A New Methodology to Preliminary Design Structural Components of Re-Entry and Hypersonic Vehicles

Abstract

The aim of the hot structure design process is to ensure the structural integrity of the component minimizing two fundamental parameters: mass and thickness. The former influences the total weight of the vehicle, the latter influences the vehicle efficiency (Thornton, 1996;Kelly et al, 1983; Shih et al, 1988). In order to perform the thermo-structural sizing of the component it is necessary to evaluate the stress and temperature distribution. Usually numeric methods (finite element or finite difference codes) are adopted to estimate those distribution (Daryabeigi, 2002;Poteet et al, 2004). In a preliminary design phase where accurate results are not required, approximate analytic solutions can be used (Kunihiko, 1998). Analytic solutions, whether exact or approximate, are always useful in engineering analysis, because they provide a better insight into the physical significance of various parameters affecting the problem. When exact analytic solutions are impossible or too difficult to obtain or the resulting analytic solutions are too complicated for computational purposes, approximate analytic solutions provide a powerful alternative approach to handle such problems. There are numerous approximate analytic methods for solving the partial differential equations governing the engineering problems. One of the most powerful method is the Integral one (Crank, 1979; Syed et al, 2010). It is simple to use and gives the opportunity to solve non linear problems such as thermal radiation/conduction ones. In the frame of thermal structures preliminary design activities the adoption of the integral method together with appropriate assumptions give the possibility to develop analytic/numeric models that allow to solve non linear transient thermal phenomena. Those methods are very useful since they are very simple to use and allow to save a significant amount of time with respect to numeric Finite Element models in a thermal structure preliminary design phase. As a consequence, complex optimization analyses characterized by several design objectives, constraints and variables in a reasonable length of time could be conducted. The proposed approach allows to define a preliminary thermal design of the hot structure. Obviously, in a subsequent design phase structural sizing must be performed starting from the configuration resulted from the previous thermal sizing process. The present paper describes in detail how the proposed model works. An application of the simplified model on the wing leading edge of a re-entry vehicle is presented.