1. Session 9 Dr. Dan C. Surber, ESEP
ME Fall Introduction to Systems Engineering
Session 9
Dr. Dan C. Surber, ESEP
© Copyright 2013

2. Lecture Topics Functional Analysis Interface Analysis
Requirements Allocation
Traceability
Commercial Tools

3. ISS REQUIREMENTS
The station shall survive (no loss of internal pressure) at least 20 micrometeorite impacts per 24 hr period on orbit after achieving FOC.
The station shall operate continuously for 20 years after at least 5 main modules are installed.
The station shall provide essential power through solar radiation collection to supply at least 100K Watts per standard earth day.
The station shall maintain on orbit position using self-contained propulsion for attitude and altitude control.
The station shall maintain a positive pressure, breathable atmosphere of at least 14 PSI.
The station shall provide at least 50% of normal power through self-contained, renewable, emergency power.
The emergency power shall automatically engage in the event the essential power drops below minimum operational levels.
The emergency power shall reports is status continuously to station monitoring and control.
The station shall provide essential structural framework and common interfaces for physical connectivity of extensible, modular station elements.
The station shall maintain a continuous fire detecting and alarm (audio and visual) capability on both essential and emergency power.

4. ISS Functions Support on-orbit human habitat
1.0 Protect against micro meteorites
2.0 Provide pressurized breathable atmosphere
3.0 Provide structural framework for extensible station
4.0 Maintain orbital position
5.0 Provide station power
2.1 Store & mix breathable gasses
4.1 Maintain orbital altitude
5.1 Provide essential power
4.2 Maintain orbital attitude
5.2 Provide common interfaces
2.2 Scrub CO2
4.3 Store & distribute propellant
2.3 Recycle atmosphere
5.3 Provide emergency power

5. Functional Flow 5.3 Provide Emergency Power 5.3.1
Store Emergency Power
5.3.3
5.3.4
5.3.5
Detect Loss of Essential Power
Connect Emergency Power
Detect Return of Essential Power
AND
AND
5.3.2
Monitor Essential Power Level
5.3.7
5.3.6
Provide Status of Emergency Power Level
Disconnect Emergency Power

6. ISS Interfaces Physical
Main structural connectivity
Docking & Ports
Air locks
Fire monitoring, detecting, alarm (audio & visual)
Fire suppression
Electrical
Essential power
Emergency power
Data paths for monitoring & control
Logical
Control flow
Data flow
Data storage

7. ISS Schematic Block Diagram
Give EVERY Interface line an ID
Grnd Control
Solar Radiation & Flares
I-009
I-010
LAB
Module
Nodes 1,2,3
Fuel & attitude
propulsion
PIRs
Docking
port
Destiny
Zarya & Zveda
Core Modules
Truss Segments
I-004
I-005
Main Trusses
Micrometeorites
I-006
Port
Sections
1 - 6
I-008
I-007
Stbd
Sections
1 - 6
I-003
ISS – SOI (on orbit elements)
I-001
I-002
Progress
& ATV
Shuttle

8. ISS REQUIREMENTS - ALLOCATED
Reqmt ID
Reqmt Text
Function ID
VER
Level of VER
RATIONALE
ISS0001
The station shall survive (no loss of internal pressure) at least 20 micrometeorite impacts per 24 hr period on orbit after achieving FOC.
1.0 A
System – at least 4 modules + Trusses
20 hits on single module too extreme
ISS0002
The station shall operate continuously for 20 years after at least 5 main modules are installed.
SoS with all modules & trusses
Full system connectivity needed
ISS0003
The station shall provide essential power through solar radiation collection to supply at least 100K Watts per standard earth day.
5.1 T
Analysis & TPM, test on orbit
All trusses installed with full panels
ISS0004
The station shall maintain on orbit position using self-contained propulsion for attitude and altitude control.
4.0 D
Analysis & TPM, prove on orbit
Decompose for accuracy of pos
ISS0005
The station shall maintain a positive pressure, breathable atmosphere of at least 14 PSI.
2.0
Module level, then on orbit full test
Each module must satisfy – also ISS
ISS0006
The station shall provide at least 50% of normal power through self-contained, renewable, emergency power.
5.3 Provide Emergency Power
Subsys - Analysis, power budget TPM
Demo a full cross over with all trusses
ISS0007
The emergency power shall automatically engage in the event the essential power drops below minimum operational levels.
5.3.4 Connect Emergency Power
Subsystem
Demo in lab & full ISS mockup
ISS0008
The emergency power shall reports is status continuously to station monitoring and control.
5.3.7 Provide Status of Emergency Power Level
ISS0009
The station shall provide essential structural framework and common interfaces for physical connectivity of extensible, modular station elements.
3.0
Module Interface ICD
Common hardware interface spec
ISS0010
The station shall maintain a continuous fire detecting and alarm (audio and visual) capability on both essential and emergency power.

