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At least 73 records · Page 4

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NASA NTRS1988

A tandem mirror hybrid plume plasma propulsion facility

This paper discusses a novel concept in electrodeless plasma propulsion, in which the materials problems are ameliorated by an electrodeless magnetic confinement scheme borrowed from the tandem mirror approach to controlled thermonuclear fusion. The concept also features a two-stage magnetic nozzle with an annular hypersonic coaxial gas injector near the throat. The nozzle produces hybrid plume by the coaxial injection of hypersonic neutral gas, and the gas layer thus formed protects the material walls from the hot plasma and, through increased collisions, helps detach it from the diverging magnetic field. The tandem mirror plasma propulsion facility is capable of delivering a variable I(sp). The results of numerical simulation of this concept are presented together with those from an experimental tandem-mirror plasma propulsion device.

Yang, T. F.↗

NASA NTRS1998

Characterization of Plasma Discharges in a High-Field Magnetic Tandem Mirror

High density magnetized plasma discharges in open-ended geometries, like Tandem Mirrors, have a variety of space applications. Chief among them is the production of variable Specific Impulse (I(sub sp)) and variable thrust in a magnetic nozzle. Our research group is pursuing the experimental characterization of such discharges in our high-field facility located at the Advanced Space Propulsion Laboratory (ASPL). These studies focus on identifying plasma stability criteria as functions of density, temperature and magnetic field strength. Plasma heating is accomplished by both Electron and Ion Cyclotron Resonance (ECR and ICR) at frequencies of 2-3 Ghz and 1-30 Mhz respectively, for both Hydrogen and Helium. Electron density and temperature has measured by movable Langmuir probes. Macroscopic plasma stability is being investigated in ongoing research.

Chang-Diaz, Franklin R.↗

NASA NTRS2010

Conceptual Design of a Z-Pinch Fusion Propulsion System

This slide presentation reviews a project that aims to develop a conceptual design for a Z-pinch thruster, that could be applied to develop advanced thruster designs which promise high thrust/high specific impulse propulsion. Overviews shows the concept of the design, which use annular nozzles with deuterium-tritium (D-T) fuel and a Lithium mixture as a cathode, Charts show the engine performance as a function of linear mass, nozzle performance (i.e., plasma segment trajectories), and mission analysis for possible Mars and Jupiter missions using this concept for propulsion. Slides show views of the concepts for the vehicle configuration, thrust coil configuration, the power management system, the structural analysis of the magnetic nozzle, the thermal management system, and the avionics suite,

Adams, Robert↗

NASA NTRS2018

Instability and Target Design in a Z-Pinch Driven Pulsed Fission / Fusion Engine

Advanced forms of propulsion are required to drastically improve upon the limits of existing technology and enable deep space exploration. Nuclear reactors, both fission and fusion, have great potential as systems with high energy density for spacecraft propulsion. There are a variety of nuclear propulsion concepts that have been proposed over the last several decades. Some of these rely on the confinement of plasmas by both magnetic and inertial means. When discussing the plasma confinement one must consider the stability of the system. The conditions of the plasma dictate the burn rate of the nuclear fuel; therefore, the plasma must maintain a minimum set of conditions in order to achieve an adequate burn. Instabilities limit plasma confinement through growing fluctuations in density and pressure. This results in turbulent mixing and loss of confinement. Thus it is desirable to find ways of managing the impact of instabilities that arise in order for a sufficient burn of the fuel such that surplus energy can be converted into a propulsive force. Note that the same instabilities plague the confinement of plasmas for terrestrial power generation. Over the last several years there has been research relating to the development of a Pulsed Fission-Fusion Engine (PuFF) conducted by the authors and others at their respective institutions. The propulsion system concept centers on the use of a z-pinch to compress a plasma in order to induce nuclear reactions. The plasma along with the additional energy released by the fission and fusion processes is expanded with a magnetic nozzle to produce thrust. The concept, if developed, is expected to have an improvement in specific impulse of several orders of magnitude in comparison with chemical propulsion systems. The z-pinch has been explored in the past as a method to confine a plasma via magnetic confinement fusion (MCF) for power generation. It suffers; however, from instabilities that so far have prevented break even conditions.

Taylor, Brian↗

NASA NTRS1992

Electromagnetically driven relativistic jets - A class of self-similar solutions

A class of self-similar solutions for relativistic winds driven by rotating magnetic fields is constructed. These winds are collimated to cylindrical jet flows of finite radii and may attain supermagnetosonic speeds with high Lorentz factors. Most of the flow acceleration results from the 'magnetic nozzle' effect and occurs beyond the fast magnetosonic point, which is typically located a few light cylinder radii from the rotation axis. Approximate equipartition between the electromagnetic and flow kinetic energies is generally achieved for these jets, in contrast to the radial wind case in which the flow is magnetically dominated at all radii.

