10/9/2008
Learning Objectives
Total design solution balancing cost, schedule,
reliability and risk
Successful problem solvers should be able to clearly define a problem, simplify the complexity of requirements, quantify the options and optimally select a solution
An idea not clearly conveyed is likely to go unused, however great its potential may be
Most real world problems do not have unique solutions
Time management, group coordination and communication skills are critical
Rely on literature for historical info
Always cite your references
Establish a methodology for systematically conducting trade studies and cross check for consistency and independent verification to ensure professional quality
Primary customer base for aerospace is NASA, DoD, DARPA or Commercial (aviation / space) - general design process is the same, specific terminology often differs
Terminology,
Definitions and Acronyms
AO / RFP Announcement of Opportunity / Request for Proposal - Announces programmatic need, typically large effort, high cost, contract
DRM Design Reference Mission - Ensure hardware and operational compatibility
NOI Notice of Intent ~RSVP
Proposal - Your response to an RFP
SOW Statement of Work - What will be done
WBS/CM Work Breakdown Structure / Critical Milestones
Who does what and when it will be done
Schedule laid out to meet project milestones
Personnel, org chart, name of org,
ACD Architectural Control Document - System specs
IDD Interface Definition Document - General resources and interfaces
IRD / ICD Interface Requirements / Control Document - Ensure system compatibility of specific integration
CoDR/PDR/DDR/CDR Conceptual / Preliminary / Detailed / Critical Design Review
- Increasing levels of maturity (basic concept, design, compatible reqs, ΰ sys compat)
DDT&E Design, Development, Test and Evaluation - Hardware development and validation process
Requirement Types
~Qualitative
Customer mission profile, operational life cycle, etc.
Functional what does it have to do
~Quantitative
Performance how well does it have to be done
Design build to specs
Derived implied or transformed from higher level
Allocated division of higher levels (100 lb max for sys = 30 lb for subsys 1, 70 for subsys 2)
Functional what (basic I/Os) mass and energy
throughputs
Process time factors, drives buffer sizes
Operational how (P, M, V, crew time, MTBF, FMEA/CIL,
efficiency, lifecycle, etc.)
Constraints limits (cost, schedule, technology)
First iteration of requirements comes from objectives and insight
Negotiations between customer and designers start here
NASA Style
Requirement Hierarchy - Level 0, 1, 2, 3, and 4
Level 0 Intellectual guess, political mandate, philosophical basis overall goals, funding
Land a man safely on the moon before the end of the decade
Establish Moon base as an integral part of the
Develop cost effective, reliable space transportation to and from Mars
Stimulate the economy through commercial uses of space
Foster international cooperation in space exploration
Maintain
Level 1 Derived response, specific objective restate with constraints, caveats, assumptions, budget breakdown, management, schedule
Level 2 Detailed design requirements functional/conceptual requirements, resources
Level 3 Hardware design specs and development requirements process (DDT&E)
Level 4 Operational requirements ops
Document the pedigree from top-level requirements through final hardware design
Higher level requirements take precedence in event of a discrepancy
General Flow
Analyze Requirements and Ground Rules
Identify Constraints as related to TRL, human, mission specific, schedule, safety, test, cost, etc.
State Assumptions
Identify Candidate Solutions
Identify Trade Matrix Variables
Determine Weighting Factors
Conduct Trade Study
Define Optimal System
Requirement Analysis
Refine customer stated objectives
Define initial performance objectives
Identify and define solution limiting constraints and necessary assumptions
Define functional and performance requirements
In general, analysis should produce a clear understanding of:
Functions what the system has to do
Performance how well functions have to be performed (reliability, criticality)
Operational Interfaces with environment in which system will perform and subsystem integration
Design Phases
Phase A conceptual study and preliminary analyses
Phase B preliminary definition and design used to trade 2 or more alternatives (PDR)
Phase C/D CDR is transition from design (final plans) to development (cutting metal)
Phase E operations (ongoing for lifetime of program)
Learning Objectives
Land humans on the moon and return them safely
Broad Top Level Objectives politics and engineering
Explore lunar surface
Return regolith samples
Take photos
Set up experiments
Mission Requirements transition from politics to engineering
Derived from broad objectives
Functional and operational requirements
Constraints
Land with humans on board
Stay within budget
Complete by end of the decade
Mission Concept engineering management
What are the physical and functional elements the big picture
Launch from KSC
Launch, LEO to lunar orbit, land, return and reentry
Deploy LEM
EVA during transit and on lunar surface
Launch and Mission Control teams
3 crew to lunar orbit, 2 to lunar surface
Architecture systems engineering
How crew, orbits, elements (launch, transit/orbit, surface), mission ops (flight, ground, automated) all fit together
Human needs life, health, comfort
IVA and EVA
Trajectories launch, LEO, LLO transfer, LLO circularlize, landing, rendezvous, return, reentry, land
Saturn IV, SM, CM, LEM
Data transfer telemetry, audio, video
Control responsibilities flight, ground, automated
Elements
Identify functional requirements for each element
What does each element need to do?
Systems
Translates functional requirements into engineering specs
How will each element meet the required functions?
Subsystems design engineering
Solutions that meet the engineering requirements
Integration tasks
How do the subsystems interact?
Technologies vendors, COTS
Components that enable engineering requirements
What are the actual devices and their performance specs?