Potential adversaries of the United States have learned many lessons from military actions such as the Gulf War. Perhaps the most significant lesson is that the probability of successful military confrontations is virtually zero unless U.S. power projection assets can be prevented from closing to operational striking ranges. Consequently, these adversaries are developing access denial capabilities designed to prevent U.S. forces from coming within aircraft or missile launch range of their territories.
Key elements of access denial forces could include remote sensing networks for surveillance and tracking, numerous mines, shallow-water submarines with advanced long-range torpedoes, numerous mobile air, sea, and land platforms to launch inexpensive, long-range antiship missiles, and terminally guided ballistic missiles. Integrated command and control made possible by commercial telecommunications technology will enable relatively unsophisticated adversaries to wield these elements to great effect, and even local fishing and merchant fleets could pose substantial threats.
The Navy's near-term force structure (2002 to 2007) lacks adequate minesweeping capabilities. It cannot sustain extended operations in chemical or biological warfare environments. Antisubmarine capabilities are at their poorest in shallow waters against submarines with air-independent propulsion. The best air defenses can be saturated easily by large, readily affordable numbers of antiship cruise missiles. Planned ballistic missile defenses were designed for rear area protection and cannot protect the fleet from attacks by long-range missiles with terminally guided warheads. The Navy must be able to transit littoral waters covered by access denial threats that can reach out to 200 nautical miles (nm) from shore or farther. New tactics and new systems are required.
The Naval Warfare Development Command (NWDC) was chartered to identify new techniques, capabilities, doctrine, and forces needed within the next 20 years to permit the Navy to continue to perform its missions. Given justifiable concern over access denial, the NWDC commissioned the "Capabilities of the Navy After Next" (CNAN) study, which hypothesized development of an access ensuring force as an adjunct to other forces planned for the near term. This force was assumed to consist of four parts:
- A global network connecting all elements of the access ensuring force with other forces involved
- An expeditionary grid consisting of deployable sensors, weapons, and network connection elements
- A combatant flotilla for deploying and defending the expeditionary grid
- Logistic support
The focus here is on the combatant flotilla. Composition of the expeditionary grid was the responsibility of one CNAN team. To facilitate war gaming and analysis by other teams, the team defined a "toolbox" of subsystems that was used to determine payload weight and volume requirements for the combatant. The combatant flotilla was assumed to consist of many small, low-observable, low-cost craft. Large numbers dispersed over wide areas, coupled with low detectability, would ensure survival of sufficient craft to deliver enough expeditionary grid elements to facilitate access even in high-intensity engagements. During the 2000 academic year, NWDC asked students in the Naval Postgraduate School's Total Ship Systems Engineering Program to design a ship in support of the CNAN study. The Seaborne Expeditionary Assets for Littoral Access Necessary in Contested Environments (SEALANCE) is the product of that design study. A comprehensive report on the project is available that describes all trades performed, rationale for selection of specific components or technologies, and design details.
Operations analysis indicated the following general requirements for craft of the combatant flotilla:
- A maximum speed of 38 knots
- A minimum range of 3,000 nm at 13 knots
- Ability to carry and deploy 190 tons of expeditionary grid packages
- Ability to transit in sea state 6 and deploy grids in sea state 4
- Survivability consistent with the flotilla deploying at least half of the grid elements despite enemy action, thus requiring dramatic signature reduction as well as substantial defensive armament
The Sea Lance is actually a pair of vessels—a combatant and a tow called the grid deployment module (GDM). (See Figure 1.) The GDM has the same hull form and naval architecture characteristics as the combatant. It is semifixed and towed approximately 20 feet behind the combatant. Both vessels have a wave-piercing catamaran design form chosen because of its good seakeeping abilities, low resistance at high speeds, shallow draft (critical for ships operating in littoral waters), and large deck area. A close tow was selected over a larger single vessel to maximize payload capacity during grid deployment and preserve maximum fighting capability for possible actions after completion of grid deployment.
The Sea Lance combatant is powered by four diesel engines (two in each of the twin hulls) that produce 19,300 horsepower. The diesel engines drive four advanced waterjet propulsion units. Diesel engines were chosen over gas turbines because of better fuel consumption over the profile of mission velocities, lower weight, freedom in locating intakes and exhaust, and easier maintenance. An advanced type of waterjet propulsion was chosen over propeller drive because it promises good efficiency at both low and high speeds and does not affect the draft of the ship adversely. Electrical power is provided by power takeoffs on the main drive shafts.
The combatant is a sturdy fighting platform that provides its 13-person crew with all the support necessary to conduct grid deployment operations. From the combined control station to auxiliary equipment, all components are connected to a shipwide area network via total open systems architecture. Recent technological advances—such as remote monitoring, automated damage control, and simplicity of controls and displays—are key to the success of the austere manning concept. Figure 2 shows the general arrangement of critical components.
The combatant's manned spaces are protected by a collective protection system permitting operations in chemical and biological warfare environments. Since neither normal evolutions nor combat operations will require personnel on deck, the combatant need not retreat from a contaminated battle space. Berthing is austere, but capable of accommodating 20 individuals for two weeks. (A SEAL team or intelligence detachment could be accommodated in the extra space.) The Sea Lance will be forward based and supported by shore facilities or tenders; personnel will live on board during operational missions only.
