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a t e l l i t e

T

e s t b e d

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F

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F

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16.684 Experimental CDIO Capstone Course 1

Trade Analysis & Requirements Review

The STUFF 16.684 Experimental CDIO Capstone Course February 25, 1999

2

Presentation Outline



Program Objective and Motivations



Subsystems

– – – – –

Propulsion Power and Avionics Metrology Communications and Software Structures



Design Concept Presentation



Conclusions

GPB, AC, JAW 16.684 Experimental CDIO Capstone Course 3

Program Objective

To develop a testbed that demonstrates formation flying algorithms between multiple autonomous satellites with six degrees of freedom, in a microgravity environment

16.684 Experimental CDIO Capstone Course GPB, AC, JAW 4

Motivation

 

Demand for spacecraft to perform autonomous formation flying missions is increasing

– Smaller – Simpler – Cheaper

Current testbeds do not allow full modeling of dynamics related to formation flying

16.684 Experimental CDIO Capstone Course GPB, AC, JAW 5

Justification for Flight

Test Enviroment S p a c e ( i n o r b i tt ) S h u t tt l e P a y l o a d S h u t t l M i d d e c Simulation of Dynamics

     

DOF

  

K C 1 3 5 A i r T a b l e N e u t r a l B u o y a n c y T a n k C o m p u t e r S i m u l a t i o n H e l i u m B a l l o o n s

       16.684 Experimental CDIO Capstone Course 4 / 6

Experiment Duration Cost Comments

U n ll ii m ii t e d L o n g L o g 2 0 3 0 s c s U n ll ii m ii t e d U n ll ii m ii t e d U n ll ii m ii t e d U n ll ii m ii t e d GPB, AC, JAW $ $ $ $ $ $ $ $ $ $ $ P r o h ii b ii t ii v e ll y E x p e n s ii v e H ii g h C o s t E x c e l ll l le n t d y n a i ic at t r e s o n b l le s t G o d d y na m i ic a t l lo w m o d e t e c o O n ll y 2 – D W a t e r V ii s c o s ii t y D y n a m ii c s P r o b ll e m s D ii f f ii c u ll t t o m o d e ll E n v ii r o n m e n t a ll e f f e c t s P r o p u ll s ii o n P r o b ll e m s S p e e d o f R e s p o n s e 6

Specific Science Objectives

1. Develop a set of multiple distinct satellites that interact to maintain commanded position, orientation, and direction 2. Allow for the interchange of control algorithms, data acquisition and analysis, and a truth measure 3. Demonstrate key formation flying maneuvers 4. Demonstrate autonomy and status reporting 5. Ensure the implementation of control algorithms is adaptable to future formation flying missions 6. Allow for testbed operation on KC-135, Shuttle middeck, and ISS

GPB, AC, DRF 16.684 Experimental CDIO Capstone Course 7

Propulsion

Dan Feller Presenter 14

Propulsion Requirements



Safety

– Non-toxic byproducts – Temperatures not to exceed range (TBD) – Non-touch hazard 

Propellant

– Propellant supply sufficient to last at least 20 seconds.



Control

– System must provide for 6 DOF – System must provide constant performance throughout flight duration.



Thrust

– Large ISP (TBD) 16.684 Experimental CDIO Capstone Course GPB, DRF, BMP 15

Propulsion Options



Station Keeping / Attitude

– Compressed Gas • Highly Traceable, Cost Effective, Off-the-Shelf Components – Fans/Propellers • Simple, Cost Effective but ...

– Micro Engines and Rockets • Technology not yet operational 

Attitude Control

– Reaction Wheels • large, heavy, large size – Control Moment Gyros (CMGs) • large size – Magnetic Torquers • large size, long time to develop, large power demand GPB, DRF, BMP 16.684 Experimental CDIO Capstone Course 16

Propulsion Metrics



Safety:

– Toxicity – Thermal Hazard – Touch Hazard – Fracture Hazard 

Impulse Bit

(Smallest quanta of thrust) 

Traceability



Cost



Efficiency

– ISP, Mass ratio – ISP, Volume ratio 

Power Consumption



Ease of Replacement



Time to Develop

16.684 Experimental CDIO Capstone Course GPB, DRF, BMP 17

Propulsion Downselect

Prop System

Weighting

Compressed Gas Fans / Propellers Reaction Wheels 22% 13% 8% 3% 4 5 5 5

4 5 2 3 1 5 5 1

7% 5

2 3

22% 4

2 2

4% 5

4 1

20% 4 TOTAL 100% 4.3

5 2 3.1

3.0

KEY: Desirability of option due to applicable Metric is: Very High- 5 High- 4 Medium- 3 Low- 2 Very Low- 1 16.684 Experimental CDIO Capstone Course GPB, DRF, BMP 18

