• Your Guide: Dr. Rick Fleeter
• Tour Duration: < 2 weeks
• Starting Point: All tools, nothing to build
• Destination: You design it
• In Your Backpack:
– Elements: G&C, Structures, Orbits (?)…
– Class Presentations and Notes
• Expeditionary Party:
– The Class, Your Texts, The Internet
– Your Group
Water / Bouyancy / Fluid Mechanics
+ Breathing, Conditioning, Stroke Mechanics
=> let’s go for a swim
Four Classes
(1 and 2)
1.
What is design, What is the Design Process
What are you going to design (mission statement)
Some examples of missions and mission statements
Requirements and the design process
homework: form groups, pick mission, describe
2.
Learning from other missions
Guess their mission statement and requirements
Other ways to accomplish same mission
(in space or on ground)
“workshop” and homework: sketch your design
spacecraft / payload / orbit / launch / ground
top level requirements outline
Four Classes
3
. 5 Minute presentation of your design:1 from ea. group
What technologies are mission critical?
What are tech obstacles in space today?
4
. (All members minus 1): present design specifics
• Mission and Specific Requirements
• How to do mission with current tech
• What would change with tech innovation
Transportation: influence on mission, design, cost
Innovating around launch issues
Your missions for Next Class:
Organize into groups / squadre
- minimum 3 people
- maximum 5 people
- seek diversity
Invent / select ~ 2 missions
describe in <250 words
prepare to talk about your favorite:
- 5 minutes or less
- voluntary
What it’s all about
• Ultimately:
Design
a Space Capability
– Mission Statement
– Spacecraft / Payload
– Launch / Orbit
– Operations / User Interface
– Financing
You Are
Here
Design Roadmap
Define
Mission
Concept
Solutions &
Tradeoffs
Conceptual
Design
Requirements
Analysis
Orbit
Propulsion
/ ∆V
Comms
Attitude Determine & ControlLaunch
Ground
Station
Thermal / Structure DeployablesInfo
Processing
Top Level Design
Iterate Subsystems
Suppliers / Budgets
Parts
Specs
Mass
Power
$
∆V
Link
Bits
Materials Fab•
Mission Definition
:
–
Black tie & prime rib for 300 at the Plaza
vs.
– Beer and hot dogs in the park
•
Preliminary Design:
–
Select entré, drinks, desert, type of music
=> 1st credible cost estimate possible
•
Detailed Design:
–
# bottles of Schlitz / Perrier & Jouet, m
2of cake, place markers,
kg of beef, invitations: color, paper...
=> may commit to fixed price
•
ICD (Interface Control Document):
–
Cash bar? Who supplies the flowers? (Flowers? What flowers?).
Chairs? Valet Parking...
•
Management and Standards
–
Waiters in tuxedos, sommelier and served hors d’ouvres vs. buffet
•
Build vs. Buy
–
Can you bake those cookies for less than €7/kg? (and so what!)
–
What won’t get done while you’re busy at home baking?
Power: Supply & Demand
• Supply:
– Sun: 1.34 kW/m
2– Solar panels: η =~ 20%
=> ~250W/m
2– 50% of electricity is heat => At ops. temps,
Radiation=300 W/m
2(courtesy Stephan &
Boltzman)
• Demand
– 1 Transponder: 200W; 1 DBS XPDR:
2000W
– On - Board Housekeeping: 100W
– Iridium / Globalstar class satellite:
500W
Small v. Big approaches to Power
• Big
– Mil Spec Batteries
– Large Deployable, articulated solar
arrays
– Large Volume / Area: => Heat
matters => heaters / heat pipes /
radiators
• Small
– Commercial NiCads
(but relatively larger fraction of total
mass)
– Fixed, Body mounted cells (small V÷A =>
POWER EFFECTS
EVERYTHING
• Array & Battery Size
Volume, Mass, Cost ($10k/W), Risk
• Deployables
Cost & Risk, CG, Attitude control &
perturbations, managing
complexity
• Thermal
Larger dissipation => large fluctuations
=>
heat pipes, louvers, structure upgrade
• High η photovoltaics
High cost, tight attitude control
• Other upgrades
Power regulation & distribution,
Power: Cost Impacts
• Solar Panel Area
• Cost of Deployables
• Pointing requirements
• Cost / mass of batteries
• Tracking array
• Structural support / mount batteries
• Thermal issues:
• G&C disturbance by array
- internal dissipation • More power -> more data ->
- large day / night ∆
- more processor cost
• Heavier spacecraft
- higher radio & memory costs
- more costly launch • Higher launch cost ->
• Consider GaAs vs. Silicon
higher rel. required ->
higher parts count and cost
A weapon: Power Conservation:
- Duty cycle: 75 W Tx @ 20 min per day = 1 W equivalent
- Do all you can to cut power on 100% DC items (e.g. processor),
- Integrate payload / bus ops: 1 µp working 2x as hard is more efficient
- Limit downlink: compression, GS antenna gain, optimal modulation,
coding, use L or S band, spacecraft antenna gain / switch,
selectable downlink data rate, Rx cycling, Tx off and scheduled ops.
