advances in dense plasma for fusion power and space propulsion, with george miley, ph.d
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ADVANCES IN DENSE PLASMA FOR FUSION POWER AND SPACE PROPULSION, with George Miley, Ph.D. George Miley, Professor of Nuclear and Electrical Engineering at the University of Illinois and Fusion Studies Lab Director (http://fsl.ne.uiuc.edu) from 1975 to the present, has also been a consultant for Lawrence Livermore Laboratory, Livermore, CA, Argonne National Laboratory, Fusion Power Division, Los Alamos National Laboratory, Dept. of Energy, Idaho Operations Office and Clean Energy Technologies. Recently, George has been researching plasma focus fusion, a new and exciting form of hot fusion and presented the results at STAIF, the Space Technologies Applications Information Forum. Paul Koloc and Eric Lerner will also join a panel discussion with George on the expectations for this energy technology. Dr. Miley spoke about dense plasma focus technology, which is one of the oldest proposed approaches to fusion power. He has also worked some years on cold fusion and reported on that in the first COFE. Miley is a Professor in the Department of Nuclear, Plasma and Radiological Engineering at the University of Illinois, Urbana-Champaign. He is also Director of the Fusion Studies Laboratory.TRANSCRIPT
Presented at:
COFE 2006
Advances in Dense Plasma Focus
R&D for Space Power and Propulsion
George H. Miley
NPRE, University of Illinois, Urbana, Illinois, 61821
Acknowledgements
Largely based on:An Investigation of Bremsstrahlung Reflection in a Dense Plasma Focus Propulsion Device G.H. Miley, Robert Thomas, F.B. MeadPresented at STAIF 2006
andOn Use of D-He3 in Fusion Space PropulsionG. H. Miley, H. Momota, J. Shrestha, S. Krupakar Murali and John SantariusPresented at ANS Summer Meeting 2006
andPropulsion and Power Generation Capabilities of a Dense Plasma Focus (DPF) Fusion System for Future Military Aerospace VehiclesSean D. Knecht, Robert E. Thomas, Franklin B. Mead, George H. Miley, and H. David FroningPresented at STAIF 2006Prospects for Fusion propulsionFrancis Thio Report to FSAC on non-electrical uses of fusion, 2003.
OutlineWhy Fusion Propulsion?
Prior Fusion Propulsion Design Studies
Dense Plasma Focus Background
Applicability for Space Propulsion
DPF System Studies
Study of a key issue, Bremsstrahlung
Conclusions
Equations of Rocket Dynamics – two issues = exhaust velocity and jet power
Constant power - Rocket on full blast
Variable exhaust velocity to match the acceleration profile
exvmdt
dvm
Rocket momentum equation
Rocket energy equation
exexjet vamvmP2
1
2
1 2
3/1
1
0
20
1
2
2
3
m
mP
smt
jet
fFlight time
m0 - m1 = propellant mass burnt on the outbound2
2
0
1
22
DD qq
m
m
F
FDD mm
mq
m
m
00
,
Jet power
Exhaust velocity
v
t
Specific jet power = Pjet / m (kW/kg)
Fusion Will Provide Capabilities Not Available from Other Propulsion Options
10-5 10-410-3 10-2 10-1 101
103
104
105
106
107E
xh
au
st
ve
loc
ity
(m
/s)
Thrust-to-weight ratio
Gas-core fission
Nuclear(fission)electric
Fusion
Chemical
Nuclear thermal
1 kW/kg
10 kW/kg
0.1 kW/kg
JFS 2005 Fusion Technology Institute
Fusion PropulsionWould Enable Attractive Solar-System Travel
Comparison of trip times and payload fractions for chemical and fusion rockets
JFS 1999
Fast human transportFast human transport Efficient cargo transportEfficient cargo transport
JFS 2005 Fusion Technology Institute
The Challenges of Human Interplanetary Travel
Nearest approach to Earth(in 106 km)
Mercury 92Venus 41Mars 77Jupiter 629Saturn 1279Uranus 2725Neptune 4,354Pluto 5,750
Enormous distancesPhysiological hazardsCostsZero-g
Muscle and skeleton deterioration set in after about 100 days
Cosmic RadiationLeukemia and other cancer risks become significant after about one year in-orbit
