FusionFusion SpaceSpace Propulsion--Propulsion-- AA ShorterShorter TimeTime FrameFrame thanthan YouYou ThinkThink

JohnJohn F.F. SantariusSantarius

FusionFusion TechnologyTechnology InstituteInstitute UniversityUniversity ofof WisconsinWisconsin JANNAFJANNAF Monterey,Monterey, 5-85-8 DecemberDecember 20052005 D-3He and Pulsed-Power Fusion Approaches Would Shorten Development Times $$$ Fusion D-3HeD-3He FRC,FRC, dipole,dipole, ,spheromak, ST;ST; Pulsed-powerPulsed-power MTF,MTF, PHD,PHD, fast-ignitorfast-

JFS 2005 Fusion Technology Institute 2 D-3He Fusion Will Provide Capabilities Not Available from Other Propulsion Options

107 Fusion )

s 6 / 10 10 kW/kg m (

y 1 kW/kg t i c o l 5 0.1 kW/kg e 10 v t Nuclear

us (fission) Ga s-core fission

ha electric x 4 E 10 Nuclear thermal

Chemical 103 10-5 10-4 10-3 10-2 10-1 1 10 Thrust-to-weight ratio

JFS 2005 Fusion Technology Institute 3 Predicted Specific Power of D-3He Magnetic Fusion Is Attractive (>1 kW/kg)

• Predictions based on reasonably detailed magnetic studies.

Specific Power First Author Year Configuration (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

JFS 2005 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.

1000 Chemical (Isp=450 s) 800 )

s Nuclear

y thermal a 600 (Isp=900 s)

(d Fusion e (1 kW/kg) m i 400 t Fusion ip

r (10 kW/kg) T 200

0 Earth-Mars Earth-Jupiter (29% payload) (4% payload)

JFS 1999 JFS 2005 Fusion Technology Institute 5 Key Fusion Fuels for Space Propulsion

1st generation fuels: 2nd generation fuel: D + T → n (14.07 MeV) + 4He (3.52 MeV) D + 3He → p (14.68 MeV) + 4He (3.67 MeV)

D + D → n (2.45 MeV) + 3He (0.82 MeV) 3rd generation fuels: → p (3.02 MeV) + T (1.01 MeV) 3He + 3He → 2 p + 4He (12.86 MeV) {50% each channel} p + 11B → 3 4He (8.68 MeV) 10-21 L 1 - s

3 -22 m 10 D-3He H t a

r D-T

n p-11B

o -23 i

t 10

c 3 a He- e

Re D-D 3He 10-24 1 5 10 50 100 500 Ion temperature keV JFS 2005 Fusion Technology Institute 6

H L D-3He Fuel Requires Continuation of the Remarkable Progress of Fusion Physics

• Decades of physics progress created sophisticated tools that will facilitate the development of innovative concepts:

10,000,000,000 1,000,000,000 Computer Chip Memory (Bytes) ITER 100,000,000 10,000,000 JET TF TR 1,000,000 JET TF TR ¾ Experimental 100,000 JET JET TF TR techniques 10,000 PDX JET 1,000 DIII-D Achieved (DHe3) ¾ DIII Achieved (DD) Diagnostics 100 PLT Achieved (DT) Pro jected (DT) ¾ Computational 10 Alcator C modeling 1 (Watts) 0.1 ¾ Theory ATC, Alcator A 0.01 1970 1975 1980 1985 1990 1995 2000 2005 2010 Year

JFS 2005 Fusion Technology Institute 7 D-3He Fuel and High β Relax Engineering Constraints

• Reduced flux allows 1 D-T ¾ Smaller radiation shields, e s D-D a

e ¾ Smaller magnets, m l s e r a l

p ¾ Less activation, g r e n o 3 ¾ Easier maintenance, and r ed

fa He:D -1 10 =1:2 o ¾ Potentially, proliferation- i n s o u r fy t proof fusion power plants. u

e burn on nm n fraction = 50% 3 • Increased charged-particle s o He:D i as t c =1:1

a flux allows direct energy r 3He:D=3:1 Ff conversion to thrust or 10-2 1 10 100 electricity. Ion temperature keV ¾ Nonlinear gain in useful power / radiator mass H L ‰ Pthr/Mrad α η/(1-η)

JFS 2005 Fusion Technology Institute 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 Power Density Relative to a D TFRC with 85%and B 3T reach at least 20 T. - b= = ¾ Fusion power density scales as 2 4 2000 β B . 1000 x ¾ Potential power-density 1000 100 x 10 x improvement by increasing 1 x 0 β and B-field appears at right. 1 20 0.75 15 0.5 10 b 0.25 5 B T 0

JFS 2005 Fusion Technology Institute H L 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.

