Transcript No Slide Title

Box score: 6 /
6
• 1 - Introduction
• 2 - Propulsion & ∆V
• 3 - Attitude Control &
instruments
• 4 - Orbits & Orbit
Determination
• 5 - Launch Vehicles
–
–
–
–
–
Cost & scale observations
Piggyback vs. dedicated
Mission $ = 3xLaunch $
The end is near?
AeroAstro SPORT
Enginering 176 #6
• 6 - Power &
Mechanisms (Feb. 27)
– Photovoltaics & Solar
panels
• Maximizing the minimum
– Batteries and chargers
– Deployables:
•
•
•
•
Why moving parts don’t
Common mechanisms
Build v. buy v. modify
Reliability, testing & terrestrial
stuff
• 7 - Radio & Comms (3/6)
• 8 - Thermal / Mechanical
Design. FEA (3/20)
• 9 - Reliability (Mar. 3/13)
• 10 - Digital & Software
• 11 - Project Management
Cost / Schedule
• 12 - Getting Designs Done
• 13 - Design Presentations
Review of Last time
• Attitude Determination & Control
– Feedback Control
• Systems description
• Simple simulation
• Attitude Strategies
– The simple life
– Eight other approaches and variations
• Disturbance and Control forces (note re CD>1)
• Design build & test an Attitude Control System
• Design Activity
Set
point
Control
Algorithm
– Team designations Error
– Mission selections
– Homework - ACS for missionSensor
+ 176
CoDR
Enginering
#6
Actuator
Plant
(satellite)
Disturbances
Design Roadmap
You Are Or maybe
Here
Here
Define
Mission
Concept
Propulsion
/ ∆V
Comms
Solutions &
Tradeoffs
Attitude
Determine
& Control
Launch
Conceptual
Design
Requirements
Ground
Station
Thermal /
Structure
Deployables
Analysis
Info
Processing
Orbit
Top Level Design
Parts
Specs
Materials
Fab
Mass
Suppliers / Budgets
Power
∆V
Link
Bits
Iterate Subsystems
Detailed Design
Enginering 176 #6
$
Final Performance
Specs & Cost
STP-Sat
Requirements
(Some)
System Definition
Requirements & Sys
2.1
Mission Description
Definition go together
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
Highly structured
3.2.7.2
Commanding
outline form is
3.2.7.3
Tracking and Ephemeris
3.2.7.4
Telemetry
clearest and
3.2.7.5
Contact Availability
industry standard
3.2.7.6
Link Margin and Data Quality
3.2.7.7
Encryption
Enginering 176 #6
2.0
NB: this is
an excerpt
of the TOC
- entire
docs are
(or will be)
on the
class FTP
site
For tonight
• Requirements Doc
(mostly done)
– Mission Requirements
– System Definition
– Begin Tech
Requirements
• Launch Strategy
(also mostly done)
• Reading
– Requirements Doc
Sample
– Power:
• SMAD 11.4
• TLOM 14
– Mechanisms:
• SMAD 11.6 (11.6.8 too)
• TLOM
– Primary LV and cost
– The last mile problem
• Thinking
Enginering 176 #6
– What can you build?
– What can you test?
For next Thursday, (March
6)
• Preparation: Radios & • Technical requirements:
Create a list of technical
Comms
requirements - even if it
• SMAD Chapter 13
has “TBD”s in it.
