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At least 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Velocity and temperature decay characteristics of inverted-profile jets

In order to design efficient, lightweight flap systems for future engine under-the-wing STOL aircraft, the velocity and temperature decay rate of the jet plume must be increased relative to that for single-stream nozzles in order to provide local flap loads and structural temperatures within acceptable limits. The jet plume decay rate of dual flow engines can be increased by resorting to inverted-profile velocity and temperature nozzle concepts. The peak axial decay characteristics of model-scale, two-stream inverted-profile nozzle flows are empirically correlated. Also discussed are the radial and spreading characteristics of inverted-profile nozzle flows.

Vonglahn, U.↗
NASA NTRS1986

Plume characteristics of single-stream and dual-flow conventional and inverted-profile nozzles at equal thrust

The plume velocity and temperature decay rates of single-stream, conventional dual-flow and inverted-profile dual-flow nozzles are compared at equal values of ideal thrust over a wide range of flow conditions. The comparisons are made in terms of constant velocity and temperature contour maps. The results show that both dual-flow nozzle types have much greater plume velocity and temperature decay rates than those of equivalent thrust single-stream nozzles when the respective secondary flows were at ambient temperature. With hot secondary flows, the inverted-profile dual-flow plumes decayed significantly faster than those of single-stream nozzles; however, the decay rates for the conventional dual-flow streams were about the same as those for the single-stream nozzles. Consequently, with hot secondary flows, the inverted-profile dual-flow plumes decayed much faster than the conventional dual-flow plumes at equal thrust.

Vonglahn, U. H.↗
NASA NTRS1985

Unusual X-ray burst profiles from 4U/MXB 1636-53

During a one day Exosat observation eight X-ray bursts from 4U/MXB 1636-53 are observed. Four of these were very unusual. Their peak fluxes were relatively low, and they showed a distinct double peak in their bolometric flux profiles. These new double-peaked bursts are unexplained by presently available models of X-ray bursts. It is possible that the energy release in these bursts proceeds in two 'steps'. The burst profiles are not the result of an expansion and subsequent contraction of the photosphere of the neutron star. Thus, they are very different from previously observed bursts which do show a double peak in certain energy ranges but not in their bolometric flux profiles; these are satisfactorily explained in terms of photospheric radius expansion and contraction. The anticorrelation between the apparent blackbody radius and blackbody temperature is discussed in terms of the nonPlanckian character of burst spectra and it is concluded that the model calculations reported by London, Taam, and Howard in 1984 give a reasonable first-order description of the observed apparent radius changes in X-ray bursts.

Sztajno, M.↗
NASA NTRS1986

Velocity and temperature decay characteristics of inverted-profile jets

In order to design efficient, lightweight flap systems for future engine under-the-wing STOL aircraft, the velocity and temperature decay rate of the jet plume must be increased relative to that for single-stream nozzles in order to provide local flap loads and structural temperatures within acceptable limits. The jet plume decay rate of dual flow engines can be increased by resorting to inverted-profile velocity and temperature nozzle concepts. The peak axial decay characteristics of model-scale, two-stream inverted-profile nozzle flows are empirically correlated. Also discussed are the radial and spreading characteristics of inverted-profile nozzle flows.

Von Glahn, U.↗
NASA NTRS1986

Optical spectrophotometry of Comet P/Giacobini-Zinner and emission profiles of H2O+

Two-dimensional CCD spectrograms were obtained of Comet P/Giacobini-Zinner (1984e) on five occasions between July and October 1985. Spatial emission profiles of H2O+ were extracted at 6198 angstroms (the strongest ionic line in the visible spectrum). This emission line traces the extent of the ion, or plasma, tail. The spectrographic slit was placed approximately along the trajectory of the ICE spacecraft on September 11, 1985; the resulting H2O+ profile has a full-width-half-maximum of about 5700 km, about three times that of the plasma density profile measured by ICE, and has a full-width-zero-intensity of about 30,000 km, very similar to the ICE values. H2O production rates for the comet are derived and compared with those of Comet P/Halley (1982i).

Strauss, M. A.↗
NASA NTRS1986

A graphical treatment of combined evaporation and segregation contributions to impurity profiles for zone-refining in vacuum

Impurity concentration profiles have been calculated for zone-refining when both segregation and evaporation of impurities are operative, assuming a uniform initial concentration. Graphic profiles are presented for selected values of effective segregation coefficient k, effective evaporation coefficient g, and number of zone passes n. Some examples of impurity profiles for float-zoned silicon are also presented.

