scope:

Description of Driving Event:

Solid Rocket Motor segments are shipped from the facility in Utah to KSC horizontally on railroad cars. During the assembly process at KSC, it has become necessary to reshape case segments to make them concentric with mating segments. This has resulted in assembly difficulties and eccentric loads on the joint o-rings. Assembly difficulties resulting from the lack of concentricity include the generation of case metal slivers produced by having to force pins into the joint pin holes. The pin-topin hole tolerances are such that the pin is difficult to install if the tang and clevis pin holes are not precisely aligned. Case segment ovality (which apparently results from the horizontal shipment on railcars) can cause tight tolerances in the area of the o-ring sealing surface. This can cause assembly difficulties and result in undesirable o-ring squeeze.