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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Solar heating of common lunar minerals for the production of oxygen

The purpose of this work was to demonstrate the feasibility of vapor-phase reduction (pyrolysis) of lunar materials to produce oxygen. Solar furnace experiments were conducted on two common lunar minerals, ilmenite and anorthite. Thermodynamic equilibrium calculations predicted that ilmenite should show a larger pressure increase than anorthite under conditions of the experiments and this was confirmed by the experiments. The measured mass loss of the ilmenite sample was consistent with loss of oxygen by reduction of iron in the liquid phase; this result was also predicted from equilibrium calculations. Based on preliminary experiments and equilibrium calculations, the temperatures needed for pyrolysis are expected to be in the range of 2000 to 2500 K, giving total gas pressures of 0.01 to 1 torr. Bulk regolith can be used as a feedstock without extensive beneficiation. Further, selective condensation of metal-containing species from the gas phase may yield metallic iron and silicon as byproducts from the process.

Senior, C. L.↗
NASA NTRS1991

Compatibility of potential reinforcing ceramics with Ni and Fe aluminides

There is a great deal of interest in the possible utilization of intermetallic compounds in advanced high temperature gas turbine engines. These compounds exhibit a variety of promising properties, including reasonable strength, high melting points, relatively low densities, and good corrosion resistance. However, in general, they also show limited ductilities and toughness, and less than optimum creep strengths at elevated temperatures. In addition, in applications involving advanced gas turbine engines, it is often necessary for candidate materials to have large elastic moduli. The present study is part of a program whose objective is to identify a high temperature fiber reinforced composite. The approach adopted was to fabricate laboratory samples of the combinations of materials considered by Misra, in order to determine the extent to which the thermodynamic calculations can predict phase stability. As many of the ceramic phases considered are not currently available in fiber form, they were added as particulates to the alloy matrices. The ways in which the materials were produced and evaluated are described.

Clark, William A. T.↗
NASA NTRS1993

Rotary engine performance computer program (RCEMAP and RCEMAPPC): User's guide

This report is a user's guide for a computer code that simulates the performance of several rotary combustion engine configurations. It is intended to assist prospective users in getting started with RCEMAP and/or RCEMAPPC. RCEMAP (Rotary Combustion Engine performance MAP generating code) is the mainframe version, while RCEMAPPC is a simplified subset designed for the personal computer, or PC, environment. Both versions are based on an open, zero-dimensional combustion system model for the prediction of instantaneous pressures, temperature, chemical composition and other in-chamber thermodynamic properties. Both versions predict overall engine performance and thermal characteristics, including bmep, bsfc, exhaust gas temperature, average material temperatures, and turbocharger operating conditions. Required inputs include engine geometry, materials, constants for use in the combustion heat release model, and turbomachinery maps. Illustrative examples and sample input files for both versions are included.

Bartrand, Timothy A.↗
NASA NTRS1995

Stellar oxygen abundances. 4: Systematic effects on oxygen abundances derived from the 6300 A (O I) and 7774 A O I lines

We consider potential systematic effects on oxygen abundances derived from the 6300 A (OI) line and the 7774 A OI triplet. Our solar intensity spectra of the 7774 A triplet confirm previous results which indicate a discrepancy between the observed equivalent widths of Altrock (1968) and the values predicted by Local Thermodynamic Equilibrium (LTE) and recent NLTE models. However, this disagreement (at low micron(s)) does not seem to affect the solar O abundance as derived from flux spectra. We derive O abundances for a selection of relatively metal-rich F and G dwarfs from both the 6300 A (OI) line and 7774 A OI triplet and detail the various uncertainties which enter into the analyses. Minimizing possible systematic effects to the extent possible, we find for T(sub eff) approximately less than 6200-6300 K no systematic difference between the 6300 and 7774 A abundances. For T(sub eff) approximately greater than 6200-6300 K, however 7774 A abundances are substantially larger than the 6300 A abundances. This agreement in O abundances from the two features at cooler T(sub eff) conflicts with that of others and we suggest that the discrepancy may be due to the different model atmospheres utilized. If recently proposed, hotter T(sub eff) values for metal-poor dwarfs are correct, then there appears to be no discrepancy between the 6300 A abundances of metal-poor giants are correct, then there appears to be no discrepancy between the 6300 A abundances of metal-poor giants or dwarfs and the 7774 A abundances for dwarfs. This would seem to rule out substantial LTE departures or atmospheric inhomogeneity effects skewing metal-poor O abundances from the 7774 A triplet (for cooler stars having low metallicity anyway). Given the repeated inability of authors to reproduce each others' O abundances from the 6300 A (OI) line and the uncertainties in the solar equivalent width, we question the usual assumption that the 6300 A (OI) line and the uncertainties in the solar equivalent width, we question the usual assumption that the 6300 A (OI) abundances are more reliable than those from the permitted triplet.