The Challenges of Human Interplanetary Travel
Propellant exhaust vel > 500 km/sSpecific jet power > 10 kW/kg
Specific Flight Peak Peak Accel- TotalJet Power time exhaust velocity eration jet power(kW/kg) (days) velocity (km/s) (g) (GW)
0.1 710 173 15 0.00008 0.016 1 330 334 33 0.0003 0.16 10 153 806 71 0.0017 1.6 100 70 1740 154 0.008 16
Mission to Jupiter: IMLEO = 640 tonnes; Outbound payload = 200 tonnes; Return payload = 80 tonnes; Mass of propulsion system = 160 tonnes
Vehicle Trajcetory
0
100
200
300
400
500
600
700
800
-200 -100 0 100 200 300 400
xxx (Gm)
yyy
(Gm
)
Robotic Mission to the Outer Planets – Requires less power, but still MWs
Power System Spec. Mass (kg / kW)
Acceleration (g’s)
Payload Mass (kg)
Propellant Mass (kg)
Final Mass (kg)
IMLEO (kg)
Total of Flight (days)
Power (MW)
Isp (sec)
Thrust (N)
0.010.010.010.010.010.01
0.00310.00370.00360.00450.00520.0069
69,99869,96669,99469,99569,98469,962
186,740138,924144,32798,32668,78627,590
100,000100,000100,000100,000100,000100,000
286,740238,924244,327198,326168,786127,590
2312291731097227
3,0003,0033,0013,0013,0023,004
70,50070,50070,50070,50070,50070,500
8,6768,6858,6778,6778,6808,686
PlutoNeptuneUranusSaturnJupiterMars
Propulsion May Offer an Earlier Opportunity for Application of Fusion
The technical priorities for applying fusion to propulsion are somewhat different from those for terrestrial power generation, though the underlying plasma science and technologies have considerable overlapA qualitatively different, if not wider, window of technical options may be available to fusion for propulsion
Propulsion Terrestrial Power Generation
Conversion of fusion energy to thrust
Conversion of fusion energy to electricity
Mass per unit jet power Cost per unit electrical energy
Lower Q may be acceptable Q is a driver for COE
Vacuum without boundary is freely available in space
Vacuum with material boundary is a necessary part of the engineering
Fusion PropulsionConcepts : Past R&D Efforts (Prior to 1999)
1958 - 1978 Fusion Program NASA Rocket Propulsion,” J Lewis Research CenterRoth, J. R., “A Preliminary Study of Thermonuclear. British Planetary Society, 18, 99, (1961)Norman R. Schulze, “Fusion Energy for Space Missions in the 21st Century,” NASA Technical Memorandum 4298, Aug 1991.Hyde, Wood and Nuckolls, Laser fusion propulsion, (1972)Borowski, Spherical torus: 1000 tonne (1987)Santarius, Tandem mirror: 1200 tonne (1988)Orth, Laser fusion propulsion, VISTA: 1800 tonne (1987)Teller, et al., Dipole: 1300 tonne (1992)Carpenter, et al., Thermal barrier tandem mirror: 700 tonne (1993)Nakashima, et al, Field reversed configuration: 1000 tonne (1994)Smith, et al: Antiproton catalysed fusion, ICAN: 700 tonne (1996)Kammash/Emrich, Gasdynamic mirrors: 1000 mT (1995), 400 tonne (1998)Williams et al., Spherical Torus: 1300 tonne (1998)
Fusion Propulsion Concepts Presented at NASA Fusion Propulsion Workshop 2000
1 Spherical torus 10 Z-pinch 2 Electric tokamak 11 Field reversed configuration 3 Levitated dipole 12 Magnetokinetic compression
of compact toroid 4 Electric field bumpy torus 13 Spheromak 5 Laser driven ICF (with fast
ignition) 14 Colliding-beams FRC
6 Antimatter catalysed fusion 15 Tandem mirror 7 Dense plasma focus 16 Gasdynamic mirrors 8 Magnetized target fusion 17 Inertial Electrostatic Fusion 9 Magnetically compressed
compact toroid fusion
Physics Design “Drivers” for Fusion Propulsion
Fusion driver and fuelConversion of fusion energy into thrust
Example: Magnetic nozzle, Direct Energy conversion
Remote re-start capability becomes key issueRadiation shielding of crew and critical components – with a-neutronic fuels, space radiation sets limits for shielding
Enabling fusion technologies – confinement sys for a-neutronic fuels must be developedThermal management – must capitalize on high rejection temperature to minimize weight.
