In this book Professor Lubin lays out the fundamental physics and mathematics required to radically alter our capabilities in propulsion to enable extreme high-speed space flight both in our solar system and beyond. The case is made that the only currently viable solution to enable this transformation, including relativistic flight for the first interstellar robotic missions, is using large-scale directed energy. Traditional methods of propulsion are not capable of achieving the speed required for these missions, including fast crewed missions to Mars as well as the many robotic missions desired both in our solar system and to the nearest stars. Humanity has now reached a technological tipping point with the ability to project power over vast distances with transformational implications in a wide variety of areas, from propulsion to beaming power throughout our solar system to planetary defence. In a series of over 60 technical papers, the fundamentals of this transformation are outlined and synthesized in this book, allowing a detailed understanding of the many challenges ahead and a roadmap for human exploration far beyond our solar system. While the road ahead is long and challenging, it provides the path to radically alter humanity's future.
Author(s): Philip Lubin
Series: World Scientific Series on Emerging Technologies
Publisher: World Scientific Publishing
Year: 2022
Language: English
Pages: 717
City: Singapore
Volume 1 : Fundamentals of Directed Energy
Contents
Preface
Acknowledgments
List of Figures
Chapter 1. Introduction
Directed Energy Approaches
Phased Array Laser
Modularity and Scalability
Exponential Growth in Photonics is Key
Transformative Ideas and Exponential Growth
Long Coherence Length Amplifiers
Array Site Location
Chapter 2. Physics of Photon Propulsion
Laser Aperture Flux
Acceleration Time and Energy Implications
Spacecraft and Sail Kinetic Energy
Photon Recycling
Relativistic Corrections
Relativistic Solution
Final Speed
Closed-Form Solution
Optimization of Reflector and Spacecraft Mass in the Relativistic Limit
Energy and Momentum Transfer: Photon–Electron Interactions
Chapter 3. Optical Design
Beam Efficiency and Sidelobes
Square Aperture
Gaussian Beam
Circular Aperture
Phased Array Optical Response Function
Large Target Field Large Aperture Phased Arrays
Phased Array Shading
Array Fraction Utilization
Self-illumination: Self-shadowing Case
Dynamic Array Reconfiguration
Energy Required per Launch
Efficiency
Using Circular Polarized Radiation to Spin Payload
Sail Temperature
Levitation and Low Acceleration Tests
Scaling
Chapter 4. Laboratory Scale Testing
Achieving Laboratory Speeds Above 100 km/s
Photon Accelerator
Aerodynamic Heating of Sail in Laboratory Testing
Gas Hits Along Photon Accelerator Pipe
Drag Pressure
Scaling of Drag Force
Drag Power
Scaling of Drag Power
Wind Tunnel Testing
High Acceleration Testing Using Gas
Acceleration Comparison
Long Baseline Beam Formation Testing
Eye Safety Limits in Ground Testing
Rayleigh and Particulate Backscatter
Reflector Back Illumination Hazards
Sidelobes: Hazards to Aircraft and Satellites
Chapter 5. Ground Testing and Deployment
Ground-Based Atmospheric Perturbations: Fried Parameter and Seeing
Variation of Fried Length with Zenith Angle
Isoplanatic Angle
Constant Perturbation: Fixed c2n Case
Modeling the Earth’s Atmosphere
Case Where c2n Scales with Atmospheric Density
Case Where c2n Scales with a Power Law of Atmospheric Density
Sum of Power Laws: Case Where c2n Scales with Different Power Laws with Atmospheric Density and Scale Factor at Different Heights
Sum of Power Laws: Case Where c2n Scales with a Different Powers vs. Altitude
High Altitude Vehicle Case Options
Approximations to C2n: Hufnagel-Valley and Related Models
Atmospheric Scintillation: Rytov Number
Fried Parameter: Seeing and Rytov Variance from Army Clear 1 Data
Atmospheric Wind vs. Altitude
Greenwood wind model
Horizontal wind direction
Standard Bufton Wind Model Parameters
Greenwood Frequency and First-Order AO Loop Closure Bandwidth
Strehl Ratio and Perturbations
Atmospheric Refraction
Index of Refraction and Dispersion Relationship
Corrections to the Index of Refraction of Air
Atmospheric Transmission
Thermal Blooming
First Principles Analysis
Energy Considerations
Example — sea level air:
Beam Perturbations Due to Changes in the Index of Refraction
Effect on Target Flux
Scaling Relations and Atmospheric Modeling
Example of large array:
Wind Speed Modeling
Single Wind Speed Exponential
