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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Upwind MacCormack Euler solver with non-equilibrium chemistry

A computer code, designated UMPIRE, is currently under development to solve the Euler equations in two dimensions with non-equilibrium chemistry. UMPIRE employs an explicit MacCormack algorithm with dissipation introduced via Roe's flux-difference split upwind method. The code also has the capability to employ a point-implicit methodology for flows where stiffness is introduced through the chemical source term. A technique consisting of diagonal sweeps across the computational domain from each corner is presented, which is used to reduce storage and execution requirements. Results depicting one dimensional shock tube flow for both calorically perfect gas and thermally perfect, dissociating nitrogen are presented to verify current capabilities of the program. Also, computational results from a chemical reactor vessel with no fluid dynamic effects are presented to check the chemistry capability and to verify the point implicit strategy.

Sherer, Scott E.↗
NASA NTRS1988

Direct simulation of AFE forebody and wake flow with thermal radiation

Calculated results for the flowfield structure and surface quantities are presented for an axisymmetric representation of an aeroassist flight experiment vehicle. The direct simulation Monte Carlo (DSMC) method is used to perform the calculations, since the flow is highly nonequilibrium about the vehicle during both the compression and expansion phases. The body configuration is an elliptically blunt nose followed by a skirt with a circular radius and an afterbody. Freestream conditions correspond to a single point along the entry trajectory at an altitude of 90 km and a velocity of 9.9 km/s. The calculations account for nonequilibrium in the translational and internal modes, dissociation, ionization, and thermal radiation. The degree of dissociation is large, but the maximum ionization is only about 2 percent by mole fraction. The bluntforebody flow experiences a high degree of thermal nonequilibrium in which the translational temperature is generally greater than the internal temperature. However, as the flow expands about the aerobrake skirt and afterbody, the internal temperature is generally greater than the translational temperature.

Moss, James N.↗
NASA NTRS1989

Direct simulation of AFE forebody and wake flow with thermal radiation

Calculated results for the flowfield structure and surface quantities are presented for an axisymmetric representation of an aeroassist flight experiment vehicle. The direct simulation Monte Carlo (DSMC) method is used to perform the calculations, since the flow is highly nonequilibrium about the vehicle during both the compression and expansion phases. The body configuration is an elliptically blunt nose followed by a skirt with a circular radius and an afterbody. Freestream conditions correspond to a single point along the entry trajectory at an altitude of 90 km and a velocity of 9.9 km/s. The calculations account for nonequilibrium in the translational and internal modes, dissociation, ionization, and thermal radiation. The degree of dissociation is large, but the maximum ionization is only about 2 percent by mole fraction. The blunt forebody flow experiences a high degree of thermal nonequilibrium in which the translational temperature is generally greater than the internal temperature. However, as the flow expands about the aerobrake skirt and afterbody, the internal temperature is generally greater than the translational temperature.

Moss, James N.↗
NASA NTRS1995

Convective and radiative heating for vehicle return from the Moon and Mars

The aerothermal environment is examined for two vehicle forebodies near the peak heating points of lunar and martian return-to-earth trajectories at several nominal entry velocities. The first vehicle forebody is that of a 70 deg aerobrake for entry into earth orbit; the second, a capsule of Apollo configuration for direct entry into the earth's atmosphere. The configurations and trajectories are considered likely candidates for such missions. Two-temperature, thermochemical nonequilibrium models are used in the flow field analyses. In addition to Park's empirical model for dissociation under conditions of thermal nonequilibrium, the Gordiets kinetic model for the homonuclear dissociation of N2 and O2 is also considered. Temperature and emission profiles indicate nonequilibrium effects in a 2 to 5 cm post shock region. Substantial portions of the shock layer flow appear to be in equilibrium. The shock layer over an aerobrake for return from the moon exhibits the largest extent of nonequilibrium effects of all considered missions. Differences between the Gordiets and Parks kinetic model were generally very small for the lunar return aerobrake case, the greatest difference of 6.1 percent occurring in the radiative heating levels.

