TAILORED FORCE FIELDS FOR SPACE-BASED CONSTRUCTION: KEY TO A SPACE-BASED ECONOMY Narayanan Komerath, Sam Wanis, Joseph Czechowski, Bala Ganesh, Waqar Zaidi, Joshua Hardy, Priya Gopalakrishnan School of Aerospace Engineering, Georgia Institute of Technology
Source: www.nasa.gov School of Aerospace Engineering, Georgia Institute of Technology OUTLINE
1. Forces on objects in steady and unsteady potential fields 2. Generalization: Optical and other E-Mag fields; and acoustic fields 3. Application Horizons 4. Near term: Acoustic Shaping: results & applications 5. Far Horizon: Electromagnetic force fields 6. Middle Term – Magnetic Fields to demonstrate a particular solution -Sample Problem : the O’Neill Habitat - Architecture 7. Costing Using a Space-Based Economy Approach
Source: www.nasa.gov School of Aerospace Engineering, Georgia Institute of Technology INTRODUCTION
In space, minor forces exerted over long periods can achieve major results. Generation of forces by interaction with steady potential fields is well-known
ESL: NASA MSFC/ LORAL NASA .
Solar Sail: NASA M2P2: NASA / U. Wash.
Here we consider: 1. Radiation Force due to unsteady interactions Laser/ Microwave Sail: JPL between beamed energy and matter – near & far term applications. 2. Quasi-steady magnetic fields: middle term architecture to get to the far horizon .
Relevance: automatic construction of large/complex objects from random-shaped materials.
School of Aerospace Engineering, Georgia Institute of Technology FORCES IN UNSTEADY POTENTIAL FIELDS
1. Radiation Force Due to Beamed Energy
Radiation pressure due to plane wave on surface = k*E. ( E = Energy density) Absorbing surface: k =1. Reflective surface: k=2. Gradient forces: Beam waist acts as particle trap for transmitting particles, due to intensity gradient.
Optical Tweezers: Particles are forced to the focus / waist of a CW laser beam -interpreted using geometric optics and refractive index for particles >> λ. -also works using Mie theory where particle size ~ λ -recently found to work for Rayleigh regime – nanoparticles << λ
Satellite Positioning: Lapointe, NIAC study 2001.
Ultrasonic beams - “Fingers of Sound / Space Drums” Used to hold and manipulate levitated/ suspended particles. R. Oeftering, NASA
Radiation pressure on objects due to coherent beams is used in optics and acoustics.
School of Aerospace Engineering, Georgia Institute of Technology FORCES IN UNSTEADY POTENTIAL FIELDS 2. STANDING WAVE FIELDS: Particles Drift into Stable “Traps”. •For particle size << λ, standing wave trap force ~ 103 times the single-beam force.
•Trap stiffness in standing wave trap ~ 107 times the single-beam trapping stiffness.
D ( z) 2 1 0 1 2 •Source only needs to provide small gain over losses -
0.02
0.04 Force
0.06 Potential z
Trap regions can be of complex shape: Stable Trap Pressure distribution for a higher- order mode in a rectangular acoustic resonator.
With standing waves in a low-loss resonator, small input intensity suffices to produce substantial forces on particles. Various mode shapes can be generated by varying frequency and resonator geometry.
School of Aerospace Engineering, Georgia Institute of Technology CONSERVATION EQUATIONS
∂ ()()density of quantity + ∇ • flux of quantity = sources − sin ks ∂t General
∂ 1 1 B 2 E × B ε E 2 + + ∇ • = − ()J • E ∂ o µ µ t 2 2 o o
Electromagnetic Poynting work done on energy density flux Particles by EM field Electromagnetic
∂ 1 p 2 1 + ρ u 2 + ∇ • ()pu = X • ()∇p ∂ ρ 2 o t 2 o c 2 Acoustic Work done on Acoustical potential Acoustical kinetic Acoustic Particles by acoustic Energy density, ep Energy density, ek Intensity flux, I field
ep = potential energy that can be stored in the fluid by compressing it ek = kinetic energy due to acoustically energized fluid I = rate at which work is being done by unit area of fluid supporting an externally induced normal stress p and moving with velocity u is pu, i.e. rate (and direction) at which acoustic energy crosses unit area of space
School of Aerospace Engineering, Georgia Institute of Technology IMPORTANT PARAMETERS & ORDERS OF MAGNITUDE
Optics Acoustics
z Maxwell’s stress tensor z Radiation stress tensor z Rayleigh regime diameters: z Rayleigh regime diameters: millimeters nanometers to centimeters z Mie regime: microns z Mie regime: meters
z Refractive Index z Particle density vs. density of acoustic medium
z Optical intensity z Sound intensity z From Zemanek (1998): z Wanis[1999]: GT acoustic chamber, 514.5 nm laser in water; beam waist 156 dB at 800 Hz (1 0 0) mode at of 8 wavelengths; glass sphere of 2mm radius rigid particles radius 5nm; refractive index 1.51; Force = 3.3 micro-newtons Force = 2.5 *10-22 N.
