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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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At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Dispersion relation of electrostatic ion cyclotron waves in multi-component magneto-plasma

Electrostatic ion cyclotron waves in multi component plasma composed of electrons (denoted by e{sup −}), hydrogen ions (denoted by H{sup +}), helium ions (denoted by He{sup +}) and positively charged oxygen ions (denoted by O{sup +})in magnetized cold plasma. The wave is assumed to propagate perpendicular to the static magnetic field. It is found that the addition of heavy ions in the plasma dispersion modified the lower hybrid mode and also allowed an ion-ion mode. The frequencies of the lower hybrid and ion- ion hybrid modes are derived using cold plasma theory. It is observed that the effect of multi-ionfor different plasma densities on electrostatic ion cyclotron waves is to enhance the wave frequencies. The results are interpreted for the magnetosphere has been applied parameters by auroral acceleration region.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1981

Acceleration of electrons by interplanetary shocks

Ion acceleration is a well known phenomenon at both interplanetary shocks, while there have been only a few reports concerning an acceleration of electrons at interplanetary shocks. The considered investigation reports that electron acceleration occurs at many shocks. The instrumentation used is discussed, taking into account the ISEE 3 (International Sun Earth Explorer) spacecraft and the electrostatic analyzer employed for the measurement of electrons. Changes in the electron distribution function caused by shocks are found to be quite varied. Some events show a simple step to a higher flux level, some show fluctuations as the flux rises, and some have one or more pulses at the time of the shock. Attention is given to data obtained on July 26, 1979, December 25, 1978, and November 12, 1978. A calculation of shock geometries is also reported.

Potter, D. W.↗
NASA NTRS2005

Non-contact Creep Resistance Measurement for Ultra-high temperature Materials

Continuing pressures for higher performance and efficiency in propulsion are driving ever more demanding needs for high-temperature materials. Some immediate applications in spaceflight include combustion chambers for advanced chemical rockets and turbomachinery for jet engines and power conversion in nuclear-electric propulsion. In the case of rockets, the combination of high stresses and high temperatures make the characterization of creep properties very important. Creep is even more important in the turbomachinery, where a long service life is an additional constraint. Some very high-temperature materials are being developed, including platinum group metals, carbides, borides, and silicides. But the measurement of creep properties at very high temperatures is itself problematic, because the testing instrument must operate at such high temperatures. Conventional techniques are limited to about 1700 C. A new, containerless technique for measuring creep deformation has been developed. This technique is based on electrostatic levitation (ESL) of a spherical sample, which is heated to the measurement temperature and rotated at a rate such that the centrifugal acceleration causes creep deformation. Creep of samples has been demonstrated at up to 2300 C in the ESL facility at NASA MSFC, while ESL itself has been applied at over 3000 C, and has no theoretical maximum temperature. The preliminary results and future directions of this NASA-funded research collaboration will be presented.

Hyers, Robert W.↗
NASA NTRS1972

Effects of electrostatic rocket material deposited on solar cells.

If solar arrays on solar-electric spacecraft protrude into the exhaust hemisphere of the electric thrusters, they will receive fluxes (usually small) of both propellant and accelerator grid atoms. Unlike propellants, grid materials have low vapor pressures and will not reevaporate. An analysis is presented of degradation in the optical, thermal, and electrical performance of solar cells resulting from thin deposits of grid material (aluminum and molybdenum) on various array surfaces. The classical optical theory of thin films, heat balance equations, and a typical relationship for solar cell efficiency vs temperature are used to compute curves showing optical properties, temperature, and power output as functions of film thickness. The results compare favorably with available experimental data. It is shown that a few monolayers of metal deposition on the illuminated surface will seriously degrade cell performance. A means of estimating the arrival rate of these materials is provided.