Compressed Gas Options



CO 2

(Liquid or Gas) – Readily Available, Easy Containment, Adequate Thrust, Toxic 

N 2 / Air

(Liquid or Gas) – High Thrust, Non-Toxic, Difficult Containment 

Onboard Compressor

– Heavy, High Power Consumption, Low Thrust 16.684 Experimental CDIO Capstone Course GPB, DRF, BMP 19

Compressed Gas Downselect

Prop System

Weighting

CO 2 (gas) CO 2 (liquid) Air / N 2 (gas) Air / N 2 (liquid) Onboard Compressor 16.684 Experimental CDIO Capstone Course

25% 17% 3%

3 5 5

15% 22%

5 2 3 5 4 5 5 5 5 3 2 5 5 4 4 2 5

18% evelop TOTAL 100%

5 3.8

5 5 4 4.3

4.3

4.3

5 1 4 2 1 GPB, DRF, BMP 5 3.0

20

Propulsion Budget



Sub-system demands:

– – – –

Power: 2W Volume: 1.5 liter Mass: 3 kg Cost: $3000



Sub-system provides:

–

Thrust: TBD

16.684 Experimental CDIO Capstone Course GPB, DRF, BMP 21

Structures

Dan Feller Presenter 22

Structures Requirements



Structural integrity

– –

Must survive Shuttle launch and landing loads Must survive a drop of 4 feet in 2-g



Satisfaction of mass and volume constraints

–

Container requirement

• •

Mass: 60lbs = 27kg Dimensions: Max. 9 in. = 22 cm diameter (middeck locker)

– – –

Single satellite should be less than 7 kg Structure should be ~10% of total satellite mass (0.7 kg) Structure should provide easy accessibility to internal components



Must be manufacturable and safe under crew handling

DAC, AC, DRF, JES 16.684 Experimental CDIO Capstone Course 23

Structures Options



Shape

–

Cube

– –

Sphere Polyhedron



Assembly

–

Truss

–

Shell (no internal truss)

–

Hybrid (a truss structure with paneling)



Materials

–

Alloys and metals

– –

Composites Plastics and polycarbonates

DAC, DRF, JES 16.684 Experimental CDIO Capstone Course 24

Structures Criteria



Integrity

–

Internal and external load carriage



Safety

–

Fracture toughness (structure cannot shatter)

–

Sharp edges & corners



Feasibility

– – –

Manufacturing Internal accessibility Cost

DAC, DRF, JES 16.684 Experimental CDIO Capstone Course 25

Shape Downselect

Cube Sphere Polyhedron Integrity Safety

30% 30%

Feasibility TOTAL

40% 100% 4 2 5 3.8

5 4 5 4 1 4 3.4

4 DAC, DRF, JES 16.684 Experimental CDIO Capstone Course 26

Assembly Downselect

Truss Shell Hybrid Integrity Safety Feasibility TOTAL

30% 3 30% 4 40% 5 100% 4.1

3 4 4 4 3 4 3.3

4 DAC, DRF, JES 16.684 Experimental CDIO Capstone Course 27

Materials Downselect

Metals & Alloys

Composites Plastics Integrity

30% 4 5 3

Safety

30% 3 3 4

Feasibility

40% 5 3 4

TOTAL

100% 4.1

3.6

3.7

16.684 Experimental CDIO Capstone Course DAC, DRF, JES 28

Structures Budget



Mass

–

TBD, pending estimates of other sub-systems



Volume

–

TBD, but must fit within a STS mid-deck locker,

i.e.

greatest dimension < 9 in.



Cost

–

TBD, pending allowance notification

DAC, DRF, JES 29 16.684 Experimental CDIO Capstone Course

Power and Avionics

Chad Brodel Presenter 30

Power and Avionics Requirements



Total power should be approximately 18 W

–

Total Volts and Amps TBD



All hardware must be contained in individual satellite



Data storage must be adequate



Components must be compatible with KC 135, Shuttle, and ISS environments



System should be traceable to existing satellites

JAW, SEC 31 16.684 Experimental CDIO Capstone Course

Power Distribution

16.684 Experimental CDIO Capstone Course JAW, SEC 32

Power Options



Battery Power

–

Non-rechargeable batteries

• • • • • •

Alkaline Carbon Zinc Lithium Silver Oxide Zinc Air Silver Zinc

–

Rechargeable

• •

Nickel Cadmium Nickel Metal Hydride



Solar Cells

16.684 Experimental CDIO Capstone Course JAW, SEC 33

Power Criteria



Energy Density

– By mass – By volume 

Size

– Weight – Volume 

Cost



Safety



Number of Batteries for 12V



Operating Temperature Range



Capacity



Approximate Lifetime

34 16.684 Experimental CDIO Capstone Course JAW, SEC

Power Downselect

Non-rechargeable

Alkaline Carbon Zinc

Lithium

Silver Oxide Zinc Air Silver Zinc 10% 3 3

3

4 5 ?

