TAILORED FORCE FIELDS FOR SPACE-BASED CONSTRUCTION: …€¦ · • “Bernal sphere” + toroidal agriculture stations on either side. Near 1-g at equator •Shell made of aluminum

School of Aerospace Engineering, Georgia Institute of Technology

Source: www.nasa.gov

Narayanan Komerath, Sam Wanis,

Joseph Czechowski, Bala Ganesh, Waqar Zaidi, Joshua Hardy, Priya Gopalakrishnan


TAILORED FORCE FIELDS FOR SPACE-BASED CONSTRUCTION: KEY TO A SPACE-BASED

ECONOMY


Source: www.nasa.gov

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

OUTLINE


In space, minor forces exerted over long periods can achieve major results.

Generation of forces by interaction with steady potential fields is well-known

Relevance: automatic construction of large/complex objects from random-shaped materials.

Solar Sail: NASA

Here we consider:

1. Radiation Force due to unsteady interactions between beamed energy and matter – near & far term applications.

2. Quasi-steady magnetic fields: middle term architecture to get to the far horizon

.

ESL: NASA MSFC/ LORAL

M2P2: NASA / U. Wash.

NASA .

INTRODUCTION

Laser/ Microwave Sail: JPL


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.

1. Radiation Force Due to Beamed Energy

Radiation pressure on objects due to coherent beams is used in optics and acoustics.

Ultrasonic beams -“Fingers of Sound / Space Drums” Used to hold and manipulate levitated/ suspended particles.

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.

R. Oeftering, NASA

FORCES IN UNSTEADY POTENTIAL FIELDS


•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.

•Source only needs to provide small gain over losses -2 1 0 1 2

0.06

0.04

0.02

D z( )

z

2. STANDING WAVE FIELDS: Particles Drift into Stable “Traps”.

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.

Trap regions can be of complex shape: Pressure distribution for a higher-order mode in a rectangular acoustic resonator.

FORCES IN UNSTEADY POTENTIAL FIELDS

Force

Potential

Stable Trap


CONSERVATION EQUATIONSCONSERVATION EQUATIONS

( ) ( ) kssinsourcesquantityoffluxquantityofdensityt

−=•∇+∂∂

( )EJBEBEt oo

o •−=

µ×•∇+

µ

+ε∂∂ 2

2

21

21

Electromagnetic energy density

Poyntingflux

work done onParticles by EM field

Gen

eral

Elec

trom

agne

ticA

cous

tic

( ) ( )pXpuuc

pt o

o

∇•=•∇+

ρ+

ρ∂∂ 2

2

2

21

21

Acoustical potentialEnergy density, ep

Acoustical kineticEnergy density, ek

AcousticIntensity flux, I

Work done onParticles by acousticfield

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


IMPORTANT PARAMETERSIMPORTANT PARAMETERS & ORDERS OF MAGNITUDE& ORDERS OF MAGNITUDE

Radiation stress tensorRayleigh regime diameters: millimeters to centimetersMie regime: meters

Particle density vs. density of acoustic mediumSound intensityWanis[1999]: GT acoustic chamber, 156 dB at 800 Hz (1 0 0) mode at 2mm radius rigid particles Force = 3.3 micro-newtons

Maxwell’s stress tensorRayleigh regime diameters: nanometersMie regime: microns

Refractive Index

Optical intensityFrom Zemanek (1998): 514.5 nm laser in water; beam waist of 8 wavelengths; glass sphere of radius 5nm; refractive index 1.51; Force = 2.5 *10-22 N.

AcousticsOptics


Tailored Force Fields (TFF): Tailored Force Fields (TFF): Time Line / Size / Application MapTime Line / Size / Application Map

STEADY BEAM ACOUSTICS

STEADY MAGNETICTELEPRESENCE LONG-WAVE

ELECTROMAGNETIC

STANDING WAVE

ACOUSTCS10-6m

10-3m

103m

105m

1 – 5yrs 5-20 yrs 20-30yrs 30- 50 yrs.

100m:

ULTRASONIC

ISS PARTS

HEAT SHIELDS

HABITAT PARTS/FUEL TANKS

FORMATIONFLIGHT

HABITAT CONSTRUCTION

ASTEROID

RECONSTRUCTION


ACOUSTIC RADIATION FORCE: PRIOR APPLICATIONSACOUSTIC 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.


