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Logistics Analysis of the Littoral Logistics Analysis of the Littoral Combat ShipCombat Ship

David Rudko and David Schrady

Naval Postgraduate School

Monterey, California

20th ISMOR

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The Littoral Combat ShipThe Littoral Combat Ship

Part of the U.S. Navy’s transformation in support of the Sea Shield component of Sea Power 21

To counter an enemy’s littoral denial strategy Must incorporate endurance, speed, payload

capacity, sea-keeping, shallow draft, mission re-configurability in a small ship

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HistoryHistory

This will be the fourth time in the last 40 years the Navy has sought a small, fast, capable ship

Asheville class patrol gunboats (PG) of the 1960s Pegasus class patrol hydrofoils (PHM) of the

1970-80s Cyclone class patrol craft (PC) of the 1990s

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HistoryHistory

The PGs were 50 meters in length, displaced 240 tons, and had a top speed of 37 knots

The PHMs were 44 meters in length, displaced 255 tons, and had a top speed of 45 knots

The PCs were 52 meters in length, displaced 350 tons, and had a top speed of 35 knots

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HistoryHistory

Each of these classes of small, fast ships was more expensive than planned, had limited military usefulness, had limited endurance, was not provided with a mother ship, and was decommissioned early

The LCS will be a fourth attempt to develop a small, capable fast ship

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LCS SurrogateLCS Surrogate

The littoral combat ship does not exist at this time Since October 2001, the U.S. Army and Navy

have leased a wave-piercing catamaran, the Joint Venture, HSV-X1

Because it exists and there is some operational data on it, the Joint Venture will be used as the surrogate LCS

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Joint Venture Joint Venture HSV-X1HSV-X1

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Joint Venture Joint Venture HSV-X1HSV-X1

HSV-X1 was built by INCAT Tasmania as a commercial ferry; 96 meters in length, 1671 tons (all tons are long tons) full displacement, aluminum construction

Payload and endurance reduced by modifications for U.S. Military

Top speed is 45 knots at light displacement and 39 knots at full displacement

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Logistics AnalysisLogistics Analysis

Analysis will examine relationship between speed, payload, and endurance

Methodology includes modeling displacement and fuel consumption

With displacement and fuel consumption models, endurance of the LCS surrogate can be examined

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Displacement ModelDisplacement Model

Model needed because HSV-X1 is being operated in near-ferry configuration w/o military payload

922 tons - Seaframe hull and propulsion plants 34 tons - Self-defense, sensors, C2 suite 42 tons - Ship’s gear 219 tons - Modular mission packages 189 tons - Crew, water, stores, ordnance 1406 tons displacement without fuel

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Displacement ModelDisplacement Model

1406 tons displacement without fuel 4 service tanks and 2 long-range tanks with

capacity for 150,000 gallons total = 472 tons Full displacement limited to 1671 tons, so, with

payload, only 266 tons of fuel possible Tradeoffs between fuel and payload

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Fuel Consumption ModelFuel Consumption Model

4 Caterpillar diesels, 38,000 hp Fuel consumption depends on speed,

displacement, and significant wave height Multiple nonlinear regression used to fit published

HSV-X1 operational data for speeds 15-40 kts, 1300-1600 tons displacements, and 3.5 - 7 foot wave heights

Regression R2 = 0.996, standard error = 65 gph

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EnduranceEndurance

Depends on fuel carried, fuel consumption, and fuel reserve level

Reserve level normally 50%, 20% also examined Fix fuel carried, reserve level, displacement, and

wave height, then endurance may be calculated For 266 tons of fuel, full displacement, 6-foot

wave height, next side shows endurance

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EnduranceEndurance

Impact of Speed on Endurance

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15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Knots

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20% Reserve

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EnduranceEndurance

Clearly endurance decreases with speed, also with displacement and wave height

Sanity check on models: In transit configuration of the seaframe, ship’s gear, crew, water, stores, and full fuel, displacement estimated to be 1477 tons

Endurance at this displacement with 6-foot wave height, 27 knots, and 20% fuel reserve is 5 days and 18 hours

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EnduranceEndurance

In February, 2002 HSV-X1 did a 3600 nm Atlantic transit at an average of 27 kts in 5 days and 17 hours.

Carrying no payload allows full fuel tanks and still yields a lower displacement, lower fuel burn rate, and greatly increased endurance

Example of tradeoff between payload and endurance

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Logistics AnalysisLogistics Analysis

Need a concept of operations (conops) to model how the ship might be operated

Original 5-day focused mission and 21-day continuous mission had ship at high speed (48 kts) 4% and .4% of the time; both missions later deleted

Our mission was 14-day with 68% of time at 17 kts, 22% of time at 27 kts, and 10% of time at 40 kts

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Logistics AnalysisLogistics Analysis

Assumes ship at full displacement with full military payload, 84,313 gallons of fuel (266 tons), and 20% reserve

Total fuel required is 285,000 gallons. 20% reserve implies use of 67,450 gallons between refuelings; mission required 4 or 5 refuelings

Transit out 150 nm at 27 kts to oiler operating with a strike group takes 5.5 hours each way; approach, rig/unrig, and pump time estimated at 1.7 hours; total refueling time off station is 12.7 hours

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Logistics AnalysisLogistics Analysis

Limited endurance causes the LCS surrogate in this mission to be offstation roughly a half day every third day

Higher speeds and/or need to replenish ordnance will increase offstation time

Change any parameter – mission speed profile, wave height, reserve level, or other - and results change; easily done with spreadsheet

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ConclusionConclusion

Any small, high-speed ship whether Bernoulli (get hull out of water) or Archimedean hullform has serious payload and endurance issues due to high power-density requirement for high speed

The purpose-built ship Destriero holds transLant crossing record at 53 kts average speed; engines and fuel are 90% of her full displacement

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ConclusionConclusion

HSV-X1 design traded payload and endurance for speed, acceptable in its role as a ferry

As an LCS surrogate, HSV-X1 would have to carry military payload (capability) and thus be even more limited in endurance

The small, capable, high-speed ship seems to remain elusive

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PostscriptPostscript

In July, the 5 LCS proposals were reduced to 3 and 7-month preliminary design efforts awarded

Lockheed Martin is proposing a semi-planing aluminum monohull based on Destriero

General Dynamics/Bath is proposing a trimaran based on the British RV Triton

Raytheon is proposing a surface effects ship based on the Norwegian Skjold composite ship

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Post PostscriptPost Postscript

“It must be plain to everyone who has ever taken part in any discussion on speed . . . that those who favour very high speed . . . are extremely sensitive on this point, and are usually ready to meet even a historical and undisputed statement with a vigorous rejoinder, as though an appeal to history were regarded as a controversion of their opinions.”

-Admiral Sir Cyprian Bridge, Discussion on Trafalgar Papers, The Institution of Naval Architects, July, 1905

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