10% 3 3

4

4 5 ?

10% 3 4

4

5 4 ?

8% 4 5

4

5 4 ?

5% 3 2

4

4 4 ?

10% 5 5

4

2 5 ?

10% 4 4

3

4 1 ?

12.5% 4 4

4

2 4 ?

2.5% 4 3

5

3 3 ?

10% 3 3

5

2 5 ?

12% 3 3

5

1 5 ?

100% 3.03

3.135

3.645

2.945

3.695

Rechargeable

NiCad

NiMH

2

2

3

4

2

2

2

2

4

4

2

2

3

4

2

2

4

3

3

5

3

4

2.37

2.865

16.684 Experimental CDIO Capstone Course JAW, SEC 35

Power Recommendations



Batteries

–

Non-rechargeable: Lithium

•

Lifetime approximately 40 minutes

–

Rechargeable: NiMH

•

Lifetime approximately 30 minutes



Solar cells should be considered

JAW, SEC 16.684 Experimental CDIO Capstone Course 36

Power Budget



Sub-system demands:

–

Weight : 300 g

–

Volume : 250 cm 3

–

Cost : TBD



Sub-system provides:

–

18 W

–

Voltage and Amps TBD

JAW, SEC 16.684 Experimental CDIO Capstone Course 37

Specific Avionics Requirements



Sufficient data storage capacity



Volume and weight TBD



System must be compatible with communications, propulsion, and metrology



Low power drain

JAW, SEC 16.684 Experimental CDIO Capstone Course 38

Avionics Options



Build Custom Processors



Purchase Processors

–

Commercial Processor Options

• • • •

Tattletale TFX - 11 Tattletale 5F/5F - LCD Spectrum INDY Crickets

JAW, SEC 16.684 Experimental CDIO Capstone Course 39

Communication and Software

Chad Brodel Presenter 40

Communication & Software

•

Communication Requirements:



Satellite to Satellite (STS)

– Real time – Send, receive, and temporarily store data – Compatible with KC-135 / Shuttle systems – Must be traceable to existing satellite technology 

Satellite to Ground (STG)

– Does not have to be real time – Data must be recorded for post-flight analysis – Must be compatible with KC-135 / Shuttle systems GPB, CSB, SLC 41 16.684 Experimental CDIO Capstone Course

Software Requirements



Software is the interface between input (metrology) and output (propulsion)



Requirements :

– Must have common programming language – Must be flexible to allow execution of complex maneuvers – Must develop efficient code compiling techniques 16.684 Experimental CDIO Capstone Course GPB, CSB, SLC 42

Communication Methodology Options



All equal authority

– Satellites interact to decide how to execute array maneuver 

Master / Slave

– One satellite gives commands to all others 

Hierarchy / Command Chain

– Satellites ranked in authority – Easy command transition in case of failure GPB, CSB, SLC 43 16.684 Experimental CDIO Capstone Course

Communication Methodology Selection



Hierarchy / Command chain ensures no confusion

– –

Satellites numbered 1-3: one control stream No. 1 Satellite

•

Receives control algorithm from ground

• • •

Determines each satellite’s position in array Sends commands to other satellites Sends own health status info to ground

–

Other Satellites

• • •

Communicate position, velocity and acceleration data to No. 1 Sends own health status data to ground If No. 1 fails, each satellite will shift up in hierarchy

GPB, CSB, SLC 44 16.684 Experimental CDIO Capstone Course

Data Transfer Options



Download Data:

–

Continuously

• •

Larger power requirement Uses up bandwidth

–

Post Flight

• • •

Possibility of losing on-board data Long download time Larger on-board memory cache required

–

At regular intervals

• •

Efficient combination of options Our recommendation

GPB, CSB, SLC 16.684 Experimental CDIO Capstone Course 45

Communication Downselect

Notes Weighting RF (radio ethernet)

