1047bae[1]

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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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Precision Formation Flying

TPF

LISA SPECS

MAXIM

SI Mission

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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 Concepts Tether + Electrodynamics → Ultrahigh Precision (nano-m accuracy) Baseline Distance Maintenance

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Proposed Formation Flying (FF) Method z

Force Structure: Counter Balance of Two Forces: Contracting Force: Tether Tension Extending Force: Photon Thrust - Intracavity Arrangement - Thrust Multiplied by Tens of Thousand Times by Bouncing of Photons between Spacecraft

z

Geometrical Structure: Crystalline Structure

z

Interspacecraft Distance Accuracy: better than nm

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Maximum Operation Range: Tens of km (Limited by Mirror Size)

z

Can be Used for both Static and Dynamic Applications

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Advantages of the Proposed FF Method z

Propellantless -- System Mass Savings -- Contamination Free -- Long Operation Lifetime

z

Inherent Capability of Efficient Damping of Tether Vibration

by Modulating Laser Thrust

z

Dual Usage of Photon Thruster Laser for Interferometric Ranging System -- Simplified System Architecture and Control -- Low System Weight

z

Readily Downscalable to Nano- and Pico- Satellites Usage

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Nano-Precision Formation Flying System Architecture Satellite II

Satellite I Lens

Photon Thruster System

Intracavity Laser Beam

Interferometric Ranging System

Diode Pump Laser

Ultrahigh Precision CW Photon Thrust

Precision Laser Power Meter

Partial Mirror

Pump Laser Beam

Laser Gain Media

Partial Mirror

HR Mirror

HR Mirror

HR Mirror

Photodetector HR Mirror

Partial Mirror

Tether

Tether System

Tether Reel

Tension Clamp

Piezo-Translator

Stepper Motor

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Photon Thruster System: TRL 3

Satellite II

Satellite I

Laser Gain Media

Lens

Intracavity Laser Beam Ultrahigh Precision CW Photon Thrust

Precision Laser Power Meter z

z

HR Mirror

HR Mirror

Laser System -- Diode Pumped Intracavity Laser -- Lifetime of Diodes 1 Year for Continuous Operation Pump Diode Carousel Design – Tens of Years

Pump Laser Beam Diode Pump Laser

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Intracavity Photon Thrust as a Function of the Mirror Reflectance (R) 10 W System 10000

1000

Photon Thrust (ÂľN)

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100

10

Off-the-Shelf Super Mirror

1 Predicted Capability of the Proposed System

0.1 10

100

1000

1 1 - R

10000

100000

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Specific thrusts as functions of Isp of various conventional and photon thrusters.

Intracavity Multiplication Factors

0

10

X 20,000 X 10,000

-1

Specific Thrust (mN/W)

10

-2

10

Photon Thrusters

Electric Thrusters

-3

X 1,000

10

X 100

-4

10

-5

10

-6

10

-7

10

10

2

10

3

10

4

10

5

Isp (sec)

10

6

10

7

10

8

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Photon Thruster System: Mirror Diameter vs. Operation Distance

Mirror Diamter (cm)

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10

1 0.01

0.1

1

Intersatellite Distance (km)

10

100

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Interferometric Ranging System: TRL 5

Satellite II

Satellite I Precision Laser Power Meter

Lens

Pump Laser Beam

Laser Gain Media

Parti al Mirror

Intracavity Laser Beam Ultrahigh Precision CW Photon Thrust

Partial Mirror

HR Mirror

HR Mirror

HR Mirror

Photodetector

Partial Mirror z

HR Mirror

Dual Usage of Photon Thruster Laser for Interferometric Ranging System Source Laser -- System Architecture Simplification -- System Mass Reduction

Diode Pump Laser

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Heterodyne Interferometric Ranging System Integrated with Photon Thruster System

Satellite II

Satellite I Lens

Laser Gain Media

Parti al Mirror

Intracavity Laser Beam Ultrahigh Precision CW Photon Thrust

Precision Laser Power Meter

HR Mirror

HR Mirror

Beam Splitter

AOM

AOM

Mirror

Retroreflector Measurement Detector

ODL

Reference Detector

Pump Laser Beam Diode Pump Laser

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Tether System: TRL 5 Satellite I

Electromechnical Damper

Satellite II

Tether Tether Reel

Clamp

Inchworm Piezo-Translator

z

Coarse Control: Reel System-- mm Accuracy

z

Fine Control: Inchworm or Stepper Motor-- Âľm Accuracy

z

Ultrafine Control: Piezo-Translator (off-the-shelf) -- 0.1 nm Accuracy

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Method of Tether Vibration Suppression • Major Tether Vibrations will Result from Reorientation of the Whole Formation Structure, and other Sudden Environmental Perturbations, such as Meteoroid Impacts.