Costs at Initial Orbit in Space (IOS) – set bottom line
Costs at Initial Orbit in SpaceMission cost = Propulsion cost + Costs to achieve mission
objectivesPropulsion cost = Costs at IOS* + In-space Cost + Cost at DestinationCosts at IOS = Launch cost + Cost of producing the
propulsion unitThis must be reasonable ($5 B ~ $10 B?)Launch cost ~ $10,000/kg - today’s cost ~ $1,000/kg in 2025Cost of producing the propulsion unit ~ $20 K - $100K/kgFor a propulsion cost < $5 B Mass of propulsion system
< 250 tonnes
(*IOS – Initial Orbit in Space)
Examples of concepts for some fusion propulsion engines weighing less than 80 MT Dry studies prior to 2000
Flowing Liquid Metal Heat Exchanger/ Breeder
~ 20 m
BURN CHAMBER (Rc ~ 13 mm)
5 m
MagneticExpansion Nozzle
1 m
Accelerator Source
IMPAC
MKCCT: 20 MT, 300 MW (UW)
Colliding-beams FRC: 13 MT, 68 MW (UCI)
MTF: 80 MT, 4 GW
FIGURE 1. Image of 100 MWe IEC Fusion Powered Spacecraft with Ion Thruster Propulsion.
IEC: ? MT, ? MW (jet power)
VISTA: Fusion Propulsion Using Inertial-Confinement Fusion (ICF)
Charles Orth, et al., “The VISTA Spacecraft--Advantages of ICF for Interplanetary Fusion Propulsion Applications,” IEEE 12th SOFE
JFS 2005 Fusion Technology Institute
A-neutronic fusion fuels are essential
D+T = n + He4 = std DOE fuelProblems Neutrons – radiation effects and
materail damage Tritium – radiactive and must breed Direct conversion of energy to thrust
low
Aneutronic – all charged particles D-He3; p-B11;He3-He3
Fusion cross sections illustrate the issues for going to a-neutronic fuels.
UIUC Design study of D-He3 IEC propulsion unit
Illustrates promises and issues Intended for relative near tern – uses DEC and proven ion thruster designIEC shares many features in common with DPF
Image of Fusion Ship II, 750 MWe IEC Fusion Powered Manned Spacecraft with Ion Thruster Propulsion
Orbital path leaving earth showing earth as the central circle.Initial orbit is at Geosynchronous orbit with spacecraft spiraling from that orbit outward to an escape velocity of 2.1 km/s at 29 earth radii.
Launching - Geosynchronous Orbit
Orbital Path Entering Jupiter’s Orbit and Reverse Thrust Braking
Orbital path entering Jupiter’s orbit showing location of stages of the transfer, achieved at full thrust to minimize time
Size Comparison of Several Current Spacecraft Designs & Two Fusion Spacecraft Designs
While fusion ship II deminsions are much large than for a Saturn rocket it must be remembered that Fusion ship II is for a much more demanding Jupiter round trip.
S p a c e S h u t t l e 2 , 0 4 1 M T I s p = 3 5 0 T h r u s t = 3 1 , 0 5 4 k N
S a t u r n V 2 , 7 6 6 M T I s p = 3 0 0 T h r u s t = 3 3 , 3 6 2 k N
I E C F u s i o n S h i p I 5 0 0 M T I s p = 1 6 , 0 0 0 T h r u s t = 1 0 2 8 N
I E C F u s i o n S h i p I I 5 0 0 M T I s p = 3 5 , 0 0 0 T h r u s t = 4 3 6 9 N
Dense Plasma Focus (DPF) – a key approach to p-B11
One of first fusion concepts - originally developed in the mid 1950’s
Prior to ITER funded by US Government (NASA, DOE).
