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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Feasibility Study of Laboratory Simulation of Single-Stage-to-Orbit Vehicle Base Heating

The feasibility of simulating in a laboratory the heating environment of the base region of the proposed reusable single-stage-to-orbit vehicle during its ascent is examined. The propellant is assumed to consist of hydrocarbon (RP1), liquid hydrogen (LH2), and liquid oxygen (LO2), which produces CO and H2 as the main combustible components of the exhaust effluent. Since afterburning in the recirculating region can dictate the temperature of the base flowfield and ensuing heating phenomena, laboratory simulation focuses on the thermochemistry of the afterburning. By extrapolating the Saturn V flight data, the Damkohler number, in the base region with afterburning for SSTO vehicle, is estimated to be between 30 and 140. It is shown that a flow with a Damkohler number of 1.8 to 25 can be produced in an impulse ground test facility. Even with such a reduced Damkohler number, the experiment can adequately reproduce the main features of the flight environment.

Park, Chung Sik↗
NASA NTRSDate not supplied

The Use of Immersion Rigs for High Temperature Hydrogen Exposure Testing Within the Nuclear Thermal Rocket Element Environmental Simulator (NTREES): NTREES-5 Hydrogen Heat Exchanger (N5HHX-01)

The Nuclear Thermal Rocket Element Environmental Simulator (NTREES) facility at NASA’s Marshall Space Flight Center (MSFC) subjects materials and components typically found on nuclear thermal propulsion (NTP) systems to non-nuclear simulations of prototypic NTP reactor thermohydraulic environments. With 1.2 MW of inductive power available, the currently employed methods to simulate nuclear heating in NTREES consist of 1) inductively heating a test specimen, which typically cannot be performed on ceramic materials, or 2) heating gas that envelops the test specimen. The latter of these has provided a basis for developing so-called “immersion rigs” to be used in NTREES. Furthermore, immersion rigs are especially useful in the case of smaller, technically challenging test specimens. One such device, the “NTREES-5 Hydrogen Heat Exchanger” (N5HHX-01), designed and deployed to test small material coupons to ~0.5 g/s of 2800 K, 500 psi Hydrogen, is discussed herein. To achieve this desired delivery temperature level, the most suitable material for the N5HHX’s construction was pure tungsten, which imposed budgetary and manufacturing challenges. Also discussed in this paper is the design of the N5HHX rig’s sample container, which became the first iteration of improving NTREES small material coupon test operations by permitting rapid changeout of different material samples.

Reactor Testing↗
NASA NTRS2016

Simulations of the Mg II K and Ca II 8542 Lines From an Alfvén Wave-Heated Flare Chromosphere

We use radiation hydrodynamic simulations to examine two models of solar flare chromospheric heating: Alfven wave dissipation and electron beam collisional losses. Both mechanisms are capable of strong chromospheric heating, and we show that the distinctive atmospheric evolution in the mid-to-upper chromosphere results in Mg II k-line emission that should be observably different between wave-heated and beam-heated simulations. We also present Ca II 8542 A profiles that are formed slightly deeper in the chromosphere. The Mg II k-line profiles from our wave-heated simulation are quite different from those from a beam-heated model and are more consistent with Interface Region Imaging Spectrograph observations. The predicted differences between the Ca II 8542 A in the two models are small. We conclude that careful observational and theoretical study of lines formed in the mid-to-upper chromosphere holds genuine promise for distinguishing between competing models for chromospheric heating inflares.

Kerr, Graham S.↗
NASA NTRS2012

Changes in the Intensity and Frequency of Atmospheric Blocking and Associated Heat Waves During Northern Summer Over Eurasia in the CMIP5 Model Simulations

