Fusion Space Propulsion-A Shorter Time Frame than You Think John F. Santarius
Fusion Technology Institute University of Wisconsin JANNAF Monterey, 5-8 December 2005
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D-3He and Pulsed-Power Fusion Approaches Would Shorten Development Times
D-3He D-3HeFRC, FRC,dipole, dipole, spheromak, spheromak,ST; ST; Pulsed-power Pulsed-powerMTF, MTF, PHD, PHD,fast-ignitor fast-ignitor
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Fusion Rocket
2
D-3He Fusion Will Provide Capabilities Not Available from Other Propulsion Options 10
7
Exhaust velocity (m/s)
Fusion 10
6
10 kW/kg 1 kW/kg
10
5
0.1 kW/kg Nuclear (fission) electric
10
Gas-core fission
4
Nuclear thermal Chemical
3
10 -5 10
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10
-4
-3
-2
-1
10 10 10 Thrust-to-weight ratio
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1
10
3
Predicted Specific Power of D-3He Magnetic Fusion Rockets Is Attractive (>1 kW/kg)
•
Predictions based on reasonably detailed magnetic fusion rocket studies.
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First Author
Year
Configuration
Specific Power (kW/kg)
Borowski
1987
Spheromak
10.5
Borowski
1987
Spherical torus
5.8
Santarius
1988
Tandem mirror
1.2
Bussard
1990
Riggatron
3.9
Teller
1991
Dipole
1.0
Nakashima
1994
Field-reversed configuration
1.0
Emrich
2000
Gasdynamic mirror
130
Thio
2002
Magnetized-target fusion
50
Williams
2003
Spherical torus
8.7
Cheung
2004
Colliding-beam FRC
1.5
Fusion Technology Institute
4
Fusion Propulsion Would Enable Fast and Efficient Solar-System Travel
• Fusion propulsion would dramatically reduce trip times (shown below) or increase payload fractions.
Trip time (days)
1000 800 600 400 200
Chem ical (Isp=450 s) Nuclear therm al (Isp=900 s) Fusion (1 kW/kg) Fusion (10 kW/kg)
0 Earth-Mars (29% payload) JFS 1999
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Earth-Jupiter (4% payload) 5
Key Fusion Fuels for Space Propulsion 1st generation fuels:
2nd generation fuel:
D + T → n (14.07 MeV) + 4He (3.52 MeV) D + D → n (2.45 MeV) + 3He (0.82 MeV) → p (3.02 MeV) + T (1.01 MeV) {50% each channel}
D + 3He → p (14.68 MeV) + 4He (3.67 MeV) 3rd generation fuels: 3He
+ 3He → 2 p + 4He (12.86 MeV)
p + 11B → 3 4He (8.68 MeV)
Reaction rate H m3 s-1L
10-21
10-22 D-T
p-11B
10-23
3He-
D-D 10-24
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D-3He
1
5
3He
10 50 100 Ion temperature HkeVL
Fusion Technology Institute
500 6
D-3He Fuel Requires Continuation of the Remarkable Progress of Fusion Physics
• Decades of plasma physics progress created sophisticated tools that will facilitate the development of innovative concepts: 10,000,000,000 1,000,000,000 10,000,000 1,000,000
¾ ¾ ¾ ¾
Experimental techniques Diagnostics Computational modeling Theory
ITER
Computer Chip Memory (Bytes)
100,000,000
JET
JET TFTR
JET
100,000 10,000
JET
PDX
1,000
DIII-D
A chiev ed (D He3 )
DIII
PLT
100
JET TFTR TFTR
A chiev ed (D D ) A chiev ed (D T)
10
Pro jected (DT)
Alcator C
1 0.1
ATC, Alcator A
0.01 1970
1975
1980
1985
Fusion Power (Watts) 1990
1995
2000
2005
2010
Year JFS 2005
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D-3He Fuel and High β Relax Engineering Constraints
•
Fraction of fusion energy released as neutrons from plasma
1 D-T D-D
Reduced neutron flux allows ¾ Smaller
radiation shields,
¾ Smaller
magnets,
¾ Less
¾ Easier
3
He:D =1:2
10-1 Tritium burn fraction = 50%
10-2
1
10 Ion temperature H keVL
proliferationproof fusion power plants.
•
=1:1
100
Increased charged-particle flux allows direct energy conversion to thrust or electricity. ¾ Nonlinear
gain in useful power / radiator mass
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maintenance, and
¾ Potentially,
3He:D 3He:D=3:1
activation,
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Pthr/Mrad α η/(1-η) 8
D-3He Fuel Could Make Good Use of the High Power Density Capability of Some Innovative Fusion Concepts
•
D-T fueled innovative concepts become limited by neutron wall loads or surface heat loads well before they reach β or B-field limits.