- Local DC / DC conversion where / when needed
Mission Cost / Complexity Drivers
Technical - slide #1
Feature
Impact
Electric Power • Array size • High efficiency photovoltaics (more of it and • Deployables • Batteries
at higher duty cycle) • Thermal Effects • RFI and stray fields • Tracking arrays
Thermal • Design / Analysis complexity • How to test?
(special thermal • Reduces overall thermal mass • Heaters, coolers => more power requirements for • Power supply reliability • Transients (deployment, slews, discrete components) • Restricts attitude options lock loss...)
Data Rate • Large memory • Data analysis cost
(fast downlink) • Wider frequency allocation • Large Ground Station antenna • Processor: push speed • More complex GS receiver • Software efficiency • Directional on-board antenna(s)
Processing Power • Electric power, volume, mass • Mature development environment? (using latest, greatest • lack of "space" features (e.g. EDAC • Integrated support circuits?
available µprocessors) multiple copies, current monitor...) • Available development boards? • "Efficient" code (i.e. complex • H'wr, s'wr, documentation bugs expensive, non-readable, test?)
Mission Cost / Complexity Drivers
Technical - slide #2
Feature
Impact
Raw Mass • Bigger test fixtures • No piggyback / shared launch slots ("250 kg of silicon • Difficult to transport • ACS actuator scale up
doesn't add to • Launch cost increase -> tougher standards system wide complexity") (rules, reviews, signoffs, meetings, unwinnable arguments...)
• Difficult safety qual. • 50 kg to Pluto: not a small spacecraft!
Attitude Control & • Sensor upgrades: no home brews • Actuator upgrades: quieter wheels Determination • Different sensor suite • Different actuator suite
(0.25° v. 0.05°) (e.g. HCI no better than 0.1°) (e.g. mag coils = insufficient authority) • Need higher loop bandwidth: rate sensors (gyros)
• Structure rigidity: heavier and more complex modeling
• Thermal effects significant: more complex thermal mgt & modeling • Alignment precision: complex machining, testing, calibration
(plus maintaining alignment in transport, test, launch environments) • ACS Algorithmic complexity - more perturbations count - how to test?
