Preliminary Structural Sizing and Alternative Material Trade Study for the CEV Crew Module

This paper presents the results of a preliminary structural sizing and alternate material trade study for NASA’s Crew Exploration Vehicle (CEV) Crew Module (CM). This critical CEV component will house the astronauts during ascent, docking with the International Space Station, reentry, and landing. The alternate material design study considers three materials beyond the standard metallic (aluminum alloy) design that resulted from an earlier NASA Smart Buyer Team analysis. These materials are graphite/epoxy composite laminates, discontinuously reinforced SiC/Al (DRA) composites, and a novel integrated panel material/concept known as WebCore. Using the HyperSizer (Collier Research and Development Corporation) structural sizing software and NASTRAN finite element analysis code, a comparison is made among these materials for the three composite CM concepts considered by the 2006 NASA Engineering and Safety Center Composite Crew Module project. I. Introduction In an effort to develop a strong in-house understanding of the design drivers for the CEV CM (see fig. 1), NASA formed a multi-center Smart Buyer Team in January 2006 to perform a preliminary design. This 10 week effort focused on a grid-stiffened aluminum-lithium (Al-Li) design with ring frames and longerons, but also considered composite materials through a simple material substitution. It was determined that composites could potentially deliver a 12 percent mass savings (ref. 1), with even greater mass savings possible through tailoring the overall design to composites. In order to pursue these additional mass savings, the NASA Engineering and Safety Center (NESC) formed a multi-center composite CM team to perform a preliminary design and characterize additional design drivers as they apply to composites, such as manufacturability, crashworthiness, damage tolerance, inspectability, reparability, and the effects of micro-meteoroid orbital debris (MMOD) impacts (ref. 2). This team concluded its work after four months, in September 2006. A second phase of the NESC composite CM project commenced in January 2007, with the goal of completing the design and fabrication of a composite CM in 18 months. This paper presents the authors’ contributions to the 2006 NESC composite CM project. These contributions primarily involve preliminary design trade studies among materials and panel concepts across the three major CM concepts investigated by the team (see fig. 2). The focus of the present paper is on identifying weight advantages, while other important design issues (manufacturability, inspectability, etc.) are not addressed herein. Trade studies were performed using the HyperSizer structural sizing software (ref. 3), in conjunction with the NASTRAN finite element analysis (FEA) software (ref. 4).