Extra orus taken to orbit reduces available upmass

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Unformatted text preview: ing navigation satellite inputs? Figure B-10 is an example of a maintenance TLS which illustrates that availability of an item (a distiller) is dependent upon the completion of numerous maintenance tasks accomplished concurrently. Furthermore, it illustrates the traceability to higher level requirements by referencing the appropriate FFBD and requirement allocation sheet (RAS). NASA Systems Engineering Handbook NASA Systems Engineering Handbook NASA Systems Engineering Handbook Appendix B.8 -- The Effect of Changes in ORU MTBF on Space StationFreedom Operations The reliability of Space Station Freedom's (SSF) Orbital Replacement Units (ORUs) has a profound effect on its operations costs. This reliability is measured by the Mean Time Between Failures (MTBF). One study of the effects, by Dr. William F. Fisher and Charles Price, was SSF External Maintenance Task Team Final Report (JSC, July 1990). Another, by Anne Accola, et al., shows these effects parametrically. Appendix B.8 excerpts this paper, Sensitivity Study of SSF Operations Costs and Selected User Resources (presented at the International Academy of Astronautics Symposium on Space Systems Costs Methodologies and Applications, May 1990). ••• There are many potential tradeoffs that can be performed during the design stage of SSF. Many of them have major implications for crew safety, operations cost, and achievement of mission goals. Operations costs and important non-cost operations parameters are examined. One example of a specific area of concern in design is the reliability of the ORUs that comprise SSF. The implications of ORU reliability on logistics upmass and downmass to and from SSF are great, thus affecting the resources available for utilization and for other operations activities. In addition, the implications of reliability on crew time available for mission accomplishment (i.e., experiments) vs. station maintenance are important. The MTBF effect on operations cost is shown in Figure B-11. Repair and spares costs are influenced gr...
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This document was uploaded on 02/26/2014 for the course E 515 at University of Louisiana at Lafayette.

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