U.S. Navy aircraft carriers are among the most survivable surface ships afloat today. They are built to withstand multiple hits and continue projecting firepower ashore. Yet a number of recent articles have charged that carriers are vulnerable to asymmetric threats, such as mines, torpedoes, cruise missiles, and—at least in the future—theater ballistic missites (TBMs). But, with the exception of TBMs, the Navy coped successfully with these same "antiaccess" threats during the Cold War.
Antiaccess analyses focus on remote potentialities in the future, rather than probable future threats. They do not account adequately for the complexity of an adversary's search and attack problem, battle group defense in depth enhanced by connecting sensors and weapons in new ways, and advantages of the carrier's inherent mobility and hull survivability. Indeed, if carriers at sea are vulnerable, the loss of fixed bases ashore must be a foregone conclusion.
Targeting Ships at Sea
Carriers and other surface ships cannot be threatened until the enemy locates, identifies, and maintains them as targets and can get within range to release weapons. This adds up to a most difficult task. Around the world, there are countless potential carrier operating areas; U.S. carriers move constantly among them to conduct operations. Consequently, the general locating information available is not sufficient for targeting. Because carriers are almost always on the move, ranging over hundreds of square miles, general locating information covers a huge geographic area.
Identifying and targeting carriers is much harder than finding their general operating areas. The intelligence, surveillance, and reconnaissance challenge is complex and intensive. The greatest advantage ships have in avoiding targeting is mobility, which requires a short detect-to-engage timeline and close geographic proximity that preclude most third-party (surveillance platform-to-shooter) targeting. Carriers conducting flight operations or transiting move routinely at speeds of 30 knots. As Chief of Naval Operations Admiral Vern Clark said recently at the Navy League's annual conference, "This movement translates into a 700 square mile area of uncertainty in 30 minutes. In an hour-and-a-half, it grows to 6,300 square miles; and, friends, that presents one heck of a targeting problem." It takes a high level of technical and operational sophistication to maintain accurate, real-time surveillance over such a large area. Thus, third-party targeting—which is likely to be challenged by U.S. forces in any event—is ineffective against moving targets because the area of uncertainty increases exponentially. At the same time, of course, the Navy seeks to destroy enemy reconnaissance and strike platforms as a key part of its defense-in-depth philosophy.
Although space systems are often presented as a panacea for targeting ships, currently there are no systems capable of continuously targeting moving ships because the cost benefits of such systems are not justifiable. For regional coverage of targeting quality, more than a hundred expensive, low-earth-orbit satellites are required to maintain continuous coverage. Fewer satellites can provide only gapped coverage, each gap representing a large, growing area of uncertainty in ship location that may cause confusion in ship tracks. Reacquisition by a follow-on satellite then correlates ships incorrectly, presenting a deceptive "seamless" picture that is simply inaccurate. Further, military satellites cannot gain and maintain track of moving carriers. While commercial sensor systems can target fixed sites, they are not designed for the moving-target task. Even the proposed—and extremely expensive—American Discoverer II satellite system, which is designed specifically to support time-critical strikes, will be incapable of targeting moving ships at sea except with gapped coverage. Moreover, when adequate space-based systems are fielded, they will be as vulnerable to blinding, jamming, deception, and destruction as they are now.
Navy Responses to the Threat Spectrum
Rather than rolling over and conceding battle space in the face of antiaccess challenges, the Navy continues to develop systems, concepts of operations, and tactics to counter evolving threats. Adversary platforms and weapons are becoming increasingly vulnerable as improved U.S. sensors sharpen clarity of the battle space and new weapons bring greater lethality and precision. Sensors on, above, and under the sea enable the real-time command structures of carrier battle groups to react rapidly with over-the-horizon attacks using weapon systems such as Aegis, Link-16, and Tomahawk missiles. A host of network-centric warfare initiatives—for example, cooperative engagement capability (CEC), unmanned underwater vehicles (UUVs), unmanned aerial vehicles (UAVs), advanced deployable system (ADS), and organic mine hunting—are being tested and will be deployed soon.
The CEC provides "sensors in depth" that increase greatly the effectiveness of defense-in-depth weapon systems. It is a well-tested fire-control data link that allows units to build composite tracks from fragmented data and to engage tracks with weapons even if the track is not held by a ship's own sensors. With CEC, ships can identify threat aircraft and missiles with near certainty and engage them at safe distance, rather than on the horizon. In addition, some of the CEC-capable E-2C Hawkeyes are to be outfitted with radar modernization; they will be able to identify threats over land and add further to battle group collective defenses. UUVs will map the ocean floor with high fidelity and detect and neutralize mines. UAVs will operate from surface combatants or carriers to provide battle space surveillance and awareness 24 hours a day.
