Tether Laser 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, USA www.baeinstitute.com Collaborators: C. W. Larson, Ph.D., AFRL T. Presilla, Ph.D., Northrop Grumman C. Phipps, Ph.D., Photonic Associates J. Carroll, Tether Applications, Inc.
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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)
• 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.