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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Design for pressure regulating components

The design development for Pressure Regulating Components included a regulator component trade-off study with analog computer performance verification to arrive at a final optimized regulator configuration for the Space Storable Propulsion Module, under development for a Jupiter Orbiter mission. This application requires the pressure regulator to be capable of long-term fluorine exposure. In addition, individual but basically identical (for purposes of commonality) units are required for separate oxidizer and fuel pressurization. The need for dual units requires improvement in the regulation accuracy over present designs. An advanced regulator concept was prepared featuring redundant bellows, all metallic/ceramic construction, friction-free guidance of moving parts, gas damping, and the elimination of coil springs normally used for reference forces. The activities included testing of actual size seat/poppet components to determine actual discharge coefficients and flow forces. The resulting data was inserted into the computer model of the regulator. Computer simulation of the propulsion module performance over two mission profiles indicated satisfactory minimization of propellant residual requirements imposed by regulator performance uncertainties.

Wichmann, H.↗
NASA NTRS1977

The characteristics of sealed nickel-cadmium cells during voltage reversal

A mechanism which allows a cell voltage reversal in a nickel cadmium battery are discussed. The effects of reconditioning and the characteristics of Ni-Cd cells during voltage reversal at low overdischarge rates are outlined. Graphs are presented for: (1) hydrogen pressure decay-effect of state of charge (open circuit stand); (2) hydrogen pressure increase during overdischarge; (3) hydrogen pressure decay-effect of temperature (cells terminals connected through resistors); (4) cell, positive and negative electrode voltage during reversal when reconditioning a 13 cell-24-Ah battery pack through a 40 Omega resistor; (5) pressure discharge current and recombination current during voltage reversal when reconditioning a 13 cell-24-Ah battery pack through a 40 Omega resistor; (6) theoretical hydrogen gas pressure if there were no recombination; and (7) effect of hydrogen pressure on recombination rate during overcharge.

Ritterman, P. F.↗
NASA NTRS1975

Studies of discharge mechanisms in high pressure gases-applications to high efficiency high power lasers

By measuring the absorption and emission cantinua of various states in the cesium/xenon molecule, the collisional rates critical in populating the alkali/rare gas excimer levels have been estimated. Cs atomic states that are weakly optically connected to ground have been shown to form excimer levels that are attractive as potential dissociation lasers. In particular, the (Cs/7 2S/Xe) excited molecule appears promising as a source of high energy laser radiation due to its large dissociation energy, stimulated emission cross section, and small population inversion densities. Monitoring of the optically pumped Cs2 molecular absorption profile in the presence of xenon shows a drastic change with increasing xenon pressure for the Cs2C band. Dominant absorption at large xenon densities is centered around approximately 6380 A as opposed to 6300 A for lower perturber pressure.

Cherrington, B. E.↗
NASA NTRS2013

Photo-Induced Deuterium Enrichment in Residues Produced from the UV Irradiation of Pyrimidine in H2O and H2O+NH3 Ices

Organic compounds found in meteorites often show isotopic signatures of their interstellar/protosolar heritage as enrichments in D and 15N. Meteoritic organics found to be enriched in D include amino acids, hydroxy and dicarboxylic acids, as well as polycyclic aromatic hydrocarbons (PAHs). Processes that can produce isotopic enrichments in presolar/protosolar materials include gas-phase ion-molecule reactions, gas-grain surface reactions, and unimolecular photo-dissociation reactions involving PAHs. Because many molecules in interstellar clouds are enriched in D, the presence of D anomalies in meteorites is thought to originate from preserved or slightly altered interstellar/protostellar materials. However, the link between isotopic enrichments seen in space and those in meteoritic compounds and their relationship remain unclear. In this work, we present results of hydrogen isotopic fractionation for compounds in organic residues produced from the UV irradiation using an H2- discharge UV lamp of H2O:pyrimidine = 20:1 and H2O:NH3:pyrimidine = 20:2:1 ice mixtures at low temperature (is less than 20 K). After irradiation, the resulting residues are dissolved in H2O and analyzed with gas chromatography-mass spectrometry coupled with isotope ratio mass spectrometry (GC-MS/IRMS) [1], following a protocol similar to that used for previous analyses of comparable samples [2,3]. We used this technique to measure compound-specific D/H isotopic ratios for the initial pyrimidine and for two photo-products present in the residues, namely, 2,2'-bipyrimidine and an unidentified bipyrimidine isomer [2-4]. Measuring D enrichments in bipyrimidines has the advantage that the H atoms on these molecules are not easily exchangeable with other compounds, in particular the H2O and NH3 present in the ices or the solvents used to extract the samples for GC-MS/IRMS measurements. The δD value for the initial pyrimidine, measured with a high-temperature conversion elemental analyzer connected to the IRMS, was found to be -30% per mille. Preliminary measurements made on a residue produced from the UV irradiation of an H2O:NH3:pyrimidine = 20:2:1 ice mixture indicate δD values of +118% per mille for 2,2'- bipyrimidine and +92% per mille for the other bipyrimidine isomer, and therefore show a significant D enrichment during the photo-processing and warm-up that lead to their formation [5]. New measurements are currently being performed on a number of residues produced from simpler H2O:pyrimidine = 20:1 ice mixtures under different experimental conditions and will be presented here.