Ciszek, T. F.↗
NASA NTRS1985

Experimental radar Doppler wind profile measurements at Kennedy Space Center

A wind profile radar demonstration project was sponsored by the Space Transportation System (STS) Program Office to study the feasibility of incorporating continuous, high time resolution radar wind data into STS operations. This project required wind profile radars to be deployed in the vicinity of the Shuttle launch site into an environment quite unlike typical VHF profiler sites. Two 50 MHz radars were operated at the Kennedy Space Center in environments that were noisy in terms of RFI, large stationary ground clutter sources, non-stationary clutter sources, and heavy local aircraft traffic. Processing compensation for these operational constraints magnified design limitations of the research-level radars used in the demonstration. This report addresses the importance of system design for unique or particular applications with reference to finite radiation patterns, zero-Doppler processing, radar frequency, and beam pointing.

Jost, R. J.↗
NASA NTRS1985

Intercomparison of satellite ozone profile measurements

Ozone profile data are intercompared with those from the LIMS and SBUV flown on Nimbus 7, SAGE flown on Atmospheric Explorer Mission 2, and the Ultraviolet and Infrared Spectrometers flown on the SME. Ozone data were derived from the measurements with independently derived processing algorithms. The data cover different time periods and have different spatial and temporal resolutions. The similarities and differences between the individual data sets are determined with effort focused on directly comparing the spacecraft data sets in the form of individual profiles, zonal mean profiles and global analyses. Comparisons with ground data from balloons and Umkehr stations are made.

Fleig, A. J.↗
NASA NTRS1986

Plume characteristics of single-stream and dual-flow conventional and inverted-profile nozzles at equal thrust

The plume velocity and temperature decay rates of single-stream, conventional dual-flow and inverted-profile dual-flow nozzles are compared at equal values of ideal thrust over a wide range of flow conditions. The comparisons are made in terms of constant velocity and temperature contour maps. The results show that both dual-flow nozzle types have much greater plume velocity and temperature decay rates than those of equivalent thrust single-stream nozzles when the respective secondary flows were at ambient temperature. With hot secondary flows, the inverted-profile dual-flow plumes decayed significantly faster than those of single-stream nozzles; however, the decay rates for the conventional dual-flow streams were about the same as those for the single-stream nozzles. Consequently, with hot secondary flows, the inverted-profile dual-flow plumes decayed much faster than the conventional dual-flow plumes at equal thrust.

Von Glahn, U. H.↗
NASA NTRS1986

Geostationary Operational Environmental Satellite (GOES) mission profile

The GOES mission profile used to achieve geostationary orbit following separation from the Delta launch vehicle is described. The mission profile was constrained by the solid-propellant apogee kick motor which was undersized relative to the spacecraft weight. The resulting deficiency in delivered delta-V had to be made up by the spacecraft hydrazine propulsion system. The mission profile which best utilizes the on-board hydrazine requires that the transfer orbit apogee height be biased 13,800 km above geosynchronous altitude. This maximizes the effectiveness of the apogee motor in performing the plane change necessary to achieve near-equatorial orbit. The highly eccentric drift orbit which results from the apogee motor firing has an average drift rate of 60 deg/day. Circularizing this orbit requires maneuvers designed to achieve geostationary position within a tightly constrained hydrazine allocation. The sequence takes advantage of the orbit changes resulting from attitude maneuvers and combined inplane/out-of-plane maneuvers to achieve hydrazine savings.

Bryant, W. C.↗
NASA NTRS1986

Optimal filtration of the atmospheric parameters profiles

The idea of optimal Marcovian filtration of fluctuating profiles from lidar signals is developed but as applied to a double-frequency sounding which allows the use of large cross sections of elastic scattering and correct separation of the contributions due to aerosol and Rayleigh scatterings from the total lidar return. The filtration efficiency is shown under different conditions of sounding using a computer model. The accuracy of restituted profiles (temperature, pressure, density) is determined by the elements of a posteriori matrix K. The results obtained allow the determination of the lidar power required for providing the necessary accuracy of restitution of the atmospheric parameter profiles at chosen wavelengths of sounding in the ultraviolet and visible range.

Zuev, V. E.↗
NASA NTRS1986

Lower atmospheric temperature profile measurements using a Raman lidar

A Raman lidar system was used to measure the temperature profile of the upper troposphere and lower stratosphere. The system consists of a tripled Nd-YAG laser and a 1.5 meter diameter telescope. Two photomultipliers are used at the output of the telescope to allow for measurements at both the laser wavelength and at the Raman shifted wavelength due to atmospheric nitrogen. The signal from the photomultipliