Transcript 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.

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
The Rocket Equation
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Vexhaust = Isp * g
[d/dt(MV) = 0]
dV = Vexhaust* log( final mass / initial mass)
Material
Isp
Limitation
solid fuel
LH2/LOX
Nuclear Thermal
MHD
ION
Matter-Antimatter
Photons
200-250
350-450
825-925
2000-5000
3500-10000
~1,000,000
30,000,000-
mass-starved
mass-starved
mass-starved
energy-starved
energy-starved
mass-starved
both-starved
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How about a fast Pluto flyby?
Voyager=16 years to Pluto. A 1.6 year trip
would take dV = 5.8e12m/5e7 s ~100 km/s
Isp
100,000
10,000
1,000
400
M_rocket/M_payload
1.1
2.7
22,000
72,000,000,000
We aren’t going to use chemical rockets if we
want a fast Pluto flyby larger than a pencil
eraser.
How do solar sails work?
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Momentum of photon = E/c, if we reflect the
photon, then dp = 2 E/c. At 1 AU,
E_sunlight=1.4 kW/m2==>9mN/m2=9mPa
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!
Issues in Solar Sails
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Mass loading of reflective foils
Albedo or reflectivity of thin foils
Deployment of thin films
Extra mass of booms, deployers, etc
Survival 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
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What About The Solar Wind?
Solar wind density = 3/cc H+ at 350-800 km/s
H+ 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.
Plasma Sail Capabilities
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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
Robust
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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."
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Dusty Plasma Sails
Hybrid Vigour
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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)
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Polycyclic Aromatic Hydrocarbons
1. Phenanthrene
2.Anthracene
3.pyrene
4.benzanthracene
5.chrysene
6.naphthacene
11.triphenylene
12. o-tophenyl
13. benzopyrene
14. p-tophenyl
15. benzopyrene
16. TPN
17. PhPh
18. coronene
Diffuse Interstellar Bands
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Advantages of Dust
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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?
Hypothetical Dust Sail
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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) = 91nPa
64 N / 300 kg = 0.21 m/s2 = 2% of g!
36 days to Mars
72 days to Jupiter
7.4 months to Pluto
Dusty Plasmas
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Charged dust, when combined with a plasma, scatters
light, and can form a "Coulomb crystal"
Auburn University
University of Iowa
•
Scaling Up
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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==>Area
THEREFORE: 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.
Magnetized, levitated dust
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Saturn'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.
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Importance of rings
Spinning the magnet produces
E=vxB
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?
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UAH Spinning Terrella
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Bell jar, oil roughing pump, HV power
supply, Nd-B ceramic magnet
Needle valve used to control the
pressure from 10-400 mTorr
Negative Biassed Magnet
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Gossamer 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
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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
Phase 1: Spinning Terrella
