Session 9 Dr. Dan C. Surber, ESEP ME 59700 Fall 2014 Introduction to Systems Engineering Session 9 Dr. Dan C. Surber, ESEP © Copyright 2013

Lecture Topics Functional Analysis Interface Analysis Requirements Allocation Traceability Commercial Tools

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.

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

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

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

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

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.

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.

BACKUP SLIDES

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

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

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

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

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

N2 Diagram Example

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

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

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

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

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

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)

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”

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

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

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”