• TLOM Chapters 7,8,9
(+ revisit mission rqts)
• Systems design / CoDR:
create a good looking
“cartoon” set of the
spacecraft, orbit and
ground segments
• Get Physical
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• Tools selection:
– Finite element
– Design and layout
– Presentation & Graphics
• Tech Design / Analysis / Suppliers:
– Structure / Thermal
– Design and layout
– Orbit / Launch
– ACS / Propulsion // $$$
Elements of a CoDR
•
Mission statement
•
– why do this
•
–
–
–
–
top level requirements
– what must you accomplish
•
engineering requirements
– A top level "intercept a target"
– engineering ∆V & G&C
•
•
Orbit
Spacecraft layout
•
Launch & maneuvering
Business Case
– Organizations
(Gvt, Commercial, Military)
•
ID Critical Technologies
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Design sequence / schedule
Prototyping and proof of concept
Staffing & facilities (e.g. test)
Schedule / overlaps / synergies
Suppliers
– Costs, lead times
– Legal, safety, financing
•
-the budget – Parts, labor, testing, launch
– Supplies
– overhead: salaries, offices, labs,
health care, vacation …
– Systems: comms, payload,
propulsion, power, computing
•
•
Program Plan
•
Focus on something
– Critical subsystem
– Outstanding attribute
– Enabling situation - market
opportunity
Power: Supply & Demand
• Supply:
– Sun: 1.34 kW/m2
– Solar panels: h =~ 20% => ~250W/m2
– 50% of electricity is heat => At ops. temps,
Radiation=300 W/m2 (courtesy Stephan & Boltzman)
• Demand
–
–
–
–
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1 Transponder: 200W; 1 DBS XPDR: 2000W
On - Board Housekeeping: 100W
Iridium / Globalstar class satellite: 500W
Micro / nano: 100 W to 1 W
Design Driver: Power
• Increased Demands for Power:
– Higher bandwidth
– Wide coverage area
(10 x BW = 10 x P)
(5 x area = 5 x P)
• Increased supply of Power:
– PV efficiency now 25%
may increase to 30%
– Li-Ion Battery
may transition to sulfur sodium
(2x mass efficiency, or not)
– Digital Charge circuits
(a few % savings)
– Sharper antenna patterns:
– Small GS antenna
(1/10th diameter = 100 x P)
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(a few % savings in power)
– New array deployment
(potential 2x to 100x)
Small v. Big approaches to
Power
• Small
– Commercial NiCads
(but relatively larger fraction of total mass)
– Fixed, Body mounted cells (small V÷A =>
volume, not W, limit) => passive thermal
• Big
– Mil Spec Batteries
– Large Deployable, articulated solar arrays
– Large Volume / Area: => Heat matters =>
heaters / heat pipes / radiators
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Power Affects all Engineering Aspects
• 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 h photovoltaics
High cost, tight attitude control
• Other upgrades
Power regulation & distribution,
charging, demand side devices
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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
- Careful parts selection, dynamic clocks
Enginering 176 #6
Rechargeable Battery Options
Type
Mil?
Com?
Pros
Cons
Lead-Acid
(gel cells)
no
¦
Dense, Cheap
Wide temp range
Heavy
Seal questions
Ni-Cad
¦
¦
Widely available
Well characterized
Low capacity
Mil are large
Ni - H2
¦
rare
Higher E density
5 to 10 x
more cycles
No small sizes
Not yet available
in multi-cell pacs
NiMH
no
¦
Li-Ion
no
¦
Biggest E density No space experience
Fast charge
No space qual
More complex charging
None
¦
¦
Lowest mass
No ops in umbra
sun synch
Lowest cost
Max 65% DC most orbits interplanetary
Highest reliability State saving RAM rqd. Light-side
infinite lifetime
Enginering 176 #6
E - to Ni-H2
Lower volume
Applications
E Density
W-hr / Kg
20
Mass not
a factor
Volume constrained
Most widely
25 - 30
used in space
Higher cost, no M IL
individual ->
multi-cell ->
25 - 40
45 - 60
Consumer
electronics
40 - 60
Consumer
electronics
100 - 150
•
Battery Charging
FAST
PPT Power
SLOW
Tmp
Sns
DISCHARGE
Global Power (5V, +/- 12V)
Aux Bus
Aux Interface
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A/D
Signal
Conditioning
B
a
t
t
e
r
y
Water cooler, napkin back
& group picnic topics
• Does the mission really require batteries? Trade vs. e.g. Flash RAM
• Is Ni-Cad memory real?
• The real cost of deployables (covered in next section)
• Battery testing and flight unit substitution
• Mounting your own cells
• Real cost of body mount & not sun pointing:
- More cells
- Shadow questions
- Current loops in 3D array
- Assembly hassles
- Structural shell stiffness requirements


multiply photovoltaic area by:
2r
 (cylinder)
A vs. 6A
4 (sphere)
6 (cube)
Do you care? Probably not.
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r2 vs. 4r2
Design for Solar Power
Example: Equatorial Earth Oriented
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Power Budget
and
Power System Design
A
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
B
C
D
E
F
Initi al Deployment
Spacecr aft
Payload
Payload Inter face Board
Power (W)
Duty Cycle
G
H
I
Max Sun
Avg Pwr (W)
Power (W)
Duty Cycle
J
Min Sun
Avg Pwr (W)
Power (W)
Duty Cycle
Avg Pwr (W)
20.00
0.00%
0.00
20.00
100.00%
20.00
20.00
100.00%
20.00
2.00
0.00%
0.00
2.00
100.00%
2.00
2.00
100.00%
2.00
Payload Total
0.00
22.00
22.00
Attitude Control System
Mag netometer
1.00
100.00%
1.00
1.00
100.00%
1.00
1.00
100.00%
1.00
Sun Sensor ( cour se)
0.10
100.00%
0.10
0.10
100.00%
0.10
0.10
100.00%
0.10
Tor que Coils
4.00
50.00%
2.00
4.00
50.00%
2.00
4.00
50.00%
2.00
Momentum Wheel
4.50
100.00%
4.50
4.50
100.00%
4.50
4.50
100.00%
4.50
Sensor Interface Boar d
1.50
100.00%
1.50
1.50
100.00%
1.50
1.50
100.00%
1.50
Sun Sensor ( Adcole 18960)
2.00
0.00
2.00
100.00%
2.00
2.00
100.00%
ACS Total
Enginering 176 #6
0.00%
9.10
11.10
2.00
11.10
Potential Paradigm
Breakers
• Advanced deployables
– Inflatables
– Flexible photovoltaics
•
•
•
•
Power beaming
Cooperative swarms
Steerable Phased Arrays
Data Compression
Enginering 176 #6
L’Garde Inflatable
Astrid Spacecraft
Mass total:
27 kg
Mass platform:
22.6 kg
HxWxD:
290 x 450 x 450
Max Power
21.7 W
Battery:
22 Gates Ni-Cd
µprocessor:
80C31
ACS:
spin stabilized
sun pointing
magnetic ctrl.