During battle exercises, ADS alerts friendly forces to the presence of adversary submarines, opening them to air attack and trailing by friendly submarines and UUVs. New organic mine-hunting systems deployed from surface ships will neutralize mines and find paths through minefields. Consequently, it will be most difficult for launch platforms to position themselves successfully for attacks on carriers.
Today, surface combatants with Aegis systems and bi-static sonars, submarines, high-endurance undersea warfare helicopters, and long-range maritime patrol and combat air patrol aircraft can kill multiple enemy launch platforms before they reach effective firing ranges. Area defense ships can engage weapons aimed at the carrier with missiles such as the Standard SM-2 Block IV, a highly effective area defense weapon now in the fleet. In a busy and compressed battle space like the Persian Gulf, surveillance is complicated and reaction times are short. Nevertheless, the Navy continues to operate in that region with these systems to meet the evolving threat, asymmetric and otherwise.
Submarines pose a threat that requires dedicated resources to counter. However, to be effective, submarines must leave their ports, travel to enemy positions, and penetrate area defenses to get within range and attain a firing position. The Navy monitors ports and likely transit areas and defends carrier operating areas in depth as noted above. Carriers are fast targets that maneuver constantly to accommodate flight operations, thereby complicating enemy targeting. Alerted by communications and signals intelligence, patrolling submarines and ships, and covertly distributed advanced deployable systems, carriers can outpace submarines. They can survive attacks from side-attacking torpedoes because of their size—bigger is better in terms of hull survivability—and built-in features, such as the Torpedo Side Protection System (TSPS) that has been installed in almost half the carrier fleet. Should a submarine armed with modern under-bottom torpedoes penetrate defenses and maneuver to a firing position, the battle group can employ new countermeasures.
Carriers are unlikely to encounter bottom or moored mines when operating in water of greater than 650-foot depth. In shallow waters such as the Persian Gulf, carriers will operate in areas swept by mine-clearing helicopters and ships designed to find and neutralize mines. If a carrier hits a mine—for example, a floating mine—the damage will be mitigated by size and armor. Carriers have layered armor, double hulls, and large standoff distances. The TSPS provides hull standoff and hardening to limit damage from underwater detonations, including mines and small boats.
Surface combatants contribute substantially to defense against antiship cruise missiles and will become more effective with the introduction of cooperative engagement capability. In addition, the reliability of carrier combat systems is improving continuously. In a missile stream raid, area defense can shoot down enemy missiles while carrier self-defense systems—NATO Sea Sparrow and the Close-in Weapon System—pick up missiles that survive the outer defensive ring. New systems, such as CEC, combined with the powerful Aegis system, can network battle group sensors, thereby providing sensors and weapons in depth. Consequently, even assuming the enemy locates a carrier and vectors aircraft to weapons-release range, CEC-equipped area defense ships and the carrier's point defenses reduce substantially the danger of an antiship cruise missile hit. In the event of a hit, it is likely to be damaging but not debilitating; the carrier will remain afloat owing to its armor and hull compartmentalization, and be ready to resume air operations soon. Recall the 1969 accident on the USS Enterprise (CVN65) when aircraft engine exhaust detonated a Zuni rocket pod. A large fire and 18 munitions explosions—including nine 500-pound bombs—followed; eight holes were blown through the flight deck. The fire was put out in four hours. According to congressional testimony, flight operations could have resumed within hours thereafter.
A theater ballistic missile that is effective against ships on the high seas is beyond the current state of the art. It is so daunting technically that no such plan or program exists. A realistic assessment of missile capabilities by the Center for Naval Analyses found such an attack to be infeasible—the weapon would require a terminal seeker that could survive reentry into the atmosphere mounted on a maneuverable warhead that could hit a moving target. Finally, even if TBMs could be used to attack ships at sea, surface combatant defenses to be introduced starting in 2004 will offer a protective umbrella to airfields and ports as well as carriers.
Conclusions
Carriers are mobile targets with clear battle space awareness within their operating areas and beyond. They have highly effective area defenses, strong self-defense systems, and design characteristics that permit them to absorb damage and continue fighting. Although no ship or system is invulnerable, from now until at least 2020, the carrier will be an exceptionally elusive and rugged target. The Navy must ensure survivability of all its ships—and the costs are steep. However, considering the great utility and versatility of carriers across the entire spectrum of peace and conflict, they are a bargain for U.S. diplomacy as well as military operations.
Lieutenant Commander Duggan, a surface warfare officer, is assigned to the office of the Chief of Naval Operations (N8). Previously, he was the commissioning combat officer on the USS O’Kane (DDG-77).