As of mid-2001 the Office of Naval Research was considering construction of a Littoral Combat Ship with a displacement of 500 to 600 tons. The LCS would have a draft of about three meters, an operational range of 4,000 nautical miles, and a maximum speed of 50-60 knots. The cost per ship might be at least $90 million.
The Sea Lance concept, designed by engineering students at the Naval Post Graduates School, calls for a fast-moving missile attack ship built on a catamaran hull. Sea Lance could operate with unmanned midget submarines and fast assault craft capable of deploying as many as 1,000 troops and their equipment into combat zones at speeds of up to 50 knots.
The President of the Naval War College, Admiral Art Cebrowski, and others such as Capt. Wayne P. Hughes, have advocated the deployment of larger numbers of smaller ships to operate in "harm's way" in littoral waters. Cebrowski and Hughes talk of "tactical instability," where a navy is unwilling to risk its ships because the fleet is constituted principally of small numbers of expensive ships. They propose "re-balancing the fleet" by supplementing the currently planned large surface combatants with the procurement of smaller ships.
Navy leaders state that to put the Navy's warfighting environment in perspective, four navies must be considered: the "Navy of History;" "Today's Navy," the current operating force; "Tomorrow's Navy," the programmed Navy that is being acquired today for use tomorrow; and the "Navy after Next," which will follow the programmed Navy. Since the end of the Cold War, the Navy has focused most of its attention on maintaining today's Navy, due to the continuing demands of peacetime overseas presence and near-term readiness. Meanwhile, the focus of the programmed Navy has been on influencing events ashore through littoral operations. But there is increasing concern that the Navy after next might again be challenged to maintain its maritime supremacy against a near-peer in some of the world's oceans. Achieving a properly focused, appropriately balanced and affordable force structure, with adequate capabilities and flexibility for the full spectrum of possible maritime challenges the nation could face in the next decades, remains a formidable challenge for the sea services' planners.
SEA LANCE is designed as the deployment mechanism for the Expeditionary Warfare Grid proposed in the Capabilities of the Navy after Next (CNAN) study being conducted by the Naval Warfare Development Command. The system composed of the SEA LANCE and Expeditionary Grid will be capable of providing the deployability, flexibility, versatility, lethality and survivability necessary within the contested littorals to provide the operational commander with the awareness and access assurance capability lacking in the fleet of the POM.
The fleet of the POM is not ideally suited to directly operate in the highly complex and hostile littoral environment. Concealment together with the surprise factor, inherent to an adversary operating in its own littorals, will pose high risk to US conventional power projection assets.
This situation creates the need to develop a capability that will allow gaining, maintaining, sustaining and exploiting access to the littorals, in order to project power into enemy territory. SEA LANCE in conjunction with the Expeditionary Warfare Grid will be capable of performing this vital mission.
The combatant is a robust fighting platform that provides its 13-person crew with all the support necessary to conduct operations in support of the mission needs statement. From the combined control station to the auxiliary equipment, all components are connected to the Ship's Wide Area Network via a Total Open Systems Architecture (TOSA). Technology advancements like these are key to the success of the austere manning concept.
The combat systems suite of the craft is capable of detecting, classifying and engaging aircraft, missiles and small surface combatants.
The combatant has a 4-cell Harpoon/SLAM launcher capable of engaging both surface and land targets. It also has a 51-cell surface-to-surface and surface-toair missile system that is outfitted with active, semi-active and infrared guided missiles. Additionally, it has (2) 30 mm guns similar to those proposed on the AAAV and LPD-17 class.
The combat systems suite of the combatant is capable of operating in a wide range of environments. The air/surface search radar has a range of 54 Nm while the infrared search and track (IRST) as well as the fire control radar has a range of 20 Nm. The electro-optical suite has a range of 10 Nm and the mine-avoidance sonar has a detection range of approximately 350 yards. Additionally it is equipped with an ESM suite and phased array communications antennas. The entire suite is enhanced by the use of an advanced enclosed mast.
SEA LANCE is pair of vessels composed of a combatant and tow. The tow has relatively the same hull form and naval architecture characteristics as the combatant. It is a semi-fixed close proximity tow of approximately 20 feet. The tow is referred to throughout the literature and presentation as the Grid Deployment Module (GDM). Some characteristics of the two vessels are provided to the right.