Laboratory Astrochemistry↗
NASA NTRS1966

The spectrum of NV.

Theta pinch discharge study of four times ionized nitrogen /N V/ spectrum

THETA PINCH↗
NASA NTRS1987

Anode-type double layers in a nonuniform magnetic field

The properties of strong, magnetized, three-dimensional double layers are studied. The double layers are produced by drawing a discharge to a large anode plate located in the diverging magnetic field region of a cylindrical argon discharge. If the anode voltage is sufficiently high, the electrons that are accelerated through the anode sheath may become sufficiently energetic to ionize the background neutral gas and transform the anode sheath into a strong double layer. The resulting conical-shaped structures, which extend outward from the plate, have parallel, oblique, and perpendicular electric field components with respect to the magnetic field. The axial extent of these structures depends on the plate bias voltage, neutral gas pressure, and the magnetic field. At neutral gas pressures of a few millitorr, the double-layer structures are visually apparent because of the enhanced light emission from neutrals excited by the energetic electrons. Color photographs of some of these structures are shown. The scaling of the width of these double layers with electric field components perpendicular to B is also investigated.

Cartier, Steven L.↗
NASA NTRS1992

Titan's organic chemistry: Results of simulation experiments

Recent low pressure continuous low plasma discharge simulations of the auroral electron driven organic chemistry in Titan's mesosphere are reviewed. These simulations yielded results in good accord with Voyager observations of gas phase organic species. Optical constants of the brownish solid tholins produced in similar experiments are in good accord with Voyager observations of the Titan haze. Titan tholins are rich in prebiotic organic constituents; the Huygens entry probe may shed light on some of the processes that led to the origin of life on Earth.

Sagan, Carl↗
NASA NTRS1949

Spark ignition of flowing gases I : energies to ignite propane-air mixtures in pressure range of 2 to 4 inches mercury absolute

Ignition studies of flowing gases were made to obtain information applicable to ignition problems in gas-turbine and ram-jet aircraft propulsion systems operating at altitude conditions.Spark energies required for ignition of a flowing propane-air mixture were determined for pressure of 2 to 4 inches mercury absolute, gas velocities of 5.0 to 54.2 feet per second, fuel-air ratios of 0.0607 to 0.1245, and spark durations of 1.5 to 24,400 microseconds. The results showed that at a pressure of 3 inches mercury absolute the minimum energy required for ignition occurred at fuel-air ratios of 0.08 to 0.095. The energy required for ignition increased almost linearly with increasing gas velocity. Shortening the spark duration from approximately 25,000 to 125 microseconds decreased the amount of energy required for ignition. A spark produced by the discharge of a condenser directly into the spark gap and having a duration of 1.5 microseconds required ignition energies larger than most of the long-duration sparks.

Swett, Clyde C , Jr↗
NASA NTRS1980

Inert gas ion thruster development

Two 12 cm magneto-electrostatic containment (MESC) ion thrusters were performance mapped with argon and xenon. The first, hexagonal, thruster produced optimized performance of 48.5to 79 percent argon mass utilization efficiencies at discharge energies of 240 to 425 eV/ion, respectively, Xenon mass utilization efficiencies of 78 to 95 percent were observed at discharge energies of 220 to 290 eV/ion with the same optimized hexagonal thruster. Changes to the cathode baffle reduced the discharge anode potential during xenon operation from approximately 40 volts to about 30 volts. Preliminary tests conducted with the second, hemispherical, MESC thruster showed a nonuniform anode magnetic field adversely affected thruster performance. This performance degradation was partially overcome by changes in the boundary anode placement. Conclusions drawn the hemispherical thruster tests gave insights into the plasma processes in the MESC discharge that will aid in the design of future thrusters.

