THE DESIGN AND DEVELOPMENT OF A LITTORAL COMBAT SHIP: THE UNITED STATES NAVY INDEPENDENCE-CLASS

INTRODUCTION

This report will endeavour to briefly describe the impetusbehind, and the process of, the development of the AmericanIndependence-Class Littoral Combat Ship, or LCS (see Figure 1). Adescription of the general characteristics of the class will beprovided, as well as a short summary of the general reception ofthe platform with regards to its projected combat effectiveness.As we move chronologically through the life cycle of the LCS, upto its current form, links will be drawn to the stages of thedesign cycle and then discussed.

Figure 1. USS Independence (LCS-2)Source: Austal LCS 127 Datasheet

HISTORY AND BACKGROUND

After the dissolution of the USSR the United States Navy(USN) faced greatly diminished competition for dominance of theopen seas. With no real contenders challenging for navalsupremacy, the opportunity was taken to assess the direction inwhich the USN should move forward. Special attention would, by

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necessity, be afforded to the strategies employed for procuringnew ships, and the type of ships best suited to maintaining atactical advantage in future conflicts. A design problem wasbeginning to emerge; the solution the USN would eventually selectfor this design problem took the form of the Independence-ClassLCS.

THE NEED FOR CHANGE

Up to this point the USN had focused its efforts oncontrolling the Littorals by projecting power over them. This wasaccomplished via long-range guns and missiles, as well as thedeployment of aircraft from the decks of large Aegis surfacecombatants. This tactic presented a distinct issue, in that,while it was effective in most situations, occasionally it wouldbecome necessary for these larger ships to venture close to shorein order to provide support to land-based missions. When this wasrequired these large ocean going vessels would become vulnerableto attacks such as mines, swarm-boats, sea-skimming cruisemissiles, and short-range ballistic missiles (Long and Johnson,2007, pp.1). Exposing these expensive and complicated ships tosuch risks quickly becomes unfeasible, and this weakness in thelittoral zone made the growing “tactical instability” of thecurrent US Naval Fleet glaringly obvious. The concept of tacticalinstability is rooted in a growing tendency to consolidate anincreasing percentage of combat power into an ever decreasingnumber of ships (Long and Johnson, 2007 pp. 3-4). In a tacticallyunstable fleet each disabled ship correlates to a large reductionin total combat force.

A New Environment

According to Work, the littoral, when used in a navalcontext, is a broad term “describing the complex interfacebetween the operational domains of sea, sub-sea, air and landthat occurs in naval and joint warfare. As such, the littoral hasboth a seaward extension, generally defined as that area of theocean from the continental shelf shoreward, and a landward

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extension.” (2007, pp. 10). While this definition may seemexcessively verbose, it is in fact necessary to provide such athorough definition, as it aides us in understanding the need fora ship that can operate effectively in zone that is so tacticallycompromised. With the aide of the reduced depth provided by thecontinental shelf, comparatively unsophisticated tactics such asunderwater mines, and diesel powered submarines can be used toextensive advantage. These tactics are especially effectiveagainst the deep-drafted conventional mono-hulls typicallyemployed the navies of the world when competing for supremacy onthe open ocean.

At this point a design problem is evident; however, beforeany significant progress can be made more information must beascertained. Two clear paths present themselves. One, thetraditional form of military ships can be preserved andcreatively adapted to offer the best possible protection from theexploitation of the inherent weaknesses of operating in thelittoral zone; or two, a new style of vessel can be developed tominimise the tactical disadvantages of the littoral zone. Theadvantage of this second option is the increased flexibilityafforded in design and the bonus of simultaneously combating thegrowing tactical instability of the fleet.

The Way Forward

Prominent military strategists Arthur Cebrowski and Capt.Wayne Hughes outlined their solution to this problem in aconference held by the US Naval Institute in November 1999. Theso called Streetfighter concept proposed a new class of smaller shipsthat would spread combat power out among several an increasednumber of hulls. Therefore, if one or even multiple ships weredisabled the overall combative force of the fleet would notsuffer unduly. These smaller ships would also be drasticallycheaper costing theoretically under $100 million US, though theactual figure is closer to $360 million US for a singleIndependence-class ship (excluding the lead ship which cost $760million US.)