The Russia heat wave and wild fires of the summer of 2010 was the most extreme weather event in the history of the country. Studies show that the root cause of the 2010 Russia heat wave/wild fires was an atmospheric blocking event which started to develop at the end of June and peaked around late July and early August. Atmospheric blocking in the summer of 2010 was anomalous in terms of the size, duration, and the location, which shifted to the east from the normal location. This and other similar continental scale severe summertime heat waves and blocking events in recent years have raised the question of whether such events are occurring more frequently and with higher intensity in a warmer climate induced by greenhouse gases. We studied the spatial and temporal distributions of the occurrence and intensity of atmospheric blocking and associated heat waves for northern summer over Eurasia based on CMIPS model simulations. To examine the global warming induced change of atmospheric blocking and heat waves, experiments for a high emissions scenario (RCP8.S) and a medium mitigation scenario (RCP4.S) are compared to the 20th century simulations (historical). Most models simulate the mean distributions of blockings reasonably well, including major blocking centers over Eurasia, northern Pacific, and northern Atlantic. However, the models tend to underestimate the number of blockings compared to MERRA and NCEPIDOE reanalysis, especially in western Siberia. Models also reproduced associated heat waves in terms of the shifting in the probability distribution function of near surface temperature. Seven out of eight models used in this study show that the frequency of atmospheric blocking over the Europe will likely decrease in a warmer climate, but slightly increase over the western Siberia. This spatial pattern resembles the blocking in the summer of 2010, indicating the possibility of more frequent occurrences of heat waves in western Siberia. In this talk, we will also discuss the potential effect of atmosphere-land feedback, particularly how the wetter spring affects the frequency and intensity of atmospheric blocking and heat wave during summer.

Kim, Kyu-Myong↗
NASA NTRS1993

CFD Analysis of Spray Combustion and Radiation in OMV Thrust Chamber

The Variable Thrust Engine (VTE), developed by TRW, for the Orbit Maneuvering Vehicle (OMV) uses a hypergolic propellant combination of Monomethyl Hydrazine (MMH) and Nitrogen Tetroxide (NTO) as fuel and oxidizer, respectively. The propellants are pressure fed into the combustion chamber through a single pintle injection element. The performance of this engine is dependent on the pintle geometry and a number of complex physical phenomena and their mutual interactions. The most important among these are (1) atomization of the liquid jets into fine droplets; (2) the motion of these droplets in the gas field; (3) vaporization of the droplets (4) turbulent mixing of the fuel and oxidizer; and (5) hypergolic reaction between MMH and NTO. Each of the above phenomena by itself poses a considerable challenge to the technical community. In a reactive flow field of the kind occurring inside the VTE, the mutual interactions between these physical processes tend to further complicate the analysis. The objective of this work is to develop a comprehensive mathematical modeling methodology to analyze the flow field within the VTE. Using this model, the effect of flow parameters on various physical processes such as atomization, spray dynamics, combustion, and radiation is studied. This information can then be used to optimize design parameters and thus improve the performance of the engine. The REFLEQS CFD Code is used for solving the fluid dynamic equations. The spray dynamics is modeled using the Eulerian-Lagrangian approach. The discrete ordinate method with 12 ordinate directions is used to predict the radiative heat transfer in the OMV combustion chamber, nozzle, and the heat shield. The hypergolic reaction between MMH and NTO is predicted using an equilibrium chemistry model with 13 species. The results indicate that mixing and combustion is very sensitive to the droplet size. Smaller droplets evaporate faster than bigger droplets, leading to a well mixed zone in the combustion chamber. The radiative heat flux at combustion chamber and nozzle walls are an order of negligible less than the conductive heat flux. Simulations performed with the heat shield show that a negligible amount of fluid is entrained into the heat shield region. However, the heat shield is shown to be effective in protecting the OMV structure surrounding the engine from the radiated heat.

Giridharan, M. G.↗
NASA NTRS1961

Exploratory Environmental Tests of Several Heat Shields

Exploratory tests have been conducted with several conceptual radiative heat shields of composite construction. Measured transient temperature distributions were obtained for a graphite heat shield without insulation and with three types of insulating materials, and for a metal multipost heat shield, at surface temperatures of approximately 2,000 F and 1,450 F, respectively, by use of a radiant-heat facility. The graphite configurations suffered loss of surface material under repeated irradiation. Temperature distribution calculated for the metal heat shield by a numerical procedure was in good agreement with measured data. Environmental survival tests of the graphite heat shield without insulation, an insulated multipost heat shield, and a stainless-steel-tile heat shield were made at temperatures of 2,000 F and dynamic pressures of approximately 6,000 lb/sq ft, provided by an ethylene-heated jet operating at a Mach number of 2.0 and sea-level conditions. The graphite heat shield survived the simulated aerodynamic heating and pressure loading. A problem area exists in the design and materials for heat-resistant fasteners between the graphite shield and the base structure. The insulated multipost heat shield was found to be superior to the stainless-steel-tile heat shield in retarding heat flow. Over-lapped face-plate joints and surface smoothness of the insulated multi- post heat shield were not adversely affected by the test environment. The graphite heat shield without insulation survived tests made in the acoustic environment of a large air jet. This acoustic environment is random in frequency and has an overall noise level of 160 decibels.