Sea Lances are survivable and can avoid hits by missiles, torpedoes, and mines. Battle stations are located in the center hull—below the weather deck to provide maximum immediate survivability. However, if the combatant is hit and automatic damage control is inadequate to halt progressive flooding and fires, it will be abandoned. Redundant lifesaving equipment is dispersed around the craft so the crew can escape quickly and safely.
The combat systems suite of the combatant will detect, classify, and engage aircraft, missiles, and surface combatants. The combined air and surface search radar has a nominal free-space detection range of 54 nm and is supplemented by an infrared search and track (IRST) system with a detection range of 20 nm. This gives the Sea Lance a covert "silent watch" capability, its preferred operating mode. Two fire-control radars (also with 20-nm range) provide 360 weapon guidance and control. All sensors are horizon limited for low-altitude targets. Two electro-optical sensor units combine thermal imaging, television, and laser rangefinder functions for image-based search, detection, and recognition out to 10 nm. A modern electronic warfare support measures (ESM) suite and phased-array antennas complete topside sensor arrangements. The entire topside suite is housed in an advanced enclosed mast system. Key search sensors are nominally located 28 to 34 feet above the waterline. The search radar, IRST, and ESM systems are mounted on a partially telescoping structure that can extend them 42 to 48 feet above the waterline to extend the horizon beyond 10 nm for low-altitude targets. A short-range (350-yard) mine avoidance sonar located in the prow of one of the twin hulls completes the combat systems sensor suite.
The radar cross section of the Sea Lance was controlled by careful geometric shaping and elimination of all topside clutter. With a resulting cross section smaller than most fishing boats or coastal merchantmen, the craft will be difficult to target. The infrared signature is controlled by exhausting engine effluents between the twin hulls and restricting heat-- generating electronics to the interior of the center hull. Waterjet propulsion keeps acoustic signature to a minimum.
The combatant is armed with a 4-cell Harpoon stand-off land attack missile launcher capable of engaging surface combatants and land targets, and a 51-cell surface-to-air and surface-to-surface missile vertical launch system. The cells contain multipurpose, supersonic missiles with a nominal range of nine miles and with active, semiactive, and imaging infrared guidance and 15-kilogram blast and fragmentation warheads. Multimode guidance allows the same missile to be used for defense against aircraft and small surface combatants. (Although such a missile is not available currently, there are no technical bars to its rapid development.) In addition to long- and short-range missiles, the combatant mounts two 30-mm guns similar to those used on the advanced amphibious assault vehicle and the LPD-17-class amphibious ship. These guns are excellent weapons for defense against small boats and can augment air defenses as well.
The GDM carries nine half-size sensor or weapon modules. A half-size module is a container 18-feet wide X 11-feet long X 9-feet deep, Up to four full-size modules can replace half-size modules. The modules fit in bays in the center hull. Each module contains deployable weapon or sensor packages. The packages are deployed on the move from the bottom of the center hull—between the twin hulls—using a gravity feed mechanism similar to the bomb-release device on a heavy bomber. Obviously, specific module loads would be determined prior to deployment and might be different for each Sea Lance. If extra module space is available, it can be filled with additional vertical missile launchers, fuel storage, SEAL team insertion equipment, and other special mission equipment.
Each GDM carries diesel fuel in each of its twin hulls. This additional 103 tons of fuel is fed to the combatant's diesel engines through an umbilical contained in the tow bar. Fuel is drawn from the GDM before it is taken from the combatant's onboard 104 tons of fuel. This extra fuel gives the Sea Lance long operational range. In addition, the GDM contains an auxiliary generator and suite of decoy launchers. Once the expeditionary grid has been deployed, the GDM can be cast off and employed as a decoy by radiating and mimicking a Sea Lance or some other combatant. If possible, it will be recovered after the action. To save weight and keep costs at a minimum, separate propulsion for the GDM was rejected.
Once the GDM is detached, the combatant becomes a formidable fighting ship. It has a combat speed of 38 knots. A squadron of ten carries more long-range antiship missiles than an Arleigh Burke (DDG-51)-class guided-missile destroyer and ten times as many surface-to-air missiles (although they are less capable). The Sea Lance's guns are better suited to defense against small boats than 5-inch guns. A battle group with several squadrons of attached Sea Lances is considerably more powerful—and has far more tactical flexibility—than a battle group with one or two additional large combatants.
Acquisition costs for Sea Lance were estimated using available parametric cost estimating relationships. Costs were estimated at $83.9 million dollars for the first combatant and its grid deployment module. After the first ten pairs have been acquired, each additional ten-pair squadron will cost about $827 million. Thus, each Sea Lance squadron will cost roughly the same as a single DDG-51. Deployment cost—acquisition cost plus cost of expendable weapons and crew training—is expected to average about $100 million per combatant and GDM pair.
The Sea Lance is a novel yet practical concept that offers much-needed capabilities to the Navy of the future. It would ensure access to littoral operating areas and improve the survivability of power-projection forces. By adding combatants to each fleet, it would increase tactical options available to commanders. Not least, at a time of limited growth—or possibly decline—in defense spending, the Sea Lance would enhance the Navy's mission performance affordably.
Dr. Harney is Naval Sea Systems Command chair of the Total Ship Systems Engineering Program. He guided the Naval Postgraduate School team that designed the Sea Lance.