Enginering 176 #6

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– 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• 12 - Getting Designs

Done• 13 - Design Presentations

Enginering 176 #6

Return on Investment

-25000

-20000

-15000

-10000

-5000

0

5000

10000

0 5 10 15 20 25 30 35

Month

Month

Revenue - Investment

(revenue - investment)

Investment Value (with i)

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

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

Enginering 176 #6

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 - the entire doc is (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

Single vs. Two

Stage Assumptions: • R = M(i)/M(f) = 10

• ∆V required: 10 km/s

• Payload = 100 kg • Payload =10% MfSSTO: 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%

Enginering 176 #6

Orbital Insertion

Payload / kg

20,000

10,000

5,000

15,000

Ariane VProton

X

Delta /LLV

X

Pegasus / Scout

X

0

104103102

25,000Shuttle

(est.)

X

11

22

33

44

55

66

Enginering 176 #6

Optics Lesson #1: Pinhole Camera

0.01 radian

Spot diameter = 0.01 rad x L =~ 400km

(where L = 40,000 km

= GEO altitude)

Spot area =~ 1011 m2

=> every m2 of mirror yields 10-11 sun brightness: 1km2 mirror yields 10-5 sun brightness = 10 x lunar illumination

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

L = 40,000,000 m

Diffraction limit = L/D = 10-6 x 4x107 / 1 = 40 meters - not limiting

Enginering 176 #6

For tonight (/ Thursday)

• Requirements Doc– Mission

Requirements– System Definition– Begin Tech

Requirements

• Launch Strategy– 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 ?

– Fill in re ACS: TLOM:• Chapt. 6 (magnets)• Chapt. 11 (ACS)

• Thinking– What can you

build?– What can you test?

Enginering 176 #6

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 “TBD”s in it. (+ revisit mission rqts)

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

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

Graphics

• Pick Something Physical

Enginering 176 #6

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

Enginering 176 #6

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)

Enginering 176 #6

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

Enginering 176 #6

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

Enginering 176 #6

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 OptionsType Mil? Com? Pros Cons Applications E Density

W-hr / KgLead-Acid no ¦ Dense, Cheap Heavy Mass not 20(gel cells) Wide temp range Seal questions a factor

Volume constrainedVolume constrainedVolume constrainedNi-Cad ¦ ¦ Widely available Low capacity Most widely 25 - 30

Well characterizedWell characterized Mil are large used in space

Ni - H2 ¦ rareHigher E density No small sizes individual -> 25 - 40

5 to 10 x Not yet available multi-cell -> 45 - 60more cycles in multi-cell pacs

NiMH no ¦ E to Ni-H2 Consumer 40 - 60Lower volume Higher cost, no MIL electronics

Li-Ion no ¦ Biggest E densityNo space experience Consumer 100 - 150Fast charge No space qual electronics

More complex charging

None ¦ ¦ Lowest mass No ops in umbra sun synch Lowest cost Max 65% DC most orbitsinterplanetary

Highest reliabilityState saving RAM rqd. Light-sideinfinite lifetime

Enginering 176 #6

FAST

SLOW

DISCHARGE

Battery

TmpSns

Aux Interface A/D SignalConditioning

Aux Bus

PPT Power

Global Power (5V, +/- 12V)

Battery Charging

Enginering 176 #6

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

πr2 vs. 4πr2

A vs. 6A

multiply photovoltaic area by:

π(cylinder), 4 (sphere) or

6 (cube)

Do you care? Probably not.

π2r

2r

Enginering 176 #6

Design for Solar PowerExample: Equatorial Earth Oriented

1.10

1.00

0.90

0.80

0.70SummerSolstace

FallEquinox

WinterSolstace

SummerSolstace

SpringEquinox

28°

Solstace

Solstace

Equinox

Sides Only

+ 15% endplates

15% end plates normalized

Spherical Satellite

Sphere normalized

Enginering 176 #6

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

Enginering 176 #6

Potential Paradigm Breakers

• Advanced deployables– Inflatables– Flexible photovoltaics

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

L’Garde Inflatable

Enginering 176 #6

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)

Enginering 176 #6

Deployables: Why they might not

• 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)

• 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

Enginering 176 #6

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)

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/off

Servo controls:set / stop / limit

switches

Enginering 176 #6

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…

• 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: $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)

Enginering 176 #6

Death, Taxes and...Option Pro Con

Shell out for the • Will Work • If you don't change itflight-qualed gizmo • If it worked on the Big Mission (?)

• Well Defined Price • Which you probably can't afford• Interesting / educational to • You'll be tempted to do it yourself see how it was done (for 1% of the cost)• Popularity with the • 'till they see the price tag, customer & your troops delivery schedule, power, mass...

Modify existing • Works on the ground •So whatterrestrial device • Well tested • Dittothat meets the needs• Cheap • But high cost to modify and test

• Makes you a "dual use" hero • 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

• Meets all mission requirements• On paper, anyway• If it gets done in time for the launch

• Something the whole space • They'll find reasons to ignore you community can benefit from • They are requirements, not supply, driven

(or they are politically / business optimized)

Enginering 176 #6

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

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 Mechanical & 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

Enginering 176 #6

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).

Enginering 176 #6

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

Enginering 176 #6

QuickTime™ and aCinepak 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...