UAH

Characterization of Dusty Plasmas for Solar Sails

Robert Sheldon1, Dennis Gallagher2, Mark Adrian2, Paul Craven2, Ed Thomas3, Jr.

1University of Alabama in Huntsville, 2National Space Science and Technology Center,

3Auburn University

STAIF 2002

February 5, 2002

UAHThe Rocket Equation

Vexhaust = Isp * g [d/dt(MV) = 0]

dV = Vexhaust* log( final mass / initial mass)

Material Isp Limitation solid fuel 200-250 mass-starved

LH2/LOX 350-450 mass-starved

Nuclear Thermal 825-925 mass-starved

MHD 2000-5000 energy-starved

ION 3500-10000 energy-starved

Matter-Antimatter ~1,000,000 mass-starved

Photons 30,000,000-both-starved

UAHHow about a fast Pluto flyby?

Voyager=16 years to Pluto. A 1.6 year trip would take dV = 5.8e12m/5e7 s ~100 km/sIsp M_rocket/M_payload100,000 1.1 10,000 2.7 1,000 22,000 400 72,000,000,000

We aren’t going to use chemical rockets if we want a fast Pluto flyby larger than a pencil eraser.

UAHHow do solar sails work?

Momentum of photon = E/c, if we reflect the photon, then dp = 2 E/c. At 1 AU, E_sunlight=1.4 kW/m2==>9N/m2=9Pa

Then to get to Pluto in 1.6 years, we need ~0.004 m/s2 of acceleration. To get this acceleration with sunlight we need a total mass loading of <2gm/m2 !Mylar materials ~ 6 gm/m2

Carbon fiber mesh < 5 gm/m2 ( 3/2/2000)

We are getting close!

UAHIssues in Solar Sails

Mass loading of reflective foilsAlbedo or reflectivity of thin foilsDeployment of thin filmsExtra mass of booms, deployers, etcSurvival of thin films in hostile environment of UV,

flares, particle radiation, charging"packageability, areal density, structural stability, deployability,

controllability, and scalability...strength, modulus, areal density, reflectivity, emissivity, electrical conductivity, thermal tolerance, toughness, and radiation sensitivity." Gossamer AO

UAHWhat About The Solar Wind?

Solar wind density = 3/cc H+ at 350-800 km/sH+ Flux thru 1m2/s= 1m2*400km*3e6/m3=1.2e12

Pressure = 2e-27kg*1.2e12*400km/s = 1nPa

That’s 1/10,000 the pressure of light!

But Jupiter's magnetic size is HUGE =size of full moon. Winglee's idea.

UAHPlasma Sail Capabilities

It isn’t pressure, it’s acceleration we want. A plasma sail that is lighter than a solar sail will achieve higher acceleration

Magnetic fields don’t weigh much for their size.

Trapped plasma inflates the magnetic field, e.g. Jupiter is pumped up by Io.

Robust

UAHRobust

Mass loading of foils, extra mass of booms?

No support structures! B-fields weigh nothing!

Deployment of thin films?

B-fields are self-deploying. Simple!

Survival of thin films in hostile environment of UV, flares, particle radiation, charging?

B-fields are indestructible! Long-lasting. Robust."packageability, areal density, structural stability, deployability,

controllability, and scalability...strength, modulus, areal density, reflectivity, emissivity, electrical conductivity, thermal tolerance, toughness, and radiation sensitivity." Gossamer AO

UAH

Dusty Plasma Sails

UAHHybrid Vigour

Q: Can we combine a sunlight sail having high light pressure, with a robust plasma sail (M2P2) having easy deployment?

A: Yes, by suspending opaque material in M2P2.For each 1% change in albedo, we increase the thrust by

50X compared to solar wind alone (at Earth orbit).Optically thick plasma < 1% opacity

Narrow absorption lines = little opacity at the estimated densities (<1012/cc)

Rare-Earth oxides (many atomic lines)Polycyclic Aromatic Hydrocarbons

Diffuse Interstellar Bands (broad absorption lines)

UAHPolycyclic Aromatic Hydrocarbons

1. Phenanthrene2.Anthracene3.pyrene4.benzanthracene5.chrysene6.naphthacene11.triphenylene12. o-tophenyl13. benzopyrene14. p-tophenyl15. benzopyrene16. TPN17. PhPh18. coronene

UAHDiffuse Interstellar Bands

UAHAdvantages of Dust

As we move from atomic to molecular ions, the number of electronic transitions increase, giving broader absorption lines.

At some point, we encounter bulk properties of the "cluster", leading to geometric absorption, Mie scattering, etc.

This material, >109 atoms, is generally referred to as "dust", and charged dust in the presence of a charged gas, is called "dusty plasma".

