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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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NASA NTRS1973

Pulsed electromagnetic gas accelleration

Direct measurement with thermocouples of the power deposited in the anode of a multi-megawatt magnetoplasmadynamic discharge has shown the fractional anode power to decrease from 50% at 200 kW to 10% at 20 MW. Using local measurements of current density, electric potential, and electron temperature, the traditional model for heat conduction to the anode is found to be inadequate. Other experiments in which the voltage-current characteristics and exhaust velocities of MPD arcs using Plexiglas and boron nitride chamber insulators and various mass injection configurations show that ablation can affect nominal accelerator operation in several distinct ways. The incorporation of a hollow cathode in a 7 kA plasma discharge has shown that a stable current attachment can be realized in the cavity without the aid of cathode heaters, keeper electrodes, or emissive coatings.

Jahn, R. G.↗

NASA NTRS1974

Pulsed electromagnetic gas acceleration

Detailed measurements of the axial velocity profile and electromagnetic structure of a high power, quasi-steady MPD discharge are used to formulate a gasdynamic model of the acceleration process. Conceptually dividing the accelerated plasma into an inner flow and an outer flow, it is found that more than two-thirds of the total power in the plasma is deposited in the inner flow, accelerating it to an exhaust velocity of 12.5 km/sec. The outer flow, which is accelerated to a velocity of only 6.2 km/sec, appears to provide a current conduction path between the inner flow and the anode. Related cathode studies have shown that the critical current for the onset of terminal voltage fluctuations, which was recently shown to be a function of the cathode area, appears to reach an asymptote for cathodes of very large surface area. Detailed floating potential measurements show that the fluctuations are confined to the vicinity of the cathode and hence reflect a cathode emission process rather than a fundamental limit on MPD performance.

Jahn, R. G.↗

NASA NTRS1975

Pulsed electromagnetic gas acceleration

Terminal voltage measurements with long cathodes in a high power, quasi-steady MPD discharge show that the critical current for the onset of voltage fluctuations, which was previously shown to be a function of cathode area, approaches an asymptote for cathodes of very large surface area. Floating potential measurements and photographs of the discharge luminosity indicate that the fluctuations are confined to the vicinity of the cathode and hence reflect a cathode emission process rather than a fundamental limit on MPD performance. Photoelectric measurements of particular argon neutral and ion transitions show that the higher electronic states are populated more heavily than would be calculated on the basis of Saha-Boltzmann equilibrium at the local electron temperature and number density. Preliminary optical depth measurements show that for a current of 4 kA and an argon mass flow of 12 g/sec, a population inversion exists between the upper and lower states of the 4880 A argon ion transition.

Jahn, R. G.↗

NASA NTRS1975

The scattering of electromagnetic pulses by a slit in a conducting screen

A direct method for calculating the impulse response of a slit in a conducting screen is presented which is derived specifically for the analysis of transient scattering by two-dimensional objects illuminated by a plane incident wave. The impulse response is obtained by assuming that the total response is composed of two sequences of diffracted waves. The solution is determined for the first two waves in one sequence by using Green's functions and the equivalence principle, for additional waves in the sequence by iteration, and for the other sequence by a transformation of coordinates. The cases of E-polarization and H-polarization are considered.

Ackerknecht, W. E., III↗

NASA NTRS1975

Pulsed electromagnetic gas acceleration

Terminal voltage measurements with various cathodes and anodes in a high power, quasi-steady magnetoplasmadynamic (MPD) are discussed. The magnitude of the current at the onset of voltage fluctuations is shown to be an increasing function of cathode area and a weaker decreasing function of anode area. Tests with a fluted cathode indicated that the fluctuations originate in the plasma adjacent to the cathode rather than at the cathode surface. Measurements of radiative output from an optical cavity aligned to examine the current-carrying portion of a two-dimensional, 56 kA magnetoplasmadynamic discharge reveal no lasing in that region, consistent with calculations of electron excitation and resonance radiation trapping. A voltage-swept double probe technique allows single-shot determination of electron temperature and electron number density in the recombining MPD exhaust flow. Current distributions within the cavity of MPD hollow cathodes for various static prefills with no injected mass flow are examined.

Jahn, R. G.↗

NASA NTRS1984

Flight test techniques for validating simulated nuclear electromagnetic pulse aircraft responses

An attempt has been made to determine the effects of nuclear EM pulses (NEMPs) on aircraft systems, using a highly instrumented NASA F-106B to document the simulated NEMP environment at the Kirtland Air Force Base's Vertically Polarized Dipole test facility. Several test positions were selected so that aircraft orientation relative to the test facility would be the same in flight as when on the stationary dielectric stand, in order to validate the dielectric stand's use in flight configuration simulations. Attention is given to the flight test portions of the documentation program.