Greendyke, Robert B.↗
NASA NTRS2014

The Deuterium to Hydrogen Ratio in the Water that Formed the Yellowknife Bay Mudstones in Gale Crater

A suite of isotope ratios of light elements in the present martian atmosphere (13C/12C, 15N/14N, 18O/16O, 38Ar/36Ar, and D/H) are all substantially enriched in the heavy element suggesting atmospheric loss to space over the past billions of years with preferential loss of the lighter isotope from each pair. In situ measurements from MSL's Sample Analysis at Mars (SAM) instrument [e.g. 1,2,3] have considerably refined previous measurements from the Viking mass spectrometers [e.g. 4], from remote spectroscopic observations [e.g. 5,6], and from martian meteorite studies [e.g. 7,8]. The persistence of habitable environments such as the ancient Yellowknife Bay lake recently revealed by measurements from the Curiosity rover [9] depends on the surface temperatures and the duration of an atmosphere thicker than that at present. Current and planned measurements from orbit with the Mars Express and MAVEN missions respectively intend to study the processes of atmospheric escape including solar wind interaction, sputtering, thermal escape, and dissociative recombination, and determine or refine the current rate of atmospheric loss caused by these and other mechanisms. The goal of these programs is to understand the physical processes sufficiently well so that robust extrapolations over the past billions of years can be made D/H is measured by both the Tunable Laser Spectrometer (TLS) and the Quadrupole Mass Spectrometer (QMS) of the SAM suite. to predict the atmospheric and surface conditions on early Mars. However, the study of the history of martian atmospheric evolution will be greatly facilitated if we are able to also directly measure the isotopic composition of volatiles captured in rocks that are representative of the ancient atmosphere. To date, D/H is one of the most promising candidates for this study since water is the most abundant volatile thermally released from the Yellowknife Bay phylosilicates discovered by the SAM and CheMin experiments of MSL and its

Yellowknife Bay↗
NASA NTRS1993

The velocity distribution of cometary hydrogen - Evidence for high velocities?

The Hamilton Echelle spectrograph on the 3-m Shane telescope at Lick Observatory was used to obtain high-velocity and spatial resolution 2D spectra of H-alpha 6563-A emission in Comets Austin and Levy. The presence of the components expected from water dissociation and collisional thermalization in the inner coma is confirmed by the hydrogen velocity distribution. In Comet Austin, the potential high-velocity hydrogen includes velocities of up to about 40 km/s and is spatially symmetric with respect to the nucleus. In Comet Levy, the high-velocity hydrogen reaches velocities of up to 50 km/s and is situated exclusively on the sunward side of the nucleus. The two distinct signatures of high-velocity hydrogen imply two distinct sources.

Brown, Michael E.↗
NASA NTRS1987

In-Vacuum Dissociator for Atomic-Hydrogen Masers

Thermal control and vacuum sealing achieved while contamination avoided. Simple, relatively inexpensive molecular-hydrogen dissociator for atomic-hydrogen masers used on Earth or in vacuum of space. No air cooling required, and absence of elastomeric O-ring seals prevents contamination. In-vacuum dissociator for atomic hydrogen masers, hydrogen gas in glass dissociator dissociated by radio-frequency signal transmitted from surrounding 3-turn coil. Heat in glass conducted away by contacting metal surfaces.

Vessot, R. F.↗
NASA NTRS2001

Initiation of Martian Outflow Channels: Related to the Dissociation of Gas Hydrate?

