1、Public Lessons Learned Entry: 6143 Lesson Info: Lesson Number: 6143 Lesson Date: 2010-10-20 Submitting Organization: MSFC Submitted by: Kristen Kinder Subject: Excessive Program Level Requirements Abstract: Space Shuttle Program Level requirements were defined in a top level system requirements docu
2、ment National Aeronautics and Space Administration (NASA) Space Transportation (STS) NSTS 07700. The document has areas where specific design solutions are dictated at a cost with no benefit. Description of Driving Event: Post Columbia review of project certification lead to a review of the Screw Th
3、read requirements in NSTS 07700 Vol X. Two Full pages and references to five (5) specifications and two (2) standards are dedicated to the subject of screw threads and mechanical fasteners. The level of detail of these requirements increased over the duration of the Space Shuttle Program until top l
4、evel requirements excessively prescribed much lower level design solution requirements. During the time that the top level requirements were undergoing revision, systems engineering practices were gradually and intentionally reduced or eliminated for cost savings considerations. The effect was incre
5、ased burden on vendors to comply with overlyprescribed requirements at too high a level, increasing costs and personnel effort on both management and technical levels. Lesson(s) Learned: Good systems engineering requires an efficient method of requirement flowdown without burdening all levels of man
6、agement. Diligence is necessary to prevent lower level project and design requirements from entering program level documents. Government requirements can be overly prescriptive and the requirements flow-down/push-back processes can often be complicated, and not rigorously managed. Recommendation(s):
7、 Use strong system engineering approaches and techniques with adequate tools to ensure that requirements are maintained at the proper level. New programs should rigorously work to eliminate design solutions (The “How”) out of contractor requirements. When requirements are changed, ambiguity should b
8、e eliminated and any uncertainty should be addressed immediately. In addition, projects and elements need a simple, well defined process for quickly resolving program/project/element requirements push-backs. Standardizing/simplifying the ways that various projects and teams resolve issues reduces re
9、quirements flow-down to contractor, and thus cost. Use the System Requirements Review (SRR) to stabilize critical program requirements with a philosophy for handling program allocated margins to allow for system changes within the SRR definition. Evidence of Recurrence Control Effectiveness: N/A Doc
10、uments Related to Lesson: NSTS 07700, VOLUME X - NASA SPACE SHUTTLE-FLIGHT AND GROUND SYSTEM SPECIFICATION Mission Directorate(s): Human Exploration and Operations Additional Key Phrase(s): Systems Engineering Provided by IHSNot for ResaleNo reproduction or networking permitted without license from
11、IHS-,-,-Project Management Change Management Processes Requirements Flowdown Additional Info: Project: Space Shuttle Approval Info: Approval Date: 2012-03-22 Approval Name: mbell Approval Organization: HQ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
