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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 937 records · Page 52

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NASA NTRS1982

Large-aperture interferometer using local reference beam

A large-aperture interferometer was devised by adding a local-reference-beam-generating optical system to a schlieren system. Two versions of the interferometer are demonstrated, one employing 12.7 cm (5 in.) diameter schlieren optics, the other employing 30.48 cm (12 in.) diameter parabolic mirrors in an off-axis system. In the latter configuration a cylindrical lens is introduced near the light source to correct for astigmatism. A zone plate is a satisfactory decollimating element in the reference-beam arm of the interferometer. Attempts to increase the flux and uniformity of irradiance in the reference beam by using a diffuser are discussed.

Howes, W. L.↗

NASA NTRS1984

Large-aperture interferometer with local reference beam

Howes, W. L.↗

NASA NTRS1984

Rome/Goddard Space Flight Center (GSFC) magnetic field experiment: A summary of results

A triaxial flux gate magnetometer (E3) was developed and operated to accurately measure the vector magnetic field onboard Helios 1 and 2. Observations of large-scale variations and sector structure confirm theoretical descriptions and compuations. Limits on the configuration of a magnetic cloud are set, and the source of at least one magnetic cloud is identified as a coronal mass ejection. Two types of interplanetary flow pattern are identified: a corotating stream and interaction region related to the boundary, and a transient flow associated with a shock wave. Discontinuities in the direction and/or strength of the magnetic field are explained. Alfven waves and magnetic turbulence are characterized by simultaneous Helios 1 and 2 observations.

Mariani, F.↗

NASA NTRS1986

The tail lobe ion spectrometer

A two-dimensional kinetic 'tail lobe ion spectrometer' model for the transport of ionospheric ions from polar cleft ionosphere into the tail lobes is developed to semiquantitatively simulate the behavior of the observed O(+) ion streams in the magnetotail lobes. The consequences of the present model include: (1) the increase in velocity of the O(+) streams away from the tail midplane; (2) the existence of 'tongues' of O(+) density from the cleft ionosphere into the tail lobes whose distribution configuration depends on the convection electric field and the source thermal energies; and (3) very low parallel thermal energies and speeds in the lobes which are correlated with the parallel ion bulk velocities. These consequences are reasonably consistent with the trends in lobe streams observed by recent spacecraft.

Horwitz, J. L.↗

NASA NTRS1986

Radiation environment and shielding for early manned Mars missions

The problem of shielding a crew during early manned Mars missions is discussed. Requirements for shielding are presented in the context of current astronaut exposure limits, natural ionizing radiation sources, and shielding inherent in a particular Mars vehicle configuration. An estimated range for shielding weight is presented based on the worst solar flare dose, mission duration, and inherent vehicle shielding.

Hall, Stephen B.↗

NASA NTRS1987

Model for the geomagnetic ion spectrometer in the magnetotail lobes

A two-dimensional kinetic tail-lobe ion spectrometer model for the transport of ionospheric ions from the polar-cleft ionosphere into the tail lobes is developed to simulate semiquantitatively the behavior of the observed O(+) ion streams in the magnetotail lobes. The consequences of the present model include: (1) the increase in velocity of the O(+) streams away from the tail midplane and (2) the existence of tongues of O(+) density from the cleft ionosphere into the tail lobes whose distribution configuration depends on the convection electric field and the source thermal energies. These consequences are reasonably consistent with the trends in lobe streams observed by recent spacecraft.

Horwitz, J. L.↗

NASA NTRS1989

High-current plasma contactor neutralizer system

A plasma-contactor neutralizer system is described, for the stabilizing the Orbiter's potential during flights of the Atmospheric Laboratory for Applications and Science missions. The plasma contactor neutralizer will include a Xe plasma source that can provide steady-state ion-emission currents of up to 1.5 A. The Orbiter's potential will be maintained near that of the surrounding space plasma during electron-beam accelerator firings through a combination of ion emission from the Xe plasma source and electron collection from the ambient space plasma. Configuration diagrams and block diagrams are presented along with the performance characteristics of the system.

Beattie, J. R.↗

NASA NTRS1992

Purification system

A system for prolonging the life of a granulated activated charcoal (GAC) water treatment device is disclosed in which an ultraviolet light transparent material is used to constrain water to flow over carbon surfaces. It is configured to receive maximum flux from a UV radiation source for the purpose of preventing microbial proliferation on the carbon surfaces; oxidizing organic contaminants adsorbed from the water onto the carbon surfaces and from biodegradation of adsorbed microbial forms; disinfecting water; and oxidizing organic contaminants in the water.