We propose that the disruption of subpermafrost aquifers on Mars by the thermal- or pressure-induced dissociation of methane hydrate may have been a frequent trigger for initiating outflow channel activity. This possibility is raised by recent work that suggests that significant amounts of methane and gas hydrate may have been produced within and beneath the planet's cryosphere. On Earth, the build-up of overpressured water and gas by the decomposition of hydrate deposits has been implicated in the formation of large blowout features on the ocean floor. These features display a remarkable resemblance (in both morphology and scale) to the chaotic terrain found at the source of many Martian channels. The destabilization of hydrate can generate pressures sufficient to disrupt aquifers confined by up to 5 kilometers of frozen ground, while smaller discharges may result from the water produced by the decomposition of near-surface hydrate alone.

Max, Michael D.↗
NASA NTRS1986

The reactive thermal conductivity of air at high temperatures

This paper presents the thermal conductivity of air from the dissociation and ionization reactions of the nitrogen and oxygen species in air from 1000 K to 25,000 K. The results for nitrogen are compared with results for the nonreactive (frozen) contribution to the thermal conductivity of the 'nitrogen system' (N2, N, N/+/, and the electron, e). At 6000 K, the contribution to the thermal conductivity from the dissociation of N2 is more than an order of magnitude greater than the frozen thermal conductivity and, at 15,000 K, the contribution to the thermal conductivity from the ionization of nitrogen atoms is about as large as the contribution from the frozen thermal conductivity.

Biolsi, L.↗
NASA NTRS1992

The formation of magnetic cavities in comets

In this paper a unidimensional model for the formation of magnetic cavities in comets is presented. This model includes ion-neutral friction, dissociative recombination, photoionization, and thermal energetic ion pressure coupled with a nonconstant velocity profile which was chosen to simulate the flow pattern. The model explains the thermal ion population profile. Conditions under which a cavity may not form are discussed. In the paper the roles of the various processes are studied, and it is shown that focusing on ion-neutral friction as the major process in the creation of the cavity is not in general correct. In the last part of the paper, the limitations of the model are delineated.

Klopman, Z.↗
NASA NTRS1997

An Interagency Study of Depainting Techniques

Many popular and widely used paint stripping products now contain methylene chloride as their active ingredient. However, the Environmental Protection Agency (EPA) will critically curb the use of methylene chloride under an aerospace national emission standard for hazardous air pollutants (NESHAP) within the next 2-1/2 years. An effort is underway to identify and evaluate alternative depainting technologies emphasizing those believed to be both effective and environmentally benign. On behalf of the EPA and in cooperation with the U. S. Air Force (USAF), the National Aeronautics and Space Administration (NASA) is conducting a technical assessment of nine alternative technologies (i.e.: chemical stripping, two CO2 blasting processes, FLASHJET(TM) coating removal, laser stripping, plastic media blasting, sodium bicarbonate wet stripping, high-pressure water stripping, and wheat starch blasting). These depainting processes represent five removal method categories, namely abrasive, impact, cryogenic, thermal, and/or molecular bonding dissociation. This paper discusses the test plan and parameters for this interagency study. Several thicknesses of clad and non-clad aluminum substrates were used to prepare test specimens, which have been cut, cleaned, painted, and environmentally aged. Each depainting process has been assigned a specimen lot, which is now undergoing an initial strip cycle. Metallurgical impacts will be determined after these specimens complete five cycles of preparation and stripping.

Cook, B.↗
NASA NTRS1998

NASA/Air Force/Environmental Protection Agency Interagency Depainting Study

Many popular and widely used paint stripping products have traditionally contained methylene chloride as their main active ingredient. However, the Environmental Protection Agency (EPA) has critically curved the allowable use of methylene chloride under the National Emission Standard for Hazardous Air Pollutants regulating Aerospace Manufacturing and Rework Facilities . Compliance with this rule was mandatory by September 1998 for affected facilities. An effort is underway to identify and evaluate alternative depainting technologies emphasizing those believed both effective and environmentally benign. On behalf of the EPA and in cooperation with the United States Air Force, the National Aeronautics and Space Administration is conducting a technical assessment of several alternative technologies ( i.e. : chemical stripping, two CO2 blasting processes, CO2 xenon lamp coating removal, CO2 Laser stripping, plastic media blasting, sodium bicarbonate wet stripping, high pressure water stripping, and wheat starch blasting). These depainting processes represent five removal method categories, namely abrasive, impact, cryogenic, thermal, and/or molecular bonding dissociation. This paper discusses the test plan and parameters for this interagency study. Several thicknesses of clad and non-clad aluminum substrates were used to prepare test specimens. Each depainting process has been assigned a specimen lot, all of which have completed three to five stripping cycles. Numerous metallurgical evaluations are underway to assess the impact of these alternative depainting processes upon the structural integrity of the substrate.

