A Contamination-Free Ultrahigh Precision Formation Flying Method ...

Laser TetherA Contamination-Free Ultrahigh PrecisionFormation Flight MethodBased on Intracavity Photon Thrusters and Tethers2006 NIAC Fellow Meeting PresentationYoung K. Bae, Ph.D.Bae InstituteTustin, California, USAwww.baeinstitute.comCollaborators:C. W. Larson, Ph.D., AFRLT. Presilla, Ph.D., Northrop GrummanC. Phipps, Ph.D., Photonic AssociatesJ. Carroll, Tether Applications, Inc.

Laser TetherPrecision Formation FlyingTPFMAXIMSI MissionLISASPECS

Laser TetherPrior Propellant-Free Formation Flying ConceptsTether Concepts• Spin-Stabilization• Propulsive Conducting TetherElectrodynamics Concepts• Microwave Scattering Concept -- M. R. LaPointe (NIAC)• Coulomb Force Concept -- L. B. King et al. (NIAC)• Magnetic Dipole Interaction Concept -- D. W. Miller (NIAC)Present ConceptsTether + Electrodynamics → Ultrahigh Precision (nano-maccuracy) Baseline Distance Maintenance

Laser TetherProposed Formation Flying (FF) Method• Force Structure: Counter Balance of Two Forces:Contracting Force: Tether TensionExtending Force: Photon Thrust- Intracavity Arrangement- Thrust Multiplied by Tens of Thousand Times byBouncing of Photons between Spacecraft• Geometrical Structure: Crystalline Structure• Interspacecraft Distance Accuracy: better than nm• Maximum Operation Range: Tens of km (Limited by Mirror Size)• Can be Used for both Static and Dynamic Applications

Laser TetherAdvantages of the Proposed FF Method• Propellantless-- System Mass Savings-- Contamination Free-- Long Operation Lifetime• Inherent Capability of Efficient Damping of Tether Vibrationby Modulating Laser Thrust• Dual Usage of Photon Thruster Laser forInterferometric Ranging System-- Simplified System Architecture and Control-- Low System Weight• Readily Downscalable to Nano- and Pico- Satellites Usage

Laser Tether

Laser TetherNano-Precision Formation Flying System ArchitectureSatellite ISatellite IIPhoton ThrusterSystemInterferometricRanging SystemPrecision LaserPower MeterLensPartial MirrorPhotodetectorPartial MirrorHR MirrorIntracavity Laser BeamUltrahigh Precision CW Photon ThrustLaser Gain MediaHR MirrorHR MirrorPumpLaserBeamDiodePumpLaserPartial MirrorHR MirrorTether SystemTetherReelClampTetherTensionPiezo-TranslatorStepper Motor

Laser TetherPhoton Thruster System: TRL 3Satellite ISatellite IILensIntracavity Laser BeamLaser Gain MediaPumpLaserBeamPrecision LaserPower MeterUltrahigh Precision CW Photon ThrustHR MirrorHR MirrorDiodePumpLaser• Laser System-- Diode Pumped Intracavity Laser-- Lifetime of Diodes1 Year for Continuous Operation• Pump Diode Carousel Design – Tens of Years

Laser Tether10000Intracavity Photon Thrust as a Function of the Mirror Reflectance (R)10 W System1000Photon Thrust (µN)100101Predicted Capability of the Proposed SystemOff-the-ShelfSuper Mirror0.110 100 1000 10000 10000011 - R

Laser TetherSpecific thrusts as functions of I sp of various conventional and photon thrusters.Intracavity Multiplication Factors10 -110 0 X 1,000X 20,000X 10,000Specific Thrust (mN/W)10 -210 -310 -410 -5Electric ThrustersPhoton ThrustersX 10010 -610 -710 2 10 3 10 4 10 5 10 6 10 7 10 8I sp (sec)

Laser TetherPhoton Thruster System: Mirror Diameter vs. Operation DistanceMirror Diamter (cm)1010.01 0.1 1 10 100Intersatellite Distance (km)

Laser TetherSatellite IInterferometric Ranging System: TRL 5Satellite IIPrecision LaserPower MeterLensPartial MirrorIntracavity Laser BeamLaser Gain MediaPumpLaserBeamPartial MirrorHR MirrorUltrahigh Precision CW Photon ThrustHR MirrorHR MirrorDiodePumpLaserPhotodetectorPartial MirrorHR Mirror• Dual Usage of Photon Thruster Laser for InterferometricRanging System Source Laser-- System Architecture Simplification-- System Mass Reduction

Laser TetherHeterodyne Interferometric Ranging System Integrated with Photon Thruster SystemSatellite ISatellite IILensPartial MirrorIntracavity Laser BeamLaser Gain MediaPumpLaserBeamPrecision LaserPower MeterHR MirrorUltrahigh Precision CW Photon ThrustHR MirrorDiodePumpLaserBeam SplitterAOMAOMMirrorRetroreflectorMeasurementDetectorODLReferenceDetector

Laser TetherSatellite ITether System: TRL 5Electromechnical DamperSatellite IITetherTetherReelClampPiezo-TranslatorInchworm• Coarse Control: Reel System-- mm Accuracy• Fine Control: Inchworm or Stepper Motor-- µm Accuracy• Ultrafine Control: Piezo-Translator (off-the-shelf) -- 0.1 nmAccuracy