Flanagan, David T.↗

NASA NTRS1991

Effects of aeroconvective environments on 2D reinforced ceramic matrix composites

The effect of aeroconvective heating environment similar to that observed a spacecraft ascent or reentry from orbit, on the performance of a commercial carbon-reinforced ceramic matrix material specimens of two configurations (orthotropic and quasi-isotropic), fabricated by the Societe Europenne Propulsion (SEP) process was investigated using the NASA Ames Research Center 20 Megawatt Panel Test facility. The performance of the commercial material was compared with the SEP prepared materials. It was found that, whereas the quasi-isotropic SEP specimens exhibited a much higher mass loss rate and a significant dimensional change upon exposure to the thermal environment than did the orthotropic ones, the commercial SEP-like materials did not exhibit these characteristics. There was no greater mass loss rate for the quasi-isotropic specimens, and no dimension changes were observed. The Nicalon reinforced materials in both configurations, as fabricated by SEP or by the commercial source, showed no mass changes and no dimensional changes.

Riccitiello, Salvatore R.↗

NASA NTRS1994

SeaWiFS technical report series. Volume 16: The second SeaWiFS Intercalibration Round-Robin Experiment, SIRREX-2, June 1993

The results of the second Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Intercalibration Round-Robin Experiment (SIRREX-2), which was held at the Center for Hydro-Optics and Remote Sensing (CHORS) at San Diego State University on 14-25 Jun. 1993 are presented. SeaWiFS is an ocean color radiometer that is scheduled for launch in 1994. The SIRREXs are part of the SeaWiFS Calibration and Validation Program that includes the GSFC, CHORS, NIST, and several other laboratories. GSFC maintains the radiometric scales (spectral radiance and irradiance) for the SeaWiFS program using spectral irradiance standards lamps, which are calibrated by NIST. The purpose of each SIRREX is to assure that the radiometric scales which are realized by the laboratories who participate in the SeaWiFS Calibration and Validation Program are correct; that is, the uncertainties of the radiometric scales are such that measurements of normalized water-leaving radiance using oceanographic radiometers have uncertainties of 5%. SIRREX-1 demonstrated, from the internal consistency of the results, that the program goals would not be met without improvements to the instrumentation. The results of SIRREX-2 demonstrate that spectral irradiance scales realized using the GSFC standard irradiance lamp (F269) are consistent with the program goals, as the uncertainty of these measurements is assessed to be about 1%. However, this is not true for the spectral radiance scales, where again the internal consistency of the results is used to assess the uncertainty. This is attributed to inadequate performance and characterization of the instrumentation. For example, spatial nonuniformities, spectral features, and sensitivity to illumination configuration were observed in some of the integrating sphere sources. The results of SIRREX-2 clearly indicate the direction for future work, with the main emphasis on instrument characterization and the assessment of the measurement uncertainties so that the results may be stated in a more definitive manner.

Hooker, Stanford B.↗

NASA NTRS1995

Microgravity Experiments Safety and Integration Requirements Document Tree

This report is a document tree of the safety and integration documents required to develop a space experiment. Pertinent document information for each of the top level (tier one) safety and integration documents, and their applicable and reference (tier two) documents has been identified. This information includes: document title, revision level, configuration management, electronic availability, listed applicable and reference documents, source for obtaining the document, and document owner. One of the main conclusions of this report is that no single document tree exists for all safety and integration documents, regardless of the Shuttle carrier. This document also identifies the need for a single point of contact for customers wishing to access documents. The data in this report serves as a valuable information source for the NASA Lewis Research Center Project Documentation Center, as well as for all developers of space experiments.

Hogan, Jean M.↗

NASA NTRS1999

Parametric Study of Three-Stringer-Panel Compression-After-Impact Strength

Damage tolerance requirements for integrally-stiffened composite wing skins are typically met using design allowables generated by testing impact-damaged subcomponents, such as three-stringer stiffened panels. To improve these structures, it is necessary to evaluate the critical design parameters associated with three-stringer stiffened-panel compressive behavior. During recent research and development programs, four structural parameters were identified as sources for strength variation: (a) material system, (b) stringer configuration, (c) skin layup, and (d) form of axial reinforcement (tape versus pultruded carbon rods). Relative effects of these parameters on damage resistance and damage tolerance were evaluated numerically and experimentally. Material system and geometric configuration had the largest influence on damage resistance; location and extent of the damage zone influenced the sublaminate buckling behavior, failure initiation site, and compressive ultimate strength. A practical global-local modeling technique captured observed experimental behavior and has the potential to identify critical damage sites and estimate failure loads prior to testing. More careful consideration should be given to accurate simulation of boundary conditions in numerical and experimental studies.

Rousseau, Carl Q.↗

NASA NTRS2002

An Aeroacoustic Study of a Leading Edge Slat Configuration

Aeroacoustic evaluations of high-lift devices have been carried out in the Quiet Flow Facility of the NASA Langley Research Center. The present paper describes detailed flow and acoustic measurements that have been made in order to better understand the noise generated from airflow over a wing leading edge slat configuration, and to possibly predict and reduce this noise source. The acoustic database is obtained by a moveable Small Aperture Directional Array of microphones designed to electronically steer to different portions of models under study. The slat is shown to be a uniform distributed noise source. The data was processed such that spectra and directivity were determined with respect to a one-foot span of slat. The spectra are normalized in various fashions to demonstrate slat noise character. In order to equate portions of the spectra to different slat noise components, trailing edge noise predictions using measured slat boundary layer parameters as inputs are compared to the measured slat noise spectra.

