It is imperative that ESS resources, training requirements, and detailed plans (including levels of assembly and defined profiles) are in place when production begins. Therefore, it is desirable to reach this state during engineering & manufacturing development, so that hardware for qualification and reliability growth testing is of higher quality and can be screened (to prevent failures that are not design related). This implies that experimentation and planning should begin early.
The cost of rework in manufacturing escalates by orders of magnitude as the assembly process proceeds from piece part level to printed wiring assembly/ module, unit, system, and to the user. Finding defects at the lowest possible level of assembly will tend to minimize rework costs by reducing corrective action time. However, some flaw types manifest themselves only at the higher levels of assembly. Tailoring the screen by means of the vibration and thermal characteristics of the hardware coupled with defect population at each level of assembly is essential.
This document presents many management and technical
details to be considered and some of the trade-off decisions that will vary
with specific programs. The guidance presented may be limited in some areas
but there is no intent to make this a textbook on the many facets of ESS.
Because of the obvious cost, schedule and performance impacts relative to the
ESS decisions, both government and contractor program managers must not treat
their decisions lightly. Where the required ESS expertise is not available or
will not be in time to address these issues, ESS consultants may need to be
considered. Each service has at least one organization which specializes in
ESS engineering and the Institute of Environmental Sciences has published many
appropriate articles in addition to those listed in Appendix B