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Unformatted text preview: as inputs. A transition to a new stage
entails a major shift in the nature or extent of technical
activities. Control gates assess the wisdom of
progressing from one stage to another. (See Section
4.8.3 for success criteria for specific reviews.) From the
perspective of the system engineer, who must oversee
and monitor the technical progress on the system,
Figure 8 provides a more complete description of the
actual work needed through the NASA project life cycle.
In practice, the stages do not always occur
sequentially. Unfolding events may invalidate or modify goals and assumptions. This may neccessitate revisiting
or modifying the results of a previous stage. The end
items comprising the system often have different
development schedules and constraints. This is
especially evident in Phases C and D where some
subsystems may be in final design while others are in
fabrication and integration.
The products of the technical activities support
the systems engineering effort (e.g., requirements and
specifications, trade studies, specialty engineering
analyses, verification results), and serve as inputs to the
various control gates. For a detailed systems
engineering product database, database dictionary, and
maturity guidelines, see JSC-49040, NASA Systems
Engineering Process for Programs and Projects.
Several topics suggested by Figures 7 and 8
merit special emphasis. These are concurrent
engineering, technology insertion, and the distinction
between verification and validation.
Concurrent Engineering. If the project passes early
control gates prematurely, it is likely to result in a need
for significant iteration of requirements and designs late
in the development process. One way this can happen
is by failing to involve the appropriate technical experts
at early stages, thereby resulting in the acceptance of
requirements that cannot be met and the selection of
design concepts that cannot be built, tested, maintained,
Concurrent engineering is the simultaneous
consideration of product and process...
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