Development still in early stages ; to date experiments with units < 1 MJ have shown the primary feasibility of the concept
Operational Phases of DPF
1. Breakdown phase – Capacitor bank discharged across electrodes ionizing gas and forming a plasma sheath
2. Rundown Phase – J x B force accelerates plasma sheath down length of anode
3. Pinch Phase – Collapsing sheath focuses towards the central axis of the anode forming a plasma where fusion reactions take place
DPF Suitability for Space Propulsion
.
Ideally suited for p-B11 – High density pinch plasma and no B field induced radiation loses
Can provide the necessary exhaust velocity; Specific Impulse from 2000 s to 106 s, trading off lower
values with higher thrust
Can provide the necessary specific energy: ~ 100 times higher than conventional chemical systems
DPF Rocket Schematic – Advantages = simple and low mass structures; efficient thrust
development
DPF Model Assumptions set requirements
Fine structure fusion dominates giving high Ti/Te ratio
Pinch lifetimes, can be extended an order of magnitude longer than present experimental values
Fusion fuel and charged fusion products are confined during entire pinch
Refection of Bremsstrahlung above 50%
Using these assumptions we obtain:
For 500 kN, 2000 sec Isp p-B11 DPF, the required pulse power, energy, and voltage are:
3.07 Q
kV 400
MJ 80
MW 800
0
V
W
Power
Physics Issues Ascertained From Study:
Investigation of achieving a high Ti/Te
Methods of increasing pinch lifetime
Reflection of Bremsstrahlung
Direct energy conversion of plasma; e.g. B field penetration
A Recent Study of Key p-B11 Issue by R. Thomas EAFB- Bremsstrahlung Control
Investigate reflection physics for high energy Bremsstrahlung radiation emission during p-11B fusion Identifies 2 potential approaches - Hohlraum Cavities and Super Multilayers
For 500 kN Thrust Level, ~ 10 m of Reflector Material Ablated per Day (10 Hz Pulsed Continuously)
Classical Heat Transfer Analysis formulated under conditions of thermonuclear interest (Kammash) used to estimate wall ablation and temperatures
Most severe thermal loading at end of discharge when plasma “dumped” on wall
For T > 105 K, plasma forms at wall- it becomes an intense radiator itself
Plasma wall temperatures greatly exceed 106 K--- hence plasma forms at wall- Favorable to prevent ablation and use Holhraum physics for reflectivity
Use extensive data from Inertial Confinement Fusion
(ICF) Hohlraum target studies
Haan, S., “On Target Designing for Ignition,” http://www.llnl.gov/str/Haan.html
Cylindrical gold-plated cavities.
Laser used to implode fuel pellet
Confinement Arises because cavity walls heat up and becomes strong emitter of soft x-ray radiation
For numerical modeling laser replaced by fictitious source of x-rays inside cavity- in our case this is the p-11B reaction
X-Ray Reemission Model
Pakula, R., and Sigel, R., Phys. Fluids 28, 232 (1985).
At t = 0 body is brought into contact with thermal bath
For t > 0, nonlinear wave runs into undisturbed material
Heat wave overtaken by shockwave and ablative heat wave forms
Reemission flux scales by
Sre = 13.0Sint0.46
At a Bremsstrahlung Flux of 1013 W/cm2
the radiation is reflected ~10 times before being lost
Radiation reemission increases with incoming flux
10 reemissions before being lost appear possible
Alternate concept - Reflective Multilayers Provide Reflection over a Wide Energy Range
Layer spacing gradually decreased as a function of depth
Lower energy photons reflected at surface
Tungsten, Lead, Carbides typically used
Joensen, K.D., Nuc. Instr. and Methods in Phys. Research B, 132, pg. 221, 1997.
Multilayer Structures Provide Superior Reflectivities over pure Gold
Tungsten/ Silicon Mirror Used- reflectivities above 30% in entire band
Cutoff at in performance 69.5 keV
Tungsten/ Silicon Carbide successfully reflect over 100 keV (DPF photons > 200 keV)
Limited to very small angles
Joensen, K.D., Nuc. Instr. and Methods in Phys. Research B, 132, pg. 221, 1997.
