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Wash Solution Bath Life Extension for the Space Shuttle Rocket Motor Aqueous Cleaning SystemA spray-in-air aqueous cleaning system, which replaced 1,1,1 trichloroethane (TCA) vapor degreasing, is used for critical cleaning of Space Shuttle Redesigned Solid Rocket Motor (RSRM) metal parts. Small-scale testing demonstrated that the alkaline-based wash solution possesses adequate soil loading and cleaning properties. However, full-scale testing exhibited unexpected depletion of some primary components of the wash solution. Specifically, there was a significant decrease in the concentration of sodium metasilicate which forced change-out of the wash solution after eight days. Extension of wash solution bath life was necessary to ease the burden of frequent change-out on manufacturing. A laboratory study supports a depletion mechanism that is initiated by the hydrolysis of sodium tripolyphosphate (STPP) lowering the pH of the solution. The decrease in pH causes polymerization and subsequent precipitation of sodium metasilicate (SM). Further investigation showed that maintaining the pH was the key to preventing the precipitation of the sodium metasilicate. Implementation to the full scale operation demonstrated that periodic additions of potassium hydroxide (KOH) extended the useful bath life to more than four months.
Document ID
19990075878
Acquisition Source
Headquarters
Document Type
Conference Paper
Authors
Saunders, Chad
(Thiokol Propulsion Brigham City, UT United States)
Evans, Kurt
(Thiokol Propulsion Brigham City, UT United States)
Sagers, Neil
(Thiokol Propulsion Brigham City, UT United States)
Date Acquired
August 19, 2013
Publication Date
April 1, 1999
Publication Information
Publication: Third Aerospace Environmental Technology Conference
Subject Category
Engineering (General)
Distribution Limits
Public
Copyright
Public Use Permitted.
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