Theoretical and experimental nozzle and corner expansion flows of dissociated and ionized gases.
Gas dynamics of nonequilibrium flows of plasmas and dissociated gases, discussing nozzle and corner expansion flows
Glass, I. I.↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Mass-injection rate from Io into the Io plasma torus
Theoretical arguments to the effect that both plasma and energy are supplied to the Jovian magnetosphere from primarily internal sources are presented. Two major assumptions are made: (1) that Io is the source of plasma for the Jovian magnetosphere, and that the outward flow of plasma from the torus is the means of drawing from the kinetic energy of rotation of Jupiter to drive magnetospheric phenomena; thereby obtaining a new, independent estimate of the rate of mass injection from Io into the Io plasma torus, and (2) that the solar wind supplies neither plasma nor energy to the Jovian magnetosphere in significant amounts. A lower limit to the rate of mass injection into the torus, which on the average must equal the rate of mass loss from the torus, is therefore derivable through adoption of a value for the power expended to drive the various magnetospheric phenomena.
Dessler, A. J.↗
Current driven weak double layers
Double layers in plasmas can be created by different means. For example, a potential difference forms between two plasmas with different temperatures, in a plasma jet flowing along a converging magnetic field, in a quiescent plasma submitted to an external difference of potential, or in a turbulent plasma carrying an electric charge. The first three cases can be current-free, but not necessarily, although the numerical simulations were made under such conditions for the first two points. Apart from the third case, which is mainly of interest for laboratory experiments, these double layers are good candidates for accelerating the auroral electrons to the few kiloelectron volts observed.
Chanteur, Gerard↗
Computing Plasma Interactions Of A Spacecraft
NASCAP/LEO (NASA Spacecraft Charging Analyzer Program for Low Earth Orbit) implements collection of mathematical models and algorithms designed to study electrostatic interaction between cold, dense plasma and spacecraft surfaces. Computes variety of electrostatic, plasma, and flow effects. Appropriate for conditions in which temperature of plasma small in comparison with spacecraft-generated potentials and Debye screening length short in comparison with dimensions of spacecraft. Related NASCAP/GEO (LEW-12973) code (NASA Charging Analyzer Program for Geosynchronous Orbit, denoted as NASCAP) appropriate for conditions which spacecraft differential potentials result from interactions with hot plasma and Debye screening length larger than dimensions of spacecraft. Object-definition portion of NASCAP/GEO code provided as part of package. NASCAP/LEO written in FORTRAN 77 and C language.
Mandell, M. J.↗
Propagation of charge-exchange plasma produced by an ion thruster
A charge-exchange plasma is produced downstream of ion thrusters by collisions between energetic ions and neutrals escaping through the ion optics. The charge-exchange ions flow radially from the thruster beam due to electric fields produced by its density gradient. The propagation of the charge-exchange plasma after it leaves the thruster beam is the subject of this paper. Under the proper conditions there is an 'end-effect' of a long, cylindrical Langmuir probe which allows a significant increase in collected ion current when the probe is aligned with a flowing plasma. This effect is used to determine the charge-exchange plasma flow direction at various locations relative to the ion thruster. A portion of the charge-exchange plasma flows upstream of the ion thruster and can represent a contamination source to electrically propelled spacecraft. The ion current collected by the probe as a function of its angle with respect to the plasma flow allows determination of the plasma density and plasma flow velocity at the probe's location upstream of the ion thruster optics. The density value obtained from the ion current agree to within a factor of two of density values obtained by typical voltage-current Langmuir probe characteristics.
Carruth, M. R., Jr.↗
Direct observations of the solar wind by the mariner ii spacecraft.
Relation between high velocity plasma streams and solar active regions and data on plasma velocity and temperature obtained from Mariner II SPACECRAFT
MARINER II SPACE PROBE↗
A study of gas flow pattern, undercutting and torch modification in variable polarity plasma arc welding
A study on the plasma and shield gas flow patterns in variable polarity plasma arc (VPPA) welding was undertaken by shadowgraph techniques. Visualization of gas flow under different welding conditions was obtained. Undercutting is often present with aluminum welds. The effects of torch alignment, shield gas flow rate and gas contamination on undercutting were investigated and suggestions made to minimize the defect. A modified shield cup for the welding torch was fabricated which consumes much less shield gas while maintaining the weld quality. The current torch was modified with a trailer flow for Al-Li welding, in which hot cracking is a critical problem. The modification shows improved weldablility on these alloys.
