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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

• 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

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Actual • 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

Plant(satellite)

Setpoint Error

ControlAlgorithm

Sensor

Disturbances

Actuator

• Design Activity– Team designations– Mission selections– Homework - ACS for mission

+ CoDR

Review of Last time

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You Are Here

Design Roadmap

DefineMission

ConceptSolutions &Tradeoffs

ConceptualDesign

Requirements Analysis

OrbitPropulsion

/ ∆VComms

AttitudeDetermine & Control

LaunchGroundStation

Thermal /Structure

Deployables

InfoProcessing

Top Level Design

Iterate Subsystems

Suppliers / Budgets

PartsSpecs

Mass

Power

$

∆V

Link BitsMaterialsFab

Detailed DesignFinal Performance

Specs & Cost

Or maybe Here

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2.0 System Definition2.1 Mission Description2.2 Interface Design

2.2.1 SV-LV Interface2.2.2 SC-Experiments Interface2.2.3 Satellite Operations Center (SOC) Interface

3.0 Requirements3.1 Performance and Mission Requirements3.2 Design and Construction

3.2.1 Structure and Mechanisms3.2.2 Mass Properties3.2.3 Reliability3.2.4 Environmental Conditions

3.2.4.1 Design Load Factors3.2.4.2 SV Frequency Requirements

3.2.5 Electromagnetic Compatibility3.2.6 Contamination Control3.2.7 Telemetry, Tracking, and Commanding

(TT&C) Subsystem3.2.7.1 Frequency Allocation3.2.7.2 Commanding3.2.7.3 Tracking and Ephemeris3.2.7.4 Telemetry3.2.7.5 Contact Availability3.2.7.6 Link Margin and Data Quality

3.2.7.7 Encryption

(Some) STP-Sat Requirements

NB: this is an excerpt of the TOC - entire docs are (or will be) on the class FTP site

Requirements & Sys Definition go together

Highly structured outline form is clearest and industry standard

Enginering 176 #6

For tonight

• Requirements Doc(mostly done)– Mission

Requirements– System Definition– Begin Tech

Requirements

• Launch Strategy(also mostly done)– Primary LV and cost– The last mile

problem

• Reading– Requirements

Doc Sample– Power:

• SMAD 11.4• TLOM 14

– Mechanisms:• SMAD 11.6 (11.6.8

too)• TLOM

• Thinking– What can you build?– What can you test?

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For next Thursday, (March 6)

• Preparation: Radios & Comms

• SMAD Chapter 13• TLOM Chapters 7,8,9

• Technical requirements:Create a list of technical requirements - even if it has “TBD”s in it. (+ revisit mission rqts)

• Systems design / CoDR:create a good looking “cartoon” set of the spacecraft, orbit and ground segments

• Tools selection:– Finite element– Design and layout– Presentation &

Graphics

• Get Physical

• Tech Design / Analysis / Suppliers:– Structure / Thermal– Design and layout– Orbit / Launch – ACS / Propulsion // $$$

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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

– Systems: comms, payload, propulsion, power, computing

• Launch & maneuvering• Business Case

– Organizations (Gvt, Commercial, Military)

• ID Critical Technologies

• Program Plan– 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 …

• Focus on something– Critical subsystem– Outstanding attribute– Enabling situation - market

opportunity

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Power: Supply & Demand

• Supply:– Sun: 1.34 kW/m2

– Solar panels: =~ 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– Micro / nano: 100 W to 1 W

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Design Driver: Power• Increased Demands for Power:

– Higher bandwidth (10 x BW = 10 x P)

– Wide coverage area (5 x area = 5 x P)

– Small GS antenna(1/10th diameter = 100 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: (a few % savings in power)

– New array deployment (potential 2x to 100x)

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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 => volume, not W, limit) => passive thermal

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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 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

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Rechargeable Battery Options

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FASTSLOWDISCHARGEBattery

TmpSnsAux InterfaceA/DSignalConditioningAux BusPPT PowerGlobal Power (5V, +/- 12V)

Battery Charging

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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

r2 vs.r2

A vs. 6A

multiply photovoltaic area by:

(cylinder)4 (sphere)6 (cube)

Do you care? Probably not.

2r

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Design for Solar PowerExample: Equatorial Earth Oriented

1.101.000.900.800.70SummerSolstace

FallEquinoxWinter

SolstaceSummerSolstaceSpring

Equinox28°SolstaceSolstaceEquinoxSides Only+ 15% endplates15% end plates normalizedSpherical SatelliteSphere normalized

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Power Budget and

Power System Design

456789

10111213141516171819

A B C D E F G H I JInitial Deployment Max Sun Min Sun

Spacecraft Power (W) Duty Cycle Avg Pwr (W) Power (W) Duty Cycle Avg Pwr (W) Power (W) Duty Cycle Avg Pwr (W)

Payload 20.00 0.00% 0.00 20.00 100.00% 20.00 20.00 100.00% 20.00

Payload Interface Board 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

Magnetometer 1.00 100.00% 1.00 1.00 100.00% 1.00 1.00 100.00% 1.00

Sun Sensor (course) 0.10 100.00% 0.10 0.10 100.00% 0.10 0.10 100.00% 0.10

Torque 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 Board 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% 0.00 2.00 100.00% 2.00 2.00 100.00% 2.00

ACS Total 9.10 11.10 11.10

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Potential Paradigm Breakers

• Advanced deployables– Inflatables– Flexible photovoltaics

• Power beaming• Cooperative swarms• Steerable Phased Arrays• Data Compression

L’Garde Inflatable

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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 stabilizedsun pointingmagnetic 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

Astrid (Swedish Space Corp)

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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

Galil

eo:

did

n’t

x 1

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)

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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

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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)Interfaces:

- 12V, neg ground?- brackets? fuse?

- air cooled motor?

Start:100,000,000 in service; work

great; price $179,retail.

Is it l o n genough

?

Doesrotation

anglematter

?

Howheavyis thetip

mass?

EliminateSubliming / Outgassing

Plastics andLubricants

Replacements: temp range? flexibility?

metal-to-metal contact & vacuum

welding

“Minor”improve-

mentscommence

Lighter

weight

hous-

ing

Tear-down

& rebuild

toinspect

Testing: Note:

GM gets50,000,000

deploymentsper day for 2 years to “get bugs out”

Momentumeffects?Shock &

Vibration?Motor: I, Imax,

EMI, on/offServo controls:set / stop / limit

switches

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Two Simple Questionsbefore 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: $10k– Reengineer with new materials:

$50k– Lubrication, heat sinking, thermal model: $75k– DC/DC converters, surge & EMI suppression: $50k– New housing, brackets & structural analysis:

$40k– Rebuild n units for test, spares, inspection & learning:

$50k– Test program including 100,000 vacuum ops, + 10 $50k

inspections and rebuilds

• Total - assuming nothing goes wrong $325k(not always a good assumption)

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Death, Taxes and...

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What Deployables Really Cost

• 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

• Total out of pocket increased cost: $350k

Example: 4 deployable solar panels(cost ∆ compared with 1 large non-deployable panel)

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

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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...

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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...

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Deployables Spec• Performance Applied torque or force, speed, accuracy,

preload, angular momentum (eg mirror)

• Weight / Power Allocations from system design spec

• Envelope Mech. & electrical interface, dimensions& interfaces 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

Freja (Swedish Space Corp)

• 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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Galileo

• 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?

• Launched Oct. ‘89• Mass: 2.5 Mg NASA JPL

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QuickTime™ and aCinepak decompressor

are needed to see this picture.

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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...