School of Aerospace Engineering, Georgia Institute of Technology Tailored Force Fields (TFF): Time Line / Size / Application Map
1 – 5yrs 5-20 yrs 20-30yrs 30- 50 yrs. STANDING ULTRASONIC WAVE STEADY MAGNETIC 10-6m ACOUSTCS TELEPRESENCE LONG-WAVE ELECTROMAGNETIC STEADY BEAM ACOUSTICS 10-3m
FORMATION FLIGHT ISS PARTS 100m HEAT SHIELDS :
HABITAT PARTS/ FUEL TANKS
103m HABITAT CONSTRUCTION
ASTEROID 105m RECONSTRUCTION
School of Aerospace Engineering, Georgia Institute of Technology ACOUSTIC RADIATION FORCE: PRIOR APPLICATIONS
•Rayleigh – proposed expression for radiation pressure in acoustic fields, analogous to Maxwell’s stress tensor. •King 1934: Theory for radiation force in acoustic fields – formation of dust striations in water tanks. Forces considered to be insignificant except with ultrasonic frequencies and neutrally-buoyant particles in water. •Levitation experiments: Ultrasonic levitators used to lift steel spheres – to demonstrate utility in non-contact melting and positioning within furnaces. •STS experiments: Holding molten drop of metal inside a container in micro-gravity. Problem: Radiation force lost when phase change / cooling occurred. Attributed to reversal of force due to formation of envelope of heated gas around the sphere. [Wang 1998] •Liquid manipulation using ultrasonics: NASA Glenn research •NASA Hybrid electrostatic levitator / ultrasonic manipulator facility.
School of Aerospace Engineering, Georgia Institute of Technology ACOUSTIC SHAPING •GT extension: Extended the idea of positioning a single droplet, to the formation of entire walls in a chamber. Question: would particles migrate to point of minimum potential, or remain along entire surfaces of low potential? •KC-135 tests. Flight test proof that entire walls would be formed. Self-alignment seen. No particle spin.
Acoustic chamber
Ground test comparison between predicted Mode 110 Styrofoam walls formed in reduced gravity pressure contours and measured wall locations School of Aerospace Engineering, Georgia Institute of Technology ACOUSTIC SHAPING
Wall formation process: KC-135 test. Frequency 800 Hz
School of Aerospace Engineering, Georgia Institute of Technology SIMULATION: PREDICTED WALL SHAPES
2 2 0 1 1 0 3 2 0
1 0 0 + 0 2 0 2 3 0 + 1 0 0 1 1 0 + 2 2 0
School of Aerospace Engineering, Georgia Institute of Technology FAR HORIZON: ASTEROID RECONSTRUCTION? •Solar-powered radio resonators in the NEA region to reconstitute pulverized asteroids into specified shapes. •Formation-flown spacecraft to form desired resonator geometry. •Asteroids pulverized using directed beam energy or robots, •Solar energy converted to the appropriate frequencies. •Materials and structures for such an endeavor must come mostly from lunar or asteroidal sources.