Li, Zhi-Yun↗

NASA NTRS1992

Microwave Electrothermal Propulsion for Space

The microwave electrothermal thruster (MET) concept for medium or high-power spacecraft propulsion is described. The MET employs continuous wave microwave energy to create and maintain a plasma discharge in a flowing propellant gas. The discharge then acts to absorb the applied microwave energy and transform it into thermal and internal energy of the propellant. Expansion and expulsion of the hot propellant through a throat and nozzle finally converts the energy of the gas into thrust. The MET concept is electrodeless, synergistically combines high pressure and high power capability, provides external control over the energy-conversion discharge, and operates on hydrogen propellant. The potential performance of the MET on hydrogen propellant has been modeled with a two-dimensional kinetics computer code. The MET concept is particularly suitable for use with a magnetic nozzle. Apparatus is described for testing the resonant-cavity MET to power levels of 30 kW at 915 MHz on nitrogen, helium, and hydrogen. The low-ripple operation of the microwave generator has been verified, as has a procedure for starting the microwave discharge and raising the power applied to the cavity via a phase shifter-tuner.

Power, John L.↗

NASA NTRS2004

High Power Light Gas Helicon Plasma Source For VASMIR

The VASIMR space propulsion development effort relies on a high power (greater than 10kW) helicon source to produce a dense flowing plasma (H, D and He) target for ion cyclotron resonance (ICR) acceleration of the ions. Subsequent expansion in an expanding magnetic field (magnetic nozzle) converts ion lunetic energy to directed momentum. This plasma source must have critical features to enable an effective propulsion device. First, it must ionize most of the input neutral flux of gas, thus producing a plasma stream with a high degree of ionization for application of ICR power. This avoids propellant waste and potential power losses due to charge exchange. Next, the plasma stream must flow into a region of high magnetic field (approximately 0.5 T) for efficient ICR acceleration. Third, the ratio of input power to plasma flux must be low, providing an energy per ion-electron pair approaching 100 eV. Lastly, the source must be robust and capable of very long life-times (years). In our helicon experiment (VX-10) we have measured a ratio of input gas to plasma flux near 100%. The plasma flows from the helicon region (B approximately 0.1 T) into a region with a peak magnetic field of 0.8 T. The energy input per ion-electron pair has been measured at 300 plus or minus 100 eV. Recent results at Oak Ridge National Laboratory (ORNL) show an enhanced efficiency mode of operation with a high power density, over 5 kW in a 5 cm diameter tube. Our helicon is presently 9 cm in diameter and operates up to 3.5 kW of input power. An upgrade to a power level of 10 kW is underway. Much of our recent work has been with a Boswell double-saddle antenna design. We are also converting the antenna design to a helical type. With these modifications, we anticipate an improvement in the ionization efficiency. This paper presents the results from scaling the helicon in the VX-10 device from 3.5 to 10 kW. We also compare the operation with a double-saddle to a helical antenna design. Finally, we discuss modeling of these configurations using ORNL's EMIR code.

Squire, J. P.↗

NASA NTRS2001

High Power Thruster Based on Inductive Magnetized Plasmoid Acceleration

Regardless of the power source, deep space missions will require both high specific impulse (greater than 500 s) and high thrust power (greater than 100kW). These high Isp thrusters will need to have high electrical efficiency (approx. 90%) and low specific mass (alpha approximately less than 10 kg/kW) as well. Additionally they should have high thrust to allow greater mission flexibility. All these requirements can potentially be achieved with the pulsed formation and acceleration of magnetically self-confined plasmoids commonly referred to as compact toroids (CTs). An electromagnetic plasma thruster based on CT acceleration makes an ideal candidate for a high power, high Isp thruster, since the CT is magnetically isolated from the accelerator so that there is no contact between the propellant and the accelerator. The transfer of momentum to the CT occurs through an electromagnetic interaction with the magnetic field. By maintaining an axial magnetic field gradient across it, the directed velocity of the CT can be increased indefinitely. In previous experiments carried out at the University of Washington, CT's of near milligram mass were accelerated to velocities of 250 km/s in a single pulse. The ejection of the plasmoid by an external axial field also avoids the serious problem of detachment, which would occur in thrusters that employ a magnetic mirror or magnetic nozzle. To employ the CT for propulsion, one must design, construct and test a plasma source that is capable of generating a self-confined plasma inductively, and to do it repeatedly at a sufficiently high rep rate. A repetitively pulsed 100 kW level FRC thruster was built and was operated for short bursts at a 10 kHz rep rate and will be described. Another regime for the FRC thruster however is to produce an FRC in a more conventional manner at high voltage and magnetic field. With the large energy transfer with each pulse, the rep rate for this approach is much lower (approximately 100 Hz). This is the approach that is being evaluated at MSFC in the FAST experiment. The purpose of this experiment is to build an FRC thruster, measure its performance characteristics e.g. specific impulse, thrust, and efficiency. This experiment will also be described as well as various mission scenarios that that are well matched for this type of propulsion.

