on the Pulsed Fission Fusion Propulsion Concept€¦ · Initial Pulsed Nozzle Model • Test...
Transcript of on the Pulsed Fission Fusion Propulsion Concept€¦ · Initial Pulsed Nozzle Model • Test...
Marshall Space Flight CenterNational Aeronautics and Space Administration
Progress on the Pulsed Fission‐Fusion Propulsion System Concept
Robert B. Adams, Ph.D.ER24/Propulsion Research and Technology BranchGeorge C. Marshall Space Flight CenterNational Aeronautics and Space Administration
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Jason Cassibry, Ph.D., Kevin SchilloPropulsion Research CenterDepartment of Mechanical and Aerospace EngineeringUniversity of Alabama in Huntsville
https://ntrs.nasa.gov/search.jsp?R=20140008798 2020-06-09T10:14:47+00:00Z
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PuFF Concept
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Introduction to PuFF
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Magneticnozzle coils
Magneticfield lines
Lithium linerand radiation
shield
Cathode
D‐T fuel
UF6 fuel
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Operation of a Z Pinch
Anode
ICathode
Vaporized Wire Array
Plasma Cylinder
Evacuated Chamber
B, Magnetic Flux
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DT FRC TargetPlasma
Fissionableliner
Axial and Radial Thermal conduction
Fusion heating power
Bremmstrahlung and Cyclotron Radiation
MagneticField Lines
Fissionheating power
Neutron inducedFast fission reactions
Fission/DT FRC Fusion TargetLoss Mechanisms included in ModelHeating Mechanisms Included in Model
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Fusion Power Balance
• Parameter space for ignition
• Greatly broadened with embedded magnetic field
• Marginally improved with 6Li and thorium liners
• Significantly enhanced with uranium liners (235U and 238U)
Synchrotron Radiation Dominates
Fission Power Dominates as Neutron Count
Becomes Significant
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Parameters within net Power Increase
Choose R = 10‐5 at 15 keV. Let R = 1 mm, thickness of uranium liner is 5 mm, length of target is 2 cm Density of DT target is 0.1 kg/m3
Total energy in DT target is only ~5 kJ, 1% of Charger 1 stored energy
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• Solve with Smooth Particle Electromagnetic Variant of Finite-Difference Time Domain (FDTD) method
• FDTD well documented, highly accurate grid-based method for analyzing the time evolution of electric and magnetic fields, utilized in PIC codes
• Can interpolate charged fluid particles to grid to model conductivity or charge and current density
Maxwell’s Equations
• Solve with Smooth Particle Hydrodynamics (SPH)• Gridless Lagrangian technique• Vacuum/plasma boundary well defined• Leverage same engine as Maxwell Equation Solver
Multifluid Equations of Motions
Both methods yield to ‘vectorized’ coding, making multiprocessor (parallel) computing easy
Our Approach: Solve Maxwell's Equations Coupled to Multifluid (Ions, Electrons, Neutrals) Equations of Motion
Marshall Space Flight CenterWhat is SPH?
Numerical method for approximating probability densities over a domain of particles.
Developed initially to model stars by Monaghan, et al, in 1977. Currently used mostly in hydrodynamic modeling and CG effects in
film and video games.
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How does SPH work?
Integral interpolant:
I , d ′
A – quantity measured (density, temperature, etc.)W – differentiable kernel functiondr‘ – volume differentialh – smoothing length.
Summation over mass elements:
s ,
Similar to density probability calculations.How quantities are accurately calculated with a small particle domain.
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Run SPFMax
define_constants
read_input Input file?
Yes
No
run (inputfile)
input_default
set_item_defaults
define_geometryitem(ii)
GMSH?
Yes
No
load_gmsh2(filename)
define_particles
set_default_if_needed
define_static_particles
define_electromagnetic_particles
define_physics_models
define_circuit_models get_circuit_particles
define_equations_of_motion
define_numerics
run_sph_solver
Maxwell_equations
circuit
set_input_defaults
check_for_material_database
set_matter_defaults
‘brick’
isstatic?Maxwell?
emcount + 1
last_block= ‘vacuum’last_block= ‘vacuum’
Yes
set_matter_defaults
set_default_if_needed
particle
isstatic?
Yes
No
Maxwell?
Yesinpolyhedron
NoNo
initialize_thermodynamic_state
amperes_law
circuit_rlc
circuit_constant
faradays_law
hydro_Lorentz
RK1
em_leapfrog
kernel_cubicspline
hydro
motion
continuity
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_ p _run_sph_solver
While notdonep _ _ pupdate_time_step
Maxwell?