Example Point:
Particle diameter: 0.1m Wavelength: 2m Particle acceleration: 10-5 g Resonator intensity: 170 MW/m2 Resonator Q-factor: 10,000 Active field time: 13 hrs Beam diameter = 100m Collector efficiency: 10% Collector area w/o storage: 1 sq.km
School of Aerospace Engineering, Georgia Institute of Technology Can we generate radio waves intense enough?
z In 1974, the Arecibo observatory transmitted a message into outer space z Power of transmission was 20 trillion watts Courtesy of the NAIC - Arecibo Observatory, a facility of the NSF. z Frequency 2380 MHz. Wavelength of ~12.6 cm David Parker / Science Photo Library z Signal duration: 169 seconds
School of Aerospace Engineering, Georgia Institute of Technology Space Based Economy
Self-sustaining Economy
Support/Service Economy
Space Habitats e Lunar Mining Lunar Manufacturing
m
i
T Lunar Launcher Lunar Power Lunar Resources
GEO Station Orbit transfer vehicles
Maintenance Space Station Robotics Fuel Repair
Com-sats Research Exploration Military Sensing GPS
Earth Launch
School of Aerospace Engineering, Georgia Institute of Technology Middle Term Test Case for Costing: ELECTROMAGNETIC CONSTRUCTION OF A 2KM DIAMETER, 2KM LONG RADIATION SHIELD
At the 10-30 year horizon, force field tailoring can be used to build the first large human habitat at a Lagrangian point of the Earth-Moon system. Gerard O’Neill proposed such habitats and explored their construction in the 1970s.
Features of the O’Neill [1975] habitat concepts: •Economic opportunities as motivator •Moon as first source for extraterrestrial resources, •L5 as the logical location for the settlement. • “Bernal sphere” + toroidal agriculture stations on either side. Near 1-g at equator •Shell made of aluminum and glass (to admit sunlight ) •Support structure made of aluminum ribs and/or steel cable •Projected earth-LEO launch costs of $110/lb •Lunar-based mass driver to send much of the required mass into Space
Radiation shielding dominated mass of the settlement.
School of Aerospace Engineering, Georgia Institute of Technology PRESENT APPROACH TO BUILDING HABITAT
# 1975 models Present model using Tailored Force Fields (TFF)
1 $110/ lb Earth- LEO $1,300 - $14,000 per lb to LEO 2 Human labor on-site for all Robotic with Earth-based telepresence construction. supervision 3 Construction at L-5 Shell construction at L-2 followed by slow move to L-5
4 Lunar mass driver gas-powered; H2 Lunar-equatorial Solar-power fields . 20 from Earth. launchers; round-the clock launches;
5 Baseball-size loads. High Isp. 30g; Railcar-sized loads. 8-g, 40km track. 10km run
6 Entire interior pressurized for “shirt- 10 to 30 meters at rim pressurized, 30-meter sleeves” comfort. bubbles for micro-climates. 7 Machinery required to make panels Solar-heated powder sintering & furnaces, etc. robotic manufacturing on the Moon.
Such a project becomes feasible as the centerpiece of a coherent plan for a Space-based economy of the future.
School of Aerospace Engineering, Georgia Institute of Technology Shield Construction: 1
•Structural strength comes from a Grid of cables made on the Moon and deployed in orbit at Earth- Moon L-2. Rings of 12.5mm dia. cable segments, 1km in radius, spaced 4 meters apart, will be connected by longitudinal cables.
• Grid deployment: Cables with attached mini-thrusters are deployed from lunar-launched “box-cars”. Micro-thrusters separate First 4 lunar-launched cable rings and start rotation, segments Tension kept low until first boxcar ring is complete.
Each regolith-filled “boxcar” is brought by a hybrid gas/ e- mag “shepherd” craft, and guided towards the grid.
School of Aerospace Engineering, Georgia Institute of Technology Shield Construction:2 •Cable Grid is powered by solar panels, with gas thrusters for orbit corrections. Rotation holds the grid in tension during shell construction. •Each arriving load-train is captured by a winched tether attached to the rotating grid. Axial momentum is transferred to radial and tangential momentum, bringing the load to the periphery at 1kmph, into the space between the outer grid and an active, powered electromagnetic “construction grid. •Electromagnetic interaction between the loads, the construction grid, and the shepherds, moves the loads into position against the outer grid. The shepherds leave the grid. •Robots attached to the construction grid complete the attachment of the box-cars.