Multiple Wind Speed Exponential Model
Propagation Timescales of Thermal Blooming
Scaling of Blooming Parameter with Array Size: Photon Propulsion
Need for High Fidelity Multi-physics Simulation
Servo Control Mitigation: Exo-atmospheric Target
Chapter 6. Launch Options
Dispensing with the Orbital Dispenser
Drone and Balloon Launch Option
Upper Atmosphere Launch Options Prior to Space Launch
Ablation Drive Prior to Photon Drive
Suborbital Tests
Balloon Launch Scenario
Orbital Tests
Space Launch Option for Ground-Based Array
Chapter 7. Reflectors
Subwavelength Reflectors
Reflectors with Both Absorption and Reflection
Sail Temperature
Hot Reflector Thrust: Additional Photon Thrust
Isothermal Homogeneous Reflector
Generalized Shape Reflectors
Bubble: Spherical Reflectors
Pressure on Sail and Flux
Gas-Inflated Reflectors
Material Stress in Thin Wall Vessels
Reflector Diameter and Thickness vs. Material Strength and DE System Power
Common Materials
Mylar
Strength vs. Temperature
Glass
Gorilla Glass (Corning): Xensation (Schott) and Other Chemically Treated Glass
Silicon
Graphene
Mass of Gas Inside Sphere
Gas Density and Pressure Gradient Due to Acceleration
Using Pressure Gradient to Reduce Gas Mass
Using Pressure Gradient to Reduce Reflector Mass
Compression of Windward Side
Beam Taper to Optimize Reflector Mass
Adiabatic Heating of Gas Due to Acceleration
Using Adiabatic Gas Heating to Reduce Gas Mass
Scaling with Mass
Acoustical Gas Mo
Gas Heating from Illumination
Using Gas Heating from Illumination to Reduce Gas Mass
Rotation Effects
Sphere
Comparing Translational and Rotational Energy
Disk
Uniform thickness disk
Note that the rotational stress in a sphere is comparable to a disk of the same size
Different Rotation Symmetries: Disks vs. Sphere
Vibrational Modes and Damping
Charged Reflectors
Charged Sail Demo
Other Sail Support Structures
Shaped Reflectors for Propulsion and Communications
Chapter 8. Pointing and Course Correction
Transverse Course Correction Using Mass Ejection and Photon Thruster Cases
Mass ejection thrusters
Photon Thrusters
Direct RTG Photon Thruster
Ratio of Transverse Distance Between Mass Ejection and Photon Thrusters
Chapter 9. Acceleration and Deceleration
Dual Laser System Shuttle: Ping-Pong Mode
Travel to Mars at 1 gee: Ping-Pong Mode
Cost of electricity to get to Mars at 1 gee
Chapter 10. Relay Mode for Communication
Reliability of Relay Mode
Chapter 11. Radiation Effects
Cosmic-ray Bombardment
Cosmic-Ray Composition
ISM Boosting and Transverse Bombardment
Transforming to Spacecraft Coordinate System
Raised-Edge Shield
ISM Impact Rate
Electron Penetration
Proton Penetration
Secondary Particle Production
Device Radiation Tolerance
Rads and dE/dx and Impact Flux
ISM Impact Battery
ISM Radiation Dose on Reflector
Nuclear and Electronic Impact Ionization Losses
X-ray Production from ISM Impacts
Photon Production by Charged Particle Impacts
Incident Electrons
Electron Impacts Causing Bremsstrahlung
Penetration of X-rays
View Factor
X-ray Penetration in Various Materials
Incident ISM Proton Bremsstrahlung
ISM Reflector Dust Impact Damage
Chapter 12. Spacecraft Power Sources
Radioisotope Thermal Generators (RTG)
Example: Plutonium 238:
Radioisotope Betavoltaics
ISM Proton and Electron Bombardment Thermal Conversion
Photovoltaic from Laser Illumination
Protovoltaics: ISM Proton Bombardment
Electrovoltaics: ISM Electron Bombardment
Proton-Induced Fusion on Forward Edge: p-11B
Power During the Encounter Phase
Total Photovoltaic Energy from Host Star During Encounter
PV Power vs Time and Distance of Closest Approach
Total RTG Energy During Cruise Phase
Comparison of PV and RTG Energy Generation
Habitable Zone Considerations
Sources of Spacecraft Drag
ISM Particle Drag
ISM Proton Impact Power Generation
ISM Electron Impact Power Generation
Thermal to Electrical Conversion Efficiency
ISM Dust
ISM Magnetic Field
Thermal Photon Fluid Drag
CMB Drag
ISM Starlight Drag
Chapter 13. Ground vs. Space Deployment
Ground vs. Space Deployment
Limitation of Ground-Based Array Deployment
Polar Deployment
Space-Based Deployment Options
Payload Capability
Chapter 14. Science Enabled
Imaging Capability
Imaging Sensitivity
Lambertian Emitter
Reflected Light from Host Star Imaging
IR Thermal Imaging of Planet
TRL Advancement
Chapter 15. Economics: Cost Analysis
Cost Analysis
Independence of Costs of System Parameters Approximation
Physics of SPi and DO
Cost Minimum Depth
Understanding the Cost Minimum
Why Do the Costs Scale Like This?