Q: Can we trap/hold a dusty plasma in our magnetic bubble?

UAHHypothetical Dust Sail

Let’s suppose that we find an opaque dusty plasma material for our sail that weighs the same as the propellant ~ 100 kg. Then let satellite + propellant + payload =300kg

30 km diameter with 2% opacity(600m w/ 100% opacity) = 91nPa64 N / 300 kg = 0.21 m/s2 = 2% of g!36 days to Mars72 days to Jupiter7.4 months to Pluto

UAHDusty Plasmas

Charged dust, when combined with a plasma, scatters light, and can form a "Coulomb crystal"

Auburn University University of Iowa

UAH• Scaling Up

Problem: if dust fills the volume of the plasma sail, say, like a vacuum cleaner bag, THEN the dusty sail scales up very poorly.

Mass ==> Volume, Force==>AreaTHEREFORE: Mass loading= Mass/Area ==> Size!

e.g. A small sail looks good, a big one bad.

Can we confine the dust to a 2-D layer and improve the scaling (b/c Mass/Area=>const.)?

YES! Several recent papers show the way.

UAHMagnetized, levitated dust

UAHSaturn's Rings in the Lab

Charged dust is injected close to a spinning magnet

A dust ring is trapped in the vicinity of the magnet (bad fax!)

Toshiaki Yokota, Ehime Univ., April 2001.

UAHImportance of rings

Spinning the magnet produces E = v x B

Electric forces confine dust to the equatorial plane.

Charging the magnet produces analogous behaviour (Phys.Rev).

Can we combine the two approaches to achieve both dust & plasma confinement?

UAHUAH Spinning Terrella

Bell jar, oil roughing pump, HV power supply, Nd-B ceramic magnet

Needle valve used to control the pressure from 10-400 mTorr

UAHNegative Biassed Magnet

UAHGossamer S/C grant from NASA

MSFC/NSSTC Suspend single particle in a quadrupole Paul-trap. Measure the force generated by a 2W 532nm laser Study the scattered light to compare with Mie theory. Optimize the size / composition / charge / UV UAH/NSSTC Levitate many particles in electric field w/magnet Parameterize the stability regime of dusty plasmas Characterize the magnetization of dusty plasmas Optimize the size / composition / charge / UV Auburn Use PIV to understand the dusty dynamics

UAHPhase 1: Spinning Terrella

UAHDust Levitation

Plasma is confined to magnet plane. Dust follows E// along magnetic field lines. Thus magnetized plasma provides the confinement for unmagnetized dust grains.

UAHDust bunnies

UAHDust Sheet

UAHPhase 1: MSFC/NSSTC

UAHDust Grain Laser Pressure

UAHDusty Sail Mass Loading

Mass Loading g/m2 per micron

0

2

4

6

8

10

12

0 1 2 3 4 5 6

Dust radius in microns

Mas

s lo

adin

g in

g/m

2

UAHKilogram/Newton vs. Grainsize

Kg/N at different dust radii

0

500

1000

1500

2000

2500

0 1 2 3 4 5

UAHDusty Sail Parameters

Calculation of Dusty Plasma Propulsion

solar const 1.34E+03 Watt/m^2 Gravitation G6.67E-11 mks Sun power 3.92E+26 watts dust ring thick1.00E+00 mSiO2 density 1.90E+03 kg/m^3 Sun's mass1.97E+30 kg sail-Sun 1.49E+11 m 532nm cross section1.18E+00Earth-Sun 1.49E+11 m Earth's mass5.98E+24 kg solar irrad 1.41E+03 watt/m^2

solar press 4.68E-06 Pa

dust radius volume/grainmass/grain area/grain force w/efficgrains/N mass/N sun gravity buoyancy dust ring voldust densitydust mass densmass load(microns) (m^3) (kg) (m^2) (N) (#/N) (kg/N) (N) (Fr / Fg) (m^3/N) (#/cc) (kg/m^3) (g/m^2)