Ring of boxcars joined to form ribs
Winched tether “Spider” E-mag Captures load: grid Momentum transfer Final positioning Shepherds maneuver boxcars into place using e-mag field
School of Aerospace Engineering, Georgia Institute of Technology Shield Construction:3 Regolith-laden boxcars being delivered by “Shepherd” The “End Caps” Thrusters Assembled boxcars Structural Support
Radial Cables carry grappling Side Wall tethers & Filled with regolith / water winches.
E-Mag Spider
Inner Active E-Mag Grid
Outer Cable Grid
Legs Gripping Cable
School of Aerospace Engineering, Georgia Institute of Technology Construction Parameters • Radius = 1km •Solar Panel area for grid = 350 m2 • Length = 2km •Boxcar :2m x 2m x 20m • Shield Depth 2m •Mass per load: 160,000 kg • Rotates at 0.945 rpm for 1g • Regolith sp.gr.= 2 • Grid current = 15 amps •10 launchers operational at any time (20 total around lunar equator) • 500 loops of cable; • Shepherd unit current required: 15 amps • Cable dia =12.5mm • Time to build: 10 yrs.
•Lunar Solar-Power Fields made by robotic rovers around the equator •Lunar metal extraction plants; cable manufacture using robotic plants. •Lunar launcher construction initiated. •Load preparation system developed on the Moon •First cable-set deployment and spin-up. •First ring of loads completed; rigid framework for subsequent cables and loads. •Solar collectors, thrusters; hub system with tethers and “Construction Spiders” attached. •Oxygen / other propellant gas extraction from regolith to supply thrusters. •Cylinder completion; endcap framework sealed with regolith and water-filled bags; Oxygen/Earth- shipped N2 atmosphere bubbles for habitation spaces near 1-G rim; micro-g axial facilities. •Human habitation commences.
School of Aerospace Engineering, Georgia Institute of Technology Bootstrapping Infrastructure
Credit: D. Rawlings
School of Aerospace Engineering, Georgia Institute of Technology Reduction in Public Expenditure Due to Private Industry. zLunar Power: (Ignatiev et al, NIAC Phase 1, Compare with: 2000) $0.40/KwH Development cost of Alaskan oil facilities: $67B, total z Strip Mining on the Moon (extrapolated from revenue to-date $267B, incl. $55B Fed. Tax. (revenues 1979): $ 8 B from known precious resource) z Lunar Launcher System $ 37 B Space Business total annual revenue 2000: $116B zMetal cost for cylinder structure: $40B (AW&ST, April 2001 revenues from industries & technologies which were created by the new capability zTotal Cost: $150 B NASA Lunar Base construction cost estimate (published): $112B
Lunar 100 Power 80 Generation 60 40 Mining Mass
$B (Y2000) 20 Driver 0 10 12 14 16 Years
School of Aerospace Engineering, Georgia Institute of Technology “Competitive Delivered Cost” Approach
z Cost of Launch Cost from Earth to Moon: $12,000 / kg z Cost of Lunar Launch: $45 /kg in first year reducing to $37/kg by fourth year ( Cost Assessed dictated by the lowest cost from available Earth- based alternatives ) Competitive “Delivered Cost” of Shield: $ 2.5 trillion (!!)
Using Past Assessments and a Collaborative Space Economy Approach Business plans of Space Businesses patched into the network of a Space based Economy Survival of service providers depends on the survival of limited customer base.
