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Unformatted text preview: rs and the application of specialized
models described in the next section.
5.3.3 Availability and LogisticsSupportability
Modeling One reason for emphasizing availability and
logistics supportability in this chapter is that future
NASA systems are less likely to be of the
"launch-and-logistically forget" type. To the extent that
logistic support considerations are major determinants
of system effectiveness during operations, it is essential
that logistics support be thoroughly analyzed in trade
studies during the earlier phases of the project life cycle.
A second reason is that availability and logistics
supportability have been rich domains for methodology
and model development. The increasing sophistication of the methods and models has allowed the system-wide
effects of different support alternatives to be more easily
predicted. In turn, this means more opportunities to
improve system effectiveness (or to lower life-cycle
cost) through the integration of logistics considerations
in the system design.
Availability models relate system design and
integrated logistics support technical attributes to the
availability component of the system effectiveness
measure. This type of model predicts the resulting
system availability as a function of the system
component failure and repair rates and the logistics
support resources and policies. (See sidebar on
measures of availability.)
Logistics supportability models relate system
design and integrated logistics support technical
attributes to one or more "resource requirements"
needed to operate the system in the accomplishment of
its goals and objectives. This type of model focuses, for
example, on the system maintenance requirements,
number and location of spares, processing facility
requirements, and even optimal inspection policies. In
the past, logistics supportability models have typically
been based on measures pertaining to that particular
resource or function alone. For example, a system's
desired inventory of spares w...
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