Winebarger, R. M.↗

NASA NTRS1992

D region disturbances caused by electromagnetic pulses from lightning

Attention is given to a simple formulation of the propagation and absorption in a magnetized collisional plasma of EM pulses from lightning which describes the effect of discharge orientation and radiated electric field on the structure and magnitude of heating and secondary ionization in the D region. Radiation from most lightning discharges can heat substantially, but only the most intense (not less than 20 V/m) are likely to cause ionization enhancements not less than 10 percent of the ambient in a single ionization cycle. This dependence on the radiated electric field is modified by the discharge radiation pattern: a horizontal cloud discharge tends to cause larger heating and ionizaton maxima while a vertical return stroke causes disturbances of a larger horizontal extent.

Rodriguez, Juan V.↗

NASA NTRS1993

Interaction with the lower ionosphere of electromagnetic pulses from lightning - Heating, attachment, and ionization

A Boltzmann formulation of the electron distribution function and Maxwell's equations for the EM fields are used to simulate the interaction of lightning radiated EM pulses with the lower ionosphere. Ionization and dissociative attachment induced by the heated electrons cause significant changes in the local electron density, N(e). Due to 'slow' field changes of typical lightning EM pulses over time scales of tens of microsec, the distribution function follows the quasi-equilibrium solution of the Boltzmann equation in the altitude range of interest (70 to 100 km). The EM pulse is simulated as a planar 100 microsec long single period oscillation of a 10 kHz wave injected at 70 km. Under nighttime conditions, individual pulses of intensity 10-20 V/m (normalized to 100 km horizontal distance) produce changes in N(e) of 1-30 percent while a sequence of pulses leads to strong modification of N(e) at altitudes less than 95 km. The N(e) changes produce a 'sharpening' of the lower ionospheric boundary by causing a reduction in electron density at 75-85 km (due to attachment) and a substantial increase at 85-95 km (due to ionization) (e.g., the scale height decreases by a factor of about 2 at about 85 km for a single 20 V/m EM pulse). No substantial N(e) changes occur during daytime.

Taranenko, Y. N.↗

NASA NTRS2006

An Optimization of Pulsed ElectroMagnetic Fields Study

To date, in our research we have focused on the use of normal human neuronal progenitor (NHNP) cells because of their importance in human nervous system regeneration, development and maintenance, but we have developed 2-D and 3-D bioreactors that can accommodate any cell line. In this Project, we will include the use of tissues important for physiological regeneration: Human osteoblasts or chondrocytes, and vascular cells. Our initial results with the NHNP cells were quite startling using extremely low-level electromagnetic fields (5 microtesla at 10Hz; 6mA). The low-amplitude, rapidly time-varying electromagnetic fields exert a very potent effect on the proliferation, morphology, and gene expression of the cells in culture, both in standard 2-dimensional culture plates as well as cells organized into 3-dimensional tissue-like assemblies (TLAs) in a 3D bioreactor. We have replicated our preliminary results many, many times, have analyzed the gene expression using gene arrays (followed by Luminex analysis for protein production), and have monitored cell proliferation, orientation, morphology, and glucose metabolism, and we are confident that we have a stable and reliable model to study the control of high-level cellular processes by application of low-amplitude, time varying electromagnetic fields (TVEMF) (1, 2). In additional studies at the University of Michigan, we have been able to generate functional in vitro engineered mammalian skeletal muscle, and have employed nerve-muscle co-culture techniques to promote axonal sprouting. We believe that nearly all tissues, in particular, neural, are susceptible to the influences of low-level TVEMF.

Goodwin, Thomas J.↗

NASA NTRS1977

Common approach to solving SGEMP, DEMP, and ESD survivability

System Generated Electromagnetic Pulse (SGEMP) and Dispersed Electromagnetic Pulse DEMP) are nuclear generated spacecraft environments. Electrostatic discharge (ESD) is a natural spacecraft environment resulting from differential charging in magnetic substorms. All three phenomena, though differing in origin, result in the same problem to the spacecraft and that is Electromagnetic Interference (EMI). A common design approach utilizing a spacecraft structural Faraday Cage is presented which helps solve the EMI problem. Also, other system design techniques are discussed which minimize the magnitude of these environments through control of materials and electrical grounding configuration.