9. ISS RQMTS TRACEABILITY
Requirements
Analysis
Development
Allocation To
Functions
Reqmt-Functn
Architecture
Functional
Flow
Mission
Event
Timelines
Phases
Repeat @
Lower
Interface
Decomposition
MAP from ISS requirements down to SUBSYSTEM, CONFIG ITEM, Assembly, & Component levels.

10. BACKUP SLIDES

11. Functional Analysis Requirements Analysis Functional Analysis Mission
Interface
Analysis
Requirements
Development
Functional
Flow
Analysis
Mission
Event
Timelines
Interface
Decomposition
Requirements
Allocation To
Functions
Mission
Phases
Interface
Allocation
Reqmt-Functn
Allocation To
Architecture
Repeat @
Lower
Architecture

12. Requirements to Design
Analysis
Development
Allocation To
Functions
Reqmt-Functn
Architecture
Functional
Flow
Mission
Event
Timelines
Phases
Repeat @
Lower
Interface
Decomposition

13. Functional Flow Text Book: Chapter 3 Section 3.7 Appendix A
Recommended order of actions
Functional Block Diagram – FIRST
Decompose each function down 2-3 levels
Flows may begin to show but wait to do them
Functional Flow Block Diagram – SECOND
Use the FBD, Mission Analysis, & Interface Analysis
INPUT – PROCESS - OUTPUT

14. Interface Analysis Context diagram N2 matrix Data flow diagram
Figure 3.12
Figures A.2, A.3 and A.4
Schematic block diagram
Architecture Block Diagram

15. CONTEXT DIAGRAM Environ. System A System of Interest Support Mission
SOI
Users
System B

16. N2 Diagram Example

17. N2 Diagram F1 Measure Voltage F2 Convert Voltage to Degree
F3 Pass Reading to Output
F4 Report Data F1
-> F2 F2
-> F3 F3
-> F4 F4 F3 F4

18. Schematic Block Diagram
ENVIRONMENTS
External #2
External #32
External #1
Component 1 2
Subsystem 1
Subsystem 2
Segment 1
Component 1 2
Subsystem 1
Segment 2
System of Interest

19. Architecture Block Diagram (ABD)
SYSTEM
Hardware
Software
Data
Facilities
Tools &
STE
Training &
Tech Data
What goes underneath each of these boxes – and WHY?

20. Requirements Analysis
RA = understanding the sources of requirements
Market & regulatory constraints
Mission threads for the system
Environments encountered by the system
System specification may list sources
Standards
Specifications
System requirements
Interfaces
Design Constraints
Functional Analysis

21. Requirements Allocation
Weight Allocation
FBD & Mission Event Timelines
Total System
WEIGHT
< 5 K lbs.
FFBD & Mission Profile (1 – n)
Data Flow & Control Flow
Product #1
WEIGHT
< 1.5 K lbs.
Product #2
WEIGHT
< 2 K lbs.
Product #3
WEIGHT
< 1.5 K lbs.
Interface
Analysis
&
Decomposition
Architecture
Decomposition
Reliability Analysis & Allocation
Life Cycle Cost Analysis
Other Specialty
Engineering
Analyses
Design-to-Cost Cost Allocation

22. Requirements Development
Examine System Level Requirements
Gaps & Conflicts
Direct Flow down, derived flow down
Expand functional analysis
Develop budget allocations
Performance
Error
Constraints (weight, cost, Ao, reliability)

23. Requirements Tracing System Level = “Parent” Subsystem Level = “Child”
Product (Configuration Item) = “Grand child”
Component (portion of a CI) = “Great grand child”
Assy, subassy, or part = “Great, great grand child”

24. Requirements Allocation & Traceability
Comp-1
module
System Spec
SuS-1
module
Comp-2
module
Subsystem Spec
Subsystem Spec
SuS-2
module
Comp-2
module
Subsystem Spec
Subsystem Spec
SYS
module
SuS-3
module
Prod-1
module
Product Spec
Product Spec
SuS-4
module
Prod-2
module
Product Spec
Prod-3
module
Component Spec
Component Spec
Component Spec

25. Budgets Performance requirements may need budgets
Direct allocations of physical property may be solely allocated to an entity
Derived requirements stem from analysis & trades needed to satisfy higher levels
Budgets are “rolled up” to their summary level: system, subsystem, product, or CI

26. Commercial Tools DOORS SLATE CORE by VITECH CRADLE by 3SL
TEAMCENTER by UGS/SIEMENS
Integrated Project Lifecycle Management (PLM) suite
UML 2.0 based OOA & OOD tools
SysML extended UML modeling tools
Search “system modeling software”