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Unformatted text preview: ed two extra
crew members. It should be noted that no attempt was
made to assess the design capability or design cost
impacts to accommodate these extra crew members.
The savings of crew due to halving the number of ORU
replacements is small, effectively one less crew
member for half the year.
Figure B-15 shows the number of Space Shuttle
flights over five years needed to maintain the nominal
available upmass. The Space Shuttle flights were
rounded upward to obtain whole flights. Doubling the
number of ORU replacements would mean eight extra
Space Shuttle flights would be needed over five years.
Halving the ORU replacements would require two fewer
Space Shuttle flights over five years. No attempt was
made to assess the Space Shuttle capability to provide
the extra flights or the design cost impacts to create the
ORUs with the different reliabilities.
Figure B-16 shows the effect of assessing the
cost impact of the previous two figures and combining
them with the five-year operations cost. The influence of
MTBF is effectively doubled when the resources of
available upmass and crew time are maintained at their
nominal values. NASA Systems Engineering Handbook NASA Systems Engineering Handbook Appendix B.9 -- An Example of a Verification
Appendix B.9 is a small portion of the Verification
Requirements Matrix (VRM) from the National Launch System Level III System Requirements Document,
originally published at the Marshall Space Flight Center.
Its purpose here is to illustrate the content and one
possible format for a VRM. The VRM coding key for this
example is shown on the next page. NASA Systems Engineering Handbook NASA Systems Engineering Handbook Appendix B.10—A Sample Master Verification
1.2 Applicable Documents
1.3 Document Maintenance and Control 2.0 Program/Project Description
2.1 Program/Project Overview an d
Verification Master Schedule
2.2 Systems Descriptions
2.3 Subsystems Descriptions 3.0 4.0 5.0 Integration and Verification (I&V)
Organization and Staffing
3.1 Program/Project Management
3.2 NASA Field Center I&V
3.3 International Partner I&V...
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