A Solution to the Inherent List on Nimitz Class Aircraft Carriers

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emain at least 60% full at all times. These ships have a very specific warfighting requirement that must be achieved, and a reduction in capabilities is unacceptable. There must be a solution <strong>to</strong> <strong>the</strong> inherent list problem beyond limiting ships payload or using <strong>the</strong> DC voids outside of <strong>the</strong>ir designed intent. This report evaluates o<strong>the</strong>r alternatives <strong>to</strong> finding a solution <strong>to</strong> fix <strong>the</strong> inherent list on Nimitz class aircraft carriers. 1.2.1 Past Research A <strong>the</strong>sis was performed in 2001 by Michael Malone, a graduate of MIT. His <strong>the</strong>sis, titled "An Alternate Method for <strong>the</strong> Determination of Aircraft Carrier Limiting Displacement for Strength;" determined that although all Nimitz class aircraft carriers are approaching <strong>the</strong>ir limiting displacement for strength, <strong>the</strong> traditional methods of such calculations are conservative. In fact, <strong>the</strong> Nimitz class carriers can accommodate more weight than previously thought. Because of this <strong>the</strong>sis, <strong>the</strong> U.S. Navy Aircraft Carrier Program Office (PMS 312) later directed N.S. NAPPI Associates <strong>to</strong> conduct a detailed analysis on estimating <strong>the</strong> limiting displacement for strength. Again, it was proven that <strong>the</strong> Nimitz class hull is capable of sustaining additional weights which would exceed <strong>the</strong> current established limiting displacement for strength. 1.2.2 Stability The stability status for USN ships is defined in [4] and is supported by [11]. The Chief of Naval Operations has directed that <strong>the</strong> Navy's ships will be kept within naval architectural limits <strong>to</strong> ensure that essential survivability features are maintained. For each ship class, <strong>the</strong> Naval Sea Systems Command's Weights and Stability Division is <strong>to</strong> keep track of <strong>the</strong> weight and stability status, limiting draft and o<strong>the</strong>r limitations including being an advocate for weight and moment status and moment compensation necessary <strong>to</strong> adhere <strong>to</strong> <strong>the</strong> established limits. Surface ships are 10
classified in<strong>to</strong> four status conditions for vertical center of gravity (KG) and limiting drafts. As specified in [4], <strong>the</strong> definitions for <strong>the</strong> status listings are: • STATUS 1 An increase in weight and a rise of <strong>the</strong> ship's center of gravity are acceptable. Added weight and moment resulting from changes will not require any compensation unless <strong>the</strong> magnitude of <strong>the</strong> additions is so large as <strong>to</strong> make <strong>the</strong> ship approach stability limits. • STATUS 2 accepted. Nei<strong>the</strong>r an increase in weight nor a rise of a ship's center of gravity can be • STATUS 3 An increase in <strong>the</strong> ship's weight is acceptable, but a rise of <strong>the</strong> ship's center of gravity must be avoided. • STATUS 4 A rise of <strong>the</strong> ship's center of gravity is acceptable, but increase in weight must be avoided. Compensation for added weight may be obtained by removal of an equal or greater weight at any level. Status 1 is <strong>the</strong> only acceptable ship status. The goal is for ships in <strong>the</strong> fleet <strong>to</strong> remain in Status 1. In <strong>the</strong> o<strong>the</strong>r three status conditions, <strong>the</strong> displacement and KG must be closely moni<strong>to</strong>red <strong>to</strong> ensure <strong>the</strong> condition does not worsen and steps must be taken <strong>to</strong> try <strong>to</strong> bring <strong>the</strong> ship back within acceptable design limits. Typically, when an in-service carrier requires a modification that will add weight <strong>to</strong> <strong>the</strong> ship, it is <strong>the</strong> responsibility of <strong>the</strong> program office and <strong>the</strong> planning yard <strong>to</strong> put <strong>to</strong>ge<strong>the</strong>r a package that includes maintenance and repair items, as well as modernization changes. First, a preliminary weight estimate of <strong>the</strong> modernization changes are put <strong>to</strong>ge<strong>the</strong>r in <strong>the</strong> package and made ready for installation. Once <strong>the</strong> package is installed, <strong>the</strong> planning yard or shipyard keeps track of <strong>the</strong> weights being installed. At <strong>the</strong> end of <strong>the</strong> availability, an actual weight report for <strong>the</strong> installed changes is generated. This report is passed from <strong>the</strong> shipyard <strong>to</strong> <strong>the</strong> program office where it is incorporated in<strong>to</strong> <strong>the</strong> stability baseline of <strong>the</strong> pertinent ship. 11
Page 1 and 2: A Solution <strong
Page 3 and 4: A Solution <strong
Page 5 and 6: Table of Contents Abstract 3 Acknow
Page 7 and 8: 1.0 Introduction 1.1 Motivation Air
Page 9: class. Changes to
Page 13 and 14: o Control the KG g
Page 15 and 16: the intact stabili
Page 17 and 18: for ships propulsion, respectively.
Page 19 and 20: combined with the
Page 21 and 22: 1.3.7 Ballast Addition 1.3.7.1 Wate
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Page 25 and 26: Tank name Tank volume Ballast type
Page 27 and 28: was successfully performed and <str
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Page 31 and 32: 2.3 Preliminary Decision-Making Cos
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Page 39 and 40: 2.4.1 Structural Modifications 2.4.
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Page 45 and 46: 3.1 Final POSSE Results The minimum
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A Solution to the Inherent List on Nimitz Class Aircraft Carriers

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