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
– 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
• 8 - Thermal / Mechanical
Design. FEA
• 9 - Reliability
• 10 - Digital & Software
• 11 - Project Management
Cost / Schedule
the word from our sponsor: $$$
A large number of small monthly
payouts -----…adds up to a lot of negative
equity ------
…and even more with foregone interest
included -----Enginering 176 #6
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
- the
entire doc
is (or will
be) on the
class FTP
site
Single vs. Two Stage
Assumptions:
• R = M(i)/M(f) = 10
• ∆V required: 10 km/s
• Payload = 100 kg
• Payload =10% Mf
SSTO: 100 kg payload
∆V = gIspln(R):
Isp = 420 (H2 / O2)
Launch mass: 12,500 kg
Structure = 1000 kg
=> R = 12.5
Stage payload Mass Fraction: 0.8%
TwoSTO: S-1
∆V(s)=5000m/s
(2 stages, equal ∆V)
S-2 mass: 505 kg
S-2 structure: 150 kg
S-2 PMF: 20%
TwoSTO: S-2
∆V(s)=5000m/s
S-1 mass: 2595 kg
S-1 structure: 770 kg
S-2 PayMF: 20%
TwoSTO: ∑
∆V =10000m/s
Total Mass: 3100 kg
Total PayMF: 3.2%
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Orbital Insertion
2
4
5
3
1
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6
Pinhole
Camera
Optics Lesson #1:
=> every m2 of mirror yields
10-11 sun brightness:
1km2 mirror yields 10-5 sun
brightness = 10 x lunar
illumination
Spot diameter = 0.01 rad
xL
=~ 400km
(where L = 40,000 km
= GEO altitude)
Spot area =~ 1011 m2
0.01
radian
L = 40,000,000 m
From 400 km LEO every m2 of mirror
yields 10-7 sun brightness: 10x10m
yields 10-5 sun brightness = 10 x lunar
illumination
over diameter = 4km
Enginering 176 #6
Diffraction limit = lL/D
= 10-6 x 4x107 / 1
= 40 meters - not
For tonight (/ Thursday)
• Reading
• Requirements Doc
– Mission
Requirements
– System Definition
– Begin Tech
Requirements
– Requirements Doc
Sample
– Power:
• SMAD 11.4
• TLOM 14
– Mechanisms:
• SMAD 11.6 (11.6.8 too)
• TLOM ?
• Launch Strategy
– Primary LV and
cost
– The last mile
problem
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176 #6
– Fill in re ACS: TLOM:
• Chapt. 6 (magnets)
• Chapt. 11 (ACS)
• Thinking
– What can you
build?
For next Thursday, (March
7)
• Preparation: Radios &
Comms
• SMAD Chapter 13
• TLOM Chapters 7,8,9
• Technical
requirements:
Create a list of
technical
requirements even if it has
• Toolsin
selection:
“TBD”s
it.
– Finitemission
element
(+ revisit
– Design and layout
rqts)
• Systems design:
create a good
looking “cartoon”
set of the
– Presentation
spacecraft, orbit
Graphics
and ground
• Pick Something
segments
Enginering 176 #6
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
– 1 Transponder: 200W; 1 DBS XPDR:
2000W
– On - Board Housekeeping: 100W
– Iridium / Globalstar class satellite:
500W
Enginering 176 #6
Design Driver: Power
• Increased Demands for
Power:
– Higher bandwidth
(10 x BW
= 10 x P)
– Wide coverage area
= 5 x P)
(5 x area
• 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:
(a few % savings in power)
– New array deployment
Enginering 176 #6
(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
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176 #6
matters
=> heaters / heat
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
control
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High cost, tight attitude
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
¦
E - to Ni-H2
Lower volume
Li-Ion
no
¦
Biggest E density
Fast charge
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
Applications
E Density
W-hr / Kg
20
Mass not
a factor
Volume constrained
Most widely
25 - 30
used in space
Higher cost, no MIL
No space experience
No space qual
More complex charging
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
π2r
2r
Enginering 176 #6
multiply photovoltaic
area by:
π(cylinder),
4 (sphere) or
6 (cube)
A vs. 6A
πr2 vs. 4πr2
Design for Solar Power