Slough, John↗

NASA NTRS1973

Flow characteristics in the exhaust of a pulsed megawatt gas fed arc

The transient flow generated by a pulsed, megawatt-level, gas-fed arc with an applied magnetic nozzle has been examined with a new design piezoelectric pressure transducer. Sensor thermal conduction and accelerations have been examined and eliminated in the 500 microsec period of plasma flow. Existence of a large magnitude cold gas pressure front of 20 microsec duration has been reconfirmed and its relationship to the following plasma flow of about 200 microsec duration has been examined for the first time. At a point 30 cm from the arc source, initially near vacuum conditions (typically with an arc current of 11.2 kA and 1 tesla applied magnetic field), a pressure pulse of unionized gas with a magnitude of 10,000 N/sq m is followed by plasma flows with nearly constant impact pressure of 1000 N/sq m. Pressure and number density in this plasma region are seen to decrease with applied magnetic field strength.

Michels, C. J.↗

NASA NTRS2000

Magnetic Flux Compression Concept for Aerospace Propulsion and Power

The objective of this research is to investigate system level performance and design issues associated with magnetic flux compression devices for aerospace power generation and propulsion. The proposed concept incorporates the principles of magnetic flux compression for direct conversion of nuclear/chemical detonation energy into electrical power. Specifically a magnetic field is compressed between an expanding detonation driven diamagnetic plasma and a stator structure formed from a high temperature superconductor (HTSC). The expanding plasma cloud is entirely confined by the compressed magnetic field at the expense of internal kinetic energy. Electrical power is inductively extracted, and the detonation products are collimated and expelled through a magnetic nozzle. The long-term development of this highly integrated generator/propulsion system opens up revolutionary NASA Mission scenarios for future interplanetary and interstellar spacecraft. The unique features of this concept with respect to future space travel opportunities are as follows: ability to implement high energy density chemical detonations or ICF microfusion bursts as the impulsive diamagnetic plasma source; high power density system characteristics constrain the size, weight, and cost of the vehicle architecture; provides inductive storage pulse power with a very short pulse rise time; multimegajoule energy bursts/terawatt power bursts; compact pulse power driver for low-impedance dense plasma devices; utilization of low cost HTSC material and casting technology to increase magnetic flux conservation and inductive energy storage; improvement in chemical/nuclear-to-electric energy conversion efficiency and the ability to generate significant levels of thrust with very high specific impulse; potential for developing a small, lightweight, low cost, self-excited integrated propulsion and power system suitable for space stations, planetary bases, and interplanetary and interstellar space travel; potential for attaining specific impulses approaching 10 (exp 6) seconds, which would enable missions to the outer planets within ten years and missions at interstellar distances within fifty years.

Litchford, Ron J.↗

DOE OSTI2021

Laboratory disruption of scaled astrophysical outflows by a misaligned magnetic field

The shaping of astrophysical outflows into bright, dense, and collimated jets due to magnetic pressure is here investigated using laboratory experiments. Here we look at the impact on jet collimation of a misalignment between the outflow, as it stems from the source, and the magnetic field. For small misalignments, a magnetic nozzle forms and redirects the outflow in a collimated jet. For growing misalignments, this nozzle becomes increasingly asymmetric, disrupting jet formation. Our results thus suggest outflow/magnetic field misalignment to be a plausible key process regulating jet collimation in a variety of objects from our Sun’s outflows to extragalatic jets. Furthermore, they provide a possible interpretation for the observed structuring of astrophysical jets. Jet modulation could be interpreted as the signature of changes over time in the outflow/ambient field angle, and the change in the direction of the jet could be the signature of changes in the direction of the ambient field.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2024

3D radiated power analysis of JET SPI discharges using the Emis3D forward modeling tool