Laser TetherMethod of Tether Vibration Suppression• Major Tether Vibrations will Result from Reorientation of theWhole Formation Structure, and other Sudden EnvironmentalPerturbations, such as Meteoroid Impacts.• Longitudinal Tether Wave Damping• Tether Material Friction• Modulation of Photon Thruster Power• Transverse Tether Wave Damping• Electromechanical Damper with Impedance MatchingDamping AppliedElectromechanical DampingSimulation by Lorenzini et al.For 1 km Baseline System

Laser TetherExample of Formation Flying at L2LaserTetherAltitude: 1.5 x 10 6 kmSatellite Mass: 100 kg1 kmCross-sectional Area perSpacecraft: 1m 2Base Line Distance: 1 kmTether Material: KevlarTether Diameter: 4 mm(99.9 % survival at L2for 5 years)Not to Scale

Laser TetherExemplary System Design• Major Perturbation ForcesSolar Pressure Force Per Pair: < 20 µNOther Perturbations Including Gravitational Perturbations Per Pair: < 30 µNTotal Differential Force Per Pair : < 50 µN• The Tethers are extended with ~ 100 µN with Photon Thrust Per Pair-- 0.16 µm Extension• The Change in Tether Length due to the Perturbation:Countered with Length Adjustment with Piezo-Translator (sub nm Accuracy)• Laser Requirements with Off-the-Shelf Components:Power Requirement ~ 1 W with 0.99995 MirrorsWith 20 % Wall-Plug Efficiency: The Total Laser System Power ~ 5 WStability Requirement: ~10 -3 (Lab Laser Stability ~ 10 -5 )Mirror Diameter: > 7 cm

Laser TetherApplication ExampleRequirements for New World Imager Freeway MissionBy Prof. W. Cash – 2005 NIAC Fellow Meeting-- Searching for Advanced Civilization in Exo-Planets• 300 m resolution at 10 parsecs = 0.02 nano-arcseconds• 500,000 km based line distance between Collectors• Huge collecting area – one square kilometer“Right now this is impossibly expensive,but not necessarily tomorrow,” by Prof. Cash 2005

Laser TetherOne-Year Later …“Km-Diameter Membrane Space TelescopeBased on Photon Thrusters and Tethers”Image ProcessingWith Real-TimeHolographicAberrationCorrection (NIAC)Membrane Mirror (NIAC)James WebbSpace Telescope

Laser TetherRoadmap• Optimized Photon Thruster Design and Development• Overall System Integration including the Interferometric RangingSystem and Tether System• Overall System Stability and Control including TetherVibration Related Issues• Development of Methods for Reorientation and Alignment of theWhole Formation Structure• Mission Specific Studies

Laser TetherTechnology Readiness Assessment Summary• Photon Thrusters: TRL 3• Interferometric Ranging System: TRL 5• Tether System: TRL 5• System Integration and Control: TRL 2• R&D 3 : II - III (moderate -high) (Degree of Difficulty)Requires to optimize photon thrust design based on the current laboratorysystem and system integration, and to develop control system.

Laser TetherPhase I Study Accomplishment Summary• Theoretically proved that the proposed FF method is capable ofmaintaining the interspacecraft distance with accuracy of nm at themaximum baseline distance of tens of kms.• Successfully developed the engineering architecture of unification ofphoton thruster system with interferometric ranging system for simplifiedarchitecture control and system weight reduction.• Developed the method of controlling tether vibrations usingelectromechanical dampers and photon thruster power modulation.• Orbit specific mission applications have been identified andinvestigated.• Identified Phase II program topics and designed the Phase IIexperimental system.

Laser TetherPhase II Proposed Work• Proof-of-Concept Demonstration of Photon Thruster• Construction of a Thrust Stand with nN Accuracy• Overall System Stability and Control• Tether Vibration Dynamics• Environment Perturbation• 3-D Simulation• Design of Prototype Interferometric Ranging System• Design of Prototype Tether System• Detailed Study of Specific Applications• In-Depth Revisits of Existing Concepts -- SPECS and MAXIM• Ultralarge Membrane Space Telescopes• Ultralarge Sparse Aperture Space Telescopes• Others

Laser TetherPhase II Proposed WorkPhoton Thruster Development with Nano-Newton Accuracy Test StandCounterWeightCorner CubeInterference PatternOptical FiberTorsionFiberLow Power LaserPhoto Detectorfor Fringe CountingWindowsLaser MediaConcave HR MirrorIntracavity Laser BeamHR MirrorPump Laser DiodeLaser Power MeterVacuum Chamber

Laser TetherConclusions• The proposed system needs thorough study.• If successful, the proposed system will open newinnovative (revolutionary) ways to implementing new andexisting mission concepts.• Mission Specific Applications• Simplifies the Architecture and Reduces the Weight inDistributed Interferometery Missions -- TPF, DARWIN, MAXIM,SPECS etc.• Ultralarge Membrane Space Telescopes -- For New World Imager(300 m Resolution – Freeway Mission with km Mirror) and EarthImaging/Monitoring/Surveillance (10 cm Resolution Monitoring at GEOwith 200 m Mirror)• Ultralarge Sparse Aperture Space Telescopes

Laser TetherThe Support by NIAC and NASA for this project is greatly appreciated.“I believe in intuitions and inspirations.I sometimes feel that I am right.I do not know that I am.”by Albert Einstein