Encyclopedia Astronautica
1968.11.13 - Effects of moisture on the Apollo launch adapter structure


ASPO Manager Low asked Aaron Cohen, one of his staff assistants, to lead an investigation to determine detrimental effects of moisture on the strength of the bonded covering of the launch adapter structure.

His action stemmed directly from a presentation the same day by James A. Chamberlin to the Structures Advisory Board explaining the adapter failure on Apollo 6. Moisture in the adapter not only raised the pressures generated by heating during the boost phase of the flight through the atmosphere, but it also weakened the structural bonding either directly or by hampering venting through the holes in the honeycomb material. Low asked Cohen to take precautions that no water be allowed to enter the adapter. All joints in the material should be sealed with a waterproof tape even before the countdown demonstration test and should remain on the vehicle throughout the flight, so that the adapter would absorb no moisture even if it rained during the final count before launch. On the other hand, the tape must then withstand boost phase heating and must not impair spacecraft separation and panel jettisoning. (North American Rockwell, in compliance with CCBD, August 10, 1968, Master Change Record 7727, modified the SLA panels by drilling vent holes in the inner skin of the panels of all subsequent SLAs to allow release of moisture during ascent. These holes were to be kept sealed until immediately before launch to avoid collection of moisture in the honeycomb.)

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