• •
D-T fueled FRC’s (β~85%) optimize at B ≤ 3 T. D-3He needs a factor of ~80 above D-T fusion power densities. ¾
Superconducting magnets can reach at least 20 T.
¾
Fusion power density scales as β2 B4.
¾
Potential power-density improvement by increasing β and B-field appears at right.
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Power Density Relative to a D-T FRC with b=85%and B=3 T
2000
1000 x
1000
100 x 10 x 1x
1
0.75
0.5 b 0.25
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0
10 5 B HTL
15
0 20
9
Plasma Power Flows in Linear Devices Give More Design Flexibility than Flows in Toroidal Devices
• Power density can be very high due to β2B4 scaling, but first-wall heat fluxes would remain manageable. ¾
Charged-particle power transports from internal plasmoid to edge region and then out ends of fusion core.
¾
Magnetic flux tube can be “pinched” on one end by increasing the magnetic field on that side, giving primarily single-ended flow.
• Pulsed concepts gain similar advantages by reflecting plasma from a magnetic nozzle. Not to scale
Neutrons
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FRC core region Bremsstrahlung
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Expanded flux tube to reduce heat flux
Thrust
Charged particles
10
Maximum Structural Temperature (°C)
Low Radiation Damage in D-3He Reactors Allows Permanent First Walls and Shields to be Designed 120 0 UWMAK-III (Mo)
100 0
HSR (AS)
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ARIES-III Apollo-L3
400
ARIES-RS (V) WITAMIR-I (FS) ASRA-6C (AS)
TITAN (V)
ARIES-II (V) ARIES-ST (FS)
MARS (FS) MINIMARS (FS)
NUWMAK (Ti)
STARFIRE (AS) UWMAK-I (AS) UWTOR-M (FS) Apollo-L
200
0
ARIES-I (SiC)
UWMAK-II (AS)
800
600
ARIES-IV (SiC)
0
“Permanent life regime for steel
DT Fuel D3He Fuel
1000 2000 Maximum dpa per 30 Full Power Years Fusion Technology Institute
3000 11
Radioactive Waste Disposal is Much Easier for D-3He Reactors than for D-T Reactors D-3He
D-T
30 full-power years
5 full-power years
Class A Lowactivation Tenelon
Class C Lowactivation Tenelon
HT-9 steel
Deep Geologic Burial HT-9 steel
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Fusion Rockets Would Provide Electricity Production and Materials Processing Capabilities at Destination
• Direct conversion to electricity could take advantage of the natural vacuum in space. Barr & Moir experiment, LLNL (Fusion Technology, 1973)
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• Plasmas provide many 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).
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A Well Documented Lunar 3He Resource Exists
• Lunar 3He concentration verified from Apollo 11, 12, 14, 15, 16, & 17 plus USSR Luna 16 & 20 samples.
• Analysis indicates that ~109 kg of 3He
exists on the lunar surface, or ~1000 y of world energy supply.
• One-way Earth-Mars trip requires ~100 kg 3He.
• 40 tonnes of
3He
would supply the entire 2004 US electricity needs.
• ~400 kg 3He (8 GW-y fusion energy) is accessible on Earth for R&D.
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L.J. Wittenberg, J.F. Santarius, and G.L. Kulcinski, “Lunar Source of 3He for Commercial Fusion Power,” Fusion Technology 10, 167 (1986).
Fusion Technology Institute, University of Wisconsin
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Well-Developed Terrestrial Technology Gives Access to ~109 kg of Lunar 3He
• Bucket-wheel • 33 kg / year • ~600 tonnes volatiles / year • 556 km2 / year • v = 23 m / h 3He
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• • •
excavators Bulk heating Heat pipes Conveyor belt
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Lunar 3He Mining Produces Other Useful Volatiles
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D-3He Field-Reversed Configuration (FRC) Appears Attractive for Fusion Propulsion
• Recent encouraging results:
• FRCs possess key desired characteristics for D-3He fusion: high β≡Pplasma/PB-field ¾ Linear external B field ¾ Very
¾ Cylindrical
geometry
¾ Emerging
understanding of why FRCs appear far more stable than MHD theory predicts.
¾ Attractive
current drive by rotating magnetic fields (RMF) demonstrated.
From Univ. of Washington web page for the Star Thrust Experiment (STX): www.aa.washington.edu/AERP/RPPL/STX.html JFS 2005
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Spherical Torus Space Propulsion Would Benefit from the Substantial DOE ST Research Effort • Very low aspect-ratio version of the tokamak. • High β, implying high power density. • Critical issues: recirculating power and providing thrust.
• Glenn Research Center design: C.H. Williams, et al., NASA TM 2005213559.
