Special Tooling for Joining Tubing in Place

The Saturn S-II stage and the Apollo spacecraft will include in their design and construction various pressurized tubing systems that will encounter service temperatures of 280° F to -423° F. Design engineering and reliability requirements and weight restrict ions have dictated new concepts to assure leak-tight joints for rocket engine fuel lines, pressurization systems, utility systems, and hydraulic systems. An investigation was initiated at North American Aviation, Inc., Space and Information Systems Division, utilizing the in-place automatically controlled miniaturized fusion-welding equipment originally developed by the Los Angeles Division of NAA and modified to meet the needs of Apollo and Saturn welded tubular systems. The objective was to make circumferential flanged weld joints in any position in 304L stainless for Saturn S-II and sleeve-type joints in 304L for Apollo. Inconel X, commercially pure titanium, 5052-0 aluminum, and 6061 T6 aluminum were also tested experimentally. Extensive environmental, static, and dynamic testing programs were conducted to determine the as-welded mechanical properties, design allowables, and reliability for the tube joints. This paper discusses both the experimental and production phases. Subsequently, the new tube welding process was approved and incorporated into manufacturing fabrication methods for tube joining.