intentioned efforts at nonproliferation have failed to slow the spread of SRBM technology since the end of the Cold War—and are unlikely to do so now. Even worse, given the history of the nations possessing SRBM technology, it is likely that the deployed forces of the United States will face further ballistic missile bombardment in the future.
A History of Terror
Operation Desert Storm was not the first conflict in which ballistic missiles were used widely. Nazi Germany alone launched more V-2/A-4 guided missiles at Allied targets in England and Belgium than have been fired in all other conflicts combined (see Table 4). In general, SRBM operational use has been limited to acts of psychological terror and political coercion. An extreme example of this was China's firing of four CSS-X-7/M-9/11 missiles into the waters around Taiwan. Though these were announced as part of an "exercise," the firings clearly were designed to intimidate the people of Taiwan during their 1996 elections. Amazingly, only the Germans during World War II ever tried to use ballistic missiles in a concerted campaign to disrupt a major target: the port of Antwerp. Should an enemy of the United States ever decide to follow the German example, it could prove to be a severe impediment to our attaining our military goals and objectives.
More than other services, the expeditionary forces of the Navy and Marine Corps have a vulnerability to ballistic missile attack. Experiences from World War II and Operation Desert Storm clearly illustrate that port and airfield facilities, so necessary for the delivery of amphibious units and other follow-on forces, can be interdicted easily by ballistic missile attack. So great is the concentration of vulnerable targets in such facilities that a steady barrage of missiles (say, six a day) inevitably would hit something vital. In addition, such attacks also have a significant morale and terror effect on the civilian/military workforce that must unload and transport the material and equipment passing through these portals. Unfortunately, the small number of Army/allied Patriot fire units means that the sea services must develop an organic TBMD capability, if future expeditionary operations are to proceed successfully.
The Navy Area TBMD System
Though rarely acknowledged in the media, the U.S. Navy Aegis fleet has been tracking ballistic missile engagements and tests since Desert Storm. These efforts have proved that the Aegis combat system is capable of engaging ballistic missiles in combat, given an appropriate interceptor surface-to-air missile (SAM). This was the starting point for the initial Aegis ballistic missile defense capability. Known as the Navy Theater Area system, it leverages a six-decade investment in SAM technology, as well as the infrastructure of the existing Aegis combat system. This includes:
- Ships . Twenty-two Mk 41 vertical launch system (VLS) equipped Aegis cruisers and more than two dozen Arleigh Burke (DDG-51)-class destroyers currently are in the fleet. Eventually, the fleet of VLS-equipped Aegis ships may grow to more than 80 vessels.
- Aegis Combat System . The mature system includes the SPY-1 (S-Band) radar, the Mk 99 fire-control system, and Mk 41 VLS launchers.
- Missiles . The family of SAMs used by the Aegis combat system has evolved over more than five decades. To date, this had included six separate generations of missile, dating back to the early Terrier/Tartar systems.
- Aegis Contractor Team . The Aegis combat system is backed by a huge industry team, which has more than a half-century of experience developing SAM, radar, and other key systems needed for a successful theater ballistic missile defense program.
- Aegis Personnel/Training Base . With more than 15 years of fleet operational experience and hundreds of ship deployments, the Aegis-experienced base of personnel is large and capable. In addition, there is a well-established Aegis schoolhouse system that keeps fleet crews ready and up to date.
With this experience and infrastructure in place, the U.S. Navy has embarked on a program to imbed a basic endoatmospheric theater ballistic missile defense capability into the planned upgrades of the Aegis combat system. This upgrade, which takes advantage of a number of recent system improvements, actually will reduce the number of system variants, and help reduce the operations and maintenance costs of the entire Aegis fleet.
The Theater Area upgrade is a simple series of add-ons, composed of the following subsystem improvements:
- SM-2 Block IVA Surface-to-Air Missile. An improved version of the existing SM-2, this version includes a new booster rocket and fuse, modified warhead, and improved dual-mode seeker.
- Computers. To add the needed power to determine TBMD intercepts, several commercial off-the-shelf processor boards will be added to the existing computer arrays.
- Firmware. A number of Aegis subsystems (SPY-1 radar, Mk 41 vertical-launch system, etc.) will receive upgrades to their onboard "firmware" code to accommodate the new Area TBMD capabilities.
- Software. To add the Area TBMD capabilities, around 400,000 lines of computer code had to be either written or modified.
These modest upgrades will allow any VLS-equipped Aegis cruiser or destroyer to conduct ballistic missile defense operations, as well as provide improved air defense capabilities against high-speed and sea-skimming airborne targets. All are based on existing system components and software, taking advantage of the large growth margins that were designed into Aegis at its conception.
Perhaps the most impressive upgrade is the new variant of the Standard missile, the SM-2 Block IVA (RIM156A). This new interceptor is designed to become the new baseline U.S. Navy antiair/TBMD weapon, and will be used to engage everything from supersonic sea-skimming cruise missiles to ballistic missiles. To accommodate this wide range of targets, several improvements have been made:
- Mk 72 Booster. To give the SM-2 Block IV the needed kinematic performance to engage ballistic missile targets, a 21-inch/533-mm diameter booster rocket has been added to the basic Standard missile. This fast-burning motor allows the SM-2's Mk 104 motor to function as a second stage/sustainer, helping the missile maintain speed and energy for engagement.
