1 ME Fall 2014 Introduction to Systems Engineering Session 4 Dr. Dan C. Surber, ESEP © Copyright 2013

2 Lecture Topics Continue looking into CONCEPT of ISS Mission System Support System

System Context for ISS System Of Interest (SOI) International Space Station Natural Environment Induced Environment Man-made Environment Threat Environment Other Systems Micro meteorites Space Debris A-Sat Weapon comet tail debris other LEO satellites ammonia coolant leaks lost tools and parts leaking fuel from robot resupply internal comms between ISS & EVA RF energy from Shuttle radar laser landing/alignment signals UHF comms from ISS comms experiments in autonomous operations (electromagnetic fields) vacuum of space solar winds & flares hot & cold extremes g-forces (Sun & Moon) robotic resupply vehicles NASA ground control TDRSS comm satellites

Mission Event Timelines Understand the mission events performed by the Mission System –Operational suitability –Operational effectiveness Understand how the Support System prepares the Mission System for its next mission cycle Orbit the station core Orbit & attach truss with solar panels Orbit air lock module Add on-orbit spares Add science modules & air locks Add remaining truss & solar panels On-orbit assembly of the ISS MS = on-orbit modules SS = space shuttle, robot resupply, ground control

Types of System Requirements PERFORMANCE – station shall remain on orbit for at least 20 years. INTERFACE – station shall interface with US Space shuttle and Russian resupply vessels. ENVIRONMENT – station shall survive micro meteorite impacts without loss of pressurization or power for the life of its time on orbit. DESIGN CONSTRAINT – station shall accommodate 99 percentile males and 1 st percentil females. TECHNICAL PERFORMANCE MEASURES ACQUISITION & TECHNICAL –KEY PERFORMANCE PARAMETERS (KPP) MEASURES OF EFFECTIVENESS (MOE) – station batteries can handle full discharge and up to 1,000 recharges within a 5 year period before replacement. –MEASURES OF PERFORMANCE (MOP) – full discharge in coldest conditions followed by full recharge in nominal time of 1 hour per battery followed by full discharge within 1 hour and repeat 1,000 times with 1% of each lot of batteries manufactured for ISS. »DATA ELEMENTS – voltage value at full and discharged; temperature during discharge (min/max); temperature during recharge (min/max); amps during discharge and recharge. –THRESHOLD CRITERIA – 1 hour for recharge at nominal amperage inflow. –OBJECTIVE CRITERIA – 30 minutes for recharge at max rate amps inflow.

PBS Breakdown System of Interest ISS SoS Support System ISS Supt Sys Mission System ISS US Space Shuttle NASA Msn Control Unity ModuleZarya Module 12 other Modules Subsystems Astronaut Tng Facility

Roles of the System Elements System of Interest (SOI) –Performs the mission-oriented operations and tasks that accomplish the performance based objectives of the customer in a way that is operationally suitable and operationally effective. Mission System (MS) –Performed by system element that delivers products and services that achieve performance-based outcome objectives. Support System (SS) –Performed by system element to ensure that the mission system is operationally ready to conduct and support another mission cycle.

SoS, SOI, MS, & SS SoS - Systems that interact with each, but were not all intentionally designed to work together, may exhibit unexpected behaviors upon interaction. Interoperability – the capacity for two or more systems to exchange inputs & outputs across an interface without adversely affecting operational effectiveness and suitability System of Interest (SOI) Mission System (MS) Support System (SS) Mission System performs the functions that yield results that are operationally suitable and effective for the User’s Need. Support System performs the functions that enable the Mission System to complete its operations and execute the mission life cycles defined by the User’s Need.

Wasson’s Purpose Examine interactions between MS & SS Examine interactions between the System Elements WITHIN either the MS or the SS Extract Mission Event Timeline understanding and Mission Scenario understanding based upon how SS supports replenishment/reconfiguration of MS for its VARIOUS Mission Scenarios

SOI & System Architecture Support System (SS) Mission System (MS) Personnel Equipment Msn Resources Procedural Data Facilities Sys Responses Mission Resources Element Procedural Data Element Personnel Element Equipment Element System Responses Element Operating Environment SYSTEM OF INTEREST (SOI) Operating Environment

System Context for ISS Natural Environment Induced Environment Man-made Environment Threat Environment Other Systems Micro meteorites Space Debris A-Sat Weapon ammonia coolant leaks lost tools and parts leaking fuel from robot resupply RF energy from Shuttle radar laser landing/alignment signals UHF comms from ISS comms vacuum of space solar winds & flares hot & cold extremes robotic resupply vehicles NASA TDRSS comm satellites MS SS System Of Interest (SOI) International Space Station Astronauts & ISS Crew Members

ISS Breakdown MS –On-orbit modules, nodes, ports & air locks –Truss structures & solar panels –Orbit keeping engines, controls, ECS & Comms SS –Ground control stations –Shuttles, robotic resupply vehicles –Multi-purpose logistics modules –Training facilities at Houston

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 Baseline Functional Baseline Allocated Baseline

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

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, A o, 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 System Spec Subsystem Spec Product Spec Component Spec SYS module SuS-1 module SuS-2 module SuS-3 module SuS-4 module Prod-1 module Prod-2 module Prod-3 module Comp-2 module Comp-2 module Comp-1 module