• Longitudinal Tether Wave Damping • Tether Material Friction • Modulation of Photon Thruster Power

• Transverse Tether Wave Damping • Electromechanical Damper with Impedance Matching Damping Applied

Electromechanical Damping Simulation by Lorenzini et al.

For 1 km Baseline System

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Example of Formation Flying at L2

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Tether Altitude: 1.5 x 106 km Satellite Mass: 100 kg

1 km

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 z

Major Perturbation Forces Solar Pressure Force Per Pair: < 20 µN Other Perturbations Including Gravitational Perturbations Per Pair: < 30 µN Total Differential Force Per Pair : < 50 µN

z

The Tethers are extended with ~ 100 µN with Photon Thrust Per Pair -- 0.16 µm Extension

z

The Change in Tether Length due to the Perturbation: Countered with Length Adjustment with Piezo-Translator (sub nm Accuracy)

z

Laser Requirements with Off-the-Shelf Components: Power Requirement ~ 1 W with 0.99995 Mirrors With 20 % Wall-Plug Efficiency: The Total Laser System Power ~ 5 W Stability Requirement: ~10-3 (Lab Laser Stability ~ 10-5) Mirror Diameter: > 7 cm

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Application Example Requirements for New World Imager Freeway Mission

By 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 Telescope Based on Photon Thrusters and Tethers”

Image Processing With Real-Time Holographic Aberration Correction (NIAC)

James Webb Space Telescope

Membrane Mirror (NIAC)

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Roadmap z

Optimized Photon Thruster Design and Development

z

Overall System Integration including the Interferometric Ranging System and Tether System

z

Overall System Stability and Control including Tether Vibration Related Issues

z

Development of Methods for Reorientation and Alignment of the Whole Formation Structure

z

Mission Specific Studies

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Technology Readiness Assessment Summary z

Photon Thrusters: TRL 3

z

Interferometric Ranging System: TRL 5

z

Tether System: TRL 5

z

System Integration and Control: TRL 2

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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 Summary z

Theoretically 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.

z

Successfully developed the engineering architecture of unification of photon thruster system with interferometric ranging system for simplified architecture control and system weight reduction.

z

Developed the method of controlling tether vibrations using electromechanical dampers and photon thruster power modulation.

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Orbit specific mission applications have been identified and investigated.

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Identified Phase II program topics and designed the Phase II experimental system.

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Phase II Proposed Work z

Proof-of-Concept Demonstration of Photon Thruster z

z

Construction of a Thrust Stand with nN Accuracy

Overall System Stability and Control z z z

Tether Vibration Dynamics Environment Perturbation 3-D Simulation

z

Design of Prototype Interferometric Ranging System

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Design of Prototype Tether System

z

Detailed Study of Specific Applications z z z z

In-Depth Revisits of Existing Concepts -- SPECS and MAXIM Ultralarge Membrane Space Telescopes Ultralarge Sparse Aperture Space Telescopes Others

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Phase II Proposed Work Photon Thruster Development with Nano-Newton Accuracy Test Stand Counter Weight

Interference Pattern Corner Cube

Optical Fiber Torsion Fiber

Low Power Laser

Photo Detector for Fringe Counting

Windows Laser Media

Intracavity Laser Beam HR Mirror Concave HR Mirror

Laser Power Meter

Vacuum Chamber

Pump Laser Diode

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Conclusions z

The proposed system needs thorough study.

z

If successful, the proposed system will open new innovative (revolutionary) ways to implementing new and existing mission concepts.

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Mission Specific Applications z

Simplifies the Architecture and Reduces the Weight in Distributed Interferometery Missions -- TPF, DARWIN, MAXIM, SPECS etc.

z

Ultralarge Membrane Space Telescopes -- For New World Imager

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Ultralarge Sparse Aperture Space Telescopes

(300 m Resolution â&#x20AC;&#x201C; Freeway Mission with km Mirror) and Earth Imaging/Monitoring/Surveillance (10 cm Resolution Monitoring at GEO with 200 m Mirror)

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The Support by NIAC and NASA for this project is greatly appreciated.

â&#x20AC;&#x153;I believe in intuitions and inspirations.

I sometimes feel that I am right.

I do not know that I am.â&#x20AC;?

by Albert Einstein