Ramsey, W. D.↗
NASA NTRS1984

Discharge Extracts Oxygen From CO2

Process under development supplies oxygen for life support in hazardous environments. Prototype CO2 reactor vessel produces oxygen from carbon dioxide at expense of about 100 watt-hours of electricity per liter of gas reduced. Design changes to improve efficiency include narrowing gap between walls to operate at lower voltages and increasing area of one electrode while decreasing area of other to reduce capacitance.

Luce, R. S.↗
NASA NTRS1977

Small, high-pressure liquid hydrogen turbopump

A high pressure, liquid hydrogen turbopump was designed, fabricated, and tested to a maximum speed of 9739 rad/s and a maximum pump discharge pressure of 2861 N/sq. cm. The approaches used in the analysis and design of the turbopump are described, and fabrication methods are discussed. Data obtained from gas generator tests, turbine performance calibration, and turbopump testing are presented.

Csomor, A.↗
NASA NTRS2004

Paschen Considerations for High Altitude Airships

Recently, there have been several proposals submitted to funding agencies for long-lived high altitude (about 70,000 feet) airships for communications, surveillance, etc. In order for these airships to remain at altitude, high power, high efficiency, lightweight solar arrays must be used, and high efficiency power management and distribution systems must be employed. The needs for high power and high efficiency imply high voltage systems. However, the air pressure at these extreme altitudes is such that electrical power systems will be near the Paschen discharge minimum over a wide range of electrode separations. In this paper, preliminary calculations are made for acceptable high voltage design practices under ambient, hydrogen and helium gas atmospheres.

Ferguson, D. C.↗
NASA NTRS2006

Insulator - Insulator Contact Charging as a Function of Pressure

Metal - metal and metal - insulator contact or triboelectric charging are well known phenomena with good theoretical understanding of the charge exchange mechanism. However, insulator - insulator charging is not as well understood. Theoretical and experimental research has been performed that shows that the surface charge on an insulator after triboelectric charging with another insulator is rapidly dissipated with lowered atmospheric pressure. This pressure discharge is consistent with surface ions being evaporated off the surface once their vapor pressure is attained. A two-phase equilibrium model based on an ideal gas of singly charged ions in equilibrium with a submonolayer adsorbed film was developed to describe the pressure dependence of the surface charge on an insulator. The resulting charge density equation is an electrostatic version of the Langmuir isotherm.

Hogue, Michael D.↗
NASA NTRS2018

Development of the Electrostatic Precipitator (ESP) for Mars and Electrodynamic Dust Shield (EDS)

Kennedy Space Center's Swamp Works is a fast-paced and diverse technology development laboratory that aims to advance commercial and government capabilities to colonize extraterrestrial environments. As a part of Swamp Works, the Electrostatic and Surface Physics Laboratory (ESPL) is currently developing new technologies that will further NASA's capabilities to colonize lunar and Martian environments. At the ESPL, the objective of the overall project is to aid in the dust mitigation of robotic and human exploration missions to the moon and Mars. The moon and Mars are covered with layers of dust, which can make long-term exploration missions very difficult. The team at the ESPL is developing an electrostatic precipitator (ESP) to aid in the reduction of interference from airborne Martian dust on equipment. The ESP is designed to mitigate the dust in an intake of CO2-rich dusty gas (i.e., the Martian atmosphere). The ESP is essentially a cylindrical tube with a coaxial wire electrode. Applying a high voltage through this electrode induces a corona discharge (a glowing plasma that envelops the electrode), which is used to charge the inflowing dust. The electric field caused by the corona pushes the charged dust to the walls of the precipitator, preventing the dust to flow out of the tube. Environmental dust can make long-term exploration missions very difficult, and settled dust is no exception. Settled lunar or Martian dust can hinder the performance and lifetime of equipment. For example, dust can settle on the solar panels of a lunar or Martian rover, decreasing its performance while increasing its charging time. To address this, the team at the ESPL is also developing an electrodynamic dust shield (EDS), which is designed to remove lunar or Martian dust from the surfaces of equipment. The EDS uses a non-uniform electric field to generate a dielectrophoretic force, which pushes the particles away from the surface of the shield. A number of dust shields will be tested on the exterior of the International Space Station (ISS) via MISSE-11, a flight payload to the ISS that will test the effects of long-term exposure to space on materials. During my internship at the ESPL, I aided in the development of these technologies. For the ESP, I helped characterize the electrical properties of various geometries and helped redesign the hardware of the testbed (the precipitator used to test this technology in the lab). To characterize the electrical properties of the ESP, I ran various tests of the precipitator, which consisted of varying the environmental conditions and geometry of the testbed. Analyzing the electrical properties of the ESP in various environmental conditions is necessary to characterize its collection efficiency, since it will be used in the dusty Martian environment. For the EDS, I helped analyze the dielectric strength of the surface of the shield via high-voltage testing. A dielectrically strong surface will help the shield survive the harsh environment of space, which will enable it to have both lunar and Martian applications.