∆V • Complexity: control, integration, launch prep
• Safety: pressure, chemicals, pyros... • Mass distribution restriction • Additional ACS modes • Higher launch mass (see above) • Orbit determination • Cost of propulsion system itself
Mission Cost / Complexity Drivers
Technical - slide #3
Feature
Impact
Reliability / • Redundancy: 2+x mass / volume • Limited selection of hardware Lifetime • Hi Rel parts: older, longer lead, more $, lower performance
(usually results in higher parts count and lower reliability)
• Mil-Spec batteries: 100x cost, only large sizes, redundancy difficult • Analysis cost: FMECA - how to prove reliability - extensive testing
"Special" • Clean spec: overhead of clean facilities, access hassle • Special orbit: custom launch and/or on-board propulsion • Highly integrated design (payload / bus / launch vehicle):
religious wars, pre-integration test fixturing, finger pointing @ integration, full team cooperation throughout mission ops phase
• Low mass: modeling, high cost materials, testing
• low magnetic environment: booms, testing, materials and wiring, rework, retest • Low Outgas: materials restrictions, bake-out
Mission Cost / Complexity Drivers
Management - slide #1
Feature
Conventional
Small / Low Cost
QC / Traceability • Separate QC Team • Responsibility of each engineer
Documentation • Documentation team: imposes • Minimal documentation -
overhead on engineers restricted to docs needed and read by engineers
Heritage • De Facto Mandatory • Used only when cheaper / faster
Reviews • Infrequent, huge, critical, • frequent, small, focused, brief, week(s) long non- critical
Contract • CPFF • Fixed Price - delivery on orbit
Risk • not tolerated (infinite failure cost) • accepted (risk v. $ traded off) (officially)
Standards • externally imposed - infinite price • created / negotiated by engineers price is negotiable
Staffing • by slot • Diverse team - all always busy
Mission Cost / Complexity Drivers
Management - slide #2
Feature
Conventional
Small / Low Cost
Tools • minimum: large # hours @ low $/hr • maximize: thus minimize total $, minimum organizational complexity
Operations • dedicated staff @ dedicated facility • minimal staff, GS on site • "person in the loop" • local ops or via internet • exploit spacecraft autonomy
Intra-team interface • Documentation • engineer - to - engineer
Staff Organization • segregated by technical specialty • integrated project
Hardware Flow • specialty group to specialty group • same team cradle to on-orbit ops
Cost Driver
Cost Saving Tactics
Power Requirement • Duty Cycle • Sun Pointing • offload secondary payloads • Reduce margins
Tight Attitude Control • Tight attitude determination instead
High Speed Downlink • Duty cycle (truncate instrument data flux)
• On-board compression (2:1 is easy, 10:1 possible)
• Do the best you can - it's better than you think: variable data • Choose orbit for better linkrate / tolerate link fallibility
Tight Thermal • Power down during hot seasons Requirements • Use instruments as heaters
General Budget • Let mass grow • Offload some of payload • Don't conformal coat Panics • Let volume grow - no deployables
• Higher inclination orbit - local, not remote, GS • No clean room - use "remove before flight" covers • Startup related program - give people someplace to go • Use flight-spare and leftover components
• Fly protoflight hardware - don't build flight hardware
How to succeed in microspace...
...without really trying
1.
It doesn’t have to be difficult to be good
Your engineering education =
your #1 asset and your #1 liability
2.
Pick easy problems (or simplify hard ones)
Low power / Low data rate
Minimal stabilization / short life time
No propulsion
Small & Aluminum
3.
Solve appropriately
Match tools to job
Documentation
•
Basic Rule: Don’t write what no one will read.
•
Easy documentation:
– Email exchanges
- Photographs of everything
– Manufacturer’s data on purchased parts
- Test & failure logs
– Videos of procedures
- Well documented code
•
Automatic documentation
– Fabrication drawings & schematic diagrams
- Block diagrams
•
Documents worth writing
– ICDs
- System Requirements Documents
– (H&S’wr)
- Launch environment
– Cabling diagram
- Thermal / Structure analysis
reports
– Users’ manual
- Test plans & results
– Contracts, change orders etc.
2.0 System Definition
2.1 Mission Description 2.2 Interface Design
2.2.1 SV-LV Interface
2.2.2 SC-Experiments Interface
2.2.3 Satellite Operations Center (SOC) Interface 3.0 Requirements
3.1 Performance and Mission Requirements 3.2 Design and Construction
3.2.1 Structure and Mechanisms 3.2.2 Mass Properties
3.2.3 Reliability
3.2.4 Environmental Conditions 3.2.4.1 Design Load Factors
3.2.4.2 SV Frequency Requirements 3.2.5 Electromagnetic Compatibility 3.2.6 Contamination Control
3.2.7 Telemetry, Tracking, and Commanding (TT&C) Subsystem
3.2.7.1 Frequency Allocation 3.2.7.2 Commanding
3.2.7.3 Tracking and Ephemeris 3.2.7.4 Telemetry
3.2.7.5 Contact Availability
3.2.7.6 Link Margin and Data Quality 3.2.7.7 Encryption