Abstract Precise values for radiated energy in tokamak disruption experiments are needed to validate disruption mitigation techniques for burning plasma tokamaks like ITER and SPARC. Control room analysis of radiated power ( P rad ) on JET assumes axisymmetry, since fitting 3D radiation structures with limited bolometry coverage is an under-determined problem. In mitigated disruptions, radiation is toroidally asymmetric and 3D, due to fast-growing 3D MHD modes and localized impurity sources. To address this problem, Emis3D adopts a physics motivated forward modeling (‘guess and check’) approach, comparing experimental bolometry data to synthetic data from user-defined radiation structures. Synthetic structures are observed with the Cherab modeling framework and a best fit chosen using a reduced χ 2 statistic. 2D tomographic inversion models are tested, as well as helical flux tubes and 3D MHD simulated structures from JOREK. Two nominally identical pure neon shattered pellet injection (SPI) mitigated discharges in JET are analyzed. 2D tomographic inversions with added toroidal freedom are the best fits in the thermal quench (TQ) and current quench (CQ). In the pre-TQ, 2D reconstructions are statistically the best fits, but are likely over-optimized and do not capture the 3D radiation structure seen in fast camera images. The next-best pre-TQ fits are helical structures that extend towards the high-field side, consistent with an impurity flow under the magnetic nozzle effect also observed in JOREK simulations. Whole-disruption radiated fractions of 0.98 + 0.03 / − 0.29 and 1.01 + 0.02 / − 0.17 are found, suggesting that the stored energy may have been fully mitigated by each SPI, although mitigation efficiencies well below ITER and SPARC requirements for high energy pulses are still within the large uncertainties. Emis3D is also used to validate JOREK SPI simulations, and confirms improvements in matching experiment from changes to impurity modeling. Time-dependent toroidal peaking factors are calculated and discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS1989

An RF heated tandem mirror plasma propulsion study

Experimental results on a tandem mirror hybrid plume rocket involving a three-stage system of plasma injection, heating, and subsequent injection through a magnetic nozzle are presented. In the experiments, a plasma is created by breaking down the gas with electron cyclotron resonance heating at 2 kW in the central cell, and the ion species is then heated to high temperatures with ion cyclotron resonance heating at 10 kW in the end cell. A Langmuir probe measured an electron density of 2.5 x 10 to the 16th/cu m and a temperature of 100 eV in the central cell and an ion density of 1.25 x 10 to the 17th/cu m and a temperature of 500 eV in the end cell.

Yang, T. F.↗

NASA NTRS1991

Coaxial plasma thrusters for high specific impulse propulsion

A fundamental basis for coaxial plasma thruster performance is presented and the steady-state, ideal MHD properties of a coaxial thruster using an annular magnetic nozzle are discussed. Formulas for power usage, thrust, mass flow rate, and specific impulse are acquired and employed to assess thruster performance. The performance estimates are compared with the observed properties of an unoptimized coaxial plasma gun. These comparisons support the hypothesis that ideal MHD has an important role in coaxial plasma thruster dynamics.

Schoenberg, Kurt F.↗

NASA NTRS1991

MPD thruster research issues, activities, strategies

The following activities and plans in the MPD thruster development are summarized: (1) experimental and theoretical research (magnetic nozzles at present and high power levels, MPD thrusters with applied fields extending into the thrust chamber, and improved electrode performance); and (2) tools (MACH2 code for MPD and nozzle flow calculation, laser diagnostics and spectroscopy for non-intrusive measurements of flow conditions, and extension to higher power). National strategies are also outlined.

Source record↗

NASA NTRS1992

Magnetoplasmadynamic thruster flows: Problems and progress

The topics are presented in viewgraph form and include the following: overall strategy for magnetoplasmadynamic (MPD) thruster development; high power MPD flows; moderate power MPD thrusters and components; qualitative spectroscopic studies of magnetic nozzle flow; hollow cathode studies; and anode flow studies.

Turchi, Peter J.↗

NASA NTRS1992

Scaling and applied field studies of MPD thrusters with laser diagnostics

The topics are presented in viewgraph form and include the following: self-field magnetoplasmadynamics; 1/4-scale applied-field MPD; scaling of arcs and MPD-arcs; magnetic nozzle studies; advanced diagnostic techniques needed for obtaining particle velocity, temperature, and current distributions in plasma thrusters; nonintrusive laser diagnostics for arcs and MPD-arcs; and schematic of multi-beam interferometer for electron density profile determination.

York, Thomas M.↗

NASA NTRS1991

An inertial fusion propulsion scheme for solar system exploration

The paper analyzes a novel fusion scheme that combines the favorable aspects of both inertial and magnetic confinement approaches as a propulsion device for potential application in solar system exploration. An appropriate set of equations for the plasma dynamics and the magnetic nozzle is used to assess the system's propulsive capability by applying the results to a round trip mission to Mars. It is found that such a device would allow a massive vehicle to make the journey in less than five months. It is shown that catalyzed deuterium-deuterium fuel results in a somewhat poorer propulsion performance than deuterium-tritium though at a significantly lower neutron production. The velocity increment generated by this system and the corresponding trip time are in excellent agreement with the predictions of Irving and Blum (1959).

Kammash, Terry↗