Goodman, George P.↗
NASA NTRS2006

Comparison of AMZIRC and GRCop-84

The mechanical properties of two copper alloys with high thermal conductivity, GRCop-84 and AMZIRC, were compared. These are competing alloys in high temperature, high heat flux applications such as rocket nozzles. The GRCop-84 data presented was taken from previous work. The results of new tensile, creep, and compression tests on AMZIRC are presented. Tests were done on as-received hard drawn material, and on material that had been subjected to a heat treatment designed to simulate a brazing operation at 935 C. As-received AMZIRC was found to have excellent properties at temperatures below 550 C, with room temperature yield and ultimate tensile strengths of about 500 MPa, and ductile failures. By comparison, GRCop-84 s room temperature tensile yield and ultimate strengths are about 200 and 380 MPa respectively. However, the simulated brazing heat treatment substantially decreased the mechanical properties of AMZIRC; and the strength of as-received AMZIRC dropped precipitously as test temperatures exceeded 500 C. The properties of GRCop-84 were not significantly affected by the 935 C heat treatment. As a result, there appear to be advantages to GRCop- 84 over AMZIRC if use or processing temperatures of greater than 500 C are expected. Tensile creep tests were done at 500 and 650 C. At these temperatures, the creep properties of GRCop-84 were superior to AMZIRC s. At equivalent rupture life and stress, GRCop-84 was found to have a 150 C temperature advantage over AMZIRC; for equivalent rupture life and temperature GRCop-84 was two times stronger.

de Groh, Henry C. III↗
NASA NTRS1980

Preliminary Arc-Jet tests of ablator/RSI joints in simulated space shuttle ascent and entry heating

Five ablator/RSI panels were tested in simulated Shuttle heating conditions to determine heat pulse effects on the ablator and the ablator/RSI joints. Two of the panels were subjected to both ascent and entry heating. The other three panels were subjected to entry heating only. The double-pulse heating (ascent plus entry) had no significant effect on char-layer integrity. Evaluation of the effects of entry heating on the ablator/RSI joints was difficult because, with the panel configuration used, severe pressure gradients developed within some of the joints during testing causing hot-gas flow through the joints. In joints where pressure leaks apparently did not develop, temperatures within the joints were reasonable compared to ablator and RSI back surface temperatures.

Brewer, W. D.↗
NASA NTRS1973

Computer simulation of temperatures on the Centaur standard shroud during heated jettison tests

A heating fixture for simulating the heating and environment encountered by the Centaur standard shroud (CSS) during its ascent through the earth's atmosphere is discussed. A computer program was developed to provide a means of determining the overall temperature profile of a free-skin model of the CSS during the heating portion of the heated jettison tests. The program treats the energy contribution of each lamp on the heater to various points on the CSS surface. The analytic model was verified by adapting the computer program to the configuration of the hardware used in a series of Intermediate Scale Tests performed on a 2.4 meters by 2.4 meters section of the CSS corrugated structure. A comparison of some predicted versus experimental results from these tests is presented.

Hemminger, J. A.↗
NASA NTRS1985

Heat transfer from a simulated shuttle external tank in the naturally turbulent outdoor environment

To estimate the local heat-transfer coefficients around an external-tank (ET) surface, a 9.8-m-high by 8.4-m-diameter ET simulator is constructed, instrumented, and tested in the naturally turbulent outdoor environment. Two different configurations under which the testing is conducted are described. The time-average, local values of Nusselt number at time-average Reynolds numbers of 2.2 x 10 to the 6th, 2.6 x 10 to the 6th, and 4.5 x 10 to the 6th are presented. It is shown that, at the same Reynolds numbers, the heat transfer coefficients due to the atmospheric airflow are higher than those due to airflow in a low-turbulent-intensity wind tunnel.

