Abstract
Survivor curves forBacillus subtilis var.Niger spores were determined during cure within à solid propellant containing a saturated hydrocarbon binder. Cure temperatures of 82, 93, 105, and 115°C were selected for evaluation. Upon completion of the propellant mix, samples of approximately 5 g were weighed, placed into aluminum planchets, and subjected to dry heat cure. The results indicated that the survivor curves were polyphasic at all cure temperatures evaluated. The polyphasic nature of the survivor curves reflect the physico-chemical changes occuring during polymerization. Selected portions of each survivor curve were delineated and subjected to linear regression analysis. D values were calculated for selected portions of each survivor curve at each test temperature. Sterility (considering the nature and consistency of the propellant system under investigation, sterility has been defined as no viable particles recovered-N.V.P.R.) was not achieved with samples cured at 82 and 93°C for 7 day. Samples cured at 105°C experienced a four-log reduction in number of spores within 4 h; however, sterility was not achieved by 48-h cure. A temperature of 115°C was necessary to achieve sterility within 12 h. The results indicated that thermally stable binders will permit the sterilization of solid propellant motors during routine cure cycles, prior to terminal sterilization.
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This paper presents the results of one phase of research carried out by the Planetary Quarantine Group, Environmental Requirements Section of the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. NAS 7-100, sponsored by the National Aeronautics and Space Administration.
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Brewer, W.A., Paik, W.W., Smith, C.D. et al. The effects of various cure cycles upon the viability ofBacillus subtilis var.niger spores within solid propellant. Space Life Sciences 3, 198–205 (1972). https://doi.org/10.1007/BF00928164
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DOI: https://doi.org/10.1007/BF00928164