# Presentation: 522007

## Section 1

_***Section 1***_
***Background***

*** ******. . . Bryant Cramer***
*EO-1 Mission Implementation Manager*

## Residual Risk

***Residual Risk***

***Residual Risk is that risk remaining at launch after all mitigation efforts have been completed***
***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”***
***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:***
***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***

## Three System Engineering Tools

***Three System Engineering Tools***

***NASA Administrator has asked that we evaluate residual risk through the use of:***
***Failure Modes and Effects Analyses (FMEA)***
***Failure Tree Analysis (FTA)***
***Probabilistic Risk Analysis (PRA)***
***These are normally used during design definition to support the system engineering process***
***These tools were not used to develop the EO-1 design:***
***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***

## EO-1 Minimal Mission

***EO-1 Minimal Mission***

***Described in EO-1 Mission Success Criteria:***
***Our evaluation will focus only on the EO-1 Minimal Mission***

## EO-1 Residual Risk Assessment

***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 single-point failures that disable Minimal Mission*

***Strategies for Mitigating More Probable***
***Single-Point Failures***

***Fault Tree Analysis of Minimal Mission***

***Single-Point Failures of Minimal Mission within each Mission Element***

***Probabilistic Classification of Single-Point Failures by Similarity***

***Reliability***
***Block Diagram for Minimal Mission***

***Residual Risk Assessment of EO-1 Minimal Mission***

## Failure Mode and Effects Analysis

***Failure Mode and Effects Analysis***

***Independently developed for the following segments:***
***Flight***
***Ground System***
***Mission-Unique Launch Equipment***
***Developed in parallel with the FTA***
***All FMEAs are completed***
***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***

## Fault Tree Analysis

***Fault Tree Analysis***

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

## Probabilistic Risk Assessment

***Probabilistic Risk Assessment***

***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***
***These will be integrated into a Reliability Block Diagram identifying the predominant modes of failure for the EO-1 Minimal Mission ***
***Prioritized flight validation requirements will be organized against the calculated probability of completing the EO-1 Minimal Mission***
***This strategy will better mitigate the likelihood of the predominant failure modes***

## Reliability vs. Mission Success Criteria