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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

A theoretical evaluation of laser-sustained plasma thruster performance

An extensive numerical experiment has been conducted to evaluate rocket thruster performance using a laser-sustained hydrogen plasma as the propellant. The plasma was sustained using a 30 kW CO2 laser beam operated at 10.6 microns focused inside the thruster. The steady-state Navier-Stokes equations coupled with the laser power absorption process have been solved numerically. A pressure based Navier-Stokes solver using body-fitted coordinate was used to calculate the laser-supported rocket flow which included both recirculating and transonic flow regions. The local thermodynamic equilibrium (LTE) assumption was used for the plasma thermophysical and optical properties. Geometric ray tracing was adopted to describe the laser beam. Several different throat size thrusters operated at 150 and 300 kPa chamber stagnation pressure were studied. It was found that the thruster performance (vacuum specific impulse) was highly dependent on the operating conditions, and a properly designed laser supported thruster can attain a specific impulse around 1500 secs. The heat loading on the thruster wall was also estimated and was in the range of that for a conventional chemical rocket.

Jeng, San-Mou↗
NASA NTRS1987

Weak double layers in the auroral ionosphere

Previous work on the evolution of weak double layers in a hydrogen plasma was extended to include H(+) and O(+) with relative drift. The relative drift between hydrogen and oxygen ions due to a quasi-static parallel electric field gives rise to a strong linear fluid instability which dominates the ion-acoustic mode at the bottom of the auroral acceleration region. This ion-ion instability can modify ion distributions at lower altitudes and the subsequent nonlinear evolution of weak double layers at higher altitudes in the ion-acoustic regime. Ion hole formation can occur for smaller relative electron-ion drifts than seen in previous simulations, due to the hydrogen-oxygen two-stream instability. This results in local modification of the ion distributions in phase space, and a partial filling of the valley between the hydrogen and oxygen peaks, which would be expected at higher altitudes on auroral field lines. The observed velocity diffusion does not necessarily preclude ion hole and double layer formation in hydrogen in the ion-acoustic regime. These simulation results are consistent with the experimentally measured persistence of separate hydrogen and oxygen peaks, and the observation of weak double layers above an altitude of 3000 km on auroral field lines.

Hudson, M. K.↗
NASA NTRSDate not supplied

Hydrogen Sensor via Plasma Techniques Development

Currently, NASA Kennedy Space Center’s Exploration Ground Systems (EGS) uses liquid hydrogen (LH 2 ) as fuel for launches and ensures hydrogen is no longer in the fill lines by sampling gas into a controlled environment. Then they use a catalytic sensor that detects when hydrogen interacts with oxygen. However, this procedure requires repeatedly backfilling and flushing with helium, which can be wasteful during a global helium shortage and expensive for each sampling port. Therefore, the team at KSC set out to establish proof-of-concept of a plasma-based hydrogen sensor that is anaerobic – and can in fact detect in most environments and below atmospheric pressures – and with a small footprint and more sensitive than other hydrogen sensors currently on the market. The technology development was done by testing known concentrations of hydrogen in argon gas fed through a vacuum cube containing an electrode feedthrough at varying pressures. The resultant emission spectra were recorded with a fiber optic spectrometer and analyzed to determine the instrument's accuracy. Throughout testing, efforts were made to prove the off-the-shelf capabilities of the setup. The traditional high voltage AC-power source was switched to an affordable, handheld plasma lighter. Additionally, the spectrometer was supplemented with a double photodiode circuit to take targeted measurements of the Balmer-α and - β lines in the hydrogen spectrum. From this, we established a proof of concept sensor. SLS required it to detect as low as 100 ppm whereas we detected hydrogen in concentrations as low as 50 ppm and in an anaerobic environment. * Work supported by NASA Kennedy Space Center’s Science Mission Directorate Innovative Research and Development Fund.

Plasma↗
NASA NTRS1987

An experimental study of laser-supported plasmas for laser propulsion: Center director's discretionary fund project DFP-82-33

The rudiments of a rocket thruster, which receives its enthalpy from an energy source which is remotely beamed from a laser, is described. An experimental study, now partially complete, is discussed which will eventually provide a detailed understanding of the physics for assessing the feasibility of using hydrogen plasmas for accepting and converting this energy to enthalpy. A plasma ignition scheme which uses a pulsed CO2 laser was develped and the properites of the ignition spark documented, including breakdown intensities in hydrogen. A complete diagnostic system capable of determining plasma temperature and the plasma absorptivitiy for subsequent steady-state absorption of a high power CO2 laser beam are developed and demonstrative use is discussed for the preliminary case study, a two atmosphere laser supported argon plasma.

