Logistics analysis of the littoral combat ship
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Logistics Analysis of the Littoral Combat Ship. David Rudko and David Schrady Naval Postgraduate School Monterey, California 20 th ISMOR. The Littoral Combat Ship. Part of the U.S. Navy’s transformation in support of the Sea Shield component of Sea Power 21

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Logistics Analysis of the Littoral Combat Ship

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Logistics analysis of the littoral combat ship

Logistics Analysis of the Littoral Combat Ship

David Rudko and David Schrady

Naval Postgraduate School

Monterey, California

20th ISMOR


The littoral combat ship

The 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


History

History

  • 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


History1

History

  • 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


History2

History

  • 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


Lcs surrogate

LCS 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


Joint venture hsv x1

Joint Venture HSV-X1


Joint venture hsv x11

Joint Venture HSV-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


Logistics analysis

Logistics 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


Displacement model

Displacement 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


Displacement model1

Displacement 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


Fuel consumption model

Fuel 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


Endurance

Endurance

  • 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


Endurance1

Endurance


Endurance2

Endurance

  • 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


Endurance3

Endurance

  • 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


Logistics analysis1

Logistics 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


Logistics analysis2

Logistics 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


Logistics analysis3

Logistics 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


Conclusion

Conclusion

  • 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


Conclusion1

Conclusion

  • 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


Postscript

Postscript

  • 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


Post postscript

Post 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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