Thermal:
Passive Control
Downlink:
S-band, 131 kb/s
Uplink:
UHF, 4.8 kb/s
Mission $:
$1.4M inc. launch
Dvt. time:
1 year
Enginering 176 #6
Astrid (Swedish Space Corp)
Freja: did x 8
• Definitely not moving for a long (or too long) time
• 1-g vs. 0-g (& vacuum) matters
• Tolerance v. launch loads
• Vacuum welds, lubricants, galling
• Creating friction - rigging
• Static strength, dynamics, resonance
• Safety inhibits (it’s physical)
Enginering 176 #6
Galileo: didn’t x 1
Deployables: Why they might not
• Flaws, cracks, delamination,
vibration loosen/tighten
• Minute population & test
experience (the Buick antenna)
• Total autonomy
• High current actuation
• Statistics - ways to work v. not
Common Deployables
• Satellites (via Marmon rings)
– Bristol Aerospace, Canada
• Antennas & Radar Reflectors
• Booms: gravity gradient & instrument
– Spar, Canada
– stacer, astromast
• Solar Arrays (fixed & tracking)
– Applied Solar Energy Corp.(ASEC), City of
Industry, CA;
– Programmed Composites, Brea, CA;
– Composite Optics, Los Angles, CA)
• Doors (instrument covers)
• Mirrors & other optics
• Rocket stages
Marmon Ring
Enginering 176 #6
Common Actuators
• Pyrotechnic bolts and bolt cutters
• Melting Wires (Israeli Aircraft Industries, Lod, Israel)
• Hot Wax (not melting wax)
– Starsys Research, Boulder, CO)
Starsys also manufactures hinges for deploybles
• Memory Metal
– GSH, Santa Monica, CA
• Motors and Stepper Motors
• Carpenter tape
– hardware stores
• Sublimation (dural and others)
– DuPont, 3M
Enginering 176 #6
Buick’s deployable antenna goes to
space
(the board game you can play at home)
Enginering 176 #6
Two Simple Questions
before designing that terrestrial component into your next spacecraft
• 1) Will it really be the same part?
– If you change materials, lubricants, loading, mechanical support,
housing, coating, wiring, microswitches... It isn’t the same part.
– Almost any terrestrial part will require design mods for its
controller, non-standard power supply, cooling, emi protection,
surge reduction, structural upgrades…
• 2) How much will it cost to get around the game
board?
–
–
–
–
–
–
–
Specs and shopping:
Reengineer with new materials:
Lubrication, heat sinking, thermal model:
DC/DC converters, surge & EMI suppression:
New housing, brackets & structural analysis:
Rebuild n units for test, spares, inspection & learning:
Test program including 100,000 vacuum ops, + 10
$10k
$50k
$75k
$50k
$40k
$50k
$50k
inspections and rebuilds
• Total - assuming nothing goes wrong
(not always a good assumption)
Enginering 176 #6
$325k
Death, Taxes and...
Option
Shell out for the
flight-qualed gizmo
Pro
• Well Defined Price
• Interesting / educational to
see how it was done
• Popularity with the
customer & your troops
• If you don't change it
• If it worked on the Big Mission (?)
• Which you probably can't afford
• You'll be tempted to do it yourself
(for 1% of the cost)
• 'till they see the price tag,
delivery schedule, power, mass...