Eskridge, R. H.↗
NASA NTRS2012

Free-Free Transitions of the e-H System Inside a Dense Plasma Irradiated by a Laser Field at Very Low Incident-Electron Energies

The free-free transition is studied for an electron-hydrogen atom in ground state when a low-energy electron (external) is injected into hydrogenic plasma in the presence of an external homogenous, monochromatic, and linearly polarized laser field. The effect of plasma screening is considered in the Debye-Huckel approximation. The calculations are performed in the soft photon limit. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing the Volkov solutions in both the initial and final channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the electron exchange. The laser-assisted differential and total cross sections are calculated for single-photon absorption or emission and no-photon exchange in the soft photon limit, the laser intensity being much less than the atomic field intensity. The calculations have been carried out for various values of Debye parameter, ranging from 0.005 to 0.12. A strong suppression is noted in the laser-assisted cross sections as compared to the field-free situation. A significant difference is noted for the singlet and triplet cross sections. The suppression is much more in the triplet states.

Bhatia, A. K.↗
NASA NTRS1982

Observations of structuring in the downstream region of a large spherical model in a laboratory simulated solar wind plasma

The effects of inserting a spherical conducting model, large in comparison with the Debye length, into a free streaming high-energy 1 kV) unmagnetized hydrogen plasma are investigated in order to measure energies and compositions directly relevant to solar wind and astrophysical plasma phenomena. Holding the incident plasma parameters constant, transverse profiles of the net Langmuir probe current are plotted at various locations downstream in the model wake and are divided into three regions (the shadow, transition, and boundary). Results attributable to the use of a high-energy plasma show that enhancements in the shadow exist at downstream locations where the Mach ratio is less than one, and turbulence exists in the transition region on the shadow edges and outside in the boundary region. In addition, a small current enhancement is found in the boundary and can be attributed to the plasma/model interaction. It is concluded that many similar features observed by spacecraft downstream from planetary bodies are relatively permanent and are due to the intrinsic nature of the interaction between the solar wind plasma and the obstacle.

Intriligator, D. S.↗
NASA NTRS2012

Plasma Treatment to Remove Carbon from Indium UV Filters

The sounding rocket experiment FIRE (Far-ultraviolet Imaging Rocket Experiment) will improve the science community fs ability to image a spectral region hitherto unexplored astronomically. The imaging band of FIRE (.900 to 1,100 Angstroms) will help fill the current wavelength imaging observation hole existing from approximately equal to 620 Angstroms to the GALEX band near 1,350 Angstroms. FIRE is a single-optic prime focus telescope with a 1.75-m focal length. The bandpass of 900 to 1100 Angstroms is set by a combination of the mirror coating, the indium filter in front of the detector, and the salt coating on the front of the detector fs microchannel plates. Critical to this is the indium filter that must reduce the flux from Lymanalpha at 1,216 Angstroms by a minimum factor of 10(exp -4). The cost of this Lyman-alpha removal is that the filter is not fully transparent at the desired wavelengths of 900 to 1,100 Angstroms. Recently, in a project to improve the performance of optical and solar blind detectors, JPL developed a plasma process capable of removing carbon contamination from indium metal. In this work, a low-power, low-temperature hydrogen plasma reacts with the carbon contaminants in the indium to form methane, but leaves the indium metal surface undisturbed. This process was recently tested in a proof-of-concept experiment with a filter provided by the University of Colorado. This initial test on a test filter showed improvement in transmission from 7 to 9 percent near 900 with no process optimization applied. Further improvements in this performance were readily achieved to bring the total transmission to 12% with optimization to JPL's existing process.

Greer, Harold F.↗
NASA NTRS1972

The possibility of supersonic plasma flow in a collapsing post-sunset ionosphere.

As a result of the rapidly decreasing pressure in the topside ionosphere during twilight hours, a rapid downward flow of hydrogen plasma from the protonosphere takes place. In the case of steady state, isothermal, frictionless flow, the criterion for the existence of a critical point (transition to supersonic flow) above 1000 km is that the plasma temperature be lower than a certain limiting temperature which is a function of the field line considered. In the latitude region between 40 and 70 deg, this upper temperature limit varies from 963 to 1066 K. Since these temperatures are considerably lower than the observed temperatures, it follows that in the case of steady state, isothermal flow the velocities will always remain subsonic. When the effect of the neglected terms is examined, the temperature gradient is shown to exert the strongest influence on the nature of the flow. It is concluded that there is a definite possibility that supersonic downward flows in a post-sunset topside ionosphere may occur.