King, Jeremy R.↗
NASA NTRS2009

Evidence for Calcium Carbonate at the Phoenix Landing Site

The Phoenix mission has recently finished its study of the north polar environment of Mars with the aim to help understand both the current climate and to put constraints on past climate. An important part of understanding the past climate is the study of secondary minerals, those formed by reaction with volatile compounds such as H2O and CO2. This work describes observations made by the Thermal and Evolved-Gas Analyzer (TEGA) on the Phoenix Lander related to carbonate minerals. Carbonates are generally considered to be products of aqueous processes. A wet and warmer climate during the early history of Mars coupled with a much denser CO2 atmosphere are ideal conditions for the aqueous alteration of basaltic materials and the subsequent formation of carbonates. Carbonates (Mg- and Ca-rich) are predicted to be thermodynamically stable minerals in the present martian environment, however, there have been only a few indications of carbonates on the surface by a host of orbiting and landed missions to Mars. Carbonates (Mg-rich) have been suggested to be a component (2-5 wt %) of the martian global dust based upon orbital thermal emission spectroscopy. The identifications, based on the presence of a 1480 cm-1 absorption feature, are consistent with Mgcarbonates. A similar feature is observed in brighter, undisturbed soils by Mini-TES on the Gusev plains. Recently, Mg-rich carbonates have been identified in the Nili Fossae region by the CRISM instrument onboard the Mars Reconnaissance Orbiter. Carbonates have also been confirmed as aqueous alteration phases in martian meteorites so it is puzzling why there have not been more discoveries of carbonates by landers, rovers, and orbiters. Carbonates may hold important clues about the history of liquid water and aqueous processes on the surface of Mars.

Boynton, W. V.↗
NASA NTRS2011

An Active Broad Area Cooling Model of a Cryogenic Propellant Tank with a Single Stage Reverse Turbo-Brayton Cycle Cryocooler

As focus shifts towards long-duration space exploration missions, an increased interest in active thermal control of cryogenic propellants to achieve zero boil-off of cryogens has emerged. An active thermal control concept of considerable merit is the integration of a broad area cooling system for a cryogenic propellant tank with a combined cryocooler and circulator system that can be used to reduce or even eliminate liquid cryogen boil-off. One prospective cryocooler and circulator combination is the reverse turbo-Brayton cycle cryocooler. This system is unique in that it has the ability to both cool and circulate the coolant gas efficiently in the same loop as the broad area cooling lines, allowing for a single cooling gas loop, with the primary heat rejection occurring by way of a radiator and/or aftercooler. Currently few modeling tools exist that can size and characterize an integrated reverse turbo-Brayton cycle cryocooler in combination with a broad area cooling design. This paper addresses efforts to create such a tool to assist in gaining a broader understanding of these systems, and investigate their performance in potential space missions. The model uses conventional engineering and thermodynamic relationships to predict the preliminary design parameters, including input power requirements, pressure drops, flow rate, cycle performance, cooling lift, broad area cooler line sizing, and component operating temperatures and pressures given the cooling load operating temperature, heat rejection temperature, compressor inlet pressure, compressor rotational speed, and cryogenic tank geometry. In addition, the model allows for the preliminary design analysis of the broad area cooling tubing, to determine the effect of tube sizing on the reverse turbo-Brayton cycle system performance. At the time this paper was written, the model was verified to match existing theoretical documentation within a reasonable margin. While further experimental data is needed for full validation, this tool has already made significant steps towards giving a clearer understanding of the performance of a reverse turbo-Brayton cycle cryocooler integrated with broad area cooling technology for zero boil-off active thermal control.

Guzik, Monica C.↗
NASA NTRS2016

Optical Probe of the Superconducting Normal Mixed State in a Magnetic Penetration Thermometer

Using ultraviolet photon pulses, we have probed the internal behavior of a molybdenum-gold Magnetic Penetration Thermometer (MPT) that we designed for x-ray microcalorimetry. In this low-temperature detector, the diamagnetic response of a superconducting MoAu bilayer is used to sense temperature changes in response to absorbed photons. We have previously described an approximate model that explains the high responsivity of the detector to temperature changes as a consequence of a Meissner transition of the molybdenum-gold film in the magnetic field applied by the superconducting circuit used to bias the detector. We compare measurements of MPT heat capacity and thermal conductance, derived from UV photon pulse data, to our model predictions for the thermodynamic properties of the sensor and for the electron cooling obtained by quasiparticle recombination. Our data on electron cooling power is also relevant to the operation of other superconducting detectors, such as Microwave Kinetic Inductance Detectors.

