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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Energy conversion for megawatt space power systems

Large nuclear space power systems capable of continuously producing over one megawatt of electrical power for a several year period will be needed in the future. This paper presents the results of a study to compare applicable conversion technologies which were deemed to be ready for a time period of 1995 and beyond. A total of six different conversion technologies were studied in detail and compared on the basis of conversion efficiency, radiator area, overall system mass, and feasibility. Three static, modular conversion technologies were considered; these include: AMTEC, thermionic, and thermoelectric conversion. The other three conversion technologies are heat engines which involve dynamic components. The dynamic systems analyzed were Brayton, Rankine, and the free piston Stirling engine. Each of the conversion techniques was also examined for limiting characteristics and an attempt was made to identify common research needs and enabling technologies.

Ewell, R.↗
NASA NTRS1985

A review of contamination issues associated with an orbiting Space Station external environment

Techniques for measuring, modeling, and limiting the effluent contamination of external spacecraft and instrument surfaces are reviewed, with an emphasis on their application to the Space Station. The major factors addressed by contamination studies are outlined; typical contamination sources are characterized; the critical measurement parameters are defined (molecular column density, background spectral intensity from UV to IR, particle size and velocity distribution, molecular deposition on ambient and cryogenic surfaces, molecular return flux for gaseous species, particulate deposition on surfaces, and optical-surface degradation); and measurement instrumentation is described. Contamination limits for quiescent operation periods of the Space Station are proposed, including column density 10 to the 11th/sq cm for H2O + CO2, 10 to the 13th/sq cm for O2 + N2, and 10 to the 10th/sq cm for other species; particle release no greater than 15-micron particle/orbit/0.00001 sr FOV for a 1-m telescope, and surface deposition 4 pg/sq cm sec for 298-K surfaces and 10 pg/sq cm sec for 4-K surfaces.

Smith, A. C.↗
NASA NTRS1983

Robot arm geometric link parameter estimation

A general method for estimating serial link manipulator geometric parameter errors is proposed in this paper. The positioning accuracy of the end-effector may be increased significantly by updating the nominal link parameters in the control software to represent the physical system more accurately. The proposed method is applicable for serial link manipulators with any combination of revolute or prismatic joints, and is not limited to a specific measurement technique.

Hayati, S. A.↗
NASA NTRS1986

Small linear wind tunnel saltation experiments: Some experiences

Since the wind tunnels proposed to be used for the Space Station Planetology Experiments are of a rather limited size, some experience and techniques used for saltation experiments in a small linear wind tunnel may be of interest. Three experiments will be presented. The first concerns a length effect of saltation mass flux in which the size of the wind tunnel exaggerates the physical process taking place. The second experiment concerns a nonoptical technique that does not interfere with flow and by which momentum flux to the floor may be measured. The technique may also be used to calculate saltation flux (using appropriate assumptions). The third experiment concerns the use of the momentum equation to estimate momentum fluxes by difference.

Gillette, D. A.↗
NASA NTRS1986

Computational aeroacoustics - Present status and future promise

The field of computational aeroacoustics (CAA), in which sound generation by unsteady flows is calculated from first principles, has recently emerged as a viable discipline. This paper describes one CAA technique which has been validated for low Mach number, low Reynolds number, two-dimensional flows. Results of its application to geometries producing both dipole and quadrupole type sound sources are presented along with theoretical and experimental comparisons. In addition, the future promise of this and other CAA techniques in removing the present limitations is evaluated.