Kemp, R. F.↗
DOE OSTI2016

Plasma electron hole kinematics. I. Momentum conservation

We analyse the kinematic properties of a plasma electron hole: a non-linear self-sustained localized positive electric potential perturbation, trapping electrons, which behaves as a coherent entity. When a hole accelerates or grows in depth, ion and electron plasma momentum is changed both within the hole and outside, by an energization process we call jetting. We present a comprehensive analytic calculation of the momentum changes of an isolated general one-dimensional hole. The conservation of the total momentum gives the hole's kinematics, determining its velocity evolution. Our results explain many features of the behavior of hole speed observed in numerical simulations, including self-acceleration at formation, and hole pushing and trapping by ion streams.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

System and method for alfvenic reconnecting plasmoid plasma acceleration

According to various embodiments, a system for using magnetic reconnection to accelerate plasma is disclosed. The system includes a pair of electrodes including two concentric rings separated by an electrode gap and held at different electrostatic potential by applying a voltage to generate an inter-electrode electric field. The system further includes a plurality of magnetic coils configured to produce magnetic field lines that connect the pair of electrodes. The system additionally includes a gas injector configured to inject gas into the electrode gap, the injected gas being partially ionized by the inter-electrode electric field to generate a poloidal current that flows along open magnetic field lines across the electrode gap. A total Lorentz force causes oppositely directed magnetic field lines to be expanded around a region of the gas injector to further create an azimuthal current in the form of an axially elongated current sheet that is unstable such that the axially elongated current sheet reconnects and breaks into plasmoids.

Ebrahimi, Fatima Arezu↗
DOE OSTI2014

Excitation of electrostatic waves in the electron cyclotron frequency range during magnetic reconnection in laboratory overdense plasmas

We report the observation of electromagnetic radiation at high harmonics of the electron cyclotron frequency that was considered to be converted from electrostatic waves called electron Bernstein waves (EBWs) during magnetic reconnection in laboratory overdense plasmas. The excitation of EBWs was attributed to the thermalization of electrons accelerated by the reconnection electric field around the X-point. The radiative process discussed here is an acceptable explanation for observed radio waves pulsation associated with major flares.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1983

The Io-control of Jupiter's decametric radiation - The Alfven wave model

Geometrical considerations based on a conical sheet model of the observed DAM sources show that DAM is generated on field lines in the active longitude sector of 200 + or - 90 deg. The present study shows how Io excites Alfven waves and calculates the propagation of these waves through the inhomogeneous torus and magnetosphere. The power flux at high latitudes is largest at two longitudes which are seen as the B1, B2, A, and C sources. The parallel electric field accompanying the Alfven wave pulses is also discussed, and it is shown that at high latitudes electrons can be accelerated to energies in excess of 1000 eV. It is suggested that these current carrying electrons excite ion-cyclotron, upper and lower-hybrid electrostatic waves which may all play crucial roles in the generation of DAM.

Goertz, C. K.↗
NASA NTRS1991

SEPAC data analysis in support of the environmental interaction program

Data analyses of the Space Experiments with Particle Accelerators (SEPAC) data and computer modeling were conducted to investigate spacecraft environmental effects associated with injection of electron beams, plasma clouds, and neutral gas clouds from the Shuttle orbiter. The data analysis indicates that Extremely Low Frequency oscillations from 150 to 200 Hz were seen in the Langmuir probe current when the beam was fired in a continuous mode. The strongest oscillations occurred when the ambient pressure was augmented by neutral gas releases from the SEPAC plasma accelerator magnetoplasma-dynamic (MPD) arcjet. To understand the dependence of spacecraft charging potential on beam density and other plasma parameters, a two-dimensional electrostatic particle code was used to simulate the injection of electron beams from an infinite conductor into a plasma. The simulations show that the conductor charging potential depends critically on the reflection coefficient of the conductor surface, which is defined as the percentage of incident particles reflected by the conductor. The ionization effects on spacecraft charging were examined by including interactions of electrons with neutral gas. The simulations show that the conductor charging potential decreases with increasing neutral background density due to the production of secondary electrons near the conductor surface. The simulations also indicate that the beam radius is generally proportional to the beam electron gyroradius when the conductor is charged to a large potential. It appears that the charge buildup at the beam stagnation point causes the beam radial expansion. A survey of the simulation results suggests that the ratio of the beam radius to the beam electron gyroradius increases with the square root of beam density and decreases inversely with beam injection velocity. These results are useful for explaining the spacecraft charging phenomena observed during SEPAC experiments from Spacelab 1.