Yes
p _ pupdate_emparticles
No
time = time +dtelectric_particle_ time_integrationelectric_particle_ time_integration
Yes
particle_time_integration
particle_time_integration
No
hydro
_ p _save_output_data
update_emparticles
Yes
No
p _pupdate_particles
save_output_data
export_to_cassplot
output_initialize_variables
Plot data
Yes
g _ p_neighbor_lookup_rh
get_local_electromagnetic_fields
vab
eos p _pupdate_particles
obj.nbrs
obj.r
g _ p_ pneighbor_lookup_spacial
obj.nbrs_mutual
obj.r_mutual
Maxwell?
Maxwell?
YesNo
get_magnetic_neighbors_for_electric
get_electric_neighbors_for_magnetic
get_fluid_neighbors_for_electric
get_electromagnetic_transport
g _ _ y _ _ _get_static_hydro_bcs_for_fluid
g _ _ _ _get_wall_bcs_for_fluid
p _pplot_particles
set_cell_index_geometry_parameters
_ pset_cell_index_geometry_parameters
_spatial
update_staticparticles
isstatic?Yes
No
_ pkernel_cubicspline
Else
isstatic?Yes_ _ pkernel_mutual_cubicspline
spline(p,ep)kernel_mutual_cubic-
spline(p,ep)
spline(p,mp)kernel_mutual_cubic-
spline(p,mp)
No
If 0isstatic? Yes
Yes
isstatic?
Yes
Else g _ _get_vacuum_nodes
get_fluid_neighbors_for_electric
g _ _ _ _get_wall_bcs_for_fluid
Maxwell?
isstatic?
Else
update_staticparticles Yes
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Equations of motion (planned)Equations of motion (completed)
Transport effects,which can be basedon nonequilibrium
distribution functions(kappa and power law)
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Initial Pulsed Nozzle Model
• Test thermal expansion of gas nozzle with various initial conditions
• Nozzle geometry• Gas
• Temperature• Density• Radius• Length• Composition
• Lays ground work and expectations for magnetic nozzle
Nozzle wall
Initial gas from z-pinch
Direction of motion
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Preliminary results
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Preliminary results
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Preliminary results
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Preliminary results
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Preliminary results
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NIAC Phase I Goals
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Crewed Mars Mission Concept
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Mission Concepts
Mars 90 Mars 30 Jupiter 550 AU
Outbound Trip Time (days) 90.2 39.5 456.8 12936Return Trip Time (days) 87.4 33.1 521.8 n/aTotal Burn Time (days) 5.0 20.2 6.7 11.2Propellant Burned (mT) 86.3 350.4 115.7 194.4Equivalent DV (km/s) 27.5 93.2 36.1 57.2
22Figure 3 Mars 90 Day Transfer Trajectories
Mars OrbitEarth OrbitTransfer Traj OrbitTransfer Trajectory
Mars OrbitEarth OrbitTransfer Traj OrbitTransfer Trajectory Polsgrove, T. et al. Design of Z‐Pinch and Dense
Plasma Focus Powered Vehicles, 2010 AIAA Aerospace Sciences Meeting
• Engine• Isp = 19,400 sec• T = 38 kN• 10 Hz pulse freq.
• Vehicle• Mdry = 552 mT• Mpay = 150 mT• 30% MGA
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Mating SPFMaX and MCNP
SPFMax gives• Ability to model 3d effects• Can propagate magnetic fields in vacuum• Easily editable
MCNP• Track neutron life, fission reactions• Flexible geometries
Second half of NIAC is to run codes concurrently• synchronize neutron population vs. time• Optimize energy output
- As function of geometry- As function of composition
– Mix of UF6, D‐T– Lithium liner thicknesses
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• Gasdynamic nozzle performance to be compared with magnetic nozzle to assess loss mechanisms in magnetic nozzles, e.g.
• Field/plasma instabilities
• Plasma detachment
Direction of current
Single turn Magnetic Nozzle
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NIAC Phase II Experimental Options
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Charger ‐ 1
A test facility for high power and thermonuclear fusion propulsion concepts, astrophysics modeling, radiation physics
Located in the UAH AerophysicsLab at Redstone
The highest instantaneous pulsed power facility in academia – 572 kJ (1 TW at 100 ns)
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Experimental Roadpath
Methodology• Incremental improvements in experimental capability• Benchmark model with experimental data• Can also run any experiments below with lower power systems• Looking for comments and suggestions here!
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Li wire DeuteratedPolyethylene
D‐D slushD‐T slushSolid U238
D‐Li solidSolid U238
Implosion Neutronflux
Plasmastability
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Long Range Plans
Charger II• Construct breadboard PuFF system capable of 10‐20 Hz operation
- Upgrade to flight weight hardware – NASA- Optimize pulse for maximum power output – DOE- Astrodynamics, radiation protection, other research goals ‐ Various
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