1602. Ship Weight Estimates Using Computerized Ratiocination
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Paper
Abstract
Although the method of ratiocination is well known for use in preparing ship weight estimates during the early design phases, this method when done using hand calculations is cumbersome and does not lend itself well to the rapidly changing and fluid designs characteristic of the early stages of naval ship design. This need to provide a more convenient and rapid method for producing a weight estimate based on minimal ship information, without any loss of accuracy, led to the use of computers and the development of the RATS program to produce these estimates.
The RATS program is an interactive program developed to use a pre-selected known base ship and certain selected characteristics of the new ship design to produce a complete three-digit SWBS weight estimate containing the weights and vertical and longitudinal centers for the design. This is done by the program through a series of equations which equate the SWBS element weight and centers with certain characteristics of the new ship, which then modify the base ship weight to reflect the new design characteristics. Since this methodology is subject to some inaccuracies if the new design has a somewhat different configuration or mission than the base ship, the program also allows the user to modify the estimate produced by this method to reflect any of the special or unique aspects of the new design. The output of the program is an eleven page estimate which also contains the base and new ship characteristics. Also produced is a summary of all of the modifications made to the estimate by the user. Options also exist to produce a delta summary from the base ship to the new ship, to prepare the estimate in a format compatible for input into the SDWE program, and to use the new ship estimate as a base ship file for sensitivity studies. The estimate may be prepared using either English or metric units.
This program has several applications. Most importantly, it allows the engineer to prepare an accurate weight estimate for a naval ship during the Feasiblity level of design in a very short amount of time. It also allows sensitivity analyses to be performed on a ship at virtually any level of design, again in a very short period of time. These sensitivity analyses would determine the impact of variation in the ship characteristics to the ship weight and centers of gravity.