Lin, Chin S.↗
NASA NTRS2001

Dual-mass vibratory rate gyroscope with suppressed translational acceleration response and quadrature-error correction capability

A microfabricated vibratory rate gyroscope to measure rotation includes two proof-masses mounted in a suspension system anchored to a substrate. The suspension has two principal modes of compliance, one of which is driven into oscillation. The driven oscillation combined with rotation of the substrate about an axis perpendicular to the substrate results in Coriolis acceleration along the other mode of compliance, the sense-mode. The sense-mode is designed to respond to Coriolis accelerationwhile suppressing the response to translational acceleration. This is accomplished using one or more rigid levers connecting the two proof-masses. The lever allows the proof-masses to move in opposite directions in response to Coriolis acceleration. The invention includes a means for canceling errors, termed quadrature error, due to imperfections in implementation of the sensor. Quadrature-error cancellation utilizes electrostatic forces to cancel out undesired sense-axis motion in phase with drive-mode position.

Clark, William A.↗
NASA NTRSDate not supplied

Electric Sail Design Sensitivities

Electric Sails (E-Sails) are a promising propulsion technology that seek to enable high characteristic propellentless acceleration for spacecraft to reach distant and/or difficult to reach orbits such as rapid transit to heliopause. The E-Sail system exchanges momentum by using positively charged electrostatic tethers to repel solar wind photons to push it through space. This concept was first theorized by Pekka Janhunen in 2004 with further developments occurring including a NASA Innovative Advanced Concepts Phase 1 and Phase 2 hosted out of NASA’s Marshall Space Flight Center (MSFC). These developments led to further maturation of the overall system, and this paper is designed to help identify different design sensitivities of an integrated Electric Sail system. To approach this, a small team at MSFC took an in-house developed three degrees of freedom (3DoF) simulation tool and a trajectory modelling tool to look at different design parameters and to determine a potential ideal E-Sail configuration. An E-Sail system has different design architectures including a barbell design, hub and spoke design, and a potential hybrid solution. The barbell design features two equally massed satellites that spin around a central point in the tether system. The hub and spoke design features a large central spacecraft with small end spacecraft to aid in formation control of the overall E-Sail system. Leveraging elements from both the hub and spoke, and barbell design, a hybrid option exists where one could have a larger central mass and one or two tethers extended to a smaller end mass [2]. In summary, the hub and spoke design is the ideal configuration for E-Sail with tethers spanning kilometers to achieve the designed design characteristic acceleration of at least one mm/s2 with this architecture being the focus of this study. Different key design parameters were varied as part of this study. These parameters include the total number of tethers, the length of the tethers, spin rate, relative spacecraft mass, tether voltage, inertia per tether, and impact of slew rate changes. These results started from an internal MSFC technology demonstration mission design and then the parameters were varied with engineering judgement to ensure that the results were consistent with expected results. These were varied in the MSFC 3DoF tool and compared to baseline results to generate a candidate ideal E-Sail design system. These results were then used to help inform the mission analysis design for the system. The 3DoF trajectory optimization was performed in the Astrodynamics and Space Science Enabling Toolbox (ASSET) and utilized collocation optimization of control vector pointing with the objective function being transfer duration. A representative model of the E-Sail force was derived as a function of the Sun-pointing vector direction. This model was initialized with a zero Sun Incidence Angle (SIA) trajectory for the initial guess generation, then with a portion of the mission optimized SIA time history for fast outbound transfers. After the trajectory is hyperbolic relative to a heliocentric frame, the SIA is maintained at 0 degrees except for any needed trajectory correction maneuvers. This trajectory optimization looked at different characteristic acceleration values to analyze the impact it had on mission performance. As a result of this study, the team can best inform mission designers and technology development efforts to mature the E-Sail system. This study will allow mission designers to have defined rules-of-thumb to design an E-Sail system to meet desired mission needs as well as providing several sample mission profiles. These design drivers will inform maturation efforts on which design requirements to consider for an integrated E-Sail design.