Materials Strength Limited vs. Manufacturing Limits
Fixed Cost Optimization of Speed
Relationship Between a1 and a2 for Fixed CT and β0 for the Minimum System Cost
A Staged Development Approach
Energy Per Shot
Cost of Energy Used
Cost of Energy Storage
Energy Storage for Large Mass Payloads
Storage Amortization and Energy Production Costs
Cost Analysis Including Energy Used and Energy Storage
Cost Comparison to Recent and Past NASA Programs
Logical Spacecraft Mass Approach
Other Benefits
Chapter 16. Vision and Inspiration
The Path Forward
Chapter 17. Conclusions
Appendix A
Appendix B
Laser Sail: Non-relativistic Solution
Circular vs. Square Array
General Case of Square or Circular Array and Square, Circular Sail or Spherical Sail
Maximizing Speed of Laser-Driven System
Solving for t(L) for L > L0
Time vs. distance with continued illumination (L > L0 or t > t0)
Thermal Photon Field Drag
CMB Zeroth-order Approximations
CMB Speedometer
Precision Speed Measurement Relative to Heliocenter
Photon Recycling
Laser power with N bounces per surface:
Calculating Speed vs. Distance
Summary: Effect of Multiple Reflections (Power and Force Enhancement)
Exact Quartic Solution for Relativistic Term
Stellar Neighborhood
Instructions for Accessing Online Supplementary Material
Bibliography
Index
Volume 2 : Applications of Directed Energy
Contents
Preface
Acknowledgements
List of Figures
Chapter 1. Optical Design Considerations
Near field vs. Far Field — Fresnel vs. Fraunhofer Diffraction
Subaperture vs. Full Aperture Diffraction: Far-Field Limits
Subaperture Tilt vs. Spacecraft Distance: Rapid Changes in F Number
Sail and Beam Shaping
Stable Reflector Shapes
Sphere Symmetry and Spin
Passive Stability Approaches with Angle-Dependent Reflection Coefficient
Chapter 2. Intermediate Steps: Deployment Strategy
Payload Sizes
Ultra Thin Wafer Scale Electronics
Road to Monoatomic Electronics and Reflectors
Chapter 3. Interactions with the Local Photon Fields
Photon-Driven Stellar Sail: Tacking and Navigation
Fixed Radial Conservative Field Case
Proxima b
Non-Conservative Fields: Using the Non-radial Local Angular-Dependent Term to Dissipate the Spacecraft Kinetic Energy
Chapter 4. Options for Slowing Down
Using Stellar Photon Pressure to Slow Spacecraft
Proxima b Case
Maneuvering Using Tacking with Stellar Photons
Using Exoplanet Atmospheres for Aerobraking
Photon Drag Chute: Stopping and Slowing Down for Various Stellar Classes
Beyond Graphene
Chapter 5. Our Stellar Neighborhood Scouting Flyby Mission’s vs. Orbital Missions
Scouting Flyby Mission’s vs. Orbital Missions
Chapter 6. Comparing DE Propulsion to Other Options for Non-relativistic Cases
Mass Loss Propulsion
Achieving High Speed with “Mass Loss” Engines
Nuclear Fusion Engines
Fission Engines
Nuclear Thermal Propulsion
Nuclear Reactors Driving Ion Engines
Annihilation Engines: Antimatter
Perfect Antimatter Engine
Annihilation Propulsion When ma m0
Energy Efficiency
Mass Ejection Propulsion: No Gravity Well
Behavior and Expansion of Terms
Beamed Energy Case
Effect of Laser Array and PV Array Size
General Propellant Mass Case
Gravity Well Case
Mass Ejection Propulsion Scaling Laws
During the thrusting phase:
Ion Engine Infrastructure Mass
Launching from the Moon or Mars
Solar System Cases Including Stopping at Target
System “Alpha” and Mission Performance
During the Thrusting Phase: Prior to Fuel Burnout (t ≤ tb)
PV Temperature and Laser Illumination Flux Limits for Ion Engine Drive
Multiple Propulsion Stages
Comparing Photonic Propulsion to Mass Loss Propulsion