Example: Equatorial Earth Oriented
Enginering 176 #6
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
In itia l Depl oyment
Spa cecraft
Paylo ad
Paylo ad Interface Board
Power (W)
Duty Cycl e
G
H
I
Max Sun
Avg Pwr (W)
Power (W)
Duty Cycl e
J
Min Sun
Avg Pwr (W)
Power (W)
Duty Cycl e
Avg Pwr (W)
20 .00
0.00%
0.00
20 .00
10 0.00 %
20 .00
20 .00
10 0.00 %
20 .00
2.00
0.00%
0.00
2.00
10 0.00 %
2.00
2.00
10 0.00 %
2.00
Paylo ad Total
0.00
22 .00
22 .00
Attitu de Con trol Sys tem
Magn etom eter
1.00
10 0.00 %
1.00
1.00
10 0.00 %
1.00
1.00
10 0.00 %
1.00
Sun Sens or (course )
0.10
10 0.00 %
0.10
0.10
10 0.00 %
0.10
0.10
10 0.00 %
0.10
To rque Co ils
4.00
50 .00%
2.00
4.00
50 .00%
2.00
4.00
50 .00%
2.00
Mome ntum Whe el
4.50
10 0.00 %
4.50
4.50
10 0.00 %
4.50
4.50
10 0.00 %
4.50
Sen sor Interface Board
1.50
10 0.00 %
1.50
1.50
10 0.00 %
1.50
1.50
10 0.00 %
1.50
Sun Sens or (Ad col e 18 960)
2.00
0.00%
0.00
2.00
10 0.00 %
2.00
2.00
10 0.00 %
ACS To tal
Enginering 176 #6
9.10
11 .10
2.00
11 .10
Potential Paradigm
Breakers
• Advanced deployables
– Inflatables
– Flexible photovoltaics
•
•
•
•
Power beaming
Cooperative swarms
Steerable Phased Arrays
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
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
Enginering 176 #6
Marmon
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…
• 1) How much will it cost to get around the game
board?
–
–
–
–
–
–
–
Specs and shopping:
$10k
Reengineer with new materials:
$50k
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
$75k
$50k
$40k
$50k
$50k
inspections and rebuilds
• Total - assuming nothing goes wrong
Enginering
176 #6 a good assumption)
(not always
$325k
Death, Taxes and...
Option
Shell out for the
flight-qualed gizmo
Pro
• Will Work
• Well Defined Price
• Interesting / educational to
see how it was done
• Popularity with the
customer & your troops
Con
•
•
•
•
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, pow er, mass...
Modify existing
• Works on the ground
terrestrial device
• Well tested
that meets the needs • Cheap
• Makes 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
• Arrow s in back
• No big company overhead
• Prodigious consumer of engineering hours
• Meets all mission requirements
• On 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
What Deployables Really Cost
Example: 4 deployable solar panels
(cost ∆ compared with 1 large non-deployable panel)
• Fab of 4 discrete paddles + 1 spare:
$40k
• 4 highly reliable actuators (hot wax)
$150k
• 4 highly overbuilt hinges & brackets
$60k
• Engineering: design, thermal, structural and
dynamic analyses
$50k
• Testing fixtures and test labor
$50k
Harder to quantify costs:
• Total out of pocket increased cost:
$350k
- risk of deployment failure
- CG complications on
G&C impact
- risk of premature deployment
- Safety qualification
- design review scrutiny
- Vigilance during
integration
/ test
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
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?
#6
• Enginering
Failure 176
tolerance
- it still may not work...
Deployables Spec
• Performance Applied torque or force, speed,
accuracy,
preload, angular momentum (eg
mirror)
• Weight / Power
design spec
Allocations from system
• Envelope
Mechanical & electrical
interface, dimensions
& interfaces
bolt patterns, interface regions...
• EnvironmentsNumber of cycles, duration
exposure to
Enginering 176 #6
environments -> parts, materials,
Freja
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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• Magnetospheric
research
• Launched October,
1992
• 214 kg, 2.2 m diameter
• Development cost:
$23M
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
Enginering 176 #6
environment?
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...
Enginering 176 #6