2m
Pegasus ST experiment, Univ. of Wisconsin
2m JFS 2005
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The Dipole Configuration Offers a Relatively Simple Design That an MIT/Columbia Team Has Begun Testing Io plasma torus around Jupiter
LDX experiment (MIT)
0.65 m
Dipole space propulsion design: E. Teller, A.J. Glass, T.K. Fowler, A. Hasegawa, and J.F. Santarius, “Space Propulsion by Fusion in a Magnetic Dipole,” Fusion Technology 22, 82 (1992). JFS 2005
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Magnetized-Target Fusion (MTF) •
•
•
Plasma jets would converge, compress, and ignite a magnetized plasmoid. Plasma-jet version invented by Francis Thio.
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Ionized material from the fusion micro-explosion would reflect from a diverging magnetic nozzle to produce thrust.
Magnetized-Target Fusion artist’s conception from 2005 Fusion Technology Institute Marshall Space Flight Center
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Pulsed High Density (PHD) Fusion • Invented by John Slough, Univ. of Washington, who provided this viewgraph. • Experimental program that takes advantage of a very compact, high energy density FRC to reach fusion conditions. ¾ The energy required to achieve fusion conditions is transferred to the FRC via simple, relatively low field acceleration/compression coils. ¾ For FRC in smaller, higher density regime, the requirement on the FRC closed poloidal flux is no greater than what has been achieved ¾ The FRC should remain in a stable regime with regard to MHD modes such as the tilt from formation through burn. BURN CHAMBER Magnetic (Dch ~ 25 mm) Expansion Chamber Accelerator Source 1m
10-60 m
~ 30 m
Flowing Liquid Metal Heat Exchanger/ Breeder 1 - FRC formed at low energy (~3 kJ) and relatively low density (~1021 m-3) 2 - FRC accelerated by low energy propagating magnetic field (~ 0.4 T) to 3 - FRC adiabatically compressed and heated as it decelerates into burn chamber 4 - FRC travels several meters during burn time minimizing wall loading 5 - If necessary, FRC flux and confinement enhanced by spatial “RMF” field 6 - FRC expands and cools converting fusion energy directly into electrical energy
It May be Possible to Efficiently Burn DD or D3He Fuels in Fast-Ignited ICF Targets Cone focus hohlraum Fast ignition laser
Slow compression driver – Laser or HI beams or Z-pinch,….
DT ignitor DD or D3He main fuel
Schematic – not to scale
Energy spectrum convertor
‡ Four unique aspects of ICF for advanced fuels: (1) The required high ignition/burn temperatures (~30/150keV) can be obtained via a precursor DT ignitor region (~10/50keV). (2) The larger driver energies (required by the larger rho-R’s for efficient advanced fuel burn-up) can be offset through fast ignition. (3) Bremsstrahlung is self-trapped in the compressed fuel (4) Tritium for the DT ignitor (~1% inventory) is self-bred as the main fuel burns
• Viewgraph contributed by John Perkins, LLNL.
D-3He Fusion Space Propulsion Can Be Developed Quickly, If the Will Exists
•
•
In parallel, experiment on several concepts with multiple devices. ¾ Winnow. ¾ Provide substantial power and diagnostic capabilities. ¾ Provide sufficient contingency funding and program flexibility to director. Incorporate existing terrestrial fusion research program where possible.
•
Total program cost ~ 6 B$.
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Summary and Conclusions
• Attractive fusion space propulsion options exist. • Development should follow the D-3He and pulsed-power paths of more physics risk and less engineering risk. ¾ Pursue
“survival of the fittest,” starting with sufficient species.
¾ Provided
sufficient program flexibility and contingency
funds. ¾ Estimated
cost < $10 B for a demonstration system in two decades.
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References • • • • • •
UW Fusion Technology Institute: http://fti.neep.wisc.edu/ J.F. Santarius, G.L. Kulcinski, L.A. El-Guebaly, and H.Y. Khater, “Could Advanced Fusion Fuels Be Used with Today's Technology?”, Journal of Fusion Energy 17, 33 (1998). J.F. Santarius and B.G. Logan, “Generic Magnetic Fusion Rocket Model,” Journal of Propulsion and Power 14, 519 (1998). J.F. Santarius, G.L. Kulcinski, and L.A. El-Guebaly, "A Passively Proliferation-Proof Fusion Power Plant," Fusion Science and Technology 44, 289 (2003). L.J. Wittenberg, J.F. Santarius, and G.L. Kulcinski, “Lunar Source of 3He for Commercial Fusion Power,” Fusion Technology 10, 167 (1986). L.J. Wittenberg, E.N. Cameron, G.L. Kulcinski, S.H. Ott, J.F. Santarius, G.I. Sviatoslavsky, I.N. Sviatoslavsky, and H.E. Thompson, “A Review of Helium-3 Resources and Acquisition for Use as Fusion Fuel,” Fusion Technology 21, 2230 (1992).
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