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Unformatted text preview: ition strategies, and risk management
Program/Project Approval Review
System Requirements Review(s)
System Definition Review
System-level Preliminary Design Review
Lower-level Preliminary Design Reviews
Safety review(s) NASA Systems Engineering Handbook
The Project Life Cycle for Major NASA Systems A Credible, Feasible Design
A feasible system design is one that can be implemented as designed and can then accomplish the system's goals within the constraints imposed by the
fiscal and operating environment. To be credible, a
design must not depend on the occurrence of
unforeseen breakthroughs in the state of the art.
While a credible design may assume likely
improvements in the state of the art, it is nonetheless
riskier than one that does not. Early in Phase B, the effort focuses on
allocating functions to particular items of hardware,
software, personnel, etc. System functional and
performance requirements along with architectures and
designs become firm as system trades and subsystem
trades iterate back and forth in the effort to seek out
more cost-effective designs. (Trade studies should
precede—rather than followsystem design decisions.
Chamberlain, Fox, and Duquette describe a
decentralized process for ensuring that such trades lead
efficiently to an optimum system design.) Major
products to this point include an accepted "functional"
baseline and preliminary "design-to" baseline for the
system and its major end items. The effort also
produces various engineering and management plans to
prepare for managing the project's downstream
processes, such as verification and operations, and for
implementing engineering specialty programs.
Along the way to these products, projects are
subjected to a Non-Advocate Review, or NAR. This
activity seeks to assess the state of project definition in
terms of its clarity of objectives and the thoroughness of
documentation, alternatives explored, and trade studies
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