611. The Derivation and Application of Non-Optimum Factors for Missiles and Spacecraft
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Paper
Abstract
For the purposes of this paper, Non-optimum Factor (referred to as NOF) is defined as the actual as-manufactured weight divided by the theoretical weight calculated at an advanced design level from the engineering drawings. Or put another way, it is a factor that needs to be applied to a calculation of the final engineering drawings to obtain actual weights when the calculation is done at the level of detail common to an advanced design project.
Data have been published in the past (SAWE Paper No. 327, C. R. Liebermann) on the derivation of NOF’s for application In advanced design to account for all sorts of unknowns involved in advanced design weight prediction. This includes such things as incomplete stress and loads analysis, the effects of testing penalties, special design considerations for handling, minimum gage limitations, manufacturing capabilities arid many other unknowns and undefinables too numerous to mention. At this time when much of the advanced design engineer’s time is not involved so much with new concepts as with improvement of an existing concept, it was felt that the need existed for factors to be used in this type of effort. This is also a time when more sophisticated computer programs are better able to predict and account for many of the items once covered in NOF.
One purpose of this paper is to furnish the advanced design weight engineer with a working tool in the form of factors to be applied to his calculations when he is simply increasing vehicle diameter and/or length, substituting new propellants, engines, structural materials, or effecting economies in packaging within an existing concept or design. Another purpose is to provide an aid to convince management and the customer that the factors being used are realistic and in line with the general design and manufacturing philosophy and capability of a company. And last, the paper describes a method by which any weight engineer can derive his own set of factors. It is a known fact that the hardware used for an example in this paper would produce somewhat different factors if it had been designed and built somewhere else.
For the advanced design weight engineer working on a completely new concept (perhaps new only to him or his company) this paper will furnish a base for factors that he must derive for use in his work.