The acquisition costs were estimated at approximately $83.9 million dollars for the first combatant and grid deployment module pair. Assuming a learning curve through the first ten ships, the cost of the 11th and subsequent pairs will be $82.7 million. The first squadron will cost $914 million with follow-on squadrons at $827 million.
The SEA LANCE hull, a wave-piercing catamaran hull, is an inherently stable hull form.
The nature of the mission determines the required power for SEA LANCE. The missions that require towing the GDM will demand more power than missions that do not require the GDM for the same speed. Because of this, the power requirements up to 15 knots, which is the grid deploying speed, are defined for both Combatant and GDM. Power requirements for speeds higher than 15 knots are defined only for the Combatant. For the safety, service life and fuel consumption, it is assumed that the maximum power that the prime movers serve will be 75% of the full power and each prime mover will operate at 80% of the maximum rated rpm. Under these conditions the required power for 15 knots with GDM is 6135 HP and 13816 HP for 40 knots without the GDM. The analysis of power requirements for various speeds shows that in the emergency conditions both Combatant and GDM can reach the speed of 23knots without exceeding 13816 HP. Speed vs.
Diesels where compared to gas turbines in the areas of specific fuel consumption, weight impact on interior volume of the ship and maintenance requirements. The marine diesels utilized in the comparison were from MTU diesel and the gas turbines were of the LM class produced by General Electric. Manufacturer data sheets where utilized for the computations.
Fuel consumption was calculated based on the hull resistances and horsepower requirements previously calculated. It is clear throughout the operating range that the MTU diesels studied have a lower SFC than the gas turbines studied for the operating range.
Gas turbines had further drawbacks for this design. The volume that would be necessary for the intake and the exhaust ducting would require volume that could be needed for grid elements or fuel tankage. The gas turbines would also require the use of a reduction gear to connect to the propellers or water jets. The diesels could be direct drive and even with their heavier weight to horsepower ratio, they still added less weight to the propulsion plant.
The weight and volume limitations for each hull of catamaran demand the use of 4 medium-size diesel engines instead of two large ones.
If 4 engines are put on the ship, the best configuration is CODAD with 2 engines on each side of the ship (15 knots with tow and up to 25 knots without tow); one engine on each side can be operated. For higher speeds all of the engines will be in operation.
For the speed of 15 knots with GDM attached, the required power is 6135 HP which means that each one of low speed engines has to have at least the maximum power of 4100HP (with 75% service factor). For the speed of 40 knots without tow, required power is 13816 HP and this means that each one of high-speed engines has to have a maximum power of at least 4610 HP (with 75% service factor). The difference between these 2 numbers is just 510 HP and for the fuel consumption, weight and size, and cost considerations this does not create a significant reason to use 2 different types of engine on the combatant. If 4 of the same type of engine are used on board, this will provide numerous advantages for the combatant (i.e. Less spare parts on board for the same maintenance program). Therefore, it is reasonable to have one type of engine, which serves the ship. The MTU Model 16V 595 TE 70 was utilized. This engine has a maximum power of 4828 Hp and this gives the opportunity of using 2 engines up to 25 knots. After tow is released and for the speeds higher than 25 knots, 4 engines should be used.
The required power for various speeds determines the fuel burn rates for these various speeds. Relatively high power requirements up to the 15 knots with GDM produces the high fuel burn rates. After GDM is released the fuel burn rates drop significantly.
For the fuel burn rate calculations typical diesel burn rate curves are used. In the case of 70% propulsion efficiency is not possible, the power requirement and fuel burn rate calculations are performed for 62%, 65%, 68% and 70% propulsive efficiencies. These calculations showed that the difference between fuel burn rates for both the speed of 15 knots with GDM and 40knots without GDM is not more than 10%.
The option of transferring engine power to the propulsion mechanism via electric drive was considered. Future naval combatants are expected to use an Integrated Power System, which includes electric drive. Electric drive benefits large gas turbine ships allowing them to burn less fuel, to increase redundancy and survivability, and to relocate prime movers to any location.
