1. Propagating Magnetic Wave Accelerator (PMWAC)
for Manned Deep Space Missions
Propagating Magnetic Field
Magnetized Plasma Toroid (from 2D MHD calculation)
Helical Transmission Coil
Parameter First Stage Final
System length 5 m 25 m
Plasma mass mp : 0.2 mg D2 (same)
Final plasma velocity: 3x105 m/sec (Isp = 30,000 s) 1x106 m/s
Acceleration (Force): 2x1010 m/s (4 kN) (same)
Thrust Power (0.2 kHz rep) 2 MW 20 MW
2. Propulsion Requirements for Deep Space
Missions
• High Specific Power - α=(kWthrust/kgspaceship)
α > 1 kW/kg
• High (and variable) exhaust velocities vex
max vex ~ 104 km/s (Isp = vex/g ~ 106 s)
• Continuous power with near zero maintenance for
months
3. Trip Time and the Specific Power
Requirement
Accelerating a mass Mss over a time=τ=implies a power P where:
Mssvc
τ
≈
2
2
P
One defines a characteristic velocity vc:
vc = (2α τ )1/ 2
where=α=is the specific power.
The trip time=τtrip=to go a distance L is given roughly as:
(months) 2L(astronomical units)
1/ 3
2 / 3
trip
2 L
c
trip
(kW/ kg)
v
α
τ ≈ τ =
4. Rapid Manned Mars Mission Power Requirement
30 day
stay
Mars
Sun
Earth
2 1 0 1 2
2
1
0
1
2
A.U.
A.U.
0 10 20 30 40 50 60 70 80 90
3.5
3
2.5
2
1.5
1
0.5
0
time in days
Isp
(104 s)
S(astronomical units) 2 (kW/ kg) 8 3 ≈
[ ] 1
(months)
τ
α =
for Mss ~ 20 MT, Pthrust = 20 MW
5. Velocity and Energy Requirements for Deep
Space Missions
(α =1 kW/kg)
Destination xtrip ~ 2 A.U. (Mars) ttrip ~ 3 months
xtrip ~ 10 A.U. (Jupiter) ttrip ~ 12 months
Characteristic vMars ~ 125 km/sec
Velocity vJupiter ~ 250 km/sec
Specific εMars ~ 8x109 J/kg
Energy εJupiter ~ 3x1010 J/kg
Propulsion System Exhaust (km/sec)
Chemical 5
Electric 30
FRC at RPPL 250
Thermal Fusion 2000
Fuel Specific Energy
Chemical 1x107 J/kg
Fission 5x1013 J/kg
Fusion 1x1015 J/kg
α=vchar
2/2ttrip
ε=vchar
2/2 =α ttrip
Nuclear Power is Necessary for Deep Space Travel
7. ICF
electron thermal
conduction
MTF ICF
MFE
PHD
MFE
CT Classical
Tokamak
ITER89-P
Mag. Force >
Material Strength
1020 1022 1024 1026 1028 1030 1032
Density (m-3)
1012
109
106
103
100
Plasma Energy (J)
Plasma Density and Energy Regimes
for Different Fusion Concepts
8. ⇔
Shiva Star Facility for MTF
~ 10 MJ
2 Auto Batteries
~10 MJ
High Voltage Energy Storage
V~ 120 kV
Low Voltage Storage
V~ 12 V
10. Field Reversed Configuration (FRC) Propulsion
Azimuthal Current
Center Line
External Field Coils
Closed Field Lines
Separatrix
Open External Field Lines
•Propellant (plasma) is magnetically insulated from thruster wall
•No plasma detachment problem
-plasma (FRC) contained separate a magnetic envelope
•Plasma is thermally isolated from thruster walls
-fully ionized plasma is vacuum isolated
•Both thrust and Isp can be varied easily over a wide range
-change of gas fill pressure is all that is required
•Thrust and Isp are decoupled from plasma thermal energy
-with vdir >> vth theoretical efficiency can approach unity
•Enables a direct, simple method to achieve fusion propulsion
with minimum investment
11. PHD Fusion Rocket
Flowing Liquid Metal
Heat Exchanger/ Breeder
~ 20 m
BURN CHAMBER
(Rc ~ 13 mm)
5 m
1 m
Magnetic
Expansion Nozzle Accelerator Source
From past FRC experiments: τE ~ τN = 1.3x10-12 xs rp
2 n1/2 (xs = rp/Rc)
with n = nfus, rp =1 cm (Rc = 1.3 cm)
with lp/rp= 5 Ep= 50 kJ
rep rate = 200 Hz 17 MW directed thrust power
•FRC formed at low energy (~5 kJ) and relatively low density (~1021 m-3)
•FRC accelerated and compressed by low energy propagating magnetic field (< 0.4 T).
