Post on 25-May-2015
TetherLaser
A Contamination-Free Ultrahigh Precision Formation Flight Method
Based on Intracavity Photon Thrusters and Tethers
2006 NIAC Fellow Meeting Presentation
Young K. Bae, Ph.D.Bae Institute
Tustin, California, USAwww.baeinstitute.com
Collaborators:C. W. Larson, Ph.D., AFRLT. Presilla, Ph.D., Northrop GrummanC. Phipps, Ph.D., Photonic AssociatesJ. Carroll, Tether Applications, Inc.
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Precision Formation Flying
TPF SI MissionMAXIM
LISA
SPECS
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Prior Propellant-Free Formation Flying Concepts
Tether Concepts• Spin-Stabilization
• Propulsive Conducting Tether
Electrodynamics 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-m accuracy) Baseline Distance Maintenance
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Proposed 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 by
Bouncing 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
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Advantages of the Proposed FF Method
Propellantless-- System Mass Savings-- Contamination Free-- Long Operation Lifetime
Inherent Capability of Efficient Damping of Tether Vibration by Modulating Laser Thrust
Dual Usage of Photon Thruster Laser for Interferometric Ranging System
-- Simplified System Architecture and Control-- Low System Weight
Readily Downscalable to Nano- and Pico- Satellites Usage
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Satellite I Satellite II
Precision Laser Power Meter
HR Mirror HR Mirror
Laser Gain Media
Ultrahigh Precision CW Photon Thrust
TetherTension
Piezo-Translator Stepper Motor
Intracavity Laser Beam
TetherReel
Clamp
Lens
DiodePumpLaser
PumpLaser Beam
HR Mirror
HR MirrorPart al Mirrori
Photodetector
Part al Mirrori
Part al Mirrori
Tether System
Photon ThrusterSystem
InterferometricRanging System
Nano-Precision Formation Flying System Architecture
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Photon Thruster System: TRL 3
Satellite I Satellite II
Precision Laser Power Meter HR Mirror
HR Mirror
Laser Gain Media
Ultrahigh Precision CW Photon Thrust
Intracavity Laser BeamLens
DiodePumpLaser
PumpLaser Beam
Laser System-- Diode Pumped Intracavity Laser-- Lifetime of Diodes
1 Year for Continuous OperationPump Diode Carousel Design – Tens of Years
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10 100 1000 10000 1000000.1
1
10
100
1000
1000010 W System
Intracavity Photon Thrust as a Function of the Mirror Reflectance (R)
Phot
on T
hrus
t (µN
)
11 - R
Off-the-ShelfSuper Mirror
Predicted Capability of the Proposed System
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Specific thrusts as functions of Isp of various conventional and photon thrusters.
Isp (sec)102 103 104 105 106 107 108
Spec
ific
Thr
ust (
mN
/W)
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
X 1,000
X 10,000
X 100
X 20,000
Electric Thrusters Photon Thrusters
Intracavity Multiplication Factors
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Intersatellite Distance (km)0.01 0.1 1 10 100
Mirr
or D
iam
ter (
cm)
1
10
Photon Thruster System: Mirror Diameter vs. Operation Distance
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Interferometric Ranging System: TRL 5Satellite I Satellite II
Precision Laser Power Meter
HR Mirror HR Mirror
Laser Gain Media
Ultrahigh Precision CW Photon Thrust
Intracavity Laser BeamLens
DiodePumpLaser
PumpLaser Beam
HR Mirror
HR MirrorPart al Mirrori
Photodetector
Part al Mirrori
Part al Mirrori
Dual Usage of Photon Thruster Laser for Interferometric Ranging System Source Laser
-- System Architecture Simplification-- System Mass Reduction
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Heterodyne Interferometric Ranging System Integrated with Photon Thruster System
Satellite I Satellite II
Precision Laser Power Meter
HR Mirror HR Mirror
Laser Gain Media
Ultrahigh Precision CW Photon Thrust
Intracavity Laser BeamLens
DiodePumpLaser
PumpLaser Beam
Part al Mirrori
Beam Splitter
MeasurementDetector Reference
Detector
AOM AOM
Retroreflector
Mirror
ODL
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Tether System: TRL 5
Satellite I Satellite II
Tether
ClampTetherReel Inchworm
Piezo-Translator
Electromechnical Damper
Coarse Control: Reel System-- mm Accuracy
Fine Control: Inchworm or Stepper Motor-- µm Accuracy
Ultrafine Control: Piezo-Translator (off-the-shelf) -- 0.1 nm Accuracy
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Method of Tether Vibration Suppression
• Longitudinal Tether Wave Damping• Tether Material Friction• Modulation of Photon Thruster Power
• Major Tether Vibrations will Result from Reorientation of the Whole Formation Structure, and other Sudden Environmental Perturbations, such as Meteoroid Impacts.