Using the diesel engines at the "design point" speeds of 15 and 40 knots and giving the electric drive the most advantageous assumptions, designers found that electric drive will be slightly more fuel efficient than conventional drive at 15 knots. When conventional drive is given a best-case assumption, it outperforms electric drive. The electric drive enjoys an average 4-5% specific fuel consumption bonus over conventional drive since the engines are free to spin at their optimal speed. Despite this possible 5% fuel efficiency bonus, the electric drive cannot overcome its inherent and constant 7% transmission efficiency loss6 when compared to conventional drive.
Further analysis makes electric drive even less desirable. Electric drive's other benefits, survivability and design arrangement flexibility, do not assist the design. Survivability of each SEA LANCE Combatant is not a design priority. Also, the ability to move the prime movers anywhere in the ship is not of real benefit to SEA LANCE: the engines are well-positioned in the hulls where conventional drive requires them to be. Electric drive also carries the liabilities of being costlier, having higher technological risk, and being heavier due to extra components (electric motors, large generators, high power distribution equipment, etc.). Cost and weight are two key parameters that we desire to minimize.
One counter-argument to the above discussion is worth considering. Since the Navy appears to be adopting electric drive for DD-21 and other naval ships, perhaps the Navy should, from a Fleet-wide perspective, consider using electric drive in the SEA LANCE Combatant. Simply put, it will be less expensive for the Navy to make mistakes and build corporate knowledge in electric drive with low-cost SEA LANCE Combatants rather than large combatants.
Including the TOSA design philosophy in SEA LANCE will allow for easier insertion of new technologies at a lower cost. TOSA will allow the SEA LANCE greater flexibility and adaptability while reducing requirements to redesign. It also helps the insertion of commercial products and promoting commonality in all Navy ships.
The organic sensors and weapons chosen for SEA LANCE are in accordance with the Operational Requirements Document (ORD). From the analysis of the ORD, the need for sensors and weapons can be summarized by the following functions: offensive (engage suface targets) and defensive (engage surface targets/point defense. engage air targets, avoid mines).
The sensors and weapons that perform the air and surface engagement functions must be able to detect, track, identify/classify and destroy/neutralize targets. Mine avoidance only requires detecting, in order to maneuver accordingly.
The objective of this analysis is to provide notional systems for the first iteration of the conceptual design. These theoretical systems will provide an initial estimation of weight, volume, power consumption, and cost, so that feasibility of the proposed platform can be assessed. The systems described in the following paragraphs have been conceptualized from existing systems in the market today. It is reasonable to assume that due to trends in technology, systems will in general, get smaller, lighter, more efficient, more reliable, and more effective.
The organic weapons that SEA LANCE will carry are:
- 4 medium range SSM.
- 51 short-range dual purpose SAM/SSM.
- 2 30mm mounts with 1200 rounds each.
The medium range SSM will give SEA LANCE the capability of engaging in surface actions. Data is based on the existing Harpoon missile.
Both air and surface point defense are allocated in two complementary layered systems. The first layer is given by a dual purpose SAM/SSM. This dual-purpose system has been conceptualized by linear regression data analysis from existing SAM and SSM missiles. The missile system has been conceived as a dual-purpose system in order to provide flexibility while saving space, weight, and manning requirements. It also provides logistic advantages regarding maintenance and parts. If different missiles were to be used for SAM and SSM, more equipment would be needed, resulting in a larger payload fraction. Also, fewer missiles would be available for each function. With a dual-purpose missile, any available missiles will always be usable against air or surface targets, enhancing the ability of SEA LANCE to retain capabilities with less need to reload.
The second point defense layer is given by 2 - 30 mm gun mounts based on the Mk 46 to be installed in LPD 17. The guns provide a cheaper alternative to destroy/neutralize targets at shorter range when the use of a missile is not justified. It also provides defense at distances below the minimum firing range for the dual-purpose missile, improving survivability. Even though the gun is not designed as a Close in Weapon System, it provides some degree of protection against incoming missiles that penetrate the SAM layer.
Although decoy systems are not weapons, their description has been included in this section. The decoy system for SEA LANCE is based on a Rafael/Manor Israeli system. It is designed to provide a layered defense against radar emitters and IR sensors. The first layer is a long-range, tactical confusion chaff rocket to be used against search radars in their detection phase. The second layer is a medium-range, distraction chaff rocket that is designed to protect against anti-ship missiles before target lock-on. The third layer is a seduction chaff rocket that protects the ship against active missiles that have achieved lock-on. The system also incorporates a rocket powered IR decoy that has both seduction and distraction roles.