•FRC is decelerated, compressed, and heated as it enters high field burn chamber
•FRC expands and cools converting thermal and magnetic energy into directed thrust
12. FRC Acceleration and Heating Expts. at UW
Formation FRC mass: Accelerator Confinement
0 2.0 4.0
Axial Position (m)
Shot 238
Radius (cm) 40
0
0.4 mg Deuterium
FRC terminal velocity:
vd = 2.5x105 m/s
Average FRC acceleration:
(5 - 30 μsec)
aavg = 9x109 m/s2
FRC Energy (final)
15 kJ
Thermal Conversion of
FRC directed Energy
First pass
of FRC FRC after reflection
in downstream mirror
0 100 200
0.6
0.4
0.2
0
Tp
(keV)
time (μsec)
13. FRC Acceleration Method Employed in UW Expts.
Bupstream
Bdc
Bdown
0
•Upper plot of flux contours taken from numerical calculations for discharge 1647
during the acceleration of an FRC at UW.
•Bottom plot illustrates phasing of the accelerator coils
Each coil in turn is switched on for one complete cycle.
Phase of each coil at time of calculation is indicated by arrow
14. Propagating Magnetic Wave Accelerator
For transmission line:
2 1
vp = 2 =
Z L
For shell capacitor (per unit length):
2 Rc 0 S
Inductance (per unit length):
From these eqs. Solving for Rc
2V S
and finally for the phase velocity:
Power Supply Switch
CP
L
C
Inner helical conductor
Dielectric Shell
Outer conductor
C
LC
V
C
π ε κ ε
=
2 n2
L = μ0 πRc
c2 B2
Rc
κ ε
=
c
2 n
1/ 2
S
3c
R
2V
vP
π
κ ε
=
m/ s
v 1.35x10 1.5
R n
c
5
P =
εS = 5x106 V/m
κ = 2500*ε0
V = ± 25 kV
BaTiO3
1 cm
vP = 106 m/s B = 0.5 T
for Rc = 5.5 cm n = 10 turns/m
16. R
(m)
0.2
0
0.2
6 5 4 3 2 1 0
Z (m)
Time
(μsec)
5
10
15
17.5
20
Resistive 2D MHD Calculation of FRC with
Propagating Magnetic Field (0.4 T)
6.0
4.0
2.0
0
vFRC
(105 m/s)
Vaccel = 30 kV, MFRC =
0 5 10 15 20
Time (μsec)
T
(keV)
1.2
0.8
0.4
0
Ti
Te
17. Time
(μsec)
5
10
15
20
25
30
PMWAC Can Also Be Employed to Provide
High Isp, High Thrust Electrical propulsion
R
(m)
Z
(m)
0.2
0
0.2
6 5 4 3 2 1
0
V = ± 3.5 kV ⇔ Bacc = 0.2 T
a = 1.2x109 g
0 5 10 15 20 25 30
vFRC
(105 m/s)
4.0
3.0
2.0
1.0
0
MFRC = 0.2 mg
T (μsec)
18. Inductive Magnetized Plasma Accelerator Source
Developed with NASA STTR funding at MSNW
Capacitor
Gas feed
Strip-line
feedplates
SS Switch Coil straps
Magnetic field
Magnetized plasma
19. PMWAC Development Program
Phase 1:
•Determine Accelerator Requirements and Parameters
•Design Proto-Accelerator for Electrical Validation
•Construct Accelerator and Measure Electrical Performance
•Develop Full Electrical Model with Plasma Interaction
Phase II:
•Design and Construct Full-scale Accelerator
•Install Accelerator and Demonstrate FRC Acceleration
to Fusion Velocities (~106 m/s).