Comparing Non-relativistic, Relativistic and Ultra-relativistic Ion Engines
Ultra-relativistic Exhaust Limit (γ 1, β ∼ 1)
General Case
Non-relativistic Exhaust Limit
Chapter 7. Communications and ISM Science
Antenna Temperature Formulation
Single Mode Diffraction Limited vs. Multi-mode Antenna Temperature
Converting Between Physical Temperature and Antenna Temperature
Non-spectrally Resolved Narrow Bandwidth Signal — Laser Communications
Signal-Level Received
Data Rates vs. Photon Rates: Increasing Peak-to-Average Power
ISM Attenuation Due to Gas and Dust
Short-Range Interstellar Communications
ISM Gas
ISM Dust
Using Laser Communications as a Probe of the ISM
Backgrounds Relevant for Detection
Effect of Subdividing Receive Array into N Partially Phased Subarrays
Size of Proxima Centauri and Synthesized Aperture Required to Resolve it
Importance of Optimizing the Laser Communication Wavelength
Importance of Understanding the Exoplanet Orbital Parameters
Host Star Background
UV Laser Communication: UV Backgrounds
Neutral Hydrogen Absorption: Lyman Alpha
Thomson Scattering
Bound Resonant Scattering: Lyman Alpha
Thermal Broadening in the ISM
Voigt Profile: Combined Natural and Thermal Profile
Cross-Section
Classical vs. Quantum Mechanical Corrections
Thermal Convolved Cross-Section
Large Cross-Section of Lyman Alpha Line
Measuring Neutral Hydrogen Density Using Lyman Alpha
Exploration of Balmer and Other Absorption Lines
Using Uplink to Probe Lyman Alpha and Other Lines
Signal to Background Ratio for the Host Star Background
SBR vs. Distance for a Mission to Proxima b
SBR for Local Stellar Neighborhood
Light Bucket vs. Synthesized Array Modes
Distant Targets and Close in Orbits
The Case of Promixa Centauri
The Case for Shorter Laser Communication Wavelengths
Imaging Exoplanets
Emitted Light Thermal IR
Light Scattered by the Planet from the Host Star
Extraterrestrial Backgrounds
Zodiacal Light
Cosmic IR Background
Unresolved Stellar Background: Faint Stars
Signal and Zodi — Faint Star
CIB backgrounds — Multiple subapertures
Shorter Wavelength Laser Communication Preferred
The Need for Optimized Narrow Bandwidths
Doppler Shifts
Gravitational Redshift
Gravitational Blueshift
Tracing Gravitational Potentials
Dynamic Filters
Optics Background
Terrestrial Backgrounds: Comparison to Extraterrestrial
Atmospheric Transmission and Radiance
Non-LTE Atmospheric Emission
Measured Total Sky Background
Terrestrial Illumination
Signal-to-Background Ratio in General
Dependence of Signal and Backgrounds on the System Design
Day vs. Night Reception for Ground-Based Reception
Comparing to Overall Sky Brightness
Telluric Line Emission
Optimizing SBR
Digging Out the Signal from the Background
Scaling of Communications Downlink with Payload Mass and Speed
Uplink from Earth to Spacecraft
Relativistic Transformations
Chapter 8. Beamed Power Applications
Beamed Power Mode
Beamed Power Modes for Specialized Interplanetary Applications
Beamed Lunar Power
Point-to-Point Lunar Power Beaming
Multiple Targets: Simultaneous vs. Time Multiplexing
Wired vs Beamed Power
Chapter 9. Wafer-Scale Spacecraft
There’s Plenty of Room at the Top: “The Bottom Has Fallen Out”
Wafer-Scale Spacecraft
Large Diameter Low Mass Wafer-Scale Spacecraft
Large Area Photovoltaics
Wafer-Level Thrusters for Attitude Control and Maneuvering
Photon thrusters
Mass ejection thrusters
The sail and the spacecraft as one unit
Multi-tasking and Multi-modal Operation
Chapter 10. Conclusions
Appendix A
Appendix B
Stellar Neighborhood
Instructions for Accessing Online Supplementary Material
Bibliography
Index