The business plan of a single industry that may appear risky when viewed by itself, becomes realistic when patched into the network of a Space based Economy
Justin Hausaman 2001
School of Aerospace Engineering, Georgia Institute of Technology Summary of Industry & Infrastructure Bootstrapped by Habitat Project
1. Power plant. 2. Metal mining. 3. Flexible manufacturing facilities for cables, metal panels, box cars, rails. 4. LEO – GEO – Lunar Orbit shipping industry 5. Tether system for delivery to the Moon. 6. Electromagnetic rail launchers – nucleus of circumlunar ground transport system. 7. Oxygen extraction plants on the Cylinder and the Moon 8. Solar panel production 9. Repair, exploration and prospecting facilities on the Moon. 10. Habitat sized for eventual population of 10,000 people in orbit. 11. Means to ship construction materials anywhere in the vicinity of Earth
School of Aerospace Engineering, Georgia Institute of Technology Concluding Remarks z Tailored electromagnetic force fields enable massive automated construction at low recurring cost. z Theoretical approaches to acoustic, optical and electromagnetic force fields unified into a common Rayleigh regime prediction capability (Phase 1) z Resonators offers large increase in force and trap stability z Acoustic shaping proven in flight and ground experiments z Optical trapping proven in microscopy. z Microwave and radio wave TFF are efficient in solar-power usage for construction z Costing using a Space-Based Economy approach illustrated using the middle term radiation shield project. z Quasi-steady magnetic fields enable telepresence-controlled construction of the radiation shield for human settlements near Earth. z Overall cost becomes practical when lunar- and Space-based industries are included. z Unlike exploration-focused government programs and isolated business plans for private ventures, a Space-Based Economy approach can unite public support for Space enterprise. z As more business visions are enabled by the assurance of a massive market provided by the infrastructure project, the level of public funding needed comes down, even before tax revenues. z Coherent plan needs to be articulated for developing a mutually-supportive network of economically-useful projects, with synergistic markets, risk evaluation and pricing. z Please visit http://www.adl.gatech.edu/research/tff/
School of Aerospace Engineering, Georgia Institute of Technology BACKGROUND
School of Aerospace Engineering, Georgia Institute of Technology TAILORED FORCE FIELDS: CONCEPT In Space, minor forces exerted over long periods can achieve major results. Force fields of various kinds can be used to build large structures. Steady potential fields: Objects
Radiation Force Due to Beamed Energy: Interact with a steady force field. Coherent beams exert pressure on scattering objects. •Electrostatic Levitation •Laser propulsion •“Fingers of Sound / Space Drums” •Magnetic attraction •Electromagnetic sails
D(z) 2 1 0 1 2
0.02 Standing wave fields: particles accumulate into walls along stable “traps”. 0.04
“Acoustic Shaping” Electromagnetic Shaping?? 0.06 z •Complex surface shapes can be tailored. f ~ IkR3 • Source only needs to provide small gain over losses - R •Radiation force in a standing wave field can be > 1000 x that of the source beam. •“Stiffness” of the stable nodes can be 7 orders of magnitude higher than in single-beam.
Present Project: Integrate these technologies to show how very large structures can be built for human habitats – in the context of a Space-Based Economy
School of Aerospace Engineering, Georgia Institute of Technology Sample Planning Architecture for SBE stakeholders
Scope of the Project: Business scenarios, Rationale.
Functional View: Role of the Organization in SBE. What will it achieve?
Business View: Technology View: Economic motivation, Technologies required, Costing, Business Components, Activity Drivers, Organization areas, R&D. structure/hierarchies
Deployment: Operations: Detailed Schedules, procedures, Production Construction plans, plans, Maintenance Implementation plans plans.
School of Aerospace Engineering, Georgia Institute of Technology Technology Options Power Metal Mining & Extraction •Preferred Option: Preferred Option: •Lunar open-pit mines for iron (est: 4 – 15% of •Lunar Solar-Power Fields made by robotic rovers. lunar soil is Fe, occurring mostly as oxides). - 20 power plants around the equator •Solar-heated metal extraction processes – Cost estimate: $0.40 per kilowatt-hr (Ignatiev et al) vapor separation more viable than chemical reduction? Alternatives: •Robotic fabrication plant shipped to the Moon •Nuclear Power Plant on the Moon for box-cars, launcher rails, structural cables, •Beamed Power from Space Solar Power Plant conductors and magnets for launcher Alternatives: •Pre-fab delivery from Earth using tethers. •Steel production on Mars, delivery to Moon. Delivery to the Moon • Start with earth-delivered boxcars to build initial structure; Ship Fabrication plant to Preferred Option: cylinder site; ship steel rods from Mars to •Tether system. cylinder site; land boxcars on Moon and re- use; Alternatives: •Asteroid resources. •Chemical rockets. •Nuclear rockets
School of Aerospace Engineering, Georgia Institute of Technology Launchers from the Moon
Preferred Option: •Electromagnetic rail launcher sized to launch boxcar-sized loads at 8G, with carriage returning to starting point. •Power from local plants. •20 launchers placed around lunar Equator to enable round-the clock operation. Alternatives: • Tethers (problem: counterweight mass; repetition rate needed) •Nuclear rockets (need propellant gas)
•80-90% of power plant capacity utitlized by Cylinder project for 10 years; • Rest used for export of oxygen & tether counter-masses •Tethers and launchers form transportation system for industrial development on the Moon.
