Manufacturing technology for a low cost, lightweight composite bulkhead for THAAD

Field: Engineering (Physical Sciences)

Beginning in 1994 the U.S. Army Research Laboratory (USARL) and the Ballistic Missile Defense Organization (BMDO) in conjunction with the U.S. Army Missile Command/THAAD Project Office (TPO) and Boeing-Rocketdyne Division (nee Rocketdyne Propulsion Company) sponsored a technology development program to develop a low cost, lightweight, all composite THAAD Aft Divert System bulkhead to replace the current aluminum bulkhead. Sparta worked with Boeing-Rocketdyne engineers to develop a design that met structural performance and envelope requirements. Sparta fabricated seven composite parts which were subsequently tested successfully. A production cost estimating model showed that the composite part could be built at a competitive price compared with the aluminum part; the production model was used to evaluate projected producibility and process enhancements which projected significantly lower composite part costs when compared with the aluminum part costs. This paper describes a joint US Army Space and Missile Defense Command (SMDC) and BMDO Manufacturing Technology (MANTECH) program whose objective is to develop the manufacturing data base necessary to 1) evaluate and select part and production process improvements to meet production cost goals, 2) project the production cost of the composite part, 3) quantify process precision and reliability and 4) analyze the cost/benefit of the composite part when compared with the current aluminum part. A production rate of 300 to 500 parts per year was used to guide the development of producibility improvements to the part and manufacturing process design. Part producibility enhancements and production processes were defined, costed, evaluated against system requirements and goals and selected for incorporation into the production design. The paper reports the results of this process and includes the results of the producibility trade studies which incorporate production rate, quantity, tolerance, process reliability and system level cost goals as parameters. A detailed cost study was performed to capture all the costs associated with the aluminum part and the projected costs of the composite part. Cost factors such as acquisition, integration, assembly, maintenance, logistics, repair/replacement were analyzed and are reported. BACKGROUND The THAAD Divert and Attitude Control System (DACS) is supported by a forward and an aft bulkhead which are currently precision machined aluminum structures. Figure 1 shows the DACS and the installation of both bulkheads while Figure 2 shows the prototype composite bulkhead. The U.S. Army Research Laboratory (USARL) in conjunction with Boeing-Rocketdyne supported a development program to demonstrate that the bulkheads could be net molded using graphite reinforced composite material. Both the Army and Boeing-Rocketdyne were interested in taking advantage of the potential weight reduction, stiffness increase and cost reduction afforded by the composite when compared with the aluminum parts. The Army and Boeing-Rocketdyne decided to focus initial program efforts on demonstrating the benefits of the Army/Sparta developed composite closed mold net molding process on the aft DACS bulkhead. A total of ten bulkheads were successfully net molded using both IM-7 and M40J fiber in F652 high temperature capable bismaleimide resin (BMI). Structural verification testing was completed which demonstrated that the bulkheads met the structural design and stiffness requirements for the system. Estimates for composite bulkhead production cost indicated a potential for substantial cost savings over the aluminum parts. The Ballistic Missile Defense Organization (BMDO) ManTech activity and the U.S. Army Space and Missile Defense Command (SMDC) began a producibility program to define production improvements to the bulkheads. This paper describes the design and fabrication processes, benchmarks process reliability, summarizes the results of testing and describes the manufacturing improvements to meet the producibility goals. The baseline manufacturing process is described and improvements and payoffs are identified. Key tooling improvements are described and discussed. Copyright © 1998 The American Institute of Aeronautics and Astronautics, Inc. All Rights Reserved