superconductivity↗
NASA NTRS2005

Computing the Thermodynamic State of a Cryogenic Fluid

The Cryogenic Tank Analysis Program (CTAP) predicts the time-varying thermodynamic state of a cryogenic fluid in a tank or a Dewar flask. CTAP is designed to be compatible with EASY5x, which is a commercial software package that can be used to simulate a variety of processes and equipment systems. The mathematical model implemented in CTAP is a first-order differential equation for the pressure as a function of time.

Willen, G. Scott↗
NASA NTRS1982

He I lines in B stars - Comparison of non-local thermodynamic equilibrium models with observations

Profiles of He gamma-gamma 4026, 4387, 4471, 4713, 5876, and 6678 have been obtained in 17 stars of spectral type B0-B5. Parameters of the nonlocal thermodynamic equilibrium models appropriate to each star are determined from the Stromgren index and fits to H-alpha line profiles. These parameters yield generally good fits to the observed He I line profiles, with the best fits being found for the blue He I lines where departures from local thermodynamic equilibrium are relatively small. For the two red lines it is found that, in the early B stars and in stars with log g less than 3.5, both lines are systematically stronger than predicted by the nonlocal thermodynamic equilibrium models.

Heasley, J. N.↗
NASA NTRS1978

The development of methods for the prediction of primary creep behavior in metals

The applicability of a thermodynamic constitutive theory of deformation to the prediction of primary creep and creep strain relaxation behavior in metals is examined. Constitutive equations derived from the theory are subjected to a parametric analysis in order to determine the influence of several parameters on the curve forms generated by the equations. A computer program is developed which enables the solution of a generalized constitutive equation using experimental data as input. Several metals were tested to form a data base of primary creep and relaxation behavior. The extent to which these materials conformed to the constitutive equation showed wide variability, with the alloy Ti-6Al-4V exhibiting the most consistent results. Accordingly, most of the analysis is concentrated upon data from that alloy, although creep and relaxation data from all the materials tested are presented. Experimental methods are outlined as well as some variations in methods of analysis. Various theoretical and practical implications of the work are discussed.

Zerwekh, R. P.↗
NASA NTRS1995

EUVE spectroscopy of epsilon Canis Majoris (B2 II) from 70 to 730 A

We present spectra of the brightest stellar source of extreme ultraviolet (EUV) radiation longward of 400 A, the B2 II star, epsilon CMa. These data were taken with the three spectrometers aboard the NASA Extreme Ultraviolet Explorer satellite (EUVE) during the first cycle of pointed observations. We report on our initial studies of the continuum and line spectrum of the stellar photosphere in the 320 to 730 A region, and on the wind emission lines observed in the 170-375 A region. This is the first EUV spectrum of an early-type star, and thus makes epsilon CMa the most comprehensively observed B star from the X-ray to infrared regimes. The radiation in both the H Lyman continuum and He I continuum (shortward of 504 A) are found to be significantly greater than predicted by both Local Thermodynamic Equilibrium (LTE) and non-LTE model atmospheres. Since epsilon CMa also exhibits a mid-infrared excess, this points to the outer layers being warmer than the models indicate. The anomalously large Lyman continuum flux, combined with the very low column density measured in the direction toward this star implies that it is the dominant source of hydrogen ionization of the local interstellar medium in the immediate vicinity of the sun. All of the lines predicted to be strong from model atmospheres are present and several wind absorption features are also identified. We have detected emission lines from highly ionized iron that are consistent with the ROSAT Position Sensitive Proportional Counter (PSPC) observations if a multi-temperature emission model is used, and the assumption is made that there is significant absorption beyond that of the neutral phase of the ISM. The spectrum shows strong O III 374 A line emission produced by the Bowen flourescence mechanism, which has not previously been observed in the spectra of hot stars.