15% 15% 20% 20% 10% 10%

2 5 2 5 5 5 IR

3 2 3 4 4 2 10%

2

3 100%

3.65 A,F

2.60

C

Ultrasonic

4 4 2 3 3 3 3 2.80

B,D,E A – may interfere with KC-135 or shuttle systems B – may interfere with metrology C – only works with sensors in direct line of sight D – not traceable for use in space E – possibly damaging to other onboard experiments F – relatively slow rate of transfer 16.684 Experimental CDIO Capstone Course GPB, CSB, SLC 46

Communication Hardware Selection



Best Option (STS, STG): RF

– Excellent range – Low power requirement – Reasonable bandwidth and accuracy – Single sensor – Cost effective – Possibility of interference on KC-135, Shuttle middeck GPB, CSB, SLC 47 16.684 Experimental CDIO Capstone Course

Budgets Constraints



Power

– Communications sensors and receivers ~ 2 Watts each (1 RF STG and 1 RF STS per satellite) 

Mass

– Communication sensors and receivers ~ 8 grams per satellite 

Volume

– Sensors relatively flat / surface mounted (small) 48 16.684 Experimental CDIO Capstone Course GPB, CSB, SLC

Metrology

Fernando Perez Presenter 49

Metrology Overview



Two subsystems

–

Navigation metrology

•

Real-time position and attitude determination

• •

On-board navigation system Accurate

–

Truth measure

• •

Verification of position and attitude Probably some sort of off-board camera or ranging system

AC, SYC, SLJ, FP 16.684 Experimental CDIO Capstone Course 50

Navigation Metrology Requirements



Real time--10 Hz



Accuracy

– –

Position to 1 cm (TBR) Attitude to 1º (TBR)



Must meet space shuttle and KC-135 interface, interference, & safety requirements



Setup in 20 minutes (TBR)



Interface with other subsystems

– – –

Communications Avionics Power

• •

Onboard = 2 W (TBR) Off-board = 10 W (TBR)

–

Structures

• •

Mass = 0.3 kg (TBR) Volume = 20 mL (TBR)

AC, SYC, SLJ, FP 51 16.684 Experimental CDIO Capstone Course

Navigation Metrology Options



Position

– – –

IR/Ultrasound Ultrasonic Ranging Gyros/ Accelerometers

–

Synchronized clock/RF/IR



Attitude

–

Gyros/ Accelerometers

– –

IR/Ultrasound Pure IR

16.684 Experimental CDIO Capstone Course AC, SYC, SLJ, FP 52

Navigation Metrology Criteria



Metrics

– – –

Complexity Cost Accuracy



Constraints

– – – – – –

Onboard Power Volume Real time Mass Safety Interference

16.684 Experimental CDIO Capstone Course AC, SYC, SLJ, FP 53

Navigation Metrology Downselect

IR/Ultrasound Ultrasonic Ranging Gyros/Accelerometers Synch Clock/RF/IR signal Complexity 30% 3 2 2 Cost 30% 3 4 2 1 1

POSITION

Accuracy 40% 4 1 1 5 TOTAL 100% 3.4

2.2

1.6

2.6

Constraints Line of sight Line of sight, accuracy Cost, power, volume, computational power, may affect satellite dynamics Cost

ATTITUDE

Gyros/Accelerometers IR/Ultrasound Pure IR Complexity 30% 3 2 1 Cost 30% 2 3 1 Accuracy 40% 4 4 5 TOTAL 100% 3.1

3.1

2.6

Constraints Cost, power, volume, may affect satellite dynamics Distance between sensors (size of flyer) Distance between sensors (size of flyer) Note: Power, Volume, Safety, and Interference were considered on a binary scale and are listed as constraints where the subsystem requirements were not met 16.684 Experimental CDIO Capstone Course AC, SYC, SLJ, FP 54

Truth Measure Metrology Requirements



Accuracy

– –

Position to 1 cm (TBR) Attitude to 1º (TBR)



Must meet space shuttle and KC-135 interface, interference, & safety requirements



Interface with other subsystems (not an onboard system)



Off-board requirements

– –

Power = 2 W (TBR) Structures

• •

Mass = 20 kg (TBR) Volume = 5000 mL (TBR)

AC, SYC, SLJ, FP 55 16.684 Experimental CDIO Capstone Course

Truth Measure Metrology Options



Position

– – –

External fixed cameras Onboard cameras External tracking cameras

–

Informed tracking cameras with rangefinders

– –

Radar ranging Reverse IR/Ultrasound



Attitude

– – –

External fixed cameras Onboard cameras Reverse IR/Ultrasound

AC, SYC, SLJ, FP 56 16.684 Experimental CDIO Capstone Course

Truth Measure Metrology Criteria



Metrics

– – –

Complexity Cost Accuracy



Constraints

– – – – – – –

Onboard power Off-board power Onboard volume Off-board volume Mass Safety Interference