Mcclure, John C.↗
Stretched three-dimensional plasma equilibria with field-aligned flow
A three-dimensional equilibrium theory for stretched plasma configurations, such as the earth's magnetotail, is extended to include the effects of field-aligned flow. The MHD equations for this case can be solved in a general way by reduction to a set of ordinary differential equations and an ordinary integral. The solutions represent lowest-order solutions of an asymptotic expansion of the MHD equations for small electric field and weak time dependence. Simplified equations are presented for two-dimensional equilibria and for incompressible flow. Possible magnetospheric applications include the configuration of the geotail near and beyond the termination of the closed field line region, the steady motion of a plasmoid (a plasma bubble severed from the earth) through the distant geotail, and configurations at the magnetopause, the interface between the magnetosphere and the shocked solar wind plasma. For illustration, solutions for the steady motion of a two-dimensional plasmoid through the distant magnetotail are presented.
Birn, J.↗
Electromagnetic Tomography of Radial Flow in the Quark-Gluon Plasma
We present a novel multimessenger approach to extract the effective radial flow of the quark-gluon plasma (QGP) by jointly analyzing thermal photon and dilepton spectra in heavy-ion collisions. A key feature of this method is that it circumvents the need for a directly unmeasurable reference—the photon temperature in the absence of flow—by establishing, within a calibrated model framework, a stable, approximately linear correlation with the dilepton-inferred temperature. This construction defines an experimentally constructible quantity, 𝑣$^{eff}_{𝑟}$, which reflects early-time collectivity and exhibits a strong correlation with the spacetime-averaged radial velocity of the QGP. Together with previous results linking dilepton slopes to the initial QGP temperature, our work establishes a consistent framework for electromagnetic tomography of the QGP. Here, our framework quantifies the experimental precision target, thereby providing a concrete road map for future measurements at RHIC and the LHC and opening a new avenue to probe the early-time dynamics of hot QCD matter.
Collective flow↗
Effect of Plasma Sheaths on Earth Re-entry MHD Processes
The first study of the full coupling between the aerothermodynamics, the magnetohydrodynamics, and the plasma sheaths within earth entry flows is here per-formed. The problem tackled herein is representative of a force-generating MHD patch located between the plenum and the frustum of a capsule entering the earth’s atmosphere at Mach 34. The reactions are obtained from a modified 11-species Park chemical solver. The physical model fully couples the drift-diffusion model for the sheaths to the multispecies Navier-Stokes equations for the plasma flow. The Hall and ion slip effects are taken into consideration within the plasma flow and within the sheaths. The effect of the electrode material on the MHD process is studied. Using thoriated tungsten instead of graphite leads to a four-fold increase in the Lorentz forces and also leads to significantly reduced heat fluxes on the cathode. This is attributed to the much higher electrical conductivity of the thoriated tungsten sheath reducing by orders of magnitude the plasma electrical resistance near the surfaces.
Bernard Parent↗
Effect of Plasma Sheaths on Earth Re-entry MHD Processes
The first study of the full coupling between the aerothermodynamics, the magnetohydrodynamics, and the plasma sheaths within earth entry flows is here per-formed. The problem tackled herein is representative of a force-generating MHD patch located between the plenum and the frustum of a capsule entering the earth’s atmosphere at Mach 34. The reactions are obtained from a modified 11-species Park chemical solver. The physical model fully couples the drift-diffusion model for the sheaths to the multispecies Navier-Stokes equations for the plasma flow. The Hall and ion slip effects are taken into consideration within the plasma flow and within the sheaths. Results obtained indicate that the cathode sheath can exert significant resistance to current flow and thus reduce the MHD-generated force by 40% or more. The effect of the sheath on the MHD force is found to be more pronounced at lower applied magnetic field.
Earth Re-entry↗
Demonstration of Separation Control Using Glow-Discharge Plasma Actuators
Active flow control of boundary-layer separation using glow-discharge plasma actuators is studied experimentally. Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modem low-pressure-turbine airfoil. The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2%) and high (2.5%) free-stream turbulence intensities are set using passive grids. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface-flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the base and controlled flows are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control.
Hultgren, Lennart S.↗
Demonstration of Separation Delay with Glow-Discharge Plasma Actuators
Active flow control of boundary-layer separation using glow-discharge plasma actuators is studied experimentally. Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modern low-pressure-turbine airfoil. The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2 percent) and high (2.5 percent) free-stream turbulence intensities are set using passive grids. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface-flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the base and controlled flows are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control.
Hultgren, Lennart S.↗
Analytical model of plasma response to external magnetic perturbation in absence of no-slip condition
Recent simulation and experimental results suggest that the magnetic island and flow on a resonant surface often do not satisfy the “no-slip” condition in the steady state. A new theoretical model on a nonlinear plasma response to external magnetic perturbation in the absence of a no-slip condition is proposed. The model is composed of the equations for the evolution of both the width and phase of the magnetic island due to forced reconnection driven by the external magnetic perturbation, and the force-balance equation for the plasma flow. When the island width is much less than the resistive layer width, the island growth is governed by the linear Hahm–Kulsrud–Taylor solution in the presence of time-dependent plasma flow. In the other regime when the island width is much larger than the resistive layer width, the evolution of both the island width and phase can be described using the Rutherford theory. The island solution is used to construct the quasilinear electromagnetic force, which, together with the viscous one, contributes to the nonlinear variation in plasma flow. The no-slip condition assumed in the conventional error field theory is not imposed here, where the island oscillation frequency depends on but does not necessarily equal to the plasma flow frequency at the rational surface.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Experimental investigation of magnetoaerodynamic flow around blunt bodies.
