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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Evaluation of outer race tilt and lubrication on ball wear and SSME bearing life reductions

Several aspects of the SSME bearing operation were evaluated. The possibility of elastohydrodynamics (EHD) lubrication with a cryogenic fluid was analyzed. Films as thick as .61 microns were predicted with one theory which may be thick enough to provide hydrodynamic support. The film formation, however, is heavily dependent on good surface finish and a low bulk bearing temperature. Bearing dynamics to determine if the radial stiffness of a bearing which are dependent on bearing misalignment were analyzed. Four ball tests were conducted at several environmental conditions from an LN2 bath to 426 C in air. Surface coatings and ball materials are evaluated. Severe wear and high friction are measured for all ball materials except when the balls have surface lubricant coatings.

Kannel, J. W.↗
NASA NTRS1984

The Solar Wind at 20-30 AU

Pioneer 10 sampled the interplanetary plasma over the range 20 to 30 astronomical units, during the period 1979-1983. The median flow speed is about 400 km/s, and at 20 AU the median density, proton temperature and dynamic pressure are, respectively, 0.025 cm-3, 10(4) K, and 6x10-11 dyne cm-2. It is shown that the average solar wind flow speed does not vary significantly with increasing heliocentric distance, and the density falls off as R-2, as predicted by simple solar wind models. The day-to-day variations in solar wind parameters are smaller at larger distance. Very large shocks however, were detected beyond 25 AU. Comparison of Pioneer 10 and 11 observations at similar distances but different phases of the solar activity cycle shows that solar wind dynamic pressure varies over a wider range during epochs of high solar activity. The variation near 20 AU is likely to be smaller at Voyager 2 Uranus encounter than observed by Pioneer 10 in the 1979-80 period.

Barnes, A.↗
NASA NTRS1987

Research sensors

The program described covers development of sensors and sensing techniques for research applications on aeropropulsion systems. In general, the sensors are used in-situ to measure the environment at a given location within a turbine engine, or to measure the response of an engine component to the imposed environment. Locations of concern are generally in the gas path and, for the most part, are within the hot section. Specific parameters of concern are dynamic gas temperature, heat flux, airfoil surface temperature, and strain on airfoils and combustor liners. In order to minimize the intrusiveness of surface-mounted sensors, a considerable effort was expended to develop thin-film sensors for surface temperature, strain, and heat flux measurements. Most of the work described is sufficiently advanced that sensors were used and useful data were obtained. The notable exception is the work to develop a high-temperature static strain measuring capability; this work is still in progress.

Englund, David R.↗
NASA NTRS1988

Research sensors

The work described is part of a program (Englund and Seasholtz, 1988) to develop sensors and sensing techniques for research applications on aircraft turbine engines. In general, the sensors are used to measure the environment at a given location within a turbine engine or to measure the response of an engine component to the imposed environment. Locations of concern are generally in the gas path and, for the most part, are within the hot section. Specific parameters of concern are dynamic gas temperature, heat flux, airfoil surface temperature, and strain on airfoils and combustor liners. To minimize the intrusiveness of surface-mounted sensors, a considerable effort was expended to develop thin-film sensors for surface temperature, strain, and heat flux measurements. In addition, an optical system for viewing the interior of an operating combustor was developed. Most of the work described is sufficiently advanced that the sensors were used and useful data were obtained. The notable exception is the work to develop a high-temperature static strain measuring capability; the work is still in progress.

Englund, David R.↗
NASA NTRS1987

Advanced solar receiver conceptual design study

High temperature solar dynamic Brayton and Stirling receivers are investigated as candidate electrical power generating systems for future LEO missions. These receivers are smaller and more efficient than conventional receivers, and they offer less structural complexity and fewer thermal stress problems. Use of the advanced Direct Absorption Storage Receiver allows many of the problems associated with working with high-volumetric-change phase-change materials to be avoided. A specific mass reduction of about 1/3 with respect to the baseline receiver has been realized.