•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

Mode 110 Styrofoam walls formed in reduced gravityGround test comparison between predicted pressure contours and measured wall locations

ACOUSTIC SHAPING


Wall formation process: KC-135 test. Frequency 800 Hz

ACOUSTIC SHAPING


2 2 0 3 2 01 1 0

1 0 0 + 0 2 0 2 3 0 + 1 0 0 1 1 0 + 2 2 0

SIMULATION: PREDICTED WALL SHAPES


•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: 0.1mWavelength: 2mParticle acceleration: 10-5 gResonator intensity: 170 MW/m2

Resonator Q-factor: 10,000Active field time: 13 hrsBeam diameter = 100mCollector efficiency: 10%Collector area w/o storage: 1 sq.km

FAR HORIZON: ASTEROID RECONSTRUCTION?


Can we generate radio waves intense enough?Can we generate radio waves intense enough?

Courtesy of the NAIC - Arecibo Observatory, a facility of the NSF. David Parker / Science Photo Library

In 1974, the Areciboobservatory transmitted a message into outer spacePower of transmission was 20 trillion wattsFrequency 2380 MHz. Wavelength of ~12.6 cmSignal duration: 169 seconds


Support/Service Economy

Tim

e

Earth Launch

Com-sats Research Exploration Military GPSSensing

Maintenance Space Station Robotics RepairFuel

Orbit transfer vehiclesGEO Station

Lunar Resources

Lunar Launcher

Lunar Mining

Lunar Power

Lunar ManufacturingSpace Habitats

Space Based EconomySpace Based Economy

Self-sustaining Economy


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.

Radiation shielding dominated mass of the settlement.

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


PRESENT APPROACH TO BUILDING HABITAT

Solar-heated powder sintering & furnaces, robotic manufacturing on the Moon.

Machinery required to make panels etc.

7

10 to 30 meters at rim pressurized, 30-meter bubbles for micro-climates.

Entire interior pressurized for “shirt-sleeves” comfort.

6

Railcar-sized loads. 8-g, 40km track. Baseball-size loads. High Isp. 30g; 10km run

5

Lunar-equatorial Solar-power fields . 20 launchers; round-the clock launches;

Lunar mass driver gas-powered; H2 from Earth.

4

Shell construction at L-2 followed by slow move to L-5

Construction at L-53

Robotic with Earth-based telepresencesupervision

Human labor on-site for all construction.

2

$1,300 - $14,000 per lb to LEO$110/ lb Earth- LEO1

Present model using Tailored Force Fields (TFF)

1975 models#

Such a project becomes feasible as the centerpiece of a coherent plan for a Space-based economy of the future.


Shield Construction: 1

First 4 lunar-launched segments

•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.

Each regolith-filled “boxcar” is brought by a hybrid gas/ e-mag “shepherd” craft, and guided towards the grid.

• Grid deployment: Cables with attached mini-thrusters are deployed from lunar-launched “box-cars”. Micro-thrusters separatecable rings and start rotation, Tension kept low until first boxcar ring is complete.


Winched tetherCaptures load:Momentum transfer

E-maggrid

“Spider”

•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.

Final positioning

Ring of boxcars joined to form ribs

Shepherds maneuver boxcars into place using e-mag field

Shield Construction:2


Regolith-laden boxcars being delivered by“Shepherd”

Assembledboxcars

The “End Caps”

Radial Cables carry grappling tethers & winches.

StructuralSupport

Side WallFilled with regolith / water

Thrusters

Outer Cable Grid

Legs Gripping Cable

E-Mag Spider

Shield Construction:3

Inner Active E-Mag Grid


• Radius = 1km

• Length = 2km

• Shield Depth 2m

• Rotates at 0.945 rpm for 1g

• Grid current = 15 amps

• 500 loops of cable;

• Cable dia =12.5mm

•Solar Panel area for grid = 350 m2

•Boxcar :2m x 2m x 20m

•Mass per load: 160,000 kg

• Regolith sp.gr.= 2

•10 launchers operational at any time (20 total around lunar equator)

• Shepherd unit current required: 15 amps

• Time to build: 10 yrs.

Construction Parameters

•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.


Bootstrapping Infrastructure

Credit: D. Rawlings


Reduction in Public Expenditure Due to Reduction in Public Expenditure Due to Private IndustryPrivate Industry..

Mass Driver

Mining

Lunar Power

Generation

020406080

100

10 12 14 16Years

$B (Y

2000

)

Lunar Power: (Ignatiev et al, NIAC Phase 1, 2000) $0.40/KwH

Strip Mining on the Moon (extrapolated from 1979): $ 8 B

Lunar Launcher System $ 37 B

Metal cost for cylinder structure: $40B

Total Cost: $150 B

Compare with:

Development cost of Alaskan oil facilities: $67B, total revenue to-date $267B, incl. $55B Fed. Tax. (revenues from known precious resource)

Space Business total annual revenue 2000: $116B(AW&ST, April 2001 revenues from industries & technologies which were created by the new capability