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

System Architecture HardwareSoftwareDataFacilitiesTools & STETrainingPeople Tech Data ISS Destiny & Station Thrusters Attitude Control Position Data (x,y,z) ISS Main Control Station FCC Test Equip Attitude Control Manual Mode FCC Trouble Shooting Fault Trees Station Cmdr Subsystem level 6 Modules Attitude Control CSCIs Position, Voice, Telemetry, Fault Mon Health & Status ISS Main Control Station FCC Test Equip Attitude Control Manual Mode FCC Trouble Shooting Fault Trees Station Comdr Nodes Docking Ports Air Locks Environmt Control CSCI Station Health & Status CSCI TRUSS (P&S) HardwareSoftwareDataFacilitiesTools & STETrainingPeople Tech Data 6 Crew Members

Our “Flow” for this Course System Context Diagram 4 Types of Requirements Functional Analysis –Functional Block Diagram (FBD) –Functional Flow Block Diagram (FFBD) Architecture Block Diagram –System level first, then –Lower levels (Subsystem, Product) Schematic Block Diagram –INTRAFACES & responsibility for INTERFACES

ISS REQUIREMENTS 1.The station shall survive (minimal loss of internal pressure, < 2 psi) at least 20 micrometeorite impacts per 24 hr period on orbit after achieving FOC. 2.The station shall operate continuously for 20 years after at least 5 main modules are installed. 3.The station shall provide essential power through solar radiation collection to supply at least 100K Watts per standard earth day. 4.The station shall maintain on orbit position using self-contained propulsion for attitude and altitude control. 5.The station shall maintain a positive pressure, breathable atmosphere of at least 14 PSI. 6.The station shall provide at least 50% of normal power through self-contained, renewable, emergency power. 7.The emergency power shall automatically engage in the event the essential power drops below minimum operational levels. 8.The emergency power shall reports is status continuously to station monitoring and control. 9.The station shall provide essential structural framework and common interfaces for physical connectivity of extensible, modular station elements. 10.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 2.0 Provide pressurized breathable atmosphere 4.2 Maintain orbital attitude 3.0 Provide structural framework for extensible station 4.1 Maintain orbital altitude 5.2 Provide common interfaces 1.0 Protect against micro meteorites 5.1 Provide essential power 2.2 Scrub CO2 2.1 Store & mix breathable gasses 2.3 Recycle atmosphere 4.3 Store & distribute propellant 5.3 Provide emergency power 4.0 Maintain orbital position 5.0 Provide station power

Functional Flow 5.3 Provide Emergency Power Store Emergency Power Monitor Essential Power Level Detect Loss of Essential Power Connect Emergency Power Detect Return of Essential Power Disconnect Emergency Power Provide Status of Emergency Power Level AND

ISS Interfaces Physical –Main structural connectivity –Docking hardware & Ports –Air locks Fire monitoring, detecting, alarm (audio & visual) Fire suppression Electrical –Essential power –Emergency power –Data paths for monitoring & control of docking Alignment targets Cues and range measurement Communications (digital) for docking signals Logical –Control flow –Data flow –Data storage

ISS Schematic Block Diagram LAB Module Nodes 1,2,3 Fuel & attitude propulsion PIRs Docking port DestinyZarya & Zveda Core Modules Port Sections Stbd Sections Main Trusses Truss Segments Grnd Control Shuttle Progress & ATV ISS – SOI (on orbit elements) Solar Radiation & Flares Micrometeorites Give EVERY Interface line an ID

ISS REQUIREMENTS - ALLOCATED Reqmt IDReqmt TextFunction IDVERLevel of VERRATIONALE ISS0001The station shall survive (no loss of internal pressure) at least 20 micrometeorite impacts per 24 hr period on orbit after achieving FOC. 1.0 ASystem – at least 4 modules + Trusses 20 hits on single module too extreme ISS0002The station shall operate continuously for 20 years after at least 5 main modules are installed. ASoS with all modules & trusses Full system connectivity needed ISS0003The station shall provide essential power through solar radiation collection to supply at least 100K Watts per standard earth day. 5.1TAnalysis & TPM, test on orbit All trusses installed with full panels ISS0004The station shall maintain on orbit position using self-contained propulsion for attitude and altitude control. 4.0DAnalysis & TPM, prove on orbit Decompose for accuracy of pos ISS0005The station shall maintain a positive pressure, breathable atmosphere of at least 14 PSI. 2.0TModule level, then on orbit full test Each module must satisfy – also ISS ISS0006The station shall provide at least 50% of normal power through self-contained, renewable, emergency power. 5.3 Provide Emergency Power TSubsys - Analysis, power budget TPM Demo a full cross over with all trusses ISS0007The emergency power shall automatically engage in the event the essential power drops below minimum operational levels Connect Emergency Power DSubsystemDemo in lab & full ISS mockup ISS0008The emergency power shall reports is status continuously to station monitoring and control Provide Status of Emergency Power Level DSubsystemDemo in lab & full ISS mockup ISS0009The station shall provide essential structural framework and common interfaces for physical connectivity of extensible, modular station elements. 3.0AModule Interface ICD Common hardware interface spec ISS0010The station shall maintain a continuous fire detecting and alarm (audio and visual) capability on both essential and emergency power. TSubsystemDemo in lab & full ISS mockup

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