NMP EO1 PROBABILISTIC RISK ASSESSMENT Section 1 Background

NMP /EO-1 PROBABILISTIC RISK ASSESSMENT Section 1 Background 06 -13 -00 . . . Bryant Cramer EO-1 Mission Implementation Manager 1 -

NMP /EO-1 PROBABILISTIC RISK ASSESSMENT Residual Risk u Residual Risk is that risk remaining at launch after all mitigation efforts have been completed u The Red Team is charged to “ascertain and document all residual risks, judged to be any level higher than low, that are remaining in the mission” u NASA Administrator has asked that 3 system engineering tools be used to estimate the likelihood of occurrence and the overall mission risk associated with the predominant failure modes as identified by: u 06 -13 -00 – Failure Modes and Effects Analyses – Fault Tree Analysis – Probabilistic Risk Analysis Red Team Charter focuses on single-point failure mechanisms as a major source of residual risk 1 -2

NMP /EO-1 Three System Engineering Tools PROBABILISTIC RISK ASSESSMENT u – Failure Modes and Effects Analyses (FMEA) – Failure Tree Analysis (FTA) – Probabilistic Risk Analysis (PRA) u These are normally used during design definition to support the system engineering process u These tools were not used to develop the EO-1 design: u 06 -13 -00 NASA Administrator has asked that we evaluate residual risk through the use of: – Single string design by policy – Hard cost cap and lots of schedule pressure – Redundancy was largely out-of-bounds -- by policy, by budget, by schedule, and by available staff – We utilized selective redundancy within the existing constraints as best we could We propose to use these 3 tools in a complementary abbreviated application to evaluate the likelihood of successfully completing the EO-1 Minimal Mission 1 -3

NMP /EO-1 PROBABILISTIC RISK ASSESSMENT EO-1 Minimal Mission 06 -13 -00 u Described in EO-1 Mission Success Criteria: u Our evaluation will focus only on the EO-1 Minimal Mission 1 -4

NMP /EO-1 PROBABILISTIC RISK ASSESSMENT EO-1 Residual Risk Assessment u – – – Fault Tree Analysis of Minimal Mission Flight Segment Ground Segment Probabilistic Classification of Single-Point Failures by Similarity F M E A Single-Point Failures of Minimal Mission within each Mission Element u Reliability Block Diagram for Minimal Mission u Residual Risk Assessment of EO-1 Minimal Mission 06 -13 -00 Strategies for Mitigating More Probable Single-Point Failures Fault-Tree Analysis: Failure of the Minimal Mission Includes all mission segments Product is mission element failures that disable the Minimal Mission FMEA: – Down to box, board or service level, as appropriate – Used to survey single-point failures – Product is all single-point board failures disabling the Minimal Mission Probability Risk Assessment: – – – Classified by similarity Reliability Block Diagram Product is probability of singlepoint failures that disable Minimal Mission 1 -5

NMP /EO-1 PROBABILISTIC RISK ASSESSMENT Failure Mode and Effects Analysis u 06 -13 -00 Independently developed for the following segments: – Flight – Ground System – Mission-Unique Launch Equipment u Developed in parallel with the FTA u All FMEAs are completed u By combining the FTA with the FMEAs, we can identify all of the potential single-point failures in each Mission Element that lead to the loss of the EO-1 Minimal Mission 1 -6

NMP /EO-1 PROBABILISTIC RISK ASSESSMENT Fault Tree Analysis u Developed for the EO-1 Minimal Mission – Advanced Land Imager (ALI) – Multispectral Imaging Technology – Wide Field Reflective Optics – Silicon Carbide Optics u 06 -13 -00 – Wideband Advanced Recorder / Processor (WARP) – Spacecraft performance adequate to flight validate the ALI To include the following segments: – Flight – Ground System – Launch (mission unique) u Proceeds to subsystem level or to board level in some cases u Serves to identify the loss of functionality that singularly and independently results in the loss of the EO-1 Minimal Mission u Serves to validate the FMEAs 1 -7

NMP /EO-1 PROBABILISTIC RISK ASSESSMENT Probabilistic Risk Assessment u 06 -13 -00 A reliability estimate will be prepared for the single-point failures causing the loss of the EO-1 Minimal Mission – These estimates normally involve lengthy calculations based on failure rates of individual parts – Time does not allow us to pursue this traditional approach – Our estimates will be done at the box or board level based on similarity with earlier projects where detailed reliability calculations already exist u These will be integrated into a Reliability Block Diagram identifying the predominant modes of failure for the EO-1 Minimal Mission u Prioritized flight validation requirements will be organized against the calculated probability of completing the EO-1 Minimal Mission u This strategy will better mitigate the likelihood of the predominant failure modes 1 -8

NMP /EO-1 PROBABILISTIC RISK ASSESSMENT Probability Reliability vs. Mission Success Criteria Minimal Mission Completely Successful Mission Minimal Mission 0 1 2 3 4 5 6 7 8 9 10 11 12 Months After Launch 06 -13 -00 1 -9