Kesseli, J. B.↗
NASA NTRS1990

Structural concept studies for a horizontal cylindrical lunar habitat and a lunar guyed tower

A conceptual structural design of a horizontal cylindrical lunar habitat is presented. The design includes the interior floor framing, the exterior support structure, the foundation mat, and the radiation shielding. Particular attention was given on its efficiency in shipping and field erection, and on selection of structural materials. Presented also is a conceptual design of a 2000-foot lunar guyed tower. A special field erection scheme is implemented in the design. In order to analyze the over-all column buckling of the mast, where its axial compression includes its own body weight, a simple numerical procedure is formulated in a form ready for coding in FORTRAN. Selection of structural materials, effect of temperature variations, dynamic response of the tower to moonquake, and guy anchoring system are discussed. Proposed field erection concepts for the habitat and for the guyed tower are described.

Yin, Paul K.↗
NASA NTRS1991

Interiors and atmospheres of the outer planets

This theoretical/observational project constrains structure of outer planet atmospheres and interiors through observational data. The primary observation tool is through observations of occultations of stars by outer solar system objects, which yield information about atmospheric temperatures and dynamics, and planetary dimensions and oblateness. The theoretical work relates the data to interior structures in a variety of ways.

Hubbard, W. B.↗
NASA NTRS1990

Fast two-dimensional model

A two dimensional (altitude and latitude) model of the atmosphere is used to investigate problems relating to the variability of the dynamics and temperature of the atmosphere on the ozone distribution, solar cycle variations of atmospheric constituents, the sensitivity of model results to tropospheric trace gas sources, and assessment computations of changes in ozone related to manmade influences. In a comparison between two dimensional model results in which the odd nitrogen family was transported together and model results in which the odd nitrogen species was transported separately, it was found that the family approximations are adequate for perturbation scenario calculations.

Jackman, Charles H.↗
NASA NTRS1990

Research sensors

The LeRC program in research sensors is directed at development of sensors and sensing techniques for research applications on turbine engines and propulsion systems. In general, the sensors are used either to measure to response of an engine component to the imposed environment. Locations of concern are generally within the gas path and, for the most part, are within the hot section of the engine. Since these sensors are used for research testing as opposed to operational use, a sensor lifetime of the order of 50 hr is considered sufficient. The following discussion presents a sample of this work, describing programs to develop a dynamic gas temperature measuring system, total heat flux sensors, a variety of thin-film sensors, and high-temperature strain measuring systems.

Englund, David R.↗
NASA NTRS1993

Optical Technologies for UV Remote Sensing Instruments

Over the last decade significant advances in technology have made possible development of instruments with substantially improved efficiency in the UV spectral region. In the area of optical coatings and materials, the importance of recent developments in chemical vapor deposited (CVD) silicon carbide (SiC) mirrors, SiC films, and multilayer coatings in the context of ultraviolet instrumentation design are discussed. For example, the development of chemically vapor deposited (CVD) silicon carbide (SiC) mirrors, with high ultraviolet (UV) reflectance and low scatter surfaces, provides the opportunity to extend higher spectral/spatial resolution capability into the 50-nm region. Optical coatings for normal incidence diffraction gratings are particularly important for the evolution of efficient extreme ultraviolet (EUV) spectrographs. SiC films are important for optimizing the spectrograph performance in the 90 nm spectral region. The performance evaluation of the flight optical components for the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument, a spectroscopic instrument to fly aboard the Solar and Heliospheric Observatory (SOHO) mission, designed to study dynamic processes, temperatures, and densities in the plasma of the upper atmosphere of the Sun in the wavelength range from 50 nm to 160 nm, is discussed. The optical components were evaluated for imaging and scatter in the UV. The performance evaluation of SOHO/CDS (Coronal Diagnostic Spectrometer) flight gratings tested for spectral resolution and scatter in the DGEF is reviewed and preliminary results on resolution and scatter testing of Space Telescope Imaging Spectrograph (STIS) technology development diffraction gratings are presented.

Keski-Kuha, R. A. M.↗
NASA NTRS1993

Mechanical energy absorber

An energy absorbing system for controlling the force where a moving object engages a stationary stop and where the system utilized telescopic tubular members, energy absorbing diaphragm elements, force regulating disc springs, and a return spring to return the telescoping member to its start position after stroking is presented. The energy absorbing system has frusto-conical diaphragm elements frictionally engaging the shaft and are opposed by a force regulating set of disc springs. In principle, this force feedback mechanism serves to keep the stroking load at a reasonable level even if the friction coefficient increases greatly. This force feedback device also serves to desensitize the singular and combined effects of manufacturing tolerances, sliding surface wear, temperature changes, dynamic effects, and lubricity.