Cassinelli, J. P.↗
NASA NTRS2006

Entropy Generation/Availability Energy Loss Analysis Inside MIT Gas Spring and "Two Space" Test Rigs

The results of the entropy generation and availability energy loss analysis under conditions of oscillating pressure and oscillating helium gas flow in two Massachusetts Institute of Technology (MIT) test rigs piston-cylinder and piston-cylinder-heat exchanger are presented. Two solution domains, the gas spring (single-space) in the piston-cylinder test rig and the gas spring + heat exchanger (two-space) in the piston-cylinder-heat exchanger test rig are of interest. Sage and CFD-ACE+ commercial numerical codes are used to obtain 1-D and 2-D computer models, respectively, of each of the two solution domains and to simulate the oscillating gas flow and heat transfer effects in these domains. Second law analysis is used to characterize the entropy generation and availability energy losses inside the two solution domains. Internal and external entropy generation and availability energy loss results predicted by Sage and CFD-ACE+ are compared. Thermodynamic loss analysis of simple systems such as the MIT test rigs are often useful to understand some important features of complex pattern forming processes in more complex systems like the Stirling engine. This study is aimed at improving numerical codes for the prediction of thermodynamic losses via the development of a loss post-processor. The incorporation of loss post-processors in Stirling engine numerical codes will facilitate Stirling engine performance optimization. Loss analysis using entropy-generation rates due to heat and fluid flow is a relatively new technique for assessing component performance. It offers a deep insight into the flow phenomena, allows a more exact calculation of losses than is possible with traditional means involving the application of loss correlations and provides an effective tool for improving component and overall system performance.

Ebiana, Asuquo B.↗
NASA NTRS1973

A model of a Martian Great dust storm.

The great Martian 1971 dust storm is described using Carrier's (1971) model of a terrestrial hurricane with a somewhat modified thermodynamic drive. The model predicts the course of development and the time elapsing in three different phases: growth, maturity, decay. All the predictions correspond reasonably well to the observed phenomena. Explanations are offered for the rarity of the storms and the time of year and location at which they most commonly commence.

Gierasch, P. J.↗
NASA NTRS1982

Solar array Shuttle flight experiment - Hardware development and testing

This paper reports on the fabrication and ground testing of (a) a large area, light-weight, flexible substrate developmental solar array wing that has been built for NASA-MSFC and of (b) the supporting structure and data acquisition system (DAS) which, with the wing, will be flown in the Shuttle as an experiment in 1984. The experiment will verify the dynamics, thermodynamic, and electrical performance predictions of the array wing and will demonstrate the structural capability of the array wing for Orbiter launch and re-entry environments. The experiment hardware verification program was designed to minimize costs and risk of experiment performance degradation while maintaining Shuttle and crew safety. The previous full-scale wing hardware tests included an extension mast water table test and wing testing for random vibration, thermal vacuum, and acoustic environments. The results of these tests were used to define wing design modifications and to scope the test program for the experiment hardware.

Elms, R. V.↗
NASA NTRS1984

High accuracy heat capacity measurements through the lambda transition of helium with very high temperature resolution

A measurement of the heat capacity singularity of helium at the lambda transition was performed with the aim of improving tests of the Renormalization Group (RG) predictions for the static thermodynamic behavior near the singularity. The goal was to approach as closely as possible to the lambda-point while making heat capacity measurements of high accuracy. To do this, a new temperature sensor capable of unprecedented resolution near the lambda-point, and two thermal control systems were used. A short description of the theoretical background and motivation is given. The initial apparatus and results are also described.

Fairbanks, W. M.↗
NASA NTRS1991

Autogenous pressurization of cryogenic vessels using submerged vapor injection

Experimental results are reported for submerged injection pressurization and expulsion tests of a 4.89 cu m liquid hydrogen tank. The pressurant injector was positioned near the bottom of the test vessel to simulate liquid engulfment of the pressurant gas inlet; a condition that may occur in low-gravity conditions. Results indicate a substantial reduction in pressurization efficiency, with pressurant gas requirements approximately five times greater than ideal amounts. Consequently, submerged vapor injection should be avoided as a low-gravity autogenous pressurization method whenever possible. The work presented herein validates that pressurent requirements are accurately predicted by a homogeneous thermodynamic model when the submerged injection technique is employed.

Stochl, Robert J.↗
NASA NTRS1991

Autogenous pressurization of cryogenic vessels using submerged vapor injection

Experimental results are reported for submerged injection pressurization and expulsion tests of a 4.89 cu m liquid hydrogen tank. The pressurant injector was positioned near the bottom of the test vessel to simulate liquid engulfment of the pressurant gas inlet, a condition that may occur in low-gravity conditions. Results indicate a substantial reduction in pressurization efficiency with pressurant gas requirements approximately five times greater than ideal amounts. Consequently, submerged vapor injection should be avoided as a low-gravity autogenous pressurization method whenever possible. The work presented herein validates that pressurant requirements are accurately predicted by a homogeneous thermodynamic model when the submerged injection technique is employed.

Stochl, Robert J.↗