• Transverse Tether Wave Damping• Electromechanical Damper with Impedance Matching
Damping Applied
Electromechanical DampingSimulation by Lorenzini et al.For 1 km Baseline System
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Example of Formation Flying at L2
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1 km
Altitude: 1.5 x 106 km
Satellite Mass: 100 kg
Cross-sectional Area per Spacecraft: 1m2
Base Line Distance: 1 km
Tether Material: Kevlar
Tether Diameter: 4 mm(99.9 % survival at L2 for 5 years)
Not to Scale
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Exemplary 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
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Application 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
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One-Year Later … “Km-Diameter Membrane Space TelescopeBased on Photon Thrusters and Tethers”
James WebbSpace Telescope
Membrane Mirror (NIAC)Image Processing With Real-TimeHolographic AberrationCorrection (NIAC)
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Roadmap
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 the Whole Formation Structure
Mission Specific Studies
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Technology Readiness Assessment Summary
Photon Thrusters: TRL 3
Interferometric Ranging System: TRL 5
Tether System: TRL 5
System Integration and Control: TRL 2
R&D3: II - III (moderate -high) (Degree of Difficulty)Requires to optimize photon thrust design based on the current laboratory system and system integration, and to develop control system.
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Phase I Study Accomplishment SummaryTheoretically proved that the proposed FF method is capable of maintaining the interspacecraft distance with accuracy of nm at the maximum baseline distance of tens of kms.
Successfully developed the engineering architecture of unification of photon thruster system with interferometric ranging system for simplified architecture control and system weight reduction.
Developed the method of controlling tether vibrations using electromechanical dampers and photon thruster power modulation.
Orbit specific mission applications have been identified and investigated.
Identified Phase II program topics and designed the Phase II experimental system.
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Phase II Proposed WorkProof-of-Concept Demonstration of Photon Thruster
Construction of a Thrust Stand with nN Accuracy
Overall System Stability and ControlTether Vibration DynamicsEnvironment Perturbation3-D Simulation
Design of Prototype Interferometric Ranging System
Design of Prototype Tether System
Detailed Study of Specific ApplicationsIn-Depth Revisits of Existing Concepts -- SPECS and MAXIMUltralarge Membrane Space TelescopesUltralarge Sparse Aperture Space TelescopesOthers
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Phase II Proposed WorkPhoton Thruster Development with Nano-Newton Accuracy Test Stand
Laser Power Meter
Concave HR Mirror
HR Mirror
Laser Media
Intracavity Laser Beam
TorsionFiber
CounterWeight
Vacuum Chamber
Interference Pattern
Low Power Laser
Corner Cube
Windows
Optical Fiber
Photo Detectorfor Fringe Counting
Pump Laser Diode
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Conclusions
The proposed system needs thorough study.
If successful, the proposed system will open new innovative (revolutionary) ways to implementing new and existing mission concepts.
Mission Specific Applications Simplifies the Architecture and Reduces the Weight in Distributed Interferometery Missions -- TPF, DARWIN, MAXIM, SPECS etc.Ultralarge Membrane Space Telescopes -- For New World Imager (300 m Resolution – Freeway Mission with km Mirror) and Earth Imaging/Monitoring/Surveillance (10 cm Resolution Monitoring at GEO with 200 m Mirror)Ultralarge Sparse Aperture Space Telescopes
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“I believe in intuitions and inspirations. I sometimes feel that I am right. I do not know that I am.”
by Albert Einstein
The Support by NIAC and NASA for this project is greatly appreciated.