0.10 4.19E-21 7.96E-18 3.14E-14 1.74E-19 5.76E+18 45.83 4.71E-20 3.69E+00 2.14E+05 2.70E+07 2.15E-04 2.15E-010.15 1.41E-20 2.69E-17 7.07E-14 3.91E-19 2.56E+18 68.74 1.59E-19 2.46E+00 2.14E+05 1.20E+07 3.22E-04 3.22E-010.20 3.35E-20 6.37E-17 1.26E-13 6.95E-19 1.44E+18 91.65 3.77E-19 1.84E+00 2.14E+05 6.74E+06 4.29E-04 4.29E-010.25 6.54E-20 1.24E-16 1.96E-13 1.09E-18 9.22E+17 114.57 7.36E-19 1.47E+00 2.14E+05 4.32E+06 5.37E-04 5.37E-010.30 1.13E-19 2.15E-16 2.83E-13 1.56E-18 6.40E+17 137.48 1.27E-18 1.23E+00 2.14E+05 3.00E+06 6.44E-04 6.44E-010.35 1.80E-19 3.41E-16 3.85E-13 2.13E-18 4.70E+17 160.39 2.02E-18 1.05E+00 2.14E+05 2.20E+06 7.51E-04 7.51E-010.40 2.68E-19 5.09E-16 5.03E-13 2.78E-18 3.60E+17 183.31 3.01E-18 9.22E-01 2.14E+05 1.69E+06 8.59E-04 8.59E-010.45 3.82E-19 7.25E-16 6.36E-13 3.52E-18 2.84E+17 206.22 4.29E-18 8.19E-01 2.14E+05 1.33E+06 9.66E-04 9.66E-010.50 5.23E-19 9.95E-16 7.85E-13 4.34E-18 2.30E+17 229.13 5.89E-18 7.37E-01 2.14E+05 1.08E+06 1.07E-03 1.07E+000.60 9.05E-19 1.72E-15 1.13E-12 6.25E-18 1.60E+17 274.96 1.02E-17 6.15E-01 2.14E+05 7.49E+05 1.29E-03 1.29E+000.70 1.44E-18 2.73E-15 1.54E-12 8.51E-18 1.18E+17 320.79 1.62E-17 5.27E-01 2.14E+05 5.51E+05 1.50E-03 1.50E+000.80 2.14E-18 4.07E-15 2.01E-12 1.11E-17 9.00E+16 366.62 2.41E-17 4.61E-01 2.14E+05 4.21E+05 1.72E-03 1.72E+000.90 3.05E-18 5.80E-15 2.54E-12 1.41E-17 7.11E+16 412.44 3.43E-17 4.10E-01 2.14E+05 3.33E+05 1.93E-03 1.93E+001.00 4.19E-18 7.96E-15 3.14E-12 1.74E-17 5.76E+16 458.27 4.71E-17 3.69E-01 2.14E+05 2.70E+05 2.15E-03 2.15E+001.50 1.41E-17 2.69E-14 7.07E-12 3.91E-17 2.56E+16 687.40 1.59E-16 2.46E-01 2.14E+05 1.20E+05 3.22E-03 3.22E+002.00 3.35E-17 6.37E-14 1.26E-11 6.95E-17 1.44E+16 916.54 3.77E-16 1.84E-01 2.14E+05 6.74E+04 4.29E-03 4.29E+002.50 6.54E-17 1.24E-13 1.96E-11 1.09E-16 9.22E+15 1145.67 7.36E-16 1.47E-01 2.14E+05 4.32E+04 5.37E-03 5.37E+003.00 1.13E-16 2.15E-13 2.83E-11 1.56E-16 6.40E+15 1374.81 1.27E-15 1.23E-01 2.14E+05 3.00E+04 6.44E-03 6.44E+003.50 1.80E-16 3.41E-13 3.85E-11 2.13E-16 4.70E+15 1603.94 2.02E-15 1.05E-01 2.14E+05 2.20E+04 7.51E-03 7.51E+004.00 2.68E-16 5.09E-13 5.03E-11 2.78E-16 3.60E+15 1833.08 3.01E-15 9.22E-02 2.14E+05 1.69E+04 8.59E-03 8.59E+004.50 3.82E-16 7.25E-13 6.36E-11 3.52E-16 2.84E+15 2062.21 4.29E-15 8.19E-02 2.14E+05 1.33E+04 9.66E-03 9.66E+005.00 5.23E-16 9.95E-13 7.85E-11 4.34E-16 2.30E+15 2291.34 5.89E-15 7.37E-02 2.14E+05 1.08E+04 1.07E-02 1.07E+01

Mass Loading g/cm2 per micron

0

2

4

6

8

10

12

0 1 2 3 4 5 6

1.0E-02

1.0E-01

1.0E+00

1.0E+01

0 1 2 3 4 5

Kg/N at different dust radii

0

500

1000

1500

2000

2500

0 1 2 3 4 5

UAHConclusions

While apparently "one-way", it can be combined with gravity assist, momentum-tethers, etc to provide complete round-trip travel to the planets.

What a dusty sail lacks in efficiency, it makes up for in deployment, weight, and durability, giving a new meaning to the word "gossamer".

Three micron diameter SiO2 dust is shown to have 3g/m2 mass loading at not-unreasonable densities

One micron dust is expected to have ~1 g/m2 mass loading