School of Aerospace Engineering, Georgia Institute of Technology Total market for lunar resources due to the Cylinder Project
• Steel 2.8 million tons over 11 years • Or Ti: 1.5 million tons over 11 years • Regolith: 50 billion tons over 11 years • Power: 44,600 GWh just for launch services; plus power for manufacturing. • Manufacturing: 314,000+ boxcars; 1600km of e-mag rails. Notes: 1. Radiation shield of 2m regolith is extremely conservative, and used only for illustration of very large-scale mass transport. Concepts for lunar hotel radiation shields use 0.4m of water with 0.1m rock wall. Shipping H2 from Earth and producing H2O in the cylinder site may cut the mass requirement by a factor of 30.
School of Aerospace Engineering, Georgia Institute of Technology Calculations z Using the E-mag Force Equation:
n1:= 1.51 n2:= 1.332 n1 m := n2
λ (a ):= 20⋅ a wavelength 2⋅π ka():= λ ()a wavenumbe
c = speed of light in vacuum, m/s rho = density of material being shaped (sand = 2000 kg/m^3)
School of Aerospace Engineering, Georgia Institute of Technology Cost-Technology Matrix Approach
•Consider the implications of synergizing technologies, with each providing assured markets / supplies / raw materials for others. •Alternative technologies for each major component of the project. •Risks mitigated by laying out alternative products and intermediate markets for each major technology developed for the project.
•Cost-Technology Matrix Approach (C-TMA)TM - factors risks and market elasticity, to select from available technologies. •Weighs technologies quantitatively on the basis of cost, and ranks qualitatively by risk-rating against Technology, Ecology and Political Environment.
The Cost Structure divided into 4 components: •Conceptualization Costs. •Capital Costs Operational Costs •Terrestrial Administrative Costs
School of Aerospace Engineering, Georgia Institute of Technology Estimating the required area needed using solar cells
z Solar Intensity from Sun at 1 AU is 1367 W/m2 z Uncertainty in Solar Cell Efficiencies – Present Day Earth-Built Cell Tech. (32%) – Present Day Lunar-Built Cell Tech. (5%) – 30 Year Lunar-Built Cell Tech. (29%)
School of Aerospace Engineering, Georgia Institute of Technology ACOUSTIC FIELD RESULTS
In micro-gravity, solid particles in a resonant chamber assume stable locations along surfaces parallel to nodal planes of the standing-wave. Liquids in finite-g form walls along nodes – which are regions of lower static pressure.
Irregular grain: microgravity
Hollow Al2O3 and Al spheres: microgravity
Powder suspended in water: 1-g
School of Aerospace Engineering, Georgia Institute of Technology School of Aerospace Engineering, Georgia Institute of Technology OBSERVATIONS & CURRENT PLANS – ACOUSTIC SHAPING
•G-Jitter effects – For a given jitter amplitude, walls survive high-frequency jitter better than low-frequency jitter because particles stay inside the nodal trap. •Long-duration micro-g needed to harden solid objects.
•SEM experiment “Student Experiment in Microgravity” Powered experiment being developed for STS launch in 2003. Miniaturized, automated electronics package; small cylindrical resonator to produce hardened disk of cured resin. Total < 6lb. •GAS experiment “Getaway Special”. Larger 30lb payload. More instrumented experiment, being developed for 2004 timeframe. •Common objectives: •Bring back solid sample for materials / structural analysis. •Record formation and curing process.
School of Aerospace Engineering, Georgia Institute of Technology Continuing Work Areas
•Acoustic & E-mag Simulations into the Mie regime & complex modes. •Mechanics of E-Mag construction: antenna & resonator design •Pulverization of asteroids •Melting/sintering in place to harden structures. •Conceptual Design: Space Experiment on E-Mag construction •Technology / market risk analysis - Long waves for asteroid reconstitution - Lunar power options - Lunar launch & delivery options - Shepherd spacecraft options •Costing approaches including synergy effects of Space-based economy plan
School of Aerospace Engineering, Georgia Institute of Technology