Mass Properties Calculation and Fuel Analysis in the Conceptual Design of Uninhabited Air Vehicles

Abstract

The determination of an aircraft's mass properties is critical during its conceptual design phase. Obtaining reliable mass property information early in the design of an aircraft can prevent design mistakes that can be extremely costly further along in the development process.

In this thesis, several methods are presented in order to automatically calculate the mass properties of aircraft structural components and fuel stored in tanks. The first method set forth calculates the mass properties of homogenous solids represented by polyhedral surface geometry. A newly developed method for calculating the mass properties of thin shell objects, given the same type of geometric representation, is derived and explained. A methodology for characterizing the mass properties of fuel in tanks has also been developed. While the concepts therein are not completely original, the synthesis of past research from diverse sources has yielded a new comprehensive approach to fuel mass property analysis during conceptual design. All three of these methods apply to polyhedral geometry, which in many cases is used to approximate NURBS (Non-Uniform Rational B-Spline) surface geometry. This type of approximate representation is typically available in design software since this geometric format is conducive to graphically rendering three-dimensional geometry.

The accuracy of each method is within 10% of analytical values. The methods are highly precise (only affected by floating point error) and therefore can reliably predict relative differences between models, which is much more important during conceptual design than accuracy. Several relevant and useful applications of the presented methods are explored, including a methodology for creating a CG (Center of Gravity) envelope graph.