Bronner, Bret

Trung, Duc

English

DigitalCommons@USU

Developing the Miniature Tether Electrodynamics ExperimentCompletion of Key Milestones and Future WorkPresented by Bret Bronner and Duc Trung2Miniature Tether Electrodynamics Experiment (MiTEE)MiTEE Spacecraft: CubeSat with picosat scale end-body on 10 meter miniature electrodynamic tether (EDT) designed to characterize and demonstrate miniature EDT technology.Mission Goals:• Provide a hands-on multidisciplinary educational experience rooted in faculty driven research• Understand the impact of  hands-on multidisciplinary participation in faculty research on STEM education for undergraduate and graduate students• Understand the functionality of  miniature electrodynamic tethered systems3Miniature Tether Electrodynamics Experiment (MiTEE)Science and Engineering ObjectivesCharacterize voltage-current transfer functions for EDT system under a variety of ionospheric plasma conditions• Measure tether current as a function of  anode/CubeSat voltage for a range of  cathode emission levelsCharacterize miniature tethered system dynamics• Cubesat and End-body attitude and position as a function of time and tether operational modes (thrusting/non-thrusting)Demonstrate use of the tether as a high gain ground-pointing traveling wave antenna• Compare primary antenna and tether-based signal strength as a function of  overpass attitude and distance4EDTs can provide propulsionDrag make-upChange inclination, altitude, etc.No consumable propellantAdditional benefits of tethers:Provided gravity gradient stabilityTether as antennaIonospheric plasma probeMiniature Electrodynamic Tethers (EDTs)Lorentz Force (Deboost)MotionalEMFIonElectronTetherCurrentPlasmaPlasmaForward MotionMotionalEMFTether BiasingPower SupplyIonElectronTetherCurrentPlasmaPlasmaForward MotionLorentz Force (Boost)7Plasma CircuitIon Current(~1uA)Hot Cathode Electron Current(up to 10 mA)Plasma PotentialTether Biasing SupplyMotional EMFAnode/Plasma Voltage Controlled Current SourceIonElectron8Plasma CircuitIon Current(~1uA)Hot Cathode Electron Current(up to 10 mA)Plasma PotentialTether Biasing SupplyMotional EMFAnode/Plasma Voltage Controlled Current SourcePassive Current Mode:• Hot cathode is off and does not contribute to electron emission• Anode/plasma voltage is very small due to required ion/electron current balance• Ion collection primarily due to ram current (~1uA)IonElectronNeutral9Ion Current(~0uA)Active Current Mode:• Hot cathode begins actively emitting  electrons• Anode/plasma potential difference rises due to electron emission • Tether current increases in response to increased anode/plasma voltage• Ion ram current cancelled by electron ram currentPlasma CircuitHot Cathode Electron Current(up to 10 mA)Plasma PotentialTether Biasing SupplyMotional EMFAnode/Plasma Voltage Controlled Current SourceIonElectronNeutral10Miniature Tether Electrodynamics Experiment (MiTEE)~10 m TetherEnvisioned ED Tethered PicoSatPicoSat End-bodyPicoSat End-bodyEach end-body equipped with tether biasing supply and active cathode for fully reversible thrustPicoSat End-bodyMonopole AntennaLangmuir Probe MastCubeSat Test-bed PlatformCubeSat platform offers mass, power, and volume necessary for technology demonstration instrumentationMiTEE CubeSat~10 m TetherTether Deployment System11Miniature Tether Electrodynamics Experiment (MiTEE)~10 m TetherEnvisioned ED Tethered PicoSatPicoSat End-bodyPicoSat End-bodyEach end-body equipped with tether biasing supply and active cathode for fully reversible thrustPicoSat End-bodyMonopole AntennaLangmuir Probe MastCubeSat Test-bed PlatformMiTEE CubeSatLangmuir Probe CircuitryEPS CircuitryC&DH BoardsADCS CircuitryTransceiverMagnetorquerHot Cathode and Power SupplyTether Biasing Power Supply Camera~10 m TetherTether Deployment SystemAdditional Payload Capacity12Electrodynamic Tether as Traveling Wave AntennaHigh gain annular radiation concentric with tether axisPeak gain occurs toward the end of  the