- Imaging Infrared (IIR) Seeker. To assist the missile in the final engagement with high-speed targets, an IIR seeker array has been added. This helps the missile impact at the precise aimpoint desired on the target.
- Fuse/Warhead. A new, ultrasensitive, forward-looking fuse is teamed with a modified Mk 125 directional blast-fragmentation warhead. This new version of the Mk 125 has an increased number of warhead firing squibs, which gives better blast directional control on detonation.
Assuming that the new bird can be produced in the numbers needed to equip the 80-odd Aegis ships of the fleet, the Navy will be able to deploy more than a dozen Area TBMD-capable warships at any time. This number might be further increased if the system improvements and SM-2 Block IVA are made available for sale to the Japanese and Spanish navies.
One major advantage of the Navy Area theater ballistic missile defense system will be that the traditional "defended footprint" will not apply. Current ground-based systems such as Patriot have such limited engagement zones that they must be co-located with the target of the incoming ballistic missile to be effective. The SM-2 Block IVA, however, is a considerably faster and more energetic missile than PAC-2 or PAC-3, and thus has a much greater engagement envelope. Also, because the ship can be rapidly and easily relocated, the engagement geometry can be optimized to generate a maximum number of shots at each target. In fact, the battlespace that a single Area TBMD-capable Aegis ship will be capable of defending is many times that of an entire Patriot battalion. Based on early test data, the SM-2 Block IVA can intercept out to ranges of 100-120 km/61-75 miles down range, and up to 40 km/25 miles altitude. All this means that the system will be able to provide a much more secure "bubble" for the forces being defended, especially when used in tandem with ground-based TBMD systems.
The Aegis Theater Area System Engagement Sequence
The planned engagement sequence for an Area TBMD action is similar to that of a normal Aegis combat situation. It will include:
- Detection/Classification. Warning of an incoming ballistic missile launch can be received directly from national-level sensors (such as the Defense Support Program satellite system or theater-level systems such as E-2C Hawkeyes or E-3 Sentrys). However, test data indicate that the ship's own SPY-1 radar system may be best for initial detection and classification.
- Tracking. Once a target has been detected and classified as a hostile ballistic missile, the Aegis combat system will assign it a track number, and begin the decision cycle of whether to engage. Also at this point, the commanding officer will order "weapons free," as the actual engagement to come will happen far too quickly for any human intervention.
- Engagement. When the Aegis combat system is ready, it will automatically engage the incoming missiles with SM-2 Block IVA missiles. Once launched, the SM-2 Block IVAs will fly a parabolic trajectory designed to take them over their targets. At the same time, the onboard autopilots will be attempting to optimize the final engagement geometry, to maximize the chances of killing hits. Once the IIR seeker picks up the incoming ballistic missile, it will dive down onto the target and begin the endgame. This should result in a kill, even against ballistic missiles armed with nuclear or chemical/biological warheads.
- Kill Assessment. The final step in the Theater Area system engagement process is to assess whether a target has been killed or requires further engagement (if possible). This will be accomplished through the onboard SPY-1 radar and the improved software developed for the Area TBMD system, as well as a real-time downlink from the onboard IIR seeker. If needed, additional missile engagements then would be initiated.
Area TBMD System Testing and Introduction
Early testing of the SM-2 Block [VA has been very successful, with the initial shot at White Sands Missile Range resulting in a direct hit on a Lance missile. In addition, tests on a high-speed rocket sled have validated the modified warhead and fuse, especially its ability to deal with nuclear and chemical/biological warheads. With the concept validation completed successfully, a system test and introduction plan called Linebacker has been formulated, which will begin in early fiscal year 1999. It will start with two Aegis cruisers, the Lake Erie (CG-70) and Port Royal (CG-73) being modified to Area TBMD combat system standard. At the same time, 35 production SM-2 Block IVA missiles will be used by the two ships in a series of firing tests off Hawaii. These will culminate in a final test, which will have one of the cruisers engaging five targets (two ballistic and three low-altitude cruise missiles) simultaneously. Should this be successful, the Linebacker ships would be ready to deploy sometime in 2000.
What comes after the Theater Area system? Current plans have every VLS-capable Aegis ship getting the capability by 2010. In addition, the U.S. Navy also is developing an exo-atmospheric ballistic missile defense capability, designed to deal with the long-range threat of IRBMs and MRBMs.
The need for an effective theater ballistic missile defense system is here and now. Fortunately for the nation and our allies, the U.S. Navy has recognized the need and is driving to deploy the Theater Area system in response. Combined with the deployment of the improved PAC-3 interceptor, the United States finally will be able to start to project a useful TBMD "bubble" over deployed forces overseas. As the Aegis fleet continues to gather data and exercise with simulated engagements, the system will grow in both effectiveness and credibility. Given the failure of nonproliferation protocols over the past few years, we can only hope that the efforts of the Navy and other services will be in time.
Mr. Gresham is an author and historian, and is the primary researcher for Tom Clancy’s Guided Tour Series of Books .