Clark-Ingram, Marceia↗
NASA NTRS1972

The degradation of space shuttle TPS metals in dissociated oxygen.

The interaction of space shuttle orbiter Thermal Protection System (TPS) metals with the chemical environment to which it is exposed during reentry is considered with emphasis on the effects of dissociated oxygen. Experimental results comparing the interactions of atomic (dissociated) and molecular oxygen with five candidate shuttle TPS metals, Ni-20Cr-2ThO2, Ni-20Cr-3.5Al-2ThO2, Ni-16Cr-15Fe-2Mn-.5Si-.3La-2ThO2, Haynes Alloy Number 188, and Ti-6Al-4V at their maximum planned use temperature are presented. As measured by metal recession, weight change, rate of oxide scale formation, and scale spalling, the first four metals show enhanced degradation in a dissociated oxygen environment. The enhanced degradation appears to result from differing rates of alloy constituent reactions in the two environments. The dissociated oxygen environmental tests are found to better assess the usefulness of shuttle skin materials for the planned mission than do conventional molecular (either flowing or static) oxidation experiments.-

Gilbreath, W. P.↗
NASA NTRS1988

Nonequilibrium thermal radiation for an aeroassist flight experiment vehicle

The direct-simulation Monte Carlo method incorporating a dissociating and ionizing gas model for air with thermal radiation is used to characterize the hypersonic flow about an axisymmetric representation of an aeroassist flight experiment (AFE) vehicle, whose freestream conditions correspond to selected points along the entry, aerobraking, and exit phases of the trajectory. Calculations for two trajectory conditions indicate that the radiative heating of the AFE forebody is lower than the convective heating, but becomes significant as the maximum convective heating rate condition is approached.

Moss, James N.↗
NASA NTRS2006

Generating Breathable Air Through Dissociation of N2O

A nitrous oxide-based oxygen-supply system (NOBOSS) is an apparatus in which a breathable mixture comprising 2/3 volume parts of N2 and 1/3 volume part of O2 is generated through dissociation of N2O. The NOBOSS concept can be adapted to a variety of applications in which there are requirements for relatively compact, lightweight systems to supply breathable air. These could include air-supply systems for firefighters, divers, astronauts, and workers who must be protected against biological and chemical hazards. A NOBOSS stands in contrast to compressed-gas and cryogenic air-supply systems. Compressed-gas systems necessarily include massive tanks that can hold only relatively small amounts of gases. Alternatively, gases can be stored compactly in greater quantities and at low pressures when they are liquefied, but then cryogenic equipment is needed to maintain them in liquid form. Overcoming the disadvantages of both compressed-gas and cryogenic systems, the NOBOSS exploits the fact that N2O can be stored in liquid form at room temperature and moderate pressure. The mass of N2O that can be stored in a tank of a given mass is about 20 times the mass of compressed air that can be stored in a tank of equal mass. In a NOBOSS, N2O is exothermically dissociated to N2 and O2 in a main catalytic reactor. In order to ensure the dissociation of N2O to the maximum possible extent, the temperature of the reactor must be kept above 400 C. At the same time, to minimize concentrations of nitrogen oxides (which are toxic), it is necessary to keep the reactor temperature at or below 540 C. To keep the temperature within the required range throughout the reactor and, in particular, to prevent the formation of hot spots that would be generated by local concentrations of the exothermic dissociation reaction, the N2O is introduced into the reactor through an injector tube that features carefully spaced holes to distribute the input flow of N2O widely throughout the reactor. A NOBOSS includes one or more "destroyer" subsystems for removing any nitrogen oxides that remain downstream of the main N2O-dissociation reactor. A destroyer includes a carbon bed in series with a catalytic reactor, and is in thermal contact with the main N2O-dissociation reactor. The gas mixture that leaves the main reactor first goes through a carbon bed, which adsorbs all of the trace NO and most of the trace NO2. The gas mixture then goes through the destroyer catalytic reactor, wherein most or all of the remaining NO2 is dissociated. A NOBOSS can be designed to regulate its reactor temperature across a range of flow rates. One such system includes three destroyer loops; these loops act, in combination with a heat sink, to remove heat from the main N2O-dissociation reactor. In this system, the N2O and product gases play an additional role as coolants; thus, as needed, the coolant flow increases in proportion to the rate of generation of heat, helping to keep the main-reactor temperature below 540 C.