Fontheim, E. G.↗
NASA NTRS1979

Dielectronic recombination rates, ionization equilibrium, and radiative energy-loss rates for neon, magnesium, and sulfur ions in low-density plasmas

Results of detailed and systematic calculations are presented for the total dielectronic recombination rate coefficients for the ions of Ne, Mg, and S in a low-density predominantly hydrogen plasma. The new recombination rates are used to calculate solar corona ionization-equilibrium distributions of the ions. The most important effect of dielectronic recombination for ions in corona equilibrium is found to be a shift in the maximum-abundance temperatures toward higher temperatures, which are in some cases reduced from those predicted on the basis of the simple Burgess formula.

Jacobs, V. L.↗
NASA NTRS1973

Active cleaning techniques for removing contamination from optical surfaces in space

Research in developing an active cleaning technique for removing contaminants from optical surfaces in space is reported. In situ contamination/cleaning experiments were conducted on gold and platimum coated mirrors, which were contaminated by exposure to UV radiation in a 1,3, butadiene environment. Argon and oxygen plasma exposure cleaned the mirrors equally well. Silicone cleaning experiments were also conducted. Exposure of the contaminated mirrors to helium, oxygen, and hydrogen plasmas restored the reflectance at the shorter wavelengths and degraded it at the longer wavelengths.

Shannon, R. L.↗
NASA NTRS1983

Steady-state turbulence with a narrow inertial range

Coupled two-dimensional wave equations are solved on a computer to model Langmuir wave turbulence excited by a weak electron beam. The model includes wave growth due to beam-plasma interaction, and dissipation by Landau damping. The inertial range is limited to a relatively small number of modes such as could occur when the ratio of masses between the negative and positive ions is larger than in a hydrogen plasma, or when there is damping in long wavelength Langmuir waves. A steady state is found consisting of quasistable, collapsed wave packets. The effects of different beam parameters and the assumed narrow inertial range are considered. The results may be relevant to plasma turbulence observed in connection with type III solar bursts.

Weatherall, J. C.↗
NASA NTRS1980

Parametric dependence of ion temperature and electron density in the SUMMA hot-ion plasma using laser light scattering and emission spectroscopy

Hot-ion plasma experiments were conducted in the NASA Lewis SUMMA facility. A steady-state modified Penning discharge was formed by applying a radially inward dc electric field of several kilovolts near the magnetic mirror maxima. Results are reported for a hydrogen plasma covering a wide range in midplane magnetic flux densities from 0.5 to 3.37 T. Input power greater than 45 kW was obtained with water-cooled cathodes. Steady-state plasmas with ion kinetic temperatures from 18 to 830 eV were produced and measured spectroscopically. These ion temperatures were correlated with current, voltage, and magnetic flux density as the independent variables. Electron density measurements were made using an unusually sensitive Thomson scattering apparatus. The measured electron densities range from 2.1 x 10 to the 11th to 6.8 x 10 to the 12th per cu cm.

Snyder, A.↗
NASA NTRS1991

Diamond film deposition using microwave plasmas under low pressures

Microwave plasma depositions of diamond films have been investigated under low pressures of 10 mTorr to 10 Torr, at low substrate temperatures of 400 to 750 C, using high methane concentrations of 5 to 15 percent and oxygen concentrations of 5 to 10 percent in hydrogen plasmas. The deposition system consists of a microwave plasma chamber, a downstream deposition chamber, and a RF induction-heated sample stage. The deposition system can be operated in either high-pressure microwave or electron cyclotron resonance (ECR) modes by varying the sample stage position. Cathodoluminescence (CL) studies on diamond films deposited at 10 Torr pressure show that CL emissions at 430, 480, 510, 530, 560, 570 and 740 nm can be employed to characterize the quality of diamond films. High-quality, well-faceted diamond films have been deposited at 10 Torr and 600 C using 5 percent CH4 and 5 percent O2 in H2 plasmas; CL measurements on these films show very low N impurities and no detectable Si impurities. Diamond nucleation on SiC has been demonstrated by depositing well-faceted diamond crystallites on SiC-coated Si substrates.