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This theory was not greeted with widespread acceptance, anda lengthy debate ensued. Few were comfortable with the concept ofacceptable losses inherent in the design and construction ofthese ships. Eventually, this concept won out over itsdetractors, the next step in the design phase was reached andextensive research and development was conducted. Numerous X-Craft or experimental craft were commissioned by the Navy andbuilt by companies including, but not limited to, Austal USA,Marinette Marine, and Nichols Brothers Boat Builders. From thevarious craft produced the USN selected two design variants forthe LCS program; namely the Independence-Class led by Austal, andthe Freedom-Class led by Marinette Marine. The Freedom-Class is amore “traditional” mono-hull and will comprise half of the shipsin the LCS program (those with odd numbered hull designationsi.e. LCS-1, LCS-3, LCS-5 etc.), however, it is beyond the scopeof this paper to discuss both ship variants.

VESSEL DESCRIPTION

The keel of the lead ship in the Independence-Class (LCS-2)was laid down at the Austal USA yard in Mobile Alabama on 19January 2006, and delivered to the USN on 18 December 2008. LCS-2is currently based out of San Diego, California. Since takingpossession of the vessel the Navy has conducted extensive testingincluding Post Delivery Testing, and Shakedown Exercises; thevessel also participated in the Rim of the Pacific Exercises orRIMPAC fleet exercises in 2014 (Petty, 2015). The vessel isscheduled to conduct additional testing moving forward.

OPERATIONAL REQUIREMENTS

The operational requirements of a vessel contribute a largenumber of the parameters used when designing it. This sectionoutlines the capabilities that the final LCS ship design wasintended to have, it also constitutes the completion of thedesign problem. Being a surface combatant planned for use in thelittoral zones and narrow seas of the world, special

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considerations were necessary for its final environment. Ashallow draft was required to extend the area within the littoralthat the ships could safely navigate, as well as to aide in itsduties as a minesweeper. As with all military craft a premium wasto be placed on speed when designing the Independence-Class.Unlike most other military craft the lowering of the price-pointwas of vital importance to the original strategy of the LCSprogram, this was to be accomplished by allowing civilian shipyards to construct the vessels. This was a viable option for thisclass of ship because of the comparatively small size, whenconsidering the larger Aegis Surface Combatants such as the Fordand Nimitz-Class Aircraft Carriers, and Ohio and Sea-Wolf-ClassSubmarines.

Complement

Another key tenet of the LCS strategy was a relatively smallcomplement, in the case of the Independence-Class a mere 40 handsare required to operate the 127 meter vessel. An additional 36“operational” crew members complete the complement of 76 sailors.In comparison the Oliver Hazard Perry-Class Frigate, a ship threemeters shorter in length, is crewed by 176 sailors andmaintenance personnel, a full 100 crew members more than theIndependence-Class. Berthing is provided for the entirety of thecrew in a combination of single, double, and quadruple berthing-compartments. (Austal USA Company Website, n.d.)

Mission Specific Modules

Arguably the most significant departure from traditionalnaval ship design assimilated into the LCS program was theconcept of Modular Payload Ships or MPS. The modular payloadsallow the LCS to be quickly and easily reconfigured in order tochange the specific mission capabilities of the ship. Another

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distinct advantage of this design philosophy is the simplicityand relative cheapness of upgrading the electronics and systemsof the modular payload, when compared to the cost of upgradingintegrated technology in a traditional military ship with anintended life span of 30 to 40 years.

Contained in each mission payload is a collection of missionsystems: these may be vehicles, weapon systems, or sensors.With these mission systems are the necessary support equipmentand software required to utilise them; in addition to supportaircraft and a specifically trained crew detachment proficient inthe use of the mission systems. These mission systems aredesigned specifically to fit into ISO standard shippingcontainers in order to simplify the rapid transportation of theentire payload often times by leveraging the use of commercialglobal shipping. In short a mission payload is a collection ofall of the components necessary to reconfigure any LCS into aform capable of completing a predefined mission (Volkert,Jackson, and Whitfield 2010, pp. 77).