Ling, D.↗

NASA NTRS1977

Qualification model spacecraft tests for DEMP, SGEMP, and ESD effects

The development of a satellite design demonstration test program is described. The test approach is comprehensive in that it includes the effects from electrostatic discharge (ESD), system generated electromagnetic pulse (SGEMP), as well as dispersed electromagnetic pulses (DEMP). The comprehensive test concept is based on the similarity of the satellite's response to several environments.

Chivington, E. P.↗

NASA NTRS2005

Overview of Advanced Electromagnetic Propulsion Development at NASA Glenn Research Center

NASA Glenn Research Center s Very High Power Electric Propulsion task is sponsored by the Energetics Heritage Project. Electric propulsion technologies currently being investigated under this program include pulsed electromagnetic plasma thrusters, magnetoplasmadynamic thrusters, helicon plasma sources as well as the systems models for high power electromagnetic propulsion devices. An investigation and evaluation of pulsed electromagnetic plasma thruster performance at energy levels up to 700 Joules is underway. On-going magnetoplasmadynamic thruster experiments will investigate applied-field performance characteristics of gas-fed MPDs. Plasma characterization of helicon plasma sources will provide additional insights into the operation of this novel propulsion concept. Systems models have been developed for high power electromagnetic propulsion concepts, such as pulsed inductive thrusters and magnetoplasmadynamic thrusters to enable an evaluation of mission-optimized designs.

Pencil, Eric J.↗

NASA NTRS1991

Nuclear electric propulsion technologies - Overview of the NASA/DoE/DoD Nuclear Electric Propulsion Workshop

Nuclear propulsion technology offers substantial benefits to the ambitious piloted and robotic solar system exploration missions of the Space Exploration Initiative (SEI). This paper summarizes a workshop jointly sponsored by NASA, DoE, and DoD to assess candidate nuclear electric propulsion technologies. Twenty-one power and propulsion concepts are reviewed. Nuclear power concepts include solid and gaseous fuel concepts, with static and dynamic power conversion. Propulsion concepts include steady state and pulsed electromagnetic engines, a pulsed electrothermal engine, and a steady state electrostatic engine. The technologies vary widely in maturity. The workshop review panels concluded that compelling benefits would accrue from the development of nuclear electric propulsion systems, and that a focused, well-funded program is required to prepare the technologies for SEI missions.

Barnett, John W.↗

NASA NTRS2018

Modeling of Initial Detonation-mode Acceleration in Pulsed Plasma and Magnetoplasmadynamic Thrusters

Gas-fed electromagnetic pulsed plasma accelerators operate by discharging electrical energy into a gas, subsequently ionizing and electromagnetically accelerating propellant. Many efforts to model pulsed accelerators have assumed that the discharge is either short and completely transient, accelerating the gas like a shock by entraining it in a moving current sheet, or that the discharge is relatively long, establishing a stable quasi-steady current distribution through which plasma flows and is accelerated. This idealization encounters problems when thrusters possess some qualities associated with both short and long-pulse-length thrusters. To capture all possible scenarios, a model is presented based upon the idea that all pulsed plasma accelerators first form an accelerating current sheet (detonation mode accelerator) and then, depending upon the pulse length and the manner in which the plasma reaches the thruster exit, it can transition to the quasi-steady acceleration configuration (deflagration mode accelerator). In the present work the detonation mode is investigated, varying controllable parameters to determine their effects on the plasma acceleration process. The primary driver affecting current sheet acceleration is the amount of gas that the plasma encounters and entrains as it moves towards the thruster exit. The amount of neutral gas the plasma entrains affects the time it takes the plasma to reach the end of the accelerator and changes the corresponding electrical discharge parameters at the end of detonation mode acceleration.

Polzin, Kurt A.↗

NASA NTRS1999

Investigations of Remote Plasma Irregularites by Radio Sounding: Applications of the Radio Plasma Imager on IMAGE

The Radio Plasma Imager (RPI) on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) mission operates like a radar by transmitting and receiving coherent electromagnetic pulses. Long-range echoes of electromagnetic sounder waves are reflected at remote plasma cutoffs. Thus, analyses of RPI observations will yield the plasma parameters and distances to the remote reflection points. These analyses assume that the reflecting plasma surfaces are cold and are sufficiently smooth that they effectively behave as plane mirrors to the incoming sounder waves, i.e., that geometric optics can be used. The RPI will employ pulse compression and spectral integration techniques, perfected in ground-based ionospheric digital sounders, in order to enhance the signal-to-noise ratio in long-range magnetospheric sounding. When plasma irregularities exist in the remote magnetospheric plasmas that are being probed by the sounder waves, echo signatures may become complicated. Ionospheric sounding experience indicates that while topside sounding echo strengths can actually be enhanced by the presence of irregularities, ground-based sounding indicates that coherent detection techniques can still be employed. In this paper we investigate the plasma conditions that will allow coherent signals to be detected by the RPI and the signatures to be expected, such as scattering and plasma resonances, in the presence of multi-scale irregularities, may possibly have on RPI signals. Sounding of irregular plasma structures in the plasmasphere, plasmapause and magnetopause are also discussed.

