8. Lesson: Use a Phase Approach to Development
A phased approach to hardware development (i.e., Preliminary Requirements Review, systems Requirements Review, Preliminary Design Review, Critical Design Review, Customer Acceptance Review, Design Certification Review, and Flight Readiness Review) is a good disciplined approach to hardware development and should always be followed. The requirements reviews formalize the task to be done by the subsystem, prior to design. The preliminary design review carefully determines that the requirements can be met and allows the design to be "base lined." The critical design review permits a detailed examination of the design and should only be conducted when virtually all drawings have been released. This permits the design to be placed under configuration control. The CAR formally reviews the test results to ensure the design meets the requirements and should immediately precede shipment. Finally, the FRR ensures that all open items (i.e., test failures, anomalies, reviews, etc.) have been closed prior to flight. Normally, the FRR is conducted just prior to the final full-scale test just preceding launch, the Countdown Demonstration Test, or the CDDT.
The documentation and support needed to conduct such reviews should be delineated at the outset of the program (i.e., a reliability plan should be available at PRR, a hard mockup at CDR), and the paperwork should be distributed to the review team at least 2 weeks prior to the review. Discrepancies, questions, or changes hsould be submitted in writing and should be closed out n writing. The Review Item Discrepancy (RID) system worked well.
In the interest of maintaining schedule, the documentation describing some experiments was not complete at the time of some reviews. This generally resulted in unsatisfactory reviews and occasioned subsequent reviews, or "delta reviews." In general, incomplete preparation for the reviews should be avoided except when there are clear gains to the program.
The use of RID's permits the discrepancies to be identified, codified, tracked, and closed out. Thus, at each subsequent review it is possible to see how previous criticisms were dispositioned.
These lessons learned are from SKYLAB LESSONS LEARNED AS APPLICABLE TO A LARGE SPACE STATION, A dissertation submitted to the faculty of The School of Engineering and Architecture Of the Catholic University of America For the Degree Doctor of Engineering by William C. Schneider, Washington, D.C., 1976.
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