Hardin, J. C.↗
NASA NTRS1988

Mast material test program (MAMATEP)

The Mast Material Test Program (MAMATEP) at NASA Lewis is discussed. Objectives include verifying the need for, and evaluating the performance of, various protection techniques for the Solar Array Assembly mast of the Space Station Photovoltaic Power Module. Mast material samples were evaluated in terms of mass and bending modulus, measured before and after environmental exposure. Test environments included atomic oxygen exposure (RF plasma asher), thermal cycling, and mechanical flexing. Protective coatings included CV-1144 silicon, a Ni/Au/InSn eutectic, and an open weave, Al braid. Results indicate that unprotected samples degrade in an atomic oxygen environment at a steady rate. Open weave, Al braid offers little protection for the fiberglass-epoxy sample in an asher environment. Ni/Au/InSn eutectic offers excellent protection in an asher environment prior to thermal cycling and mechanical flexing. Long duration asher results from unprotected samples indicate that, even though the fiberglass-epoxy degrades, a protection technique may not be necessary to ensure structural integrity. However, a protection technique may be desirable to limit or contain the amount of debris generated by the degradation of the fiberglass-epoxy.

Ciancone, Michael L.↗
NASA NTRS1988

The origin of the infrared luminosity in Centaurus A

The origin of the infrared luminosity in Centaurus A is studied using new tracking and data acquisition techniques which yield diffraction-limited profiles at both 50 and 100 microns. Ninety percent of the 100 micron flux is found to originate in a source which extends 5 kpc along the optical dust lane that bisects the galaxy; the remaining 10 percent comes from an unresolved source coincident with the active radio nucleus. The extended 100 micron emission profile is fully consistent with a uniform disk of thermally radiating particles; when combined with results of previous studies at shorter wavelengths, these measurements indicate that nearly all of the infrared luminosity is produced by thermally emitting grains which are heated by massive young stars distributed throughout the optically thick dust lane.

Joy, Marshall↗
NASA NTRS1989

Measuring Laminar-Separation Bubbles On Airfoils

Nonintrusive multielement heat-transfer sensor overcomes limitations of previous methods. New technique determines simultaneously extent of laminar boundary layer and locations of laminar separation, transition in separated layer, and turbulent reattachment. In tests, only small amounts of heat introduced, and heated thin films caused little disturbance to shear layer or to each other. Promising tool for measurements of stability of laminar boundary layers, separated shear layers, and transitional separation bubbles. Simple and capable of providing comprehensive picture of state of shear flow along entire surface. Significant savings in tunnel (or flight) test time with corresponding savings in cost.

Stack, John P.↗
NASA NTRS1987

Small linear wind tunnel saltation experiments: Some experiences

Since the wind tunnel proposed to be used for the Space Station Planetology Experiments are of a rather limited size, some experience and techniques used for saltation experiments in a small linear wind tunnel may be of interest. Three experiences are presented. The first concerns a length effect of saltation mass flux in which the size of the wind tunnel exaggerates the physical process taking place. A second experience concerns a non-optical technique that does not interfere with flow and by which momentum and mass fluxes to the flow may be measured. The technique may also be used to calculate saltation flux. The third experience concerns the use of the momentum equation to estimate momentum fluxes by differences.

Gillette, D. A.↗
NASA NTRS1988

Heterogeneity in the growth hormone pituitary gland system of rats and humans: Implications to microgravity based research

The cell separation techniques of velocity sedimentation, flow cytometry and continuous flow electrophoresis were used to obtain enriched populations of growth hormone (GH) cells. The goal was to isolate a GH cell subpopulation which releases GH molecules which are very high in biological activity, it was important to use a method which was effective in processing large numbers of cells over a short time span. The techniques based on sedimentation are limited by cell density overlaps and streaming. While flow cytometry is useful in the analytical mode for objectively establishing cell purity, the numbers of cells which can be processed in the sort mode are so small as to make this approach ineffective in terms of the long term goals. It was shown that continuous flow electrophoresis systems (CFES) can separate GH cells from other cell types on the basis of differences in surface charge. The bioreactive producers appear to be more electrophoretically mobile than the low producers. Current ground based CFES efforts are hampered by cell clumping in low ionic strength buffers and poor cell recoveries from the CFES device.