AC, SYC, SLJ, FP 16.684 Experimental CDIO Capstone Course 57

Truth Measure Metrology Downselect

POSITION

External fixed cameras (3) Onboard cameras External tracking cameras (9) Informed tracking cameras/Rangefinders Radar ranging Reverse IR/Ultrasound Complexity 40% 4 2 2 3 3 2 Cost 30% 4 2 2 3 3 3 Accuracy 30% 2 2 3 4 4 5 TOTAL 100% 3.4

2.0

2.3

3.3

3.3

3.2

Constraints Size of test area, may not be real time Volume, weight, power, not real time Size of test area, tracking system Size of test area, camera control system Safety, test area, interference Experimental bias External cameras Onboard cameras Reverse IR/Ultrasound Complexity 40% 4 2 2

ATTITUDE

Cost 30% 4 2 3 Accuracy 30% 2 3 5 TOTAL 100% 3.4

3.3

3.2

Constraints Size of test area Volume, mass, not real time Distance between sensors, experimental bias Note: Power, Volume, Safety, and Interference were considered on a binary scale and are listed as constraints where the subsystem requirements were not met 16.684 Experimental CDIO Capstone Course AC, SYC, SLJ, FP 58

Metrology Selections



Navigation Metrology

–

IR/Ultrasound for both position and attitude

• • •

Accurate Inexpensive Meets power, mass, and volume requirements



Truth Measure Metrology

–

External fixed cameras for both position and attitude

•

Could be made real time

•

Off-board system does not require onboard power, mass, or volume

AC, SYC, SLJ, FP 59 16.684 Experimental CDIO Capstone Course

Metrology Budgets

Navigation Metrology – IR/Ultrasound Truth Measure Metrology – External Cameras Power Onboard Offboard 1800 mW 6175 mW Onboard Mass Off-board 24 g 16 g Onboard Volume Off-board 8 mL 6 mL N/A 7800 mW N/A 30 g N/A 29 mL Total Onboard Power 1800 mW Total Off board Power 13,975 mW Total Onboard Mass 24 g Total Off board Mass 46 g Total Onboard Volume 8 mL Total Off board Volume 35 mL Note: Although separate downselects were performed for attitude and position determination, the same solution emerged for both parts of each metrology subsystem 16.684 Experimental CDIO Capstone Course AC, SYC, SLJ, FP 60

Design Concept Presentation & Conclusion

Stephanie Chen Presenter 61

Summary of Concept



Propulsion

–

Compressed Gas

•

Liquid CO 2 or N 2 /Air



Structure

–

Polyhedral truss and shell assembly

–

Metals and alloys

SLC, SEC 16.684 Experimental CDIO Capstone Course 62

Summary of Concept (cont.)



Power

–

Battery Power

•

Lithium, NiMH



Avionics

–

TATTLETALE processor

16.684 Experimental CDIO Capstone Course SLC, SEC 63

Summary of Concept (cont.)



Communication and Software

–

RF (Radio Ethernet)

–

Hierarchy of satellites



Metrology

–

Navigation

•

IR/ultrasound -- measures position and attitude

–

Truth Measure

•

External fixed cameras

SLC, SEC 16.684 Experimental CDIO Capstone Course 64

Budget per Satellite

Propulsion Distributed Mass (kg)

2

Needed Mass (kg)

3

Structure

0.7

TBD

Power/Avionics

2 0.27

Comm/Software

0.3

0.008

Metrology

0.3

0.024

Distributed Power (W)

10 0 4 2 2

Needed Power (W)

2 0 4 4 1.8

Total Margin

5.3

76% 3.3

47% 18 43% 11.8

37% SLC, SEC 65 16.684 Experimental CDIO Capstone Course

Preparation for PDR



Finalize Design

–

Set subsystem architecture

–

Research hardware components

–

Analyze subsystem integration

–

Identify and consult experts



Prepare Documentation

–

Compile hardware specs

–

Validate design

SLC, SEC 16.684 Experimental CDIO Capstone Course 66

Conclusions



Subsystems

–

Preliminary designs investigated

–

Component research underway



Satellite Testbed

–

Designed to be flown on KC-135 and shuttle middeck

–

Technology traceable to future satellite missions

SLC, SEC 67 16.684 Experimental CDIO Capstone Course

THE END!

16.684 Experimental CDIO Capstone Course 68