Magnetic field effect on flow field and drag of blunt body in partially ionized argon plasma, obtaining electron density and temperature
MAGNETIC EFFECT↗
Method of characteristics for supersonic flow of a guiding centre plasma.
A study of the compressive magneto-acousic waves in a guiding centre plasma shows that the wavefront that emerges point disturbance after a finite time is a simple oblate spheroid with the axis of revolution parallel to the field lines. Thus, in a steady three-dimensional supersonic flow of guiding centre plasma a simple analytic exprencan be obtained to represent the characteristic surfaces. From a proper linear combination of the governing macroscopic equations, the characteristic equation is obtained. It represents the propagation of disturbances on the characteristic surface. The characteristic theory can be used to study the interaction of the solar wind with the moon and possibly with other planetary bodies.
Whang, Y. C.↗
Flow characteristics in the exhaust of a pulsed magawatt gas fed arc
Transient pressure measurement in plasma exhaust flow of 500 microsec duration, discussing discharge temporal behavior and cold gas pressure front existence
Michels, C. J.↗
Hall Magnetohydrodynamic Power Generation and Drag Augmentation Using A Coaxial-Electrode Configuration During Hypersonic Entry
For interplanetary missions, a spacecraft must reduce its relative velocity from orbital speeds of multiple kilometers per second to zero in order to safely land on the surface of a planetary body. During this phase known as planetary reentry, the spacecraft undergoes high speed above Mach 5 up to Mach 30. This hyper-sonic flight regime imposes a strong bow shock in front of the vehicle that imparts extreme aerodynamic and thermal effects. In addition, during portions of this regime, a plasma is formed in the post-shock flow-field around the vehicle due to these high temperatures. Interaction between an applied magnetic field with this electrically conductive fluid, or magnetohydrodynamic (MHD) interaction, can be utilized to convert kinetic energy from the flow into storable electrical energy. Onboard MHD energy generation can benefit the spacecraft by increasing the power of active thermal control components and vehicle control systems during reentry. MHD interaction also exerts a Lorentz body force on the plasma flow that can be manipulated to act as an additional drag force through the vehicle body. MHD drag augmentation can benefit the spacecraft with an additional control mechanism that operates without moving parts. This can be utilized at higher altitudes and subsequently reduce convective heat transfer to the vehicle. MHD interaction with plasma flow suggests that both power generation and drag augmentation can be integrated together in one design. Modern numerical studies have only demonstrated the viability and potential of MHD energy generation and drag modulation separately for implementation into future spacecraft designs [1] [2] [3]. Steeves et. al. presented one possible generator design specifically for reentry vehicles that utilized a modular panel with two embedded electromagnets and two extruding electrodes for air plasma to flow between. Fujino et. al. presented results that indicated increased total drag with a permanent magnet embedded in the blunt body of the Orbital Reentry Experiment (OREX) trajectory. Furthermore, experimental investigations of these two MHD applications have been limited and separate due to the difficult technical nature of experimental de-sign and analysis. For MHD energy generation, there have been two designs which used a cylindrical fore-body with two embedded permanent magnets and two outward facing curved electrodes for tangency to an artificially ionized plasma that flowed along the body length [4] [5]. The first design was studied using an air microwave (MW) ionized supersonic plasma wind tunnel and the second design used radio frequency (RF) ionization of Argon, but both physically demonstrated the feasibility of MHD energy generation in reentry plasma conditions. For MHD drag modulation, one study involved a small-scale cylindrical blunt body embedded with permanent magnets immersed in plasma flow in an arcjet tunnel [6], and another utilized a spherical permanent magnet enclosed with a spherical forebody that was evaluated in a shock expansion tunnel [7]. Both experimental studies provided physical evidence of drag augmentation due to MHD interactions. Therefore, because of the multi-faceted effects of MHD along with both applications having been deemed feasible and beneficial during reentry, this indicates that a coupled power generation and drag modulation design could be achievable. The axi-symmetric nature of blunt bodies for reentry suggests that a spherical set of two ring electrodes near the nose along the body axis. Based on first principles, flow along the walls of the spherical body can then produce MHD interactions between the electrodes. As a result, two currents are generated: a Hall current that produces power and a primary inductive current that augments the drag force. The goal of this work is to provide a simulated design of a coaxial-electrode con-figuration for power generation and drag modulation for experimental testing.
E. Leong↗