Zubrin, Robert↗
NASA NTRS1994

Nonequilibrium radiation and chemistry models for aerocapture vehicle flowfields

The primary accomplishments of the project were as follows: (1) From an overall standpoint, the primary accomplishment of this research was the development of a complete gasdynamic-radiatively coupled nonequilibrium viscous shock layer solution method for axisymmetric blunt bodies. This method can be used for rapid engineering modeling of nonequilibrium re-entry flowfields over a wide range of conditions. (2) Another significant accomplishment was the development of an air radiation model that included local thermodynamic nonequilibrium (LTNE) phenomena. (3) As part of this research, three electron-electronic energy models were developed. The first was a quasi-equilibrium electron (QEE) model which determined an effective free electron temperature and assumed that the electronic states were in equilibrium with the free electrons. The second was a quasi-equilibrium electron-electronic (QEEE) model which computed an effective electron-electronic temperature. The third model was a full electron-electronic (FEE) differential equation model which included convective, collisional, viscous, conductive, vibrational coupling, and chemical effects on electron-electronic energy. (4) Since vibration-dissociation coupling phenomena as well as vibrational thermal nonequilibrium phenomena are important in the nonequilibrium zone behind a shock front, a vibrational energy and vibration-dissociation coupling model was developed and included in the flowfield model. This model was a modified coupled vibrational dissociation vibrational (MCVDV) model and also included electron-vibrational coupling. (5) Another accomplishment of the project was the usage of the developed models to investigate radiative heating. (6) A multi-component diffusion model which properly models the multi-component nature of diffusion in complex gas mixtures such as air, was developed and incorporated into the blunt body model. (7) A model was developed to predict the magnitude and characteristics of the shock wave precursor ahead of vehicles entering the Earth's atmosphere. (8) Since considerable data exists for radiating nonequilibrium flow behind normal shock waves, a normal shock wave version of the blunt body code was developed. (9) By comparing predictions from the models and codes with available normal shock data and the flight data of Fire II, it is believed that the developed flowfield and nonequilibrium radiation models have been essentially validated for engineering applications.

Carlson, Leland A.↗
NASA NTRS1996

Fullerene Propellant Research for Electric Propulsion

The large mass, low first ionization potential and large electron impact ionization cross-section make Buckminsterfullerene (carbon 60) potentially attractive as an ion engine propellant. It has the potential for significant increases in engine efficiency over that obtained with xenon at specific impulses less than 3 000 s. One problem encountered in fullerene ion engines has been dissociation of the propellant. Previously this was attributed to thermal decomposition due to operation of the ion engine at temperatures greater than 1073 K. However, during tests conducted at temperatures lower than 1073 K fullerene fragmentation was still observed. This prompted an investigation to determine if the dissociation was still due to thermal effects or if it was due to collisional processes in the discharge chamber.

fullerenes↗