dcn@ihuxl.UUCP (Dave Newkirk) (11/21/85)
I've just finished reading "Stages to Saturn - A Technological History of the Apollo/Saturn Launch Vehicles", and I thought you might like to hear some of the high points in this 510 page tome. Here's the first, about making the domes on the ends of the propellant tanks on the third stage: "We cut our eye teeth on this phase of manufacturing," recalled H. E. Bauer, a company executive who was deeply involved in the S-IV and IVB project. To join the metal `peels' together to form a hemispheric half-shell, Douglas used a rotating fixture and a `down hand' technique of welding. In this mode, the weld torch moved on a track while the molten welding `puddle' remained in the proper position from force of gravity, which also minimized undesireable porosity. While welding the orange peel segments, a strange problem developed. The tracking system for the weld torch hinged on the detection of discontinuities produced by induced eddy currents along the seams to be welded. The exasperating torch heads wandered all over the place, however, apparently unable to follow the seams at all. Oddly enough, the trouble was traced to manufacturing standards being set too high! "Because the individual segments had been so carefully formed and sized," Bauer explained, "upon butting them together no sensible level of electrical discontinuity to the instrument developed." Some insensitive soul suggested the application of a bastard file to rough up the seams and create enough discontinuity that the tracking system could to its job. After adamant protests from the manufacturing people at Long Beach, Douglas specialists refined the tracking system to give it a much higher gain, and scarfed (grooved) the segments to provide a path for the tracking sensors to follow. From "Stages to Saturn - A Technological History of the Apollo/Saturn Launch Vehicles", available from the Superindendant of Documents, U.S. Government Printing Office, Washington, DC 20402. Order NASA SP-4206, $12.00. -- Dave Newkirk, ihnp4!ihuxl!dcn