Hymer, W. C.↗
NASA NTRS1991

Determination of shuttle orbiter center of gravity from flight measurements

Flight measurements of pitch, yaw, and roll rates and the resultant rotationally induced linear accelerations during three orbital maneuvers on Shuttle mission space transportation system (STS) 61-C were used to calculate the actual orbiter center-of-gravity location. The calculation technique reduces error due to lack of absolute calibration of the accelerometer measurements and compensates for accelerometer temperature bias and for the effects of gravity gradient. Accuracy of the technique was found to be limited by the nonrandom and asymmetrical distribution of orbiter structural vibration at the accelerometer mounting location. Fourier analysis of the vibration was performed to obtain the power spectral density profiles which show magnitudes in excess of 10(exp 4) ug (sup 2)/Hz for the actual vibration and over 500 ug (sup 2)/Hz for the filtered accelerometer measurements. The data from this analysis provide a characterization of the Shuttle acceleration environment which may be useful in future studies related to accelerometer system application and zero-g investigations or processes.

Hinson, E. W.↗
NASA NTRS1991

Gas chromatographic concepts for the analysis of planetary atmospheres

Over the last few years, new gas chromatographic (GC) concepts were developed for use on board spacecraft or any other restricted environments for determining the chemical composition of the atmosphere and surface material of various planetary bodies. Future NASA Missions include an entry probe that will be sent to Titan and various spacecraft that will land on Mars. In order to be able to properly respond to the mission science requirements and physical restrictions imposed on the instruments by these missions, GC analytical techniques are being developed. Some of these techniques include hardware and mathematical techniques that will improve GC sensitivity and increase the sampling rate of a GC descending through a planetary atmosphere. The technique of Multiplex Gas Chromatography (MGC) is an example of a technique that was studied in a simulated Titan atmosphere. In such an environment, the atmospheric pressure at instrument deployment is estimated to be a few torr. Thus, at such pressures, the small amount of sample that is acquired might not be enough to satisfy the detection requirements of the gas chromatograph. In MGC, many samples are pseudo-randomly introduced to the chromatograph without regard to elution of preceding components. The resulting data is then reduced using mathematical techniques such as cross-correlation of Fourier Transforms. Advantages realized from this technique include: improvement in detection limits of several orders of magnitude and increase in the number of analyses that can be conducted in a given period of time. Results proving the application of MGC at very low pressures emulating the same atmospheric pressures that a Titan Probe will encounter when the instruments are deployed are presented. The sample used contained hydrocarbons that are expected to be found in Titan's atmosphere. In addition, a new selective modulator was developed to monitor water under Martian atmospheric conditions. Since this modulator is selective only to water, the need for a GC column is eliminated. This results in further simplification of the instrument.

Valentin, J. R.↗
NASA NTRS1992

A calculation of confusion noise due to infrared cirrus

General expressions are developed for the statistical errors to be expected in photometric measurements due to confusion in a background of fluctuating surface brightness. Backgrounds actually observed in the far IR by the IRAS satellite are used to calculate tables of these error expressions for two simple measurement techniques. The confusion-noise-limited sensitivities for NASA's planned Space IR Telescope Facility and the ESA's IR Space Observatory are estimated at a wavelength of 100 microns from these tables.

Gautier, T. N., III↗
NASA NTRS1993

Cratering in glasses impacted by debris or micrometeorites

Mechanical strength measurements on five glasses and one glass-ceramic exposed on LDEF revealed no damage exceeding experimental limits of error. The measurement technique subjected less than 5 percent of the sample surface area to stresses above 90 percent of the failure strength. Seven micrometeorite or space debris impacts occurred at locations which were not in that portion of the sample subjected to greater than 90 percent of the applied stress. As a result of this, the impact events on the sample were not detected in the mechanical strength measurements. The physical form and structure of the impact sites was carefully examined to determine the influence of those events upon stress concentration associated with the impact and the resulting mechanical strength. The size of the impact site, insofar as it determines flaw size for fracture purposes, was examined. Surface topography of the impacts reveals that six of the seven sites display impact melting. The classical melt crater structure is surrounded by a zone of fractured glass. Residual stresses arising from shock compression and from cooling of the fused zone cannot be included in the fracture mechanics analyses based on simple flaw size measurements. Strategies for refining estimates of mechanical strength degradation by impact events are presented.