Wesselski, Clarence J.↗
NASA NTRS1995

Turbulence measurements in hypersonic boundary layers using constant-temperature anemometry and Reynolds stress measurements in hypersonic boundary layers

The primary objective in the two research investigations performed under NASA Langley sponsorship (Turbulence measurements in hypersonic boundary layers using constant temperature anemometry and Reynolds stress measurements in hypersonic boundary layers) has been to increase the understanding of the physics of hypersonic turbulent boundary layers. The study began with an extension of constant-temperature thermal anemometry techniques to a Mach 11 helium flow, including careful examinations of hot-wire construction techniques, system response, and system calibration. This was followed by the application of these techniques to the exploration of a Mach 11 helium turbulent boundary layer (To approximately 290 K). The data that was acquired over the course of more than two years consists of instantaneous streamwise mass flux measurements at a frequency response of about 500 kHz. The data are of exceptional quality in both the time and frequency domain and possess a high degree of repeatability. The data analysis that has been performed to date has added significantly to the body of knowledge on hypersonic turbulence, and the data reduction is continuing. An attempt was then made to extend these thermal anemometry techniques to higher enthalpy flows, starting with a Mach 6 air flow with a stagnation temperature just above that needed to prevent liquefaction (To approximately 475 F). Conventional hot-wire anemometry proved to be inadequate for the selected high-temperature, high dynamic pressure flow, with frequent wire breakage and poor system frequency response. The use of hot-film anemometry has since been investigated for these higher-enthalpy, severe environment flows. The difficulty with using hot-film probes for dynamic (turbulence) measurements is associated with construction limitations and conduction of heat into the film substrate. Work continues under a NASA GSRP grant on the development of a hot film probe that overcomes these shortcomings for hypersonic flows. Each of the research tasks performed during the NASA Langley research grants is discussed separately below.

Spina, Eric F.↗
NASA NTRS1998

Satellite Microwave Radar Observations of Antarctic Sea Ice

Historical data on Antarctic sea ice extent and concentration have traditionally been derived from visible and near-infrared images acquired by the polar-orbiting National Oceanic and Atmospheric Agency's (NOAA) meteorological satellites, using the Advanced Very High Resolution Radiometer (AVHRR), and more recently by the Defense Meteorological Satellite Program's Operational Linescan System (OLS). The limitation of these systems is that the majority of energy imparted to the Antarctic sea-ice system is transferred during b6y fast-moving low pressure systems. Since the Southern Ocean sea-ice cover is completely bounded at its lower latitude limit by open ocean, these "polar lows" transport large amounts of moisture (contained in warm air masses) over the outer ice cover. The result is that most, if not all, noteworthy periods of wind- and temperature-driven dynamic changes in the ice cover are accompanied by periods where the region is blanketed by cloud, and when the atmosphere is inherently more electromagnetically opaque. During storms, the probability with which the area is cloud covered is extremely high, thereby ruling out use of visible or near-infrared images as a practical method of monitoring the associated changes in ice conditions. Instead, Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) and DMSP Special Sensor Microwave/imager (SSM/I) have been the primary workhorses to build up a microwave record of Antarctic sea-ice characteristics. Similar problems, however, occur in passive microwave retrievals of sea-ice concentration, and the algorithms are called into question during these periods of change. The influence of water vapor in the atmosphere alone can modify the ice concentration retrievals by fractions exceeding 105, and that retrievals of ice concentration must compensate for the atmospheric water vapor and liquid water contents.

Drinkwater, Mark R.↗
NASA NTRS2001

An Aerosol Physical Chemistry Model for the Upper Troposphere

This report is the final report for the Cooperative Agreement NCC2-1000. The tasks outlined in the various proposals are: (1) Development of an aerosol chemistry model; (2) Utilization of satellite measurements of trace gases along with analysis of temperatures and dynamic conditions to understand ice cloud formation, dehydration and sedimentation in the winter polar regions; (3) Comparison of the HALOE and SAGE II time dependencies of the Pinatubo aerosol decay. The publications are attached.

