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Composite and PCB Based Implementations of a Solar Panel Design for SwampSat

Sharan Asundi, Matthew Mahin, Vivek Nagabhushan, Tzu Yu Lin, Norman G. Fitz-Coy

08/10/2010

24th Annual AIAA/USU Conference on Small SatellitesAugust 9-12, 2010 · Utah State University · Logan, Utah USA

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Rapid Retargeting and Precision Pointing

SwampSat Mission• Rapid Retargeting and Precision Pointing

– Precision 3-axis attitude control

• Validate…– Attitude Determination System (ADS)– Command and Data Handling System (CDH)– Telemetry, Tracking and Command (TT&C)– Electrical Power System (EPS)

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SwampSat Subsystem Assembly

1. CMG Based ACS2. Electrical Power System3. SwampSat Transceiver4. SwampSat Flight Computer5. Solar Panels6. Solar Cells7. Sun Sensor8. Sun Sensor Filter9. Motor Driver Board10.Structure11.Receive Antenna Module12.Transmit Antenna Module SwampSat Subsystem Assembly

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• Satisfy requirements across subsystems• Adhere to CubeSat form factor• Surface suitable for mounting solar cells• Embed magnetic coils for angular momentum

management• Provision for mounting Sun sensors, temperature

sensors, diodes, etc• Structural members and debris abatement• Interface peripheral components with the respective

subsystem boards• Accommodate Delrin plate design and enable

access to connectors through them

Motivation and Requirements

SwampSat Solar Panel Design

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Solar Panel Design

• Sun sensor – TEMT6000• Temperature Sensor –

LM135/335• Bypass diode – BAS40-04• Connector for solar cells

and temperature sensor• Connector for magnetic

coils• Connector for Sun sensor

Solar Panel Design

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Carbon Fiber Composite Solar Panel• Magnetic coils prepared from enamel coated 30

AWG copper core wire and EPO-TEX 78-165 epoxy• Two metal plates with a spacer sandwiched

between are held together by a nut and bolt• Metal rods used for guiding the path of copper wire • Layers of magnetic coils secured together in place

by the epoxy and cured for 10 minutes at 1000 C or 30 minutes at 800 C

Magnetic Coil Fabrication Fixture and Finished Coil

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Carbon Fiber Composite Solar Panel

A Composite Panel Under Development

• Wet lay up technique using a carbon fiber fabric is chosen for implementing the composite

• Composite preparation vacuum bagged on cured for 3-4 hours at room temperature

• EPO-TEK 78-165 conductive epoxy from Epoxy Technology, conductive pen and metal foil tape used for laying electrical traces

• CV-2566 CV Silicone elastomer used for mounting solar cells

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Printed Circuit Board (PCB) Solar Panel• 6-layer 1mm thick PCB with FR-4 cores• 5-layers have electrical traces as magnetic coils• 2oz per square foot copper traces• Dual side solder mask with fully insulated vias• Immersion gold over electroplated nickel finish• Each panel accommodates ~71 turns of coil

A Multifunctional PCB Solar Panel

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Composite vs PCB Panel

Composite Solar Panel PCB Solar Panel

Composite solar panels PCB solar panels

Solar panel epoxy can lead to outgassing Suited for solder paste or epoxyHeat dissipation is not an issue Heat dissipation might be an issueElectrical traces and pads are manually laid Electrical traces and pads are machinedWet layup technique can lead to outgassing PCB boards are machine fabricatedPanel thickness ~2.5 mm (with coils) Panel thickness ~1 mm

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Tests and Results

Composite and PCB Panel Evaluation

Basis…• Composite coil has

more turns• PCB coil has more

area• Magnetic moment is

assumed to be equal

u – magnetic momentn - # of turnsI – currentA – vector area of each loop

u = nIA

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Tests and Results (cont’d…)

PCB Solar Panel Vibration Test Setup and Profile(Ref. PSD table in the Cubesat to PPOD ICD)

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Conclusion• PCB panels are selected for SwampSat mission for

reliability and compact packaging• CubeSat form factor and SwampSat mission limit the

thickness to be under ~1mm• PCB panel address the requirements of…

– EPS subsystem– ACS subsystem– ADS subsystem– Structural and cabling requirement– Facilitate TT&C subsystem

• PCB panels are well designed within the limits…– Copper pads for solar cells, sensors and pheripherals– Connectors for interfacing with subsystem boards– SwampSat power budget is designed to accommodate the

power requirement of the embedded coils

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• Precisely determine the magnetic field output by the embedded magnetic coils

• Perform thermal analysis and evaluate heat dissipation capability

• PCB panels can accommodate additional turns to accommodate future missions

• Capability of the embedded magnetic coils to manage SwampSat’s angular momentum

• Accommodate different orientations of solar cells, alternate PCB material, solar cell mounting technique…

Future Work

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Acknowledgements

• SwampSat development team– Everything and more!!

• Vijay Jagdale, Dr. Ifu and Dr. Shankar– Composite fabrication facility and assistance

• Timco Engineering– Vibration testing facility

• Peggy Evanich– Everything and much more!!

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Thank You!!

Questions?

Sharan Asundiasundi@ufl.edu, 352-846-3020

Space Systems Group @ University of Florida