Lin, F. N.↗
NASA NTRS1982

Numerical simulation of one-dimensional heat transfer in composite bodies with phase change

A numerical simulation was developed to investigate the one dimensional heat transfer occurring in a system composed of a layered aircraft blade having an ice deposit on its surface. The finite difference representation of the heat conduction equations was done using the Crank-Nicolson implicit finite difference formulation. The simulation considers uniform or time dependent heat sources, from heaters which can be either point sources or of finite thickness. For the ice water phase change, a numerical method which approximates the latent heat effect by a large heat capacity over a small temperature interval was applied. The simulation describes the temperature profiles within the various layers of the de-icer pad, as well as the movement of the ice water interface. The simulation could also be used to predict the one dimensional temperature profiles in any composite slab having different boundary conditions.

Dewitt, K. J.↗
NASA NTRS1989

Simulating transitional flow and heat transfer over the flat plate and circular cylinder using a K-epsilon turbulence model

A boundary layer computer code, called TEXSTAN, has been used to simulate external, transitional, fluid flow and heat transfer over the flat plate and circular cylinder. Turbulence modeling was accomplished by using a low-Reynolds number K-epsilon turbulence model. The study was made for free-stream turbulence intensities less than 15 percent. The comparison of the flat plate heat transfer predictions to experimental data showed good agreement, for the location of transition as well as in the heat transfer coefficient. The typical discrepancy in predicting the heat transfer coefficient was less than 5 percent of the measured value.

Sullivan, T. J.↗
NASA NTRS2002

Thermal Vacuum Facility for Testing Thermal Protection Systems

A thermal vacuum facility for testing launch vehicle thermal protection systems by subjecting them to transient thermal conditions simulating re-entry aerodynamic heating is described. Re-entry heating is simulated by controlling the test specimen surface temperature and the environmental pressure in the chamber. Design requirements for simulating re-entry conditions are briefly described. A description of the thermal vacuum facility, the quartz lamp array and the control system is provided. The facility was evaluated by subjecting an 18 by 36 in. Inconel honeycomb panel to a typical re-entry pressure and surface temperature profile. For most of the test duration, the average difference between the measured and desired pressures was 1.6% of reading with a standard deviation of +/- 7.4%, while the average difference between measured and desired temperatures was 7.6% of reading with a standard deviation of +/- 6.5%. The temperature non-uniformity across the panel was 12% during the initial heating phase (t less than 500 sec.), and less than 2% during the remainder of the test.

Daryabeigi, Kamran↗
NASA NTRS1979

Environmental effects on space shuttle reusable surface insulation coated with reaction cured glass

Sample titles of the space shuttle reusable surface insulation was subjected alternately to simulated mission heating and either real or simulated environmental exposure for up to 34 cycles. The coating cracked as a result of exposure to high temperature and moisture conditions, and insulation with cracked coatings absorbed significant quantities of water in the launch-pad environment. Cracking was a complex function of time, temperature, and moisture exposure. Cracked coatings remained adherent to the insulation for up to 24 cycles past initial cracking.

Ransone, P. O.↗
NASA NTRS1997

Thermostructural Behavior of a Hypersonic Aircraft Sandwich Panel Subjected to Heating on One Side

Thermostructural analysis was performed on a heated titanium honeycomb-core sandwich panel. The sandwich panel was supported at its four edges with spar-like substructures that acted as heat sinks, which are generally not considered in the classical analysis. One side of the panel was heated to high temperature to simulate aerodynamic heating during hypersonic flight. Two types of surface heating were considered: (1) flat-temperature profile, which ignores the effect of edge heat sinks, and (2) dome-shaped-temperature profile, which approximates the actual surface temperature distribution associated with the existence of edge heat sinks. The finite-element method was used to calculate the deformation field and thermal stress distributions in the face sheets and core of the sandwich panel. The detailed thermal stress distributions in the sandwich panel are presented, and critical stress regions are identified. The study shows how the magnitudes of those critical stresses and their locations change with different heating and edge conditions. This technical report presents comprehensive, three-dimensional graphical displays of thermal stress distributions in every part of a titanium honeycomb-core sandwich panel subjected to hypersonic heating on one side. The plots offer quick visualization of the structural response of the panel and are very useful for hot structures designers to identify the critical stress regions.

Ko, William L.↗