tether opposite the driving circuitry (nadir pointing)For demonstration purposes, tether signal strength and transmission integrity will be compared to primary antenna. Attitude and distance will play key roles in this analysis.7 dB GainPolar Gain Plot (dB)Nadir Angle3D Gain Model (dB)Peak Gain-2-14-26-38Tether Axis132014-2015 Major Design Decisions: Primary AntennaSelected four-way synchronously driven monopole antenna array for primary communications142014-2015 Major Design Decisions: Primary AntennaSelected four-way synchronously driven monopole antenna array for primary communications-4-18-32-46Peak Gain1.5 dB GainPolar Gain Plot (dB)Nadir Angle3D Gain Model (dB)Peak Gain1.2 dB GainCoupling from primary antenna to tether152014-2015 Major Design Decisions: CathodeWINCS thermionic cathode• Barium-oxide coated tungsten filament• Designed to output more than 7 mA• Manufactured by E-Beam Inc• Flying aboard then UM CADRE CubeSat later this yearFilamentRepellerAssemblyRheniumFilamentPostsLeadsCeramic Base162014-2015 Major Design Decisions: DeploymentMotorized spool and roller design for slow controlled deployment• Spring-loaded pinch rollers• Small piezo-electric motor• Structure can be 3D printedTetherTorsion-Spring LoadedPinch RollerBracketPinch RollersDrive Shaft AdapterMotorSpool17Spring-loaded bracketsMotorPinch RollersTetherSpool2014-2015 Major Design Decisions: DeploymentMotorized spool and roller design for slow controlled deployment• Spring-loaded pinch rollers• Small piezo-electric motor• Structure can be 3D printed182014-2015 Major Design Decisions: ProcessingMoved to distributed (hub and spoke) processing architecture to simplify parallel development and operation of  subsystems. Additional benefits:• Greater redundancy• Lower over-all power consumptionPayload Processor(MSP430FR5969)Main Processor(MSP430FR5969)EPS Processor(MSP430FR5969)ADCS Processor(MSP430FR5969)Camera Processor(STAMP9G20)Main Processor(STAMP9G20)192014-2015 Major Design Decisions: Form FactorConverted from 1U to 3U for increased mass, power, and volume capacity20CubeSat Launch Initiative (CSLI)• Selected for 6th round of  NASA’s CubeSat Launch Initiative• Ranked 4th among selected missions • Launch opportunities in 2016-2018Courtesy of NASA/Google Maps21Future Development and Major MilestonesFuture Development• Improved tether dynamics modelingo Software modeling (ADAMS) of  tether system with all relevant drag, thrust and gravity gradient forces well characterized• Evolving designs for end-body position characterizationo Lidar based distance determination coupled with on-board attitude determination with CubeSat link• Tether core and insulative coatings researcho Research into “semi-rigid” tether materials is ongoing as well as analysis of  potential insulative coating materials• Indium-Tin-Oxide solar cell coatingso Solar cell surfaces are required to be conductive and grounded for maximum ion ram current collection• Antenna/Tether coupling analysiso Preliminary study suggests strong coupling with primary antenna arrayMilestones• Preliminary Design Review (Ongoing)o September 2015• Critical Design Reviewo March 2016• Flight Hardware Assembly, Integration and Testingo Flight Readiness Review• Q1 2017o Hardware Delivery• Q2 201722Thank you. Questions?AcknowledgementsWe would like to thank JPL for their gracious support through the Strategic University Research Partnerships program. Additionally we wish to thank our Faculty Advisor, Professor Brian Gilchrist along with his student and MiTEE PI Dr. Iverson Bell.We would also like to thank the MiTEE Summer team for all their hard work!(Picture Right)

Developing the Minature Tether Elecrodynamics Experiment: Completion of Key Milestones and Future Work

https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=3293&amp;context=smallsat

Developing the Minature Tether Elecrodynamics Experiment: Completion of Key Milestones and Future Work

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