Critical technologies in composite wing and intertank primary structures supports RLV success

Abstract

This paper describes the development of a graphite composite wing and a graphite composite intertank primary structure for application toward Single-Stage to Orbit space vehicles such as those under development in NASA's X-33/Reusable Launch Vehicle (RLV) Program. The trade study and designs are based on a Rockwell vertical take-off and horizontal landing (VTHL) wing-body RLV vehicle. Northrop Grumman's approach using a building block development technique is described. Composite Graphite / Bismaleimide (Gr/BMI) material characterization test results are presented. Unique intertank and wing composite subcomponent test article designs are described and test results to date are presented. Wing and intertank Full Scale Section Test Article (FSTA) objectives and designs are outlined. Trade studies, supporting building block testing, and FSTA demonstrations combine to develop graphite primary structure composite technology that enables developing X 33/RLV design programs to meet critical SSTO structural weight and operations performance criteria. 'Principal Investigator, Northrop Grumman NASA NRA Technology Program Principal Engineer, B-2 Division Northrop Grumman ^Specialist, B-2 Division Northrop Grumman ^Senior Technical Specialist, B-2 Division Northrop Grumman Copyright © by Northrop Grumman, Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Introduction In 1993, NASA conducted a study of space transportation options and concluded that a new, fully reusable, Single Stage to Orbit (SSTO) launch system offered the best approach to achieving the national goal of affordable access to space. One of the critical enabling technologies identified by NASA, OMB, and OSTP as integral to the success of SSTO Reusable Launch Vehicles (RLV) is the development of graphite composite primary structures. Advanced composites applied to major structural components such as the wing and the intertank (payload bay) can significantly reduce structural weight compared to present metallic primary structures and thus help enable an RLV to meet crucial vehicle weight targets. Primary structure is the largest system weight contributor to the RLV. Reuse, manufacturability, operations requirements, and cost are also critical issues to be addressed for the successful application of composites to RLV structures. Durability of primary structure composite materials in extreme (-160°F to +350°F) environments needs to be characterized to establish appropriate design allowables. Jointly with NASA and Rockwell Space Systems Division (SSD), Northrop Grumman Advanced Technology and Development Center (ATDC) is proceeding to address these key graphite composite technology issues to enable X-33 / RLV application. Using processes and lessons learned from operational vehicle systems such as the B-2, Northrop Grumman is proceeding to demonstrate the feasibility of advanced composites in RLV wing and intertank primary structures. This paper discusses some of the challenges of applying advanced composites to an RLV wing and an intertank primary structure and describes the specific approach followed to achieve the established RLV composite development goals. Specific tasks discussed in this paper include: trade studies leading to material and construction selection; building block materials characterization test results;