# Presentation: 410946

## Introduction to Integrated System Health Engineering and Management in AerospaceDr. Stephen B. JohnsonNASA Marshall Space Flight Centersjohns22@uccs.edu

## Outline of Talk

**Definitions**
**Operational & Design Theory**
**Principles**

## Integrated System Health Engineering & Management

***ISHEM = the processes, techniques, and technologies used to design, analyze, build, verify, and operate a system to prevent faults and/or mitigate their effects***
**Technical, individual, and social aspects**
**Synonym: Dependable System Design and Operations**
**“****Dependability”**

## Complexity

**Beyond the capability of any one person to understand or keep track of all details**
**Heterogeneous (power, propulsion, etc.)**
**Deep: requires many years of study to master**
**Scale:  the system requires so many components that it is impossible for any one person to keep all in mind**
**Interactivity: interactions between internal components, and with the external environment are “messy”**

## Implication of Complexity

**By definition, beyond what any one person can master (our cognitive abilities are limited)**
**REQUIRES communication among individuals**
**Implication:**
**Engineering of a “complex” system requires excellent communication and social skills**

## Failure

**“****A loss of intended function or performance of an unintended function.”**
**Can be designer’s or user’s intent**
**Failure is both individually and socially defined**
**“****in the eye of the beholder”**
**Some “failures” are considered normal by others**

## Faults and Errors

**Fault:  The physical or logical cause of an anomaly.**
**The “root cause”, can be at various levels**
**Might or might not lead to “failure”**
**Anomaly (error): A detectable undesired state.**
**The “detector” must ultimately interpret the “state” as “undesirable”**
**Can be user, designer, others**

## Causes of Faults and Failures

**Individual performance failure (cognitive)**
**Lack of knowledge (unaware of data)**
**Misinterpreted data**
**Simple mistakes (transposition, sign error, poor solder, etc., usually from human inattention)**
**Social performance failure (communicative)**
**Miscommunication (misinterpretation)**
**Failure to communicate: information exists, but never got to the person or people who needed it**

## Embedded Knowledge

**Technologies are nothing more than “embedded knowledge”**
**Technologies embody (incarnate) the knowledge of their creators**
**“****Faults” result from flaws in the knowledge of the creators, OR mismatch in understanding between creators and users**
**Cognitive or Communicative!**

## ISHEM Functional Relationships

**Circular, “closed-loop” relationships**
**Hints at the physical architecture**

## ISHEM Operational Architecture

## Typical Functions, Mechanisms, and Characteristic Times

| Function | Physical Mechanism | Characteristic Time |
| --- | --- | --- |
| Electrical Power | Electron transport | 1-10 milliseconds |
| Attitude Control | Thruster impulse or reaction wheel acceleration | 50-500 milliseconds |
| Spacecraft Thermal Control | Radiative Heat Transfer | Minutes to hours |
| Human autonomic response | Biochemically-induced electrical signals | 500 milliseconds – 1 second |
| Human decision-making | Verbal and visual signals between humans, and brain physiology | Minutes to days |
| Data computation | Electron transport and processor cycle times | 10-100 milliseconds |
| Planetary probe radio data transfer | Electromagnetic waves | Seconds to hours |

## ISHEM in the SystemLife Cycle

## Principle of Knowledge Redundancy, and Limits

**Checking for failure or faults requires a separate, independent, credible knowledge source**
**Commonality means that reviewers share common assumptions with the reviewed **
**Independence means reviewers share nothing in common with the reviewed**
**Complete independence neither possible nor desirable**

## Clean Interfaces

**Desired and sometimes required**
**Reduce the “interactivity” between components**
**Reduce the interactivity of the people and organizations designing and operating the components**
**Simplifies communication, reduces chance for miscommunication!**

## Bureaucracy and “Situational Awareness”

**Bureaucracy needed to institute and repeat processes for dependability**
**Bureaucratization: repetition and suppression or forgetting of reasons behind the rules leads to inattention or misunderstanding, and hence to faults**
**Must foster individual “awareness” within the bureaucracy...   create bureaucracy to fight the deadening effect of bureaucracy! **

## Conclusion

**NASA has a “culture problem” that leads to occasional failures**
**The problem is social and cognitive as well as technical**
**ISHEM to be the overarching theory over the technical, social, and cognitive aspects of preventing & mitigating failure**
**We are working to install / instill ISHEM into the new Vision for Space Exploration**