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Dust Levitation
Plasma is confined to magnet plane.
Dust follows E// along magnetic field
lines. Thus magnetized plasma
provides the confinement for
unmagnetized dust grains.
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Dust bunnies
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Dust Sheet
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Phase 1: MSFC/NSSTC
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Dust Grain Laser Pressure
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Dusty Sail Mass Loading
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Mass Loading g/m2 per micron
12
10
8
6
4
2
0
0
1
2
3
Dust radius in microns
4
5
6
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Kilogram/Newton vs. Grainsize
Kg/N at different dust radii
2500
2000
1500
1000
500
0
0
1
2
3
4
5
-Sun
1.49E+11 m
Earth's mass
5.98E+24 kg
solar irrad 1.41E+03 watt/m^2
solar press 4.68E-06 Pa
Dusty Sail Parameters
adius volume/grainmass/grain area/grain force w/efficgrains/N
mass/N sun gravity buoyancy
ons) (m^3)
(kg)
(m^2)
(N)
(#/N)
(kg/N)
(N)
(Fr / Fg)
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
0.15
1.41E-20
2.69E-17 7.07E-14 3.91E-19 2.56E+18
68.74 1.59E-19 2.46E+00
0.20
3.35E-20
6.37E-17 1.26E-13 6.95E-19 1.44E+18
91.65 3.77E-19 1.84E+00
0.25
6.54E-20
1.24E-16 1.96E-13 1.09E-18 9.22E+17
114.57 7.36E-19 1.47E+00
0.30
1.13E-19
2.15E-16 2.83E-13 1.56E-18 6.40E+17
137.48 1.27E-18 1.23E+00
0.35
1.80E-19
3.41E-16 3.85E-13 2.13E-18 4.70E+17
160.39 2.02E-18 1.05E+00
0.40
2.68E-19
5.09E-16 5.03E-13 2.78E-18 3.60E+17
183.31 3.01E-18
9.22E-01
0.45
3.82E-19
7.25E-16 6.36E-13 3.52E-18 2.84E+17
206.22 4.29E-18
8.19E-01
0.50
5.23E-19
9.95E-16 7.85E-13 4.34E-18 2.30E+17
229.13 5.89E-18
7.37E-01
0.60
9.05E-19
1.72E-15 1.13E-12 6.25E-18 1.60E+17
274.96 1.02E-17
6.15E-01
0.70
1.44E-18
2.73E-15 1.54E-12 8.51E-18 1.18E+17
320.79 1.62E-17
5.27E-01
0.80
2.14E-18
4.07E-15 2.01E-12 1.11E-17 9.00E+16
366.62 2.41E-17
4.61E-01
0.90
3.05E-18
5.80E-15 2.54E-12 1.41E-17 7.11E+16
412.44 3.43E-17
4.10E-01
1.00
4.19E-18
7.96E-15 3.14E-12 1.74E-17 5.76E+16
458.27 4.71E-17
3.69E-01
1.50
1.41E-17
2.69E-14 7.07E-12 3.91E-17 2.56E+16
687.40 1.59E-16
2.46E-01
2.00
3.35E-17
6.37E-14 1.26E-11 6.95E-17 1.44E+16
916.54 3.77E-16
1.84E-01
2.50
6.54E-17
1.24E-13 1.96E-11 1.09E-16 9.22E+15 1145.67 7.36E-16
1.47E-01
3.00
1.13E-16
2.15E-13 2.83E-11 1.56E-16 6.40E+15 1374.81 1.27E-15
1.23E-01
3.50
1.80E-16
3.41E-13 3.85E-11 2.13E-16 4.70E+15 1603.94 2.02E-15
1.05E-01
4.00
2.68E-16
5.09E-13 5.03E-11 2.78E-16 3.60E+15 1833.08 3.01E-15
9.22E-02
4.50
3.82E-16
7.25E-13 6.36E-11 3.52E-16 2.84E+15 2062.21 4.29E-15
8.19E-02
5.00
5.23E-16
9.95E-13 7.85E-11 4.34E-16 2.30E+15 2291.34 5.89E-15
7.37E-02
0E+01
Kg/N at different dust radii
2500
0E+00
.0E-01
2000
0
1
2
3
4
5
1500
1000
500
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dust ring vol
dust densitydust mass mass
dens load
(m^3/N) (#/cc)
(kg/m^3) (g/m^2)
2.14E+05 2.70E+07 2.15E-04 2.15E-01
2.14E+05 1.20E+07 3.22E-04 3.22E-01
2.14E+05 6.74E+06 4.29E-04 4.29E-01
2.14E+05 4.32E+06 5.37E-04 5.37E-01
2.14E+05 3.00E+06 6.44E-04 6.44E-01
2.14E+05 2.20E+06 7.51E-04 7.51E-01
2.14E+05 1.69E+06 8.59E-04 8.59E-01
2.14E+05 1.33E+06 9.66E-04 9.66E-01
2.14E+05 1.08E+06 1.07E-03 1.07E+00
2.14E+05 7.49E+05 1.29E-03 1.29E+00
2.14E+05 5.51E+05 1.50E-03 1.50E+00
2.14E+05 4.21E+05 1.72E-03 1.72E+00
2.14E+05 3.33E+05 1.93E-03 1.93E+00
2.14E+05 2.70E+05 2.15E-03 2.15E+00
2.14E+05 1.20E+05 3.22E-03 3.22E+00
2.14E+05 6.74E+04 4.29E-03 4.29E+00
2.14E+05 4.32E+04 5.37E-03 5.37E+00
2.14E+05 3.00E+04 6.44E-03 6.44E+00
2.14E+05 2.20E+04 7.51E-03 7.51E+00
2.14E+05 1.69E+04 8.59E-03 8.59E+00
2.14E+05 1.33E+04 9.66E-03 9.66E+00
2.14E+05 1.08E+04 1.07E-02 1.07E+01
Mass Lo
12
10
8
6
4
2
0
0
1
Conclusions
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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