2120. The Use of Contingencies in Predicting and Controlling Vehicle Weight Growth From a Missile Perspective

Paper

Abstract

As a profession, the primary goal of mass properties engineering is to continue to develop its ability to predict, and ultimately control, significant weight growth on a program. A popular method to help account for this weight has been through the use of weight contingency factors. However, at the Southeastern Regional SAWE Conference in October of l991, during a discussion of weight control, some engineers questioned the proper role of such margins, arguing that they are either redundant or are viewed by designers as implicit approval to increase weight. From his experience in small missile/spacecraft design, the author presents a methodology for using weight contingency factors throughout the life of a program to help predict anticipated weight growth at the component and/or subsystem level. He begins with a contingency factor level of 10 to 30 percent in the earliest design phase, and gradually reduces that to 2 to 3 percent just prior to production. Contingency factors approach zero when production begins and calculated predictions are replaced with measured actuals, although some contingency may be retained until the vehicle reaches completely ”mature” status.