E-Sail↗
DOE OSTI2013

Nonlinear electron acceleration by oblique whistler waves: Landau resonance vs. cyclotron resonance

This paper is devoted to the study of the nonlinear interaction of relativistic electrons and high amplitude strongly oblique whistler waves in the Earth's radiation belts. We consider electron trapping into Landau and fundamental cyclotron resonances in a simplified model of dipolar magnetic field. Trapping into the Landau resonance corresponds to a decrease of electron equatorial pitch-angles, while trapping into the first cyclotron resonance increases electron equatorial pitch-angles. For 100 keV electrons, the energy gained due to trapping is similar for both resonances. For electrons with smaller energy, acceleration is more effective when considering the Landau resonance. Moreover, trapping into the Landau resonance is accessible for a wider range of initial pitch-angles and initial energies in comparison with the fundamental resonance. Thus, we can conclude that for intense and strongly oblique waves propagating in the quasi-electrostatic mode, the Landau resonance is generally more important than the fundamental one.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Recent progress in tailoring trap-based positron beams

Recent progress is described to implement two approaches to specially tailor trap-based positron beams. Experiments and simulations are presented to understand the limits on the energy spread and pulse duration of positron beams extracted from a Penning-Malmberg (PM) trap after the particles have been buffer-gas cooled (or heated) in the range of temperatures 1000 {>=} T {>=} 300 K. These simulations are also used to predict beam performance for cryogenically cooled positrons. Experiments and simulations are also presented to understand the properties of beams formed when plasmas are tailored in a PM trap in a 5 tesla magnetic field, then non-adiabatically extracted from the field using a specially designed high-permeability grid to create a new class of electrostatically guided beams.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Particle-in-cell simulation study of a lower-hybrid shock

The expansion of a magnetized high-pressure plasma into a low-pressure ambient medium is examined with particle-in-cell simulations. The magnetic field points perpendicular to the plasma's expansion direction and binary collisions between particles are absent. The expanding plasma steepens into a quasi-electrostatic shock that is sustained by the lower-hybrid (LH) wave. The ambipolar electric field points in the expansion direction and it induces together with the background magnetic field a fast E cross B drift of electrons. The drifting electrons modify the background magnetic field, resulting in its pile-up by the LH shock. The magnetic pressure gradient force accelerates the ambient ions ahead of the LH shock, reducing the relative velocity between the ambient plasma and the LH shock to about the phase speed of the shocked LH wave, transforming the LH shock into a nonlinear LH wave. The oscillations of the electrostatic potential have a larger amplitude and wavelength in the magnetized plasma than in an unmagnetized one with otherwise identical conditions. The energy loss to the drifting electrons leads to a noticeable slowdown of the LH shock compared to that in an unmagnetized plasma.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2007