SEA LANCE is conceived to operate within the capabilities of the grid. Network Centric assets will link situation awareness gathered by the grid to SEA LANCE platforms. Consequently, the main "sensor" for SEA LANCE will be the link with the network, providing detection, tracking, and identification/classification.
In the grid deployment phase, situation awareness will be limited; therefore, the platform must have its own capability to detect, track and identify/classify. Even when deployed, combatants may have to operate in areas of limited grid coverage.
A design philosophy for SEA LANCE systems is functional separation. This entails breaking system functional components and separating them from direct communications and requiring them to communicate to each other via the Ethernet LAN. For example, a RADAR system has a transmit/receive component, a data reduction function, and a decision-making component (deciding what to track, where to transmit the next RADAR pulse, etc.). Normally, these components/functions are consolidated into a single physical system that allows direct communications between them. This is efficient in operation but difficult in repair and upgrading. An entire system might need to be completely replaced to improve one small part. If these components/functions are separated and connected to the LAN, they can easily be removed and replaced individually.
Another aspect to the SEA LANCE LAN will be total integration of all ship's systems. We propose a robust level of automation and control to facilitate the small crew to operate the ship. The crew through the digital data network will interface all engineering, combat systems, operational and administrative systems. This requires software engineering to enable a reasonably trained person to operate a SEA LANCE Combatant.
To interface the ship's system, we propose a single type of multi-function console. The SEA LANCE multi-function console will require multiple touchscan screens for presenting information. The Raytheon Corporation has developed the Enhanced Command Console (ECC)22 that approaches the level of control and utility required by SEA LANCE. Raytheon has proposed similar technology for use on DD-21, but Raytheon was not at liberty to discuss this technology due to the upcoming contract decisions at the time of this writing.
Each console is capable of accessing all information available and controlling all ship systems. Each console can assume a mode (Command, Tactical, Operational, Engineering) that will limit the type of automatic alerts and prompts to the watchstander. The OOD console may have special controls (levers, stick, and/or wheel) to allow ship control by tactile sense. Voice communications will be accomplished through a light headset, which connects to the console. The multi-function consoles are located only in the SEA LANCE's Control Center. All watchstanding will occur in the SEA LANCE Control Center.
The Control Center has four multi-function consoles to support various manning requirements. An Officer of the Deck or "Ship's Navigation and Safety" watchstander could use the forward most console. If a tactical environment requires it, a TAO watchstander can use the aft most console (raised for a commanding view). In a stressing tactical environment, or whenever the situation calls for a specialized watchstander, either of the remaining consoles can be manned as required. The TAO console is actually two consoles in one; it is designed to allow the CO ready access to a console whenever needed.
Since each SEA LANCE Combatant is required to be able to support a squadron commander and his or her staff, the extra consoles can be dedicated to allowing the squadron staff access to consoles.
One other type of control interface will be available on the SEA LANCE. Each engine room will have an Engineering control station to allow maintenance actions and casualty engineering control.
SEA LANCE is a robust system of vessels that will ensure the deployability, flexibility, versatility, lethality and survivability necessary within the contested littorals to provide the operational commander with the awareness and access assurance capability lacking in the fleet of the POM. SEA LANCE in conjunction with the Expeditionary Warfare Grid will allow gaining, maintaining, sustaining and exploiting access to the littorals, in order to project power into enemy territory.
SEA LANCE embodies the capabilities discussed in the Mission Needs Statement (MNS). The design meets or exceeds all of the requirements set forth in Operational Requirements Document (ORD). The relatively low cost, flexible and stable hull form as well as the high degree of combatant capability makes SEA LANCE a very effective choice for deployment of the Expeditionary Warfare Grid. The combatant is capable of operations in the contested littoral environment against a wide range of threats without posing undue risk to the power projection assets of the fleet of the POM. The GDM has the flexibility to accept a multitude of diverse payloads. This increases the versatility of SEA LANCE far beyond those outlined in the requirements documents.
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