space engineering 2 © dr. x wu, 2008 1 space engineering 2 lecture 1
TRANSCRIPT
Space Engineering 2 © Dr. X Wu, 20081
Space Engineering 2
Lecture 1
Group Presentations
Week 5: preliminary design review / mission design (5%)
Week 13: critical design review / spacecraft bus subsystem design (5%)
Space Engineering 2 © Dr. X Wu, 20083
Outline
Introduction Systems Engineering Spacecraft Environment Spacecraft Bus Subsystems
Space Engineering 2 © Dr. X Wu, 20144
What is a Space System Ground
Spaceflight Operations Payload Operations Payload Data Processing
Space Orbits Spacecraft
Launch Launch Vehicle Integration Launch Operations
Space Engineering 2 © Dr. X Wu, 20145
Ground
Ground Activities: Spacecraft Flight
Operations Payload Operations Payload Data Processing Payload Data
Dissemination
Facilitated By: Real-Time Processing Payload Dissemination
Infrastructure Powerful Payload
Processing Facilities Mission Simulations
Can BeMerged
Space Engineering 2 © Dr. X Wu, 20146
Launch
Selection: Enough “throw weight” Enough “cube” (volume) Acceptable ride Good record…
Integration: Launch loads imparted
to spacecraft Mechanical/Electrical
Integration
Space Engineering 2 © Dr. X Wu, 20147
Space Mission Architecture
Space Engineering 2 © Dr. X Wu, 20138
Payloads and MissionsMission Trajectory type
Communications Geostationary for low latitudes, Molniya and Tundra for high latitudes (mainly Russian), Constellation of polar LEO satellites for global coverage
Earth Resources Polar LEO for global coverage
Weather Polar LEO, or geostationary
Navigation Inclined MEO for global coverage
Astronomy LEO, HEO, GEO and ‘orbits’ around Lagrange points
Space Environment Various
Military Various, but mainly Polar LEO for global coverage
Space Stations LEO
Technology Demonstration Various
Note: GEO – Geostationary Earth Orbit; HEO – Highly Elliptical Orbit; LEO – Low Earth Orbit; MEO – Medium height Earth Orbit
Space Engineering 2 © Dr. X Wu, 20139
Objectives and Requirements of a Space Mission
Space Engineering 2 © Dr. X Wu, 201310
Space System Development All systems development start with a “mission need” (the
Why) Then mission requirements are developed to meet this need
(the What) often along with a concept of operations Note: Often we make the mistake of putting “the
How” in the Mission Requirement From 1 and 2 above develop derived requirements for (the
How): Space
Mission orbit Payload Types (Communications, remote sensing, data relay) Spacecraft Design
Ground Facilities and locations Computers/Software Personnel/Training
Launch segments Note: The requirements generation process is often iterative
and involves compromises
Space Engineering 2 © Dr. X Wu, 201311
Requirements of a Spacecraft1. The payload must be pointed in the correct
direction2. The payload must be operable3. The data from the payload must be communicated
to the ground4. The desired orbit for the mission must be
maintained5. The payload must be held together, and on to the
platform on which it is mounted6. The payload must operate and be reliable over
some specified period7. All energy resource must be provided to enable the
above functions to be performed
Space Engineering 2 © Dr. X Wu, 201312
Spacecraft Subsystems
Space Segment
Payload Bus
Structure
Mechanisms
Attitude and orbit control
Thermal Propulsion
Power Telemetry and command
Data handling
Space Engineering 2 © Dr. X Wu, 201313
Spacecraft Description
Spacecraft have two main parts: Mission Payload Spacecraft Bus
Mission Payload A subsystem of the spacecraft that performs the actual mission
(communications, remote sensing etc.) All hardware, software, tele- communications of payload data
and/or telemetry and command There can be secondary payloads
Spacecraft Bus Hardware & software designed to support the Mission Payload
Provides Power Temperature control Structural support Guidance, Navigation & Control
May provide for telemetry and command control for the payload as well as the vehicle bus
Space Engineering 2 © Dr. X Wu, 201314
Spacecraft Development Process
Some types: Waterfall (sequential) Spiral (iterative)
Basic Sequence:
1. Conceptual design
2. Detailed design
3. Develop detailed engineering models
4. Start production
5. Field system
6. Maintain until decommissioned DoD mandates integrated, iterative
product development process
RequirementsDevelopment
DetailedDesign
EngineeringDevelopment
&Production
Field(IOC)
Space Engineering 2 © Dr. X Wu, 201315
Serial (waterfall) Development1. Traditional “waterfall” development
process follows logical sequence from requirements analysis to operations.
2. Is generally the only way to develop very large scale systems like weapons, aircraft and spacecraft.
3. Allows full application of systems engineering from component levels through system levels.
4. Suffers from several disadvantages:• Obsolescence of technology (and
sometimes need!)• Lack of customer
involvement/feedback• Difficult to adjust design as program
proceeds
http://www.csse.monash.edu.au/~jonmc/CSE2305/Topics/07.13.SWEng1/html/text.html
Space Engineering 2 © Dr. X Wu, 201316
Spiral Development
From: http://www.maxwideman.com/papers/linearity/spiral.htmAnd Barry Boehm, A Spiral Model of Software Development and Enhancement, IEEE Computer, 1988
Software Development Centric Example
Good features1. In this approach, the entire application is built
working with the user. 2. Any gaps in requirements are identified as work
progresses into more detail. 3. The process is continued until the code is finally
accepted. 4. The spiral does convey very clearly the cyclic
nature of the process and the project life span.
Not so good features1. This approach requires serious discipline on the
part of the users. The user must provide meaningful realistic feedback.
2. The users are often not responsible for the schedule and budget so control can be difficult.
3. The model depicts four cycles. How many is enough to get the product right?
4. It may be cost prohibitive to “tweak” the product forever.
Simply put: Build a little – Test a little!
Can this work for every type of project?
System Development Process
‘Breadboard’ system Concept development and proof of concept
Prototype First draft of complete system Implements all requirements
Engineering model Complete system without final flight configuration Plug and play with flight model
Flight model The final product Space-ready product, implements all requirements
Design Review
Preliminary Design Review (PDR) Architecture and interface specifications Software design Development, integration, verification test plans Breadboard
Critical Design Review (CDR) System Architecture Mechanical Design Elements Electrical Design Elements Software Design Elements Integration Plan Verification and Test Plan Project Management Plan
Spacecraft Integration and Test
Methodical process for test of spacecraft to validate requirements at all levels
Sequence:1. Perform component or unit level tests2. Integrate components/units into subsystems3. Perform subsystem tests4. Integrate subsystems into spacecraft5. Perform spacecraft level test6. Integrate spacecraft into system7. Perform system test when practical