Shing, Y. H.↗
NASA NTRS1993

Optimization of energy transfer in microwave electrothermal thrusters

Results are presented from preliminary tests conducted to evaluate the performance of a prototype microwave electrothermal thruster. The primary component of the device is a microwave resonant cavity. The device produces stable axial plasmas within a pressurized section of the cavity with the plasma positioned in the inlet region of the nozzle. Plasma stability is enhanced by axial power coupling, an optimal distribution of electric power density within the cavity, and a propellant gas flow which has a large vortical velocity component. The thruster has been operated with a number of propellant gases: helium, nitrogen, ammonia, and hydrogen. Plasmas can be formed in a reliable manner at cavity pressures of 1 kPa and incident power levels ranging from 50 W to 350 W, depending on the gas used, and can be operated at pressures up to 300 kPa at power levels up to 2200 W. Ideal performance results of vacuum Isp and thermal efficiency vs. specific power are presented for each gas. Representative results of this preliminary work are: He - Isp = 625 s, eta-thermal = 90 percent; N2 - Isp = 270 s, eta-thermal = 41 percent; NH3 - Isp = 475 s, eta-thermal= 55 percent; H2 - Isp = 1040 s, eta-thermal = 53 percent.

Sullivan, D. J.↗
NASA NTRS2013

Design of a Uranium Dioxide Spheroidization System

The plasma spheroidization system (PSS) is the first process in the development of tungsten-uranium dioxide (W-UO2) fuel cermets. The PSS process improves particle spherocity and surface morphology for coating by chemical vapor deposition (CVD) process. Angular fully dense particles melt in an argon-hydrogen plasma jet at between 32-36 kW, and become spherical due to surface tension. Surrogate CeO2 powder was used in place of UO2 for system and process parameter development. Particles range in size from 100 - 50 microns in diameter. Student s t-test and hypothesis testing of two proportions statistical methods were applied to characterize and compare the spherocity of pre and post process powders. Particle spherocity was determined by irregularity parameter. Processed powders show great than 800% increase in the number of spherical particles over the stock powder with the mean spherocity only mildly improved. It is recommended that powders be processed two-three times in order to reach the desired spherocity, and that process parameters be optimized for a more narrow particles size range. Keywords: spherocity, spheroidization, plasma, uranium-dioxide, cermet, nuclear, propulsion

Cavender, Daniel P.↗
NASA NTRS1990

Two-body problem in a many-particle system

The energy and wave functions of two-particle states in a dense plasma are essentially influenced by the surrounding medium. However, the two-particle bound-state energies may remain unshifted over a large density interval. Two simple examples are given to demonstrate the compensation of many-particle effects such as the self-energy and effective two-particle potentials in hydrogen plasmas. Neglecting self-energy and Pauli blocking, energy values that follow from numerical solutions of the Schroedinger equation with a Debye potential are obtained.

Kraeft, W. D.↗
NASA NTRS1989

NASA/USRA advanced space design program: The laser powered interorbital vehicle

A preliminary design is presented for a low-thrust Laser Powered Interorbital Vehicle (LPIV) intended for cargo transportation between an earth space station and a lunar base. The LPIV receives its power from two iodide laser stations, one orbiting the earth and the other located on the surface of the moon. The selected mission utilizes a spiral trajectory, characteristic of a low-thrust spacecraft, requiring 8 days for a lunar rendezvous and an additional 9 days for return. The ship's configuration consists primarily of an optical train, two hydrogen plasma engines, a 37.1 m box beam truss, a payload module, and fuel tanks. The total mass of the vehicle fully loaded is 63300 kg. A single plasma, regeneratively cooled engine design is incorporated into the two 500 N engines. These are connected to the spacecraft by turntables which allow the vehicle to thrust tangentially to the flight path. Proper collection and transmission of the laser beam to the thrust chambers is provided through the optical train. This system consists of the 23 m diameter primary mirror, a convex parabolic secondary mirror, a beam splitter and two concave parabolic tertiary mirrors. The payload bay is capable of carrying 18000 kg of cargo. The module is located opposite the primary mirror on the main truss. Fuel tanks carrying a maximum of 35000 kg of liquid hydrogen are fastened to tracks which allow the tanks to be moved perpendicular to the main truss. This capability is required to prevent the center of mass from moving out of the thrust vector line. The laser beam is located and tracked by means of an acquisition, pointing and tracking system which can be locked onto the space-based laser station. Correct orientation of the spacecraft with the laser beam is maintained by control moment gyros and reaction control rockets. Additionally an aerobrake configuration was designed to provide the option of using the atmospheric drag in place of propulsion for a return trajectory.

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