%0 Conference Paper %B 64th Annual Conference, Annapolis, Maryland %D 2005 %T 3360. Are You Sure? - Uncertainty in Mass Properties Engineering %A Zimmerman, Robert L. %A Nakai %K 12. Weight Engineering - Computer Applications %K 21. Weight Engineering - Statistical Studies %K Mike Hackney Best Paper Award %X

The Mass Property Engineer?s role in the engineering organization is ultimately to report the mass properties of the organization?s vehicle, so that the vehicle?s performance can be characterized. It is insufficient merely to report the mass properties as a discrete entity ? the characterization of performance requires the possible variations of the vehicle?s mass properties also be determined and reported by the Mass Property Engineer to the team. Mass Property Engineers have an expectation, based on precision computerized drafting and manufacturing equipment, electronic mass property tallying, and high accuracy measurement equipment, that the reported mass properties will be very close to the vehicle?s actual mass properties. This paper will unveil the proposition that the carefully determined mass properties reported by the Mass Properties group has far greater dispersions about the reported values than that expectation. The paper is divided into three parts. Part One expands on basic statistical concepts required to determine mass property parameter dispersions. Part Two derives the algorithms necessary to determine overall vehicle mass property uncertainties. Part Three illustrates Parts One and Two using an example, and produces some representative computer code to implement the algorithms.

%B 64th Annual Conference, Annapolis, Maryland %I Society of Allied Weight Engineers, Inc. %C Annapolis, Maryland %P 36 %8 5/14/05 %G eng %U https://www.sawe.org/papers/3360/buy %9 12. WEIGHT ENGINEERING - COMPUTER APPLICATIONS; 21. WEIGHT ENGINEERING - STATISTICAL STUDIES %M 3360 %1 Non-Member Price: $20.00; Member Price: $10.00 Members: First 10 product downloads are Free. %2 10.00 %3 20 %4 SAWE3360 %0 Conference Paper %B 60th Annual Conference, Arlington, Texas, May 19-23 %D 2001 %T 3156. ""Standard"" SAWE Mass Properties Calculation Software and Algorithms %A Boynton, Richard %A Nakai %A Wiener %A Strom %K 12. Weight Engineering - Computer Applications %K Mike Hackney Best Paper Award %X

Although most CAD programs now include routines for calculating the mass properties of the various elements of a system or vehicle, there is still a use for basic mass properties calculation software. If such software were written in JAVA, then it could be easily shared by all members of the SAWE and would run on any type of computer. This software could be used when estimating the mass properties of new designs, or it could be used to make quick simplified mass properties calculations to verify that the results of the CAD programs are reasonable. In addition to describing the software, this paper is a tutorial on the calculation of mass properties (moment of inertia, centerof gravity, product of inertia). We have included a discussion of the coordinate transformation of inertias using tensors and have provided a number of simple mathematical tests that can be used to verify the reasonableness of calculated values. There are numerous textbooks on dynamics that devote a few pages to the theory of these properties. However, these textbooks quickly jump from a very brief description of these quantities to some general mathematical formulas without giving adequate examples or explaining in enough detail how to use these formulas. The purpose of this paper is to provide a detailed procedure for the calculation of mass properties for an engineer who is inexperienced in these calculations. This paper will also provide a convenient reference for those who are already familiar with this subject. This paper contains a number of specific examples with emphasis on units of measurement. The examples used are rockets and re-entry vehicles. The paper then describes the techniques for combining the mass properties of sub-assemblies to yield the composite mass properties of the total vehicle. Errors due to misalignment of the stages of a rocket are evaluated numerically. Methods for calculating mass property corrections are also explained. It was hoped that an outcome of this paper will be the generation of SAWE standard mass properties utility software written in JAVA that is available on the SAWE web site. Tutorial booklets could also be downloaded which would explain the use of the software and describe the process of making mass properties calculations. Unfortunately, due to concerns regarding United States export restrictions, the JAVA software described in this paper is currently only available for distribution and licensing to United States companies and citizens.

%B 60th Annual Conference, Arlington, Texas, May 19-23 %I Society of Allied Weight Engineers, Inc. %C Arlington, Texas %P 70 %8 5/19/01 %G eng %U https://www.sawe.org/papers/3156/buy %9 12. WEIGHT ENGINEERING - COMPUTER APPLICATIONS %M 3156 %1 Non-Member Price: $35.00; Member Price: $10.00 Members: First 10 product downloads are Free. %2 10.00 %3 35 %4 SAWE3156