Fung, Shing F.↗

NASA NTRS2019

Pulsed Plasma Acceleration Modeling in Detonation and Deflagration Modes

Gas-fed electromagnetic pulsed plasma accelerators discharge electrical energy into a gas to ionize and electromagnetically accelerate propellant in the domain. Efforts to model pulsed accelerators have either assumed that the discharge is short and completely transient, accelerating the gas by entraining it in a moving current sheet, or that the discharge is relatively long, establishing a stable quasi-steady current distribution pattern that accelerates a plasma flowing through it. There have been pulsed plasma accelerator tests that appear to fit somewhere between these two bounds, exhibiting some properties that are associated with the purely transient devices while also showing others that are associated with quasi-steady-state plasma acceleration. A model is presented based upon the premise that all pulsed plasma accelerators first form an accelerating current sheet (detonation mode accelerator). Depending upon the pulse length and the gas conditions in the dis- charge channel, the plasma sheet may reach the end of the accelerator before the discharge has completed a full half-cycle, wherein the proposed model transitions to a quasi-steady description of the acceleration process (deflagration mode accelerator). A review of the entire model is presented, highlighting improvements and upgrades implemented to aid in the stability of the numerical scheme used to model the gas flow in the channel and an improved treatment of current sheet mass shedding, which adds gas to the wake of the sheet. The assumptions employed to model the transition from detonation to deflagration mode are presented and used to generate solutions to the governing equations. The modeling of the deflagration-mode under the present assumptions results in very low deflagration impulse bits relative to those obtained at the end of the detonation mode, implying that the present assumptions and modeling of the deflagration mode may not represent a fruitful approach.

Polzin, Kurt A.↗

NASA NTRS2019

Pulsed Plasma Acceleration Modeling in Detonation and Deflagration Modes

Gas-fed electromagnetic pulsed plasma accelerators discharge electrical energy into a gas to ionize and electromagnetically accelerate propellant in the domain. Efforts to model pulsed accelerators have either assumed that the discharge is short and completely tran- sient, accelerating the gas by entraining it in a moving current sheet, or that the discharge is relatively long, establishing a stable quasi-steady current distribution pattern that accel- erates a plasma flowing through it. There have been pulsed plasma accelerator tests that appear to fit somewhere between these two bounds, exhibiting some properties that are associated with the purely transient devices while also showing others that are associated with quasi-steady-state plasma acceleration. A model is presented based upon the premise that all pulsed plasma accelerators first form an accelerating current sheet (detonation mode accelerator). Depending upon the pulse length and the gas conditions in the dis- charge channel, the plasma sheet may reach the end of the accelerator before the discharge has completed a full half-cycle, wherein the proposed model transitions to a quasi-steady description of the acceleration process (deflagration mode accelerator). A review of the entire model is presented, highlighting improvements and upgrades implemented to aid in the stability of the numerical scheme used to model the gas flow in the channel and an im- proved treatment of current sheet mass shedding, which adds gas to the wake of the sheet. The assumptions employed to model the transition from detonation to deflagration mode are presented and used to generate solutions to the governing equations. The modeling of the deflagration-mode under the present assumptions results in very low deflagration im- pulse bits relative to those obtained at the end of the detonation mode, implying that the present assumptions and modeling of the deflagration mode may not represent a fruitful approach.

Polzin, Kurt A.↗

NASA NTRS2005

Galium Electromagnetic (GEM) Thruster Concept and Design

We describe the design of a new type of two-stage pulsed electromagnetic accelerator, the gallium electromagnetic (GEM) thruster. A schematic illustration of the GEM thruster concept is given. In this concept, liquid gallium propellant is pumped into the first stage through a porous metal electrode using an electromagnetic pump. At a designated time, a pulsed discharge (approx. 10-50 J) is initiated in the first stage, ablating the liquid gallium from the porous electrode surface and ejecting a dense thermal gallium plasma into the second state. The presence of the gallium plasma in the second stage serves to trigger the high-energy (approx. 500 J), second-stage pulse which provides the primary electromagnetic (j x B) acceleration.

Polzin, Kurt A.↗