Second Stage Forward Skirt

exactness, and station locating is benefited by the even gravitational force exerted during each as­sembly operation. Constant checks and verification

of station planes and stage alignment are main­tained during each joining procedure by special scopes, levels, and traditional plumb bobs.

Another reason for vertical assembly involves the welding of cylinders and bulkhead. If the stage were welded while in a horizontal position, temperatnre diversion over the circumference could result in harmful expansion near the top of the stage.

To facilitate movement of the huge components and of the stage itself, a motorized transfer table rolls from outside to inside the building. Essentially, the assembly sequence begins with the welding of the lower two cylinders. Then the common bulkhead is welded to that assembly. Next the uppermost cyl­inder is welded to the LHa forward bulkhead. The aft LOX bulkhead and the aft facing sheet of the common bulkhead are welded together to form the liquid oxygen tank, and the thrust structure and aft skirt are then assembled to it. The remaining cylinders are then welded to the stage, and the for­ward skirt is then mated to the stage stack. The interstage is fit-checked to the thrust structure before interstage systems are installed. Throughout the assembly and welding operations, hydrostatic, X-ray, dye penetrant, and other tests and quality control devices are performed to ensure that speci­fications are met. The liquid hydrogen portion of the second stage as well as the liquid oxygen tank are given a thorough cleaning after assembly. After each bulkhead is welded to its components, it is hy­drostatically tested. After completion of stack weld operations, the entire stage is pneumostatically tested. After completion of these tests, the liquid

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Reposiiisring–Second stage is turned horizontally for checkout operation.

Stage Complete…. Flight stage moves on transfer table from

assembly building to checkout building.

Engine Installation—J-2 engines are mounted in stage.

After assembly, the stage Is moved to a vertical checkout building for final checks on all stage sys­tems.