The Iterative Design Process
The Joint Strike Fighter (JSF) program portrays the
process of iteratively designing a system using the SBA process as shown in
Figure 4-2.15 The JSF
process is a building block approach, with each step building upon the
previous steps as well as iterating within the steps and between steps. It
begins with the Delphi Process, which is a method devised by the RAND
Corporation to obtain expert judgment from multiple experts without many of
the biases associated with interpersonal pressures.16 These results are then
fed into a Quality Functional Deployment (QFD) analysis, which refines the
requirements into ways to accomplish those requirements. QFD provides a way of
tracking and tracing tradeoff analyses through various levels, from
requirements through design decisions to production and support processes,
while preserving traceability to user needs.17 These results are then used to build the appropriate level of constructive simulation. At first, these simulations will be at an aggregated campaign level, but will continue to be iterated and refined back through the previous two steps and down the constructive simulation hierarchy to mission/battle, engagement, and finally the engineering level. As more is learned, the simulation progresses to interactive digital simulation and interaction within a virtual environment, which introduces the human-in-the-loop. Again, there can be much iteration within each step, as well as feedback to earlier steps to capture the knowledge gained.
As the program matures into flight test, these results
are also fed back into the program to capture the knowledge, and to help
challenge and possibly revise the inputs to the process.
Once a program reaches the constructive simulation step, it has the option
to begin interacting with other systems in a distributed interactive
environment. This can be a powerful tool for the IPPD team because it enables
them to receive feedback on their system well before the design is locked in.
Virtual systems can participate in exercises and experiments to determine
their effect on the battlefield, and those results and warfighter feedback are
captured early enough in the program to help the design team conduct more
informed tradeoff analyses. In effect, the warfighter becomes an integral part
of the design team.