Corona Discharge↗
NASA NTRS2015

Proof-of-Concept Experiments on a Gallium-Based Ignitron for Pulsed Power Applications

Ignitrons are electrical switching devices that operate at switching times that are on the order of microseconds, can conduct high currents of thousands of amps, and are capable of holding off tens of thousands of volts between pulses. They consist of a liquid metal pool within an evacuated tube that serves both the cathode and the source of atoms and electrons for an arc discharge. Facing the liquid metal pool is an anode suspended above the cathode, with a smaller ignitor electrode tip located just above the surface of the cathode. The ignitron can be charged to significant voltages, with a potential difference of thousands of volts between anode and cathode. When an ignition pulse is delivered from the ignitor electrode to the cathode, a small amount of the liquid metal is vaporized and subsequently ionized, with the high voltage between the anode and cathode causing the gas to bridge the gap between the two electrodes. The electrons and ions move rapidly towards the anode and cathode, respectively, with the ions liberating still more atoms from the liquid metal cathode surface as a high-current plasma arc discharge is rapidly established. This arc continues in a self-sustaining fashion until the potential difference between the anode and cathode drops below some critical value. Ignitrons have been used in a variety of pulsed power applications, including the railroad industry, industrial chemical processing, and high-power arc welding. In addition, they might prove useful in terrestrial power grid applications, serving as high-current fault switches, quickly shunting dangerous high-current or high-voltage spikes safely to ground. The motivation for this work stemmed from the fact that high-power, high-reliability, pulsed power devices like the ignitron have been used for ground testing in-space pulsed electric thruster technologies, and the continued use of ignitrons could prove advantageous to the future development and testing of such thrusters. Previous ignitron designs have used mercury as the liquid metal cathode, owing to its presence as a liquid at room temperatures and a vapor pressure of 10 Pa (75 mtorr) at room temperature. While these are favorable properties, there are obvious environmental and personal safety concerns with the storage, handling, and use of mercury and its compounds. The purpose of the present work was to fabricate and test an ignitron that used as its cathode an alternate liquid metal that was safe to handle and store. To that end, an ignitron test article that used liquid gallium as the cathode material was developed and tested. Gallium is a metal that has a melting temperature of 29.76 C, which is slightly above room temperature, and a boiling point of over 2,300 C at atmospheric pressure. This property makes gallium the element with the largest relative difference between melting and boiling points. Gallium has a limited role in biology, and when ingested, it will be subsequently processed by the body and expelled rather than accumulating to toxic levels. The next section of this Technical Memorandum (TM) provides background information on the development of mercury-based ignitrons, which serves as the starting point for the development of the gallium-based variant. Afterwards, the experimental hardware and setup used in proof-of-concept testing of a basic gallium ignitron are presented. Experimental data, consisting of discharge voltage and current waveforms as well as high-speed imaging of the gallium arc discharge in the gallium ignitron test article, are presented to demonstrate the efficacy of the concept. Discussion of the data and suggestions on improvements for future iterations of the design are presented in the final two sections of this TM.

