AEROSPACE REPORT NUMBER: ATR-2009(9369)-1, CRITICAL CLEARANCES IN SPACE VEHICLES (31 OCT 2008)

AEROSPACE REPORT NUMBER: ATR-2009(9369)-1, CRITICAL CLEARANCES IN SPACE VEHICLES (31 OCT 2008)., Insufficient attention to critical clearances in space and launch vehicle systems has led to repeated instances of degraded performance and failures. Critical clearance related problems have also occurred in ground tests, causing cost impacts and schedule delays. As a result, a team of subject matter experts from several National Security Space companies was formed to develop a framework for improving the critical clearance process across the industry. A review by the team of ground and flight incidents involving deployments revealed that one of the most prevalent root causes of deployment incidents was insufficient critical clearances. The team concluded that improvements should be made to Critical Clearance (CC) related processes to significantly improve ground testing and mission success rates. A basic top-level plan and a detailed process map to support that plan have been developed and are explained in this paper. The Critical Clearance process applies to clearances at an assembly level above the MMA (Moving Mechanical Assembly) or unit level of assembly and not internal to the MMA or unit level. It is believed that strict adherence to the proposed critical clearance plan and process can greatly reduce the frequency of failures due to Critical Clearance losses. This paper was presented to the Space Quality Improvement Council (SQIC) / government / aerospace industry in June, 2008, to potentially aid in further development of current standards such as AIAA S-114-2005 (Moving Mechanical Assemblies), AIAA S-110-2005 (Structures), and guides for Critical Clearances.