Modify existing
• Works on the ground
terrestrial device
• Well tested
that meets the needs • Cheap
• M akes you a "dual use" hero
•So what
• Ditto
• But high cost to modify and test
• First prize: Career as a bureaucrat
Roll your own
• Appeals to our Pioneer Spirit
• Arrows in back
• No big company overhead
• Prodigious consumer of engineering hours
• M eets all mission requirements
• O n paper, anyway
• If it gets done in time for the launch
• Something the whole space
community can benefit from
• They'll find reasons to ignore you
• They are requirements, not supply, driven
(or they are politically / business optimized)
Enginering 176 #6
• Will Work
Con
What Deployables Really Cost
Example: 4 deployable solar panels
(cost ∆ compared with 1 large non-deployable panel)
•
•
•
•
Fab of 4 discrete paddles + 1 spare:
4 highly reliable actuators (hot wax)
4 highly overbuilt hinges & brackets
Engineering: design, thermal, structural and
dynamic analyses
• Testing fixtures and test labor
$40k
$150k
$60k
• Total out of pocket increased cost:
$350k
$50k
$50k
Harder to quantify costs:
- risk of deployment failure
- CG complications on G&C impact
- risk of premature deployment
- Safety qualification
- design review scrutiny
- Vigilance during
integration / test
- Murphy: one paddle broken in test costs $20k to replace in a hurry
Enginering 176 #6
Getting Beyond Deployables
• Eliminate the need for deployables:
–
–
–
–
Larger launch envelope may be cheaper (and it’s more reliable)
Upgrade to Ga-As photovoltaics
Increase testing & trimming to reduce stray fields (e.g. for magnetometers)
Use stuffing - things that deploy when other things deploy
• Reduce Requirements
–
–
–
–
–
–
Limit power budget to achievable with fixed array
Lower duty cycles in poor orbit seasons (i.e. don’t design for worst case)
Lower accuracy (e.g. for magnetometers)
Replace GG boom with magnet or momentum wheel
Open instrument doors manually just before launch
Break mission into several smaller missions
• If all else fails...
– Design as if the deployables you can’t eliminate might not work
(graceful degradation)
– Purchase insurance
– Deployables must be testable at 1-g, 1 atm, room temp...
Enginering 176 #6
Deployables Checklist
• Withstand temperature, vibration, storage time, vacuum, radiation?
• Acceptable EMI, RFI, Magnetic moment, linear / angular momentum?
• Outgassing materials, especially plastics and lubricants but also wire
insulation and other sub-parts?
• Vacuum welding possible?
• Sufficient cooling and lubrication without air and natural convection?
• Internal µelectronics: rad hard? Bit flip and latchup protected?
• Totally autonomous and reliable?
• Document and discuss all anomalies!
• Testable on earth?
• Safety: fire, fracture, pressure, circuit protection, inadvertent
deployment?
• Power: surge, peak, voltage requirement(s)?
• Design and design mods review? Test program review?
• Large margins in design? Not compromised in ground fiddling?
• Schedule and cost margin?
• Failure tolerance - it still may not work...
Enginering 176 #6
Deployables Spec
• Performance
Applied torque or force, speed, accuracy,
preload, angular momentum (eg mirror)
• Weight / Power Allocations from system design spec
• Envelope
& interfaces
Mech. & electrical interface, dimensions
bolt patterns, interface regions...
• Environments
Number of cycles, duration exposure to
environments -> parts, materials, lubes…
• Lifetime (op/non) # operating cycles, duration exposure
• Structure
Strength, fatigue life, stiffness
• Reliability
Allocation from system rel. spec - may
drive specific approach & redundancy
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Freja
• Magnetospheric research
• Launched October, 1992
• 214 kg, 2.2 m diameter
• Development cost: $23M
Freja Facts:
•
•
•
•
•
•
•
•
8 science instruments;
deployed 6 wire booms (L=1 to 15 meters)
deployed 1m and 2m fixed boom
spacecraft separation: 4 pyro bolts plus
standard marmon ring;
Orbit insertion:2 Thiokol Star engines
Start: 8/87; shipped to Gobi Desert 8/92
High “Q” passive thermal design;
Everything worked!
(and still is working).
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Freja (Swedish Space Corp)
Galileo
• Launched
Oct. ‘89
• Mass: 2.5 Mg
NASA JPL
• Galileo HGA Info:
• Development cost about $1.5B
• HGA loss dropped data rate by 104
• Failure caused by loss of lubricant, probably
during several cross-country truck shipments
(note similarity to Pegasus failure during
HETE / SAC-B launch
• Deployable failure caused by poor lubrication
- or by misjudgement of environment?
Enginering 176 #6
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Enginering 176 #6
•
Terrestrial Stuff that works in
Space
Electronic Components:
– ICs, transistors, resistors, capaciters (beware of electrolytic), relays
• Electronic devices
– Vivitar photo strobe, timers, DC/DC Converters, many sensors
• Ni-Cad batteries
– with selection and test. Li-ion are also being flown
• Carpenter Tape
– has never failed
• Laptop computers, calculators
– in Shuttle environment
• Stacer Booms
– but rebuilt with new materials - imperfect performance on orbit
• Hard disc
– in enclosure - but why bother?
• People, monkeys, dogs, algae, bees...
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