Ali, H. K.↗
NASA NTRS1997

Predictive Modeling in Plasma Reactor and Process Design

Research continues toward the improvement and increased understanding of high-density plasma tools. Such reactor systems are lauded for their independent control of ion flux and energy enabling high etch rates with low ion damage and for their improved ion velocity anisotropy resulting from thin collisionless sheaths and low neutral pressures. Still, with the transition to 300 mm processing, achieving etch uniformity and high etch rates concurrently may be a formidable task for such large diameter wafers for which computational modeling can play an important role in successful reactor and process design. The inductively coupled plasma (ICP) reactor is the focus of the present investigation. The present work attempts to understand the fundamental physical phenomena of such systems through computational modeling. Simulations will be presented using both computational fluid dynamics (CFD) techniques and the direct simulation Monte Carlo (DSMC) method for argon and chlorine discharges. ICP reactors generally operate at pressures on the order of 1 to 10 mTorr. At such low pressures, rarefaction can be significant to the degree that the constitutive relations used in typical CFD techniques become invalid and a particle simulation must be employed. This work will assess the extent to which CFD can be applied and evaluate the degree to which accuracy is lost in prediction of the phenomenon of interest; i.e., etch rate. If the CFD approach is found reasonably accurate and bench-marked with DSMC and experimental results, it has the potential to serve as a design tool due to the rapid time relative to DSMC. The continuum CFD simulation solves the governing equations for plasma flow using a finite difference technique with an implicit Gauss-Seidel Line Relaxation method for time marching toward a converged solution. The equation set consists of mass conservation for each species, separate energy equations for the electrons and heavy species, and momentum equations for the gas. The sheath is modeled by imposing the Bohm velocity to the ions near the walls. The DSMC method simulates each constituent of the gas as a separate species which would be analogous in CFD to employing separate species mass, momentum, and energy equations. All particles including electrons are moved and allowed to collide with one another with the stipulation that the electrons remain tied to the ions consistent with the concept of ambipolar diffusion. The velocities of the electrons are allowed to be modified during collisions and are not confined to a Maxwellian distribution. These benefits come at a price in terms of computational time and memory. The DSMC and CFD are made as consistent as possible by using similar chemistry and power deposition models. Although the comparison of CFD and DSMC is interesting, the main goal of this work is the increased understanding of high-density plasma flowfields that can then direct improvements in both techniques. This work is unique in the level of the physical models employed in both the DSMC and CFD for high-density plasma reactor applications. For example, the electrons are simulated in the present DSMC work which has not been done before for low temperature plasma processing problems. In the CFD approach, for the first time, the charged particle transport (discharge physics) has been self-consistently coupled to the gas flow and heat transfer.

Hash, D. B.↗
NASA NTRS1984

Singlet oxygen generator for a solar powered chemically pumped iodine laser

The potential of solid phase endoperoxides as a means to produce single-delta oxygen in the gas phase in concentrations useful to chemical oxygen-iodine lasers was investigated. The 1,4 - endoperoxide of ethyl 3- (4-methyl - 1-naphthyl) propanoate was deposited over an indium-oxide layer on a glass plate. Single-delta oxygen was released from the endoperoxide upon heating the organic film by means of an electrical discharge through the conductive indium oxide coating. The evolution of singlet-delta oxygen was determined by measuring the dimol emission signal at 634 nm. Comparison of the measured signal with an analytic model leads to two main conclusions: virtually all the oxygen being evolved is in the singlet-delta state and in the gas phase, and there is no significant quenching other than energy pooling on the time scale of the experiment (approximately 10 msec). The use of solid phase endoperoxide as a singlet-delta oxygen generator for an oxygen-iodine laser appears promising.

Busch, G. E.↗
NASA NTRS1977

Multipole gas thruster design

The development of a low field strength multipole thruster operating on both argon and xenon is described. Experimental results were obtained with a 15-cm diameter multipole thruster and are presented for a wide range of discharge-chamber configurations. Minimum discharge losses were 300-350 eV/ion for argon and 200-250 eV/ion for xenon. Ion beam flatness parameters in the plane of the accelerator grid ranged from 0.85 to 0.93 for both propellants. Thruster performance is correlated for a range of ion chamber sizes and operating conditions as well as propellant type and accelerator system open area. A 30-cm diameter ion source designed and built using the procedure and theory presented here-in is shown capable of low discharge losses and flat ion-beam profiles without optimization. This indicates that by using the low field strength multipole design, as well as general performance correlation information provided herein, it should be possible to rapidly translate initial performance specifications into easily fabricated, high performance prototypes.

Isaacson, G. C.↗