Expanded Not to scale FRC core region flux tube to reduce heat

flux

Neutrons Bremsstrahlung ThrustThrust Charged particles

JFS 2005 Fusion Technology Institute 10 Low Radiation Damage in D-3He Reactors Allows Permanent First Walls and Shields to be Designed

120

C) 0

°

(

e UWMAK-III (Mo) ARIES-IV (SiC) ARIES-I (SiC)

r

u 100

t

a

r 0

e p UWMAK-II (AS) m 800

e

T ARIES-RS (V) TITAN (V)

l HSR (AS) WITAMIR-I (FS)

a

r ARIES-II (V)

u t 600 ASRA-6C (AS) ARIES-ST (FS) c ARIES-III

u Apollo-L3 MARS (FS)

r

t NUWMAK (Ti) MINIMARS (FS)

S

m 400

u STARFIRE (AS)

m UWMAK-I (AS) i UWTOR-M (FS)

x

a Apollo-L

M 200 “Permanent DT Fuel life regime D3He Fuel for steel 0 0 1000 2000 3000 Maximum dpa per 30 Full Power Years

JFS 2005 Fusion Technology Institute 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 Low- activation Class C Tenelon HT-9 Low- steel activation Tenelon

Deep Geologic Burial HT-9 steel

JFS 2005 Fusion Technology Institute 12 Fusion Rockets Would Provide Electricity Production and Materials Processing Capabilities at Destination

• Direct conversion to electricity • Plasmas provide many materials could take advantage of the processing capabilities. natural vacuum in space.

B.J. Eastlund and W.C. Gough, “The Fusion Barr & Moir experiment, LLNL Torch--Closing the Cycle from Use to (Fusion Technology, 1973) Reuse,” WASH-1132 (US AEC, 1969).

JFS 2005 Fusion Technology Institute 13 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. L.J. Wittenberg, J.F. Santarius, and G.L. Kulcinski, “Lunar Source of 3He for Commercial Fusion Power,” Fusion Technology 10, 167 (1986).

JFS 2004 Fusion Technology Institute, University of Wisconsin 14 Well-Developed Terrestrial Technology Gives Access to ~109 kg of Lunar 3He

• Bucket-wheel excavators • Bulk heating • 33 kg 3He / year • Heat pipes • ~600 tonnes volatiles / year • Conveyor belt • 556 km2 / year • v = 23 m / h

JFS 2005 Fusion Technology Institute 15 Lunar 3He Mining Produces Other Useful Volatiles

JFS 2005 Fusion Technology Institute 16 D-3He Field-Reversed Configuration (FRC) Appears Attractive for Fusion Propulsion

• FRCs possess key desired • Recent encouraging results: characteristics for D-3He fusion: ¾ Emerging understanding of why FRCs appear far more stable than ¾ Very high β≡Pplasma/PB-field ¾ Linear external B field MHD theory predicts. ¾ Cylindrical geometry 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 Fusion Technology Institute 17 Spherical Torus Space Propulsion Would Benefit from the Substantial DOE ST Research Effort

• Very low aspect-ratio version of the . • High β, implying high power density. • Critical issues: recirculating power and providing thrust.

• Glenn Research Center design: C.H. Williams, et al., NASA TM 2005- 2 m 213559.

Pegasus ST experiment, Univ. of Wisconsin

2 m

JFS 2005 Fusion Technology Institute 18 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 Fusion Technology Institute 19 Magnetized-Target Fusion (MTF)

• Ionized material from the fusion micro-explosion would reflect from • Plasma jets a diverging would converge, magnetic nozzle to compress, and produce thrust. ignite a magnetized plasmoid. • Plasma-jet version invented by Francis Thio.

Magnetized-Target Fusion artist’s conception from JFS 2005 MarshallFusion Space Technology Flight Institute Center 20 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. Magnetic BURN CHAMBER Expansion Chamber (Dch ~ 25 mm) Accelerator Source

1 m

~ 30 m 10-60 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

3 DD or D He 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$. JFS 2005 Fusion Technology Institute 23 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.

JFS 2005 Fusion Technology Institute 24 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).

JFS 2005 Fusion Technology Institute 25