Currently, the LCS program has modular payloads configuredfor missions including Mine Countermeasures (MCM), SurfaceWarfare (SUW), and Anti-Submarine Warfare (ASW). While moremodular payloads may be under development or even completed theyhave not been disclosed to the public. Currently LCS-2Independence is scheduled to complete the Initial Operational Testand Evaluation in August of 2015 for the MCM package. The SUWpackage has already completed this test albeit, on board aFreedom-Class vessel. (Perry, 2015)

GENERAL CHARACTERISTICS

The Independence-Class stretches 127.1 meters in length, 31.4meters in breadth, and draughts a scant 4.5 meters at full loadedcapacity. The lightship displacement is 2,307 metric tons. Theloaded displacement is just 3,104 tonnes, allowing for adeadweight capacity of 797 tonnes. The following sections outline

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the design solutions developed to meet the challenge posed by theLCS Program design problem.

Hull Form Selection

Another distinct departure from the traditional naval designphilosophy was the selection of the stabilised mono-hull design,this design is often referred to as a trimaran (Bricknell andCarlisle, 2004, pp. 1). This design gains stability from anincreased beam when compared to a conventional mono-hull. Thehull form of the Independence-Class can be seen in Figure 2.

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Figure 2. Hull Form Rendering of Independence-Class LCSSource: Austal LCS 127 Datasheet

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Visible in Figure 2 are the twin stabilisers of theIndependence-Class. These stabilisers are asymmetrical and runbetween 50 and 60 percent of the length of the vessel; theyoriginate at the aft of the vessel and terminate slightly forwardof amidships. Inherently, this ship is very stable and canoperate effectively in a variety of conditions. While designedfor sailing in the Littorals the Independence-Class is capable oftraversing the open ocean. When operating in rough seas aircraftsuch as helicopters and unmanned aerial vehicles may be recoveredup to sea state five, and Austal estimates the ship can survivesea state eight without sustaining major damage.

Designed at Austal USA the Independence-Class is believed tohave taken many of its design cues from the earlier ship,Benchijigua Express, a high-speed ferry designed by Austal. TheBenchijigua Express is of nearly identical dimensions and has a verysimilar underwater form. This being said, had the Royal Navy ofthe United Kingdom not proved the viability of multi-hulledmilitary ships with its full scale test vessel RV Triton, the USNmay have never taken the risk of funding such a radical newdesign. In fact some consider the RV Triton to be the firstlittoral combat ship, currently it is in use patrolling thewaters off the coast of Australia. In this sense the RV Triton canbe considered the direct ancestor of the Independence-Class.Regardless of the fashion in which the hull design was conceived,it cannot be denied that this radical new style of hull is alarge step forward for design within the US Naval Fleet.

Propulsion System

As a military ship the Independence-Class must have adequatepropulsive power to maintain pace with a carrier group shouldsuch duty be required of it. However, because these ships areintended for use in the Littorals for special, focused, missions,they are designed to attain much higher speeds. According to thedatasheet available on the Austal USA Company Website theIndependence-Class is capable of reaching speeds in excess of 40

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knots. The cruising range of the class is 3,500 NM according toAustal.

To reach these speeds the Independence-Class is fitted a withtwin LM2500+ gas-turbines supplied by General Electric, incombination with twin MTU 20V 8000 high-speed diesel engines.This Combined Diesels and Gas Turbines arrangement, when operatedat full capacity can produce approximately 86 MW of power. Thismotive force is directed through four Wärtsilä steerablewaterjets. For docking and other delicate manoeuvres twin,retractable, azimuthing bow-thruster pods are integrated into thehull.

Material of Construction

Unlike the RV Triton, and the Freedom-Class LCS, theIndependence-Class is not made of mild steel. This represents athird significant departure from the conventional style of navalconstruction seen in the US Naval Fleet. While the aluminium-alloy used to construct the hull and superstructure ofIndependence-Class is significantly lighter than a similar hull ofsteel construction would be, many detractors concerned with thedecreased durability that the different material inherentlyprovides. Proponents of this material choice argue that theincrease in speed allowed by the lighter hull is a sufficientadvantage to overcome the other shortcomings.

Another clear influence of the LCS Program’s ship-designphilosophy is the Swedish Visby-Class Corvette. These Corvettesare made with a composite hull, and though they are significantlysmaller than the Independence-Class, they perform many similarfunctions within the Swedish Naval Fleet. While such aconstruction was considered for the American LCS, a compromisebetween the conventional steel construction and the radical useof a composite hull was reached when the decision was made toconstruct the Independence-Class from aluminium.