Limitations of both concepts
Reemission in Hohlraum cavities increase with incoming flux- however high flux leads to higher deterioration of inner walls
Hohlraum physics does not provide reemission over broad energy range
Multilayers currently in use would be destroyed at radiation levels found in p=11B DPF fusion
Multilayers limited to small angles ( < 5 mrad)
Conclusions – Bremsstrahlung
Radiation reemitted 10-18 times depending on Hohlraum size- this may correspond to the 50% re-absorbtion rate previously assumed - further inverse Bremsstrahlung work must be done
Additional multilayer work must be done at high energies (> 150 keV)
Issue #2 – Confinement and low Te/Ti – filament dominated DPF pinches are the key approach
DPF filament formation (Nardi, et al.)
Lerner’s theory for filament dynamics, forming plasmoids
Proposed experiment – controlled filament type of DPF “cage Z-pinch”
Micro-projections anchor filament locations
Filament spacing controllable in Dielectric Barrier Discharges (DBD)
Filament spacing as a function of voltage in the DBD.
Filament DPF simulates the Sandia Labs “Z Machine”, but is much more compact
The Z-pinch principle has been demonstrated with Sandia’s Z accelerator, where very large energy output (1.8 MJ of x-rays) and power levels (up to 230 trillion watts) have been achieved by imploding wire arrays with high load currents (20 MAs).
Propulsion and Power Generation Capabilities of a Dense Plasma Focus (DPF) Fusion System for Future Military Aerospace Vehicles
Presented by Sean D. Knecht for the Space Technology & Applications International Forum (STAIF – 2006), Albuquerque, NM15 February 2006
Evaluation of System Details – assumes reflection and filaments
With system geometry and performance determined and capacitor energy assumed, other system parameters were calculatedMultiplying capacitor energy by specific energy (1.0 – 15.0 kJ/kg) the capacitor mass was found
This mass was assumed to be half of the system mass Thrust-to-weight ratio were then be determined
Capacitor bank volume and system volume were found by assuming a capacitor mass density
Current state-of-the-art is ~ 3.0 MJ/m3
Assuming for advances in the next 20 years, a value of 5.0 MJ/m3 was assumed for this study
Additional power for electricity was found by varying Q and ηprop from their baseline values
Results – Baseline Design Promising
System details that resulted in total system masses between 15 and 25 metric tons were reportedReported baseline parameters Q = 3.0 ηprop = 0.9 Thrust = 500 – 1,000 kN Isp = 1,500 – 2,000 s Capacitor specific energy = 10.0 – 15.0 kJ/kg Thrust-to-weight ratio (T/W) = 20.83 – 44.12 kN/MT System Volume = 25.5 to 54.0 m3
Can we do it??? DPF development, vs. tokomak fusion, has distinct the advantage of allowing small size near-term “products”
Examples -
neutron source for NAA, HS, etc.
Xray source
Light source for semiconductor mfg.
Longer term -- Ultra Hot Fusion Plasmas ProvideMany Materials Processing Capabilities
B.J. Eastlund and W.C. Gough, “The Fusion Torch--Closing the Cycle from Use to Reuse,” WASH-1132 (US AEC, 1969).
JFS 2005 Fusion Technology Institute
Final Comments
Fusion Propulsion is one of the main options for deep space propulsionOf the various fusion propulsion schemes, the DPF, initially using D-He3, then p-B11 is an outstanding option.Much R&D is needed, but compared to the present DOE terrestrial fusion power programs, the DPF development would be cheaper and faster. Also, there are intermediate uses possible, including as a neutron source and for a light source for semiconductor mfg.
Thank you for your attention
for further information or discussion, contactGeorge H. MileyUniversity of Illinois, UC Campus100 NEL, 103 S. Goodwin Ave.Urbana, Illinois, 61802 USA217-3333772; [email protected]
Visit my poster to discuss =The 500-W UIUC/NPL NaBH4/H2O2 Fuel Cell
The active area per cell was 144 cm2 and 15 cells were employed to provide a total stack active area of
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