Lin, Jin-Sheng↗
NASA NTRS2009

The Mechanical Design of a Kinematic Mount for the Mid Infrared Instrument Focal Plane Module on the James Webb Space Telescope

The detector assembly for the Mid Infrared Instrument (MIRI) of the James Webb Space Telescope (JWST) is mechanically supported in the Focal Plane Module (FPM) Assembly with an efficient hexapod design. The kinematic mount design allows for precision adjustment of the detector boresight to assembly alignment fiducials and maintains optical alignment requirements during flight conditions of launch and cryogenic operations below 7 Kelvin. This kinematic mounting technique is able to be implemented in a variety of optical-mechanical designs and is capable of micron level adjustment control and stability over wide dynamic and temperature ranges.

Moore Mount↗
NASA NTRS2018

Performance, Stability and Compatibility of Oxygen/RP-1 Multi-Element Oxidizer-Rich Staged-Combustion Injectors

In 2015 and 2016, the National Aeronautics and Space Administration Marshall Space Flight Center designed, fabricated, assembled and hot-fire tested an oxygen/RP-1 propellant multi-element oxidizer-rich staged-combustion test article. The main objective was to provide thrust chamber combustion stability data as part of the Combustion Stability Tool Development program, although demonstration of performance and compatibility of oxidizer-rich main injectors was also important. Funding was provided by the Air Force Space and Missile Systems Center. Five configurations of main injectors were designed and fabricated, using conventional gas-centered swirl coaxial injector element designs generally similar to those used in oxygen/kerosene oxidizer-rich staged combustion engines such as the Russian RD-180 or NK-33 engines. Variations of element features included element size, recess depth, fuel gap width, and the presence of the sleeve separating the swirling fuel flow from the axial oxidizer flow. Ablative combustion chambers were fabricated based on hardware previously used at the NASA MSFC for testing at similar size and pressure. Existing oxygen/RP-1 oxidizer-rich subscale preburner injectors and hot gas ducts from a previous NASA-funded program were modified for use to supply the oxidizer-rich combustion products to the oxidizer circuit of the main injector of the thrust chamber. Testing of the resulting integrated test article - which included the preburner, inter-connecting hot gas duct, main injector, and ablative combustion chamber - was conducted at Test Stand 116 at the East Test Area of the NASA MSFC. The test article was well instrumented with static and dynamic pressure, temperature, and vibration sensors. This paper presents and discusses all the hot-fire test results of the integrated test article thrust chamber. Eighteen successful hot-fire tests of the integrated rig were conducted. Testing was accomplished with all five of the injector element concepts. Main combustion chamber pressures ranged from 710 to 2350 psia, and main combustion chamber mixture ratios ranged from 2.47 to 2.87. A chamber barrier fuel film coolant of about 2% to 4% of the total fuel flow was used for most tests. Characteristic exhaust velocity efficiency excluding the influence of the fuel film cooling ranged from 91% to 98% of theoretical. All tests of the thrust chamber exhibited stable combustion, even down to 40% of nominal operating pressures. Compatibility of the injector face and combustion chamber walls was acceptable. This paper is a follow-on to publication of preliminary test data presented at the 2016 JANNAF Liquid Propulsion Subcommittee meeting.

Hulka, J. R.↗
DOE OSTI2020

Dynamic Tensile Response of a Fe–49Co–2V Alloy at Various Strain Rates and Temperatures

Soft ferromagnetic alloys are often utilized in electromagnetic applications due to their desirable magnetic properties. In support of these applications, the ferromagnetic alloys are also required to bear mechanical load under various loading and environmental conditions. In this study, a Fe–49Co–2V alloy was dynamically characterized in tension with a Kolsky tension bar and a Drop–Hopkinson bar at various strain rates and temperatures. Dynamic tensile stress–strain curves of the Fe–49Co–2V alloy were obtained at strain rates ranging from 40 to 230 s -1 and temperatures from - 100 to 100 °C. All dynamic tensile stress–strain curves exhibited an initial linear elastic response to an upper yield followed by Lüders band response and then a nearly linear work-hardening behavior. The yield strength of this material was found to be sensitive to both strain rate and temperature, whereas the hardening rate was independent of strain rate or temperature. The Fe–49Co–2V alloy exhibited a feature of brittle fracture in tension under dynamic loading with no necking being observed.

36 MATERIALS SCIENCE↗