Wiedlocher, David E.↗
NASA NTRS1992

Comparison of column water vapor measurements using downward-looking near-infrared and infrared imaging systems and upward-looking microwave radiometers

Remote soundings of precipitable water vapor from three systems are compared with each other and with ground truth from radiosondes. Ancillary data from a mesoscale network of surface observing stations and from wind-profiling radars are also used in the analysis. The three remote-sounding techniques are: (a) a reflectance technique using spectral data collected by the Airborne Visible-Infrared Imaging Spectrometer; (b) an emission technique using Visible-Infrared Spin Scan Radiometer Atmospheric Sounder (VAS) data acquired from the NOAA's GOES; and (c) a microwave technique using data from a limited network of three ground-based dual-channel microwave radiometers. The data were taken over the Front Range of eastern Colorado on 22-23 March 1990. The generally small differences between the three types of remote-sounding measurements are consistent with the horizontal and temporal resolutions of the instruments. The microwave and optical reflectance measurements agreed to within 0.1 cm; comparisons of the microwave data with radiosondes were also either as good or explainable. The largest differences between the VAS and the microwave radiometer at Elbert were between 0.4 and 0.5 cm and appear to be due to variable terrain within the satellite footprint.

Gao, Bo-Cai↗
NASA NTRS1985

Electronystagmography and audio potentials in space flight

Beginning with the fourth flight of the Space Transport System (STS-4), objective measurements of inner ear function were conducted in near-zero G conditions in earth orbit. The problem of space motion sickness (SMS) was approached much like any disequilibrium problem encountered clinically. However, objective testing techniques had built-in limitations superimposed by the strict parameters inherent in each mission. An attempt was made to objectively characterize SMS, and to first ascertain whether the objective measurements indicated that this disorder was of peripheral or central origin. Electronystagmography and auditory brain stem response recordings were the primary investigative tools. One of the authors (W.E.T.) was a mission specialist on board the orbiter Challenger on the eighth shuttle mission (STS-8) and had the opportunity to make direct and personal observations regarding SMS, an opportunity which has added immeasurably to our understanding of this disorder. Except for two abnormal ENG records, which remain to be explained, the remaining ENG records and all the ABR records made in the weightless environment of space were normal.

Thornton, William E.↗
NASA NTRS1993

Thermal-infrared emission spectroscopy of natural surfaces: Application to coated surfaces

Thermal-infrared vibrational spectroscopy has great potential for remotely determining the composition of planetary surface materials by taking advantage of fundamental molecular vibrational modes that produce spectral features in the range from approximately 3 to greater than 50 microns. Much of the current interest in the thermal infrared wavelength region stems from the deployment of multispectral scanners, such as the Thermal Infrared Multispectral Scanner (TIMS) and the Mars Observer Thermal Emission Spectrometer (TES). In order to support these missions, it is necessary to develop an appropriate library of laboratory measurements. The purpose of this work was to develop a technique which, with a very limited set of assumptions, can be used to determine the emissivity of natural surfaces directly by using emitted energy.

Christensen, Philip R.↗
NASA NTRS1993

First satellite mobile communication trials using BLQS-CDMA

In this paper, technical results obtained in the first MSBN Land mobile technical trial are reported. MSBN (Mobile Satellite Business Network) is a new program undertaken by the European Space Agency (ESA) to promote mobile satellite communication in Europe, in particular voice capability. The first phase of the MSBN system implementation plan is an experimental phase. Its purpose is to evaluate through field experiments the performance of the MSBN system prior to finalization of its specifications. Particularly, the objective is to verify in the field and possibly improve the performance of the novel satellite access technique BLQS-CDMA (Band Limited Quasi-Synchronous-Code Division Multiple Access), which is proposed as baseline for the MSBN.

Luzdemateo, Maria↗