Structural Design

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The influence of the Visby-Class can, perhaps, most clearlybe seen in the design of the superstructure of the Independence-Class. Above the water, the lines of both ships show distinctsimilarities, these geometric lines and planar surfaces areintended to reflect incoming signals thereby lowering magnetic,radar, acoustic, and infrared signatures in order to maintainstealth in operations. The similarities between these ship’ssuperstructures can be seen in Figures 3 and 4 below.

Figure 3. Visby-Class Corvette Figure 4.

Independence-Class LCS Source: Public Domain Source:Austal USA Website

The structural design of the trimaran involves a thickbridging section several meters high, this connects the dominantmain hull to the smaller side hulls. At least 12 transversebulkheads support the 127.1 meter main hull while approximately 7are used in the construction of the outriggers. Unfortunately,the majority of the structural design plans are classified atthis point, and as such, a more complete analysis cannot beoffered.

Weaponry

While a large portion of the weapons systems utilised by theLCS are contained within the mission payloads, the ship’sintegrated armament is designed to provide the bulk of thedefense of the vessel, while modular weapons systems will bereserved mainly for use in pursuit of the focused mission goal.

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Towards that end the Independence-Class LCS is equipped with one57 mm gun, four .50 calibre guns, one surface to air missilelauncher, and three weapons modules determined by the currentconfiguration of the ship based on the modular payload.

Layout and Special Equipment

The general arrangement of the ship is largely classified.However, certain locations have been verified and some others maybe assumed. The 2,000 plus square meter flight deck is visible atthe aft of the ship and is capable of supporting two Sikorsky SH60 helicopters and stowing them via an aircraft elevator in thelarge hangar located directly below. Presumably, this aircrafthangar is a segment of the larger mission bay. Berthing andgalley accommodations are located directly below the bridge.These locations have been verified by Austal USA’s companywebsite, it is assumed that the machinery space is locateddirectly below the air intake visible on the rear of the bridgeso that a clear service shaft may be used in the maintenance ofthe gas turbines.

The Independence-Class is equipped with twin-beam extendingcranes in order to facilitate launch and recovery of smallermission related craft. A side ramp is integrated into the hull sothat the ship may be rapidly loaded while it is beingreconfigured to a new mission focus. Most importantly the missionpayload is entirely comprised of equipment specialized for eachmission focus.

CLASSIFICATION AND SAFETY

As military ships none of the Independence-Class areinspected by class societies. They are designated by the militaryand fall under category of Littoral Combat Ship. Some earlysafety concerns have arisen from the design of the Independence-Class. Chief among these concerns is the lack of bridge-wings,

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this severely limits the visibility of the helmsmen andcommanding officers, these wings will be added to all of theships in the class to improve the safety of operation. Thisrepresents the next stage of the design cycle, from this pointforward feedback must be collected and improvements made for thesubsequent iterations of the class.

RECEPTION

Industry opinion of the Independence-Class has been somewhatmixed since the inception of the program in 2002. Despite theintervening years, some detractors have failed to accept theinitial premise of Cebrowski and Hughes. This, in conjunctionwith the lack of large scale global conflict, has afforded littleopportunity to validate the investment in the LCS program by theUSN. Time will tell whether or not the expenditure on the programwas a valid investment or a misguided tactical decision.

SHIPS ON ORDER

Despite misgivings from some defense-industry experts, theUS Naval Ship Procurement Division requisitioned Congress for tenLCS of each design variant. Austal received a contract tocontinue producing the Independence-Variant for, at least, thenext decade. At this point further analysis will provide theopportunity to down select the LCS program to one design-variant.At this point the USN is pursuing an aggressive acquisitionprogram.

CONCLUSION

As the LCS program moves forward the design of the Independence-Class will be continually refined. The design cycle will be employed as ever smaller problems are identified,

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defined, solved. Eventually these new surface combatants will be tested in genuine combat, their performance in these eventual tests will provide concrete answers to the questions posed by theprogram’s detractors. At this point the LCS Program appears to bean important segment of the US Naval Fleet moving forward. While this does not mean that Aegis Surface Combatants will become defunct we can be reasonably certain that this new focus on the Littoral zone will play a major role in future naval confrontation. Without a doubt this specially designed LCS will take center stage in any such conflicts.

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