Mendoza, J. M.↗

NASA NTRS2004

Power Conversion with a Stirling Cycle for Venus Surface Mission

The light-filtering characteristic of the dense, mostly-CO2 atmosphere of Venus, combined with the high atmospheric cloud cover, relegates the surface mission use of photovoltaic power systems and beckons for the independence and reliability of a nuclear-powered energy source. A multi-faceted Venus mission study was completed at NASA GRC in December of 2003 that resulted in the preliminary design of a helium- charged, kinematic Stirling converter, which is powered by nuclear, General Purpose Heat Source (GPHS) modules. The kinematic, Stirling power converter is configured to drive an electronics and sensor cooler in addition to a generator for electrical power. This paper briefly describes the design process and also describes and summarizes key features of the Stirling power converter preliminary design concept. With an estimated total efficiency of 23.4%, the power converter drives the electronics and sensor cooler, and also produces 100 watts of electricity. The converter rejects waste heat at a hot sink temperature of 500 C.

Mellott, Ken↗

NASA NTRS2010

On Acoustic Source Specification for Rotor-Stator Interaction Noise Prediction

This paper describes the use of measured source data to assess the effects of acoustic source specification on rotor-stator interaction noise predictions. Specifically, the acoustic propagation and radiation portions of a recently developed coupled computational approach are used to predict tonal rotor-stator interaction noise from a benchmark configuration. In addition to the use of full measured data, randomization of source mode relative phases is also considered for specification of the acoustic source within the computational approach. Comparisons with sideline noise measurements are performed to investigate the effects of various source descriptions on both inlet and exhaust predictions. The inclusion of additional modal source content is shown to have a much greater influence on the inlet results. Reasonable agreement between predicted and measured levels is achieved for the inlet, as well as the exhaust when shear layer effects are taken into account. For the number of trials considered, phase randomized predictions follow statistical distributions similar to those found in previous statistical source investigations. The shape of the predicted directivity pattern relative to measurements also improved with phase randomization, having predicted levels generally within one standard deviation of the measured levels.

Nark, Douglas M.↗

NASA NTRS2016

Isolated Open Rotor Noise Prediction Assessment Using the F31A31 Historical Blade Set

In an effort to mitigate next-generation fuel efficiency and environmental impact concerns for aviation, open rotor propulsion systems have received renewed interest. However, maintaining the high propulsive efficiency while simultaneously meeting noise goals has been one of the challenges in making open rotor propulsion a viable option. Improvements in prediction tools and design methodologies have opened the design space for next generation open rotor designs that satisfy these challenging objectives. As such, validation of aerodynamic and acoustic prediction tools has been an important aspect of open rotor research efforts. This paper describes validation efforts of a combined computational fluid dynamics and Ffowcs Williams and Hawkings equation methodology for open rotor aeroacoustic modeling. Performance and acoustic predictions were made for a benchmark open rotor blade set and compared with measurements over a range of rotor speeds and observer angles. Overall, the results indicate that the computational approach is acceptable for assessing low-noise open rotor designs. Additionally, this approach may be used to provide realistic incident source fields for acoustic shielding/scattering studies on various aircraft configurations.

Nark, Douglas M.↗

NASA NTRS2016

Dual-Telescope Multi-Channel Thermal-Infrared Radiometer for Outer Planet Fly-By Missions

The design of a versatile dual-telescope thermal-infrared radiometer spanning the spectral wavelength range 8-200 microns, in five spectral pass bands, for outer planet fly-by missions is described. The dual- telescope design switches between a narrow-field-of-view and a wide-field-of-view to provide optimal spatial resolution images within a range of spacecraft encounters to the target. The switchable dual-field- of-view system uses an optical configuration based on the axial rotation of a source-select mirror along the optical axis. The optical design, spectral performance, radiometric accuracy, and retrieval estimates of the instrument are discussed. This is followed by an assessment of the surface coverage performance at various spatial resolutions by using the planned NASA Europa Mission 13-F7 fly-by trajectories as a case study.

Aslam, Shahid↗

NASA NTRS2018

Jet-Surface Interaction Noise Models Comparison to TMP17 and Next Steps

A set of empirical jet-surface interaction noise models, developed for single-stream round nozzles exhausting over a simple surface in a static ambient, are evaluated for use in more realistic applications that include multi-stream nozzle systems with chevrons and dihedral surface geometries. The simple-single-stream models have several advantages when used in system-level noise studies: they are robust, they are quickly computed, and they are generally applicable to a wide range of configurations. However, these models rely on a fixed noise source distribution that does not account for the presence of chevrons at the nozzle exit. The effect of this omission on the prediction accuracy is shown by this comparison to experimental data. This motivates discussion of future work to develop a more robust modeling framework that can account for generalized source distributions and more complex airframe geometries. Re: Top-Mounted Propulsion (TMP17) Test Plans.

Propulsion Noise↗