Space Technology 7 : Micropropulsion and Mass Distribution

The NASA New Millennium Program Space Technology 7 (ST7) project will validate technology for precision spacecraft control. The ST7 disturbance reduction system (DRS) will contain new micropropulsion technology to be flown as part of the European Space Agency's LISA (laser interferometer space antenna) Pathfinder project. After launch into a low Earth orbit in early 2010, the LISA Pathfinder spacecraft will be maneuvered to a halo orbit about the Earth-Sun LI Lagrange point for operations. The DRS will control the position of the spacecraft relative to a reference to an accuracy of one nanometer over time scales of several thousand seconds. To perform the control the spacecraft will use a new colloid thruster technology. The thrusters will operate over the range of 5 to 30 micro-Newtons with precision of 0.1 micro-Newton. The thrust will be generated by using a high electric field to extract charged droplets of a conducting colloid fluid and accelerating them with a precisely adjustable voltage. The control position reference will be provided by the European LISA Technology Package, which will include two nearly free-floating test masses. The test mass position and attitude will be sensed and adjusted using electrostatic capacitance bridges. The DRS will control the spacecraft position with respect to one test mass while minimizing disturbances on the second test mass. The dynamic control system will cover eighteen degrees of freedom, six for each of the test masses and six for the spacecraft. In the absence of other disturbances, the test masses will slowly gravitate toward local concentrations of spacecraft mass. The test mass acceleration must be minimized to maintain the acceleration of the enclosing drag-free spacecraft within the control authority of the micropropulsion system. Therefore, test mass acceleration must be predicted by accurate measurement of mass distribution, then offset by the placement of specially shaped balance masses near each test mass. The - acceleration is characterized by calculating the gravitational effect of over ten million modeled points of a nearly 500-kg spacecraft. This paper provides an overview of the mission technology and the process of precision mass modeling of the DRS equipment.

ST-7↗
NASA NTRS1975

Local time variations of particle flux produced by an electrostatic field in the magnetosphere

The local time variations of particle distributions, which can be produced by the sudden enhancement of a cross-tail electric field, are examined by using adiabatic theory. The strong coupling between acceleration, inward motion, and east-west drift is emphasized. The model is used to interpret recent measurements of delay times of newly accelerated electrons at different local times at geostationary orbit. Observations of the asymmetric storm time 'ring current' are interpreted in terms of the model without invoking particle loss.

Kivelson, M. G.↗
DOE OSTI2014

A new standard pulsar magnetosphere

In view of recent efforts to probe the physical conditions in the pulsar current sheet, we revisit the standard solution that describes the main elements of the ideal force-free pulsar magnetosphere. The simple physical requirement that the electric current contained in the current layer consists of the local electric charge moving outward at close to the speed of light yields a new solution for the pulsar magnetosphere everywhere that is ideal force-free except in the current layer. The main elements of the new solution are as follows: (1) the pulsar spindown rate of the aligned rotator is 23% larger than that of the orthogonal vacuum rotator; (2) only 60% of the magnetic flux that crosses the light cylinder opens up to infinity; (3) the electric current closes along the other 40%, which gradually converges to the equator; (4) this transfers 40% of the total pulsar spindown energy flux in the equatorial current sheet, which is then dissipated in the acceleration of particles and in high-energy electromagnetic radiation; and (5) there is no separatrix current layer. Our solution is a minimum free-parameter solution in that the equatorial current layer is electrostatically supported against collapse and thus does not require a thermal particle population. In this respect, it is one more step toward the development of a new standard solution. We discuss the implications for intermittent pulsars and long-duration gamma-ray bursts. We conclude that the physical conditions in the equatorial current layer determine the global structure of the pulsar magnetosphere.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Influence of magnetic angle on the E × B drift in a magnetic presheath

In this work, we provide experimental measurements of the E X B flow above a non-magnetic, absorbing boundary in a magnetized plasma. Measurements are taken as a function of the angle between the background magnetic field and the boundary normal. The measurements are compared to computational predictions for oblique magnetic fields based on Chodura's model. Ion flow measurements were obtained with laser induced fluorescence and the presheath potential structure was measured with an emissive probe. The ions were found to accelerate to nearly 30% of the sound speed parallel to the boundary at oblique angles of the magnetic field (~80°) and the ion speed at the electrostatic sheath edge was found to decrease with angle. The edge of the magnetic presheath has been experimentally determined based on the appearance of the E X B drift and is found to be independent of the angle of the magnetic field. We also demonstrate that laser induced fluorescence is suitable as a non-perturbative diagnostic to measure the electric field in a magnetized sheath.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