NASA Lunar Base construction cost estimate (published): $112B


“Competitive Delivered Cost” Approach

Cost of Launch Cost from Earth to Moon: $12,000 / kgCost 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 ApproachBusiness 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


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


Concluding RemarksConcluding RemarksTailored electromagnetic force fields enable massive automated construction at low recurring cost. Theoretical approaches to acoustic, optical and electromagnetic force fields unified into a common Rayleigh regime prediction capability (Phase 1)Resonators offers large increase in force and trap stabilityAcoustic shaping proven in flight and ground experimentsOptical trapping proven in microscopy. Microwave and radio wave TFF are efficient in solar-power usage for constructionCosting using a Space-Based Economy approach illustrated using the middle term radiation shield project.Quasi-steady magnetic fields enable telepresence-controlled construction of the radiation shield for human settlements near Earth.Overall cost becomes practical when lunar- and Space-based industries are included.Unlike exploration-focused government programs and isolated business plans for private ventures, a Space-Based Economy approach can unite public support for Space enterprise.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.Coherent plan needs to be articulated for developing a mutually-supportive network of economically-useful projects, with synergistic markets, risk evaluation and pricing.

Please visit http://www.adl.gatech.edu/research/tff/


BACKGROUNDBACKGROUND


Radiation Force Due to Beamed Energy:Coherent beams exert pressure on scattering objects. •Laser propulsion•“Fingers of Sound / Space Drums”

In Space, minor forces exerted over long periods can achieve major results. Force fields of various kinds can be used to build large structures.

TAILORED FORCE FIELDS: CONCEPT

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

Standing wave fields: particles accumulate into walls along stable “traps”.

“Acoustic Shaping” Electromagnetic Shaping??

•Complex surface shapes can be tailored.

• Source only needs to provide small gain over losses -

•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.

Steady potential fields: Objects

Interact with a steady force field.

•Electrostatic Levitation

•Magnetic attraction

•Electromagnetic sails

fR ~ IkR3

2 1 0 1 2

0.06

0.04

0.02

D z( )

z


Scope of the Project: Business scenarios, Rationale.

Functional View: Role of the Organization in SBE. What will it achieve?

Business View: Economic motivation, Costing, Business Drivers, Organization structure/hierarchies

Technology View: Technologies required, Components, Activity areas, R&D.

Deployment: Schedules, Construction plans, Implementation plans

Operations: Detailed procedures, Production plans, Maintenance plans.

Sample Planning Architecture for SBE stakeholders


PowerPreferred Option:

•Lunar Solar-Power Fields made by robotic rovers.

- 20 power plants around the equator

Cost estimate: $0.40 per kilowatt-hr (Ignatiev et al)

Alternatives:

•Nuclear Power Plant on the Moon

•Beamed Power from Space Solar Power Plant

Metal Mining & Extraction•Preferred Option:

•Lunar open-pit mines for iron (est: 4 – 15% of lunar soil is Fe, occurring mostly as oxides).

•Solar-heated metal extraction processes –vapor separation more viable than chemical reduction?

•Robotic fabrication plant shipped to the Moon for box-cars, launcher rails, structural cables, conductors and magnets for launcher

Alternatives:

•Pre-fab delivery from Earth using tethers.

•Steel production on Mars, delivery to Moon.

• Start with earth-delivered boxcars to build initial structure; Ship Fabrication plant to cylinder site; ship steel rods from Mars to cylinder site; land boxcars on Moon and re-use;

•Asteroid resources.

Delivery to the MoonPreferred Option:

•Tether system.

Alternatives:

•Chemical rockets.

•Nuclear rockets

Technology Options


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)

Launchers from the Moon

•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.


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.


CalculationsCalculations

Using the E-mag Force Equation:

n1 1.51:=n2 1.332:=

mn1n2

:=

λ a( ) 20 a⋅:= wavelength

k a( )2 π⋅λ a( )

:= wavenumbe

c = speed of light in vacuum, m/s

rho = density of material being shaped (sand = 2000 kg/m^3)


•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

Cost-Technology Matrix Approach


Estimating the required area needed using solar cellsEstimating the required area needed using solar cells

Solar Intensity from Sun at 1 AU is 1367 W/m2

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%)


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.

ACOUSTIC FIELD RESULTSACOUSTIC FIELD RESULTS

Irregular grain:microgravity

Powder suspended in water: 1-g

Hollow Al2O3 and Al spheres:

microgravity



•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.

OBSERVATIONS & CURRENT PLANS – ACOUSTIC SHAPING


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-basedeconomy plan

Documents

TAILORED FORCE FIELDS FOR SPACE-BASED CONSTRUCTION: …€¦ · • “Bernal sphere” + toroidal agriculture stations on either side. Near 1-g at equator •Shell made of aluminum