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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1968

Analytical and experimental studies of the steady state combustion mechanism of solid propellants

Our present state of understanding of the steady-state combustion mechanisms of solid propellants is reviewed. Attention is focused principally on heterogeneous propellants. Both experimental and theoretical work is discussed. The recent advances considered include studies of linear pyrolysis of propellant constituents, deflagration of exothermic oxidizers, combustion of oxidizer spheres in gaseous fuels, porous-bed combustion, reactions between gaseous fuel and gaseous oxidizer components, metal combustion, propellant strand burning, rocket motor combustion and microcinematographic experimentation. A theoretical analysis of a model of homogeneous propellant combustion is outlined in detail, with special emphasis placed on surface gasification laws and on flammability limits in nonadiabatic systems. Low pressure, moderate pressure, plateau and high pressure domains of combustion are identified for ammonium perchlorate composite propellants. It is concluded that a better foundation for investigating composite propellant combustion properties is available for ammonium perchlorate than for any other oxidizer. Avenues for potentially fruitful future research are recommended.

M Barrère↗
DOE OSTI2021

Performance Demonstration of Self-Powered Neutron Detectors for Steady-State Reactor Operations

The irradiation testing of sensors in reactors is a crucial step towards calibrating and qualifying sensors prior to their deployment in experiments. This report details the process toward qualifying and calibrating custom-designed rhodium-based self-power neutron detectors (Rh-SPNDs) for steady-state reactor irradiations. This process serves to both demonstrate the performance capabilities of Rh-SPNDs as well as to provide experimental data for development of a sensor sensitivity model. Two designs of Rh-SPNDs were tested in various reactors to demonstrate: detection resolution in a low neutron flux environment, a delayed-response compensation technique, output linearity in a large range of neutron flux, and measurement accuracy verified with dosimetry. The detection resolution and compensation technique was demonstrated in the AGN-201m reactor at Idaho State University. The irradiation confirmed the sensors’ capability to perform steady-state operations in a low neutron flux of ~2E8 n/cm 2 -sec. Sensor output linearity coupled with the delayed-response compensation was investigated at the neutron radiography reactor at Idaho National Laboratory. A Rh-SPND was irradiated to neutron fluxes ranging from 2E8 to 2E13 n/cm2-sec range. The measured data demonstrated a wide and linear range of operation with a measured linear sensitivity of 1.0129 ×10 -13 A/W with a correlation-squared value of r 2 =0.9927. The measurement accuracy was investigated at the Advanced Test Reactor Critical reactor. The SPNDs were inserted into a test vehicle with collocated flux wires. Two irradiations with different flux levels were performed, and the SPNDs relative measurement between the two irradiations was calculated to be 1.2613 ± 0.0153 for the small SPND design and 1.1809 ± 0.0108 for the large SPND design. Both SPND measurements fell between the co-axial dosimetry result, which reported 1.218 ± 0.047. Additionally, the preliminary MCNP model for calculating SPND sensitivity was developed in parallel to this work. Modeled neutron spectrum with measured magnitude was used for inputs to determine the simulated SPND output. The results showed an overestimation of signal strength by a factor of 5, which was expected because of model simplification. This leads to future modeling work to account for signal losses from additional physical properties, including high temperature environments for FY-21.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1975

Experimental investigation of a simple distortion index utilizing steady-state and dynamic distortions in a Mach 2.5 mixed-compression inlet and turbofan engine

A wind tunnel investigation was conducted to determine the amplitude and spatial distribution of steady-state and dynamic distortion produced in an inlet with 45 percent of the overall supersonic area contraction occurring internally. It was found that the inlet support strut location and/or the overboard bypass flow rate has a significant effect on the spatial distribution of distortion. Because of this effect the majority of the stall points exhibited four-per-revolution patterns of distortion. Data from this test were used to formulate a simple index that combines steady-state and dynamic distortions. Distortion results obtained with this index correlated well with exhaust nozzle area. It is shown that the exhaust nozzle area of a TF30-P-3, as modified for use in this test, can be controlled in a scheme to avoid engine stall. A considerable increase in engine distortion tolerance can be achieved by opening the 7th-stage bleed. The engine exhibited higher tolerance to distortion for multiple patterns of distortion per-revolution than for a one-per-revolution pattern of distortion.

Costakis, W. G.↗
NASA NTRS1992

Venusian hydrology: Steady state reconsidered

In 1987, Grinspoon proposed that the data on hydrogen abundance, isotopic composition, and escape rate were consistent with the hypothesis that water on Venus might be in steady state rather than monotonic decline since the dawn of time. This conclusion was partially based on a derived water lifetime against nonthermal escape of approximately 10(exp 8) yr. De Bergh et al., preferring the earlier Pioneer Venus value of 200 ppm water to the significantly lower value detected by Bezard et al., found H2O lifetimes of greater than 10(exp 9) yr. Donahue and Hodges derived H2O lifetimes of 0.4-5 x 10 (exp 9) yr. Both these analyses used estimates of H escape flux between 0.4 x 10(exp 7) and 1 x 10(exp 7) cm(exp -2)s(exp -1) from Rodriguez et al. Yet in more recent Monte Carlo modeling, Hodges and Tinsley found an escape flux due to charge exchange with hot H(+) of 2.8 x 10(exp 7) cm(exp -2)s(exp -1). McElroy et al. estimated an escape flux of 8 x 10(exp 6) cm(exp -2)s(exp -1) from collisions with hot O produced by dissociative recombination of O2(+). Brace et al. estimated an escape flux of 5 x 10(exp 6) cm(exp -2)s(exp -1) from ion escape from the ionotail of Venus. The combined estimated escape flux from all these processes is approximately 4 x 10(exp 7) cm(exp -2)s(exp -1). The most sophisticated analysis to date of near-IR radiation from Venus' nightside reveals a water mixing ratio of approximately 30 ppm, suggesting a lifetime against escape for water of less than 10(exp 8) yr. Large uncertainties remain in these quantities, yet the data point toward a steady state. Further evaluation of these uncertainties, and new evolutionary modeling incorporating estimates of the outgassing rate from post-Magellan estimates of the volcanic resurfacing rate are presented.

Grinspoon, David H.↗
NASA NTRS1973

Theory of a steady-state nonisothermal positive column in a magnetic field.

The steady state of a nonisothermal cylindrical discharge in a longitudinal magnetic field is described by three moment equations in the plasma approximation for electrons and ions. Volume generation of electron-ion pairs by single-stage ionization, the presence of axial current, and collisions with neutrals are considered. The theory yields radial profiles of the charged particle velocities, density, potential, electron and ion temperatures, and demonstrates similarity laws for the positive column. The results are compared with two-moment theories and with experimental data on helium, argon, and mercury vapor found in the literature for a wide range of pressures.

Ilic, D. B.↗
NASA NTRS1974

User's instructions for the 41-node thermoregulatory model (steady state version)

A user's guide for the steady-state thermoregulatory model is presented. The model was modified to provide conversational interaction on a remote terminal, greater flexibility for parameter estimation, increased efficiency of convergence, greater choice of output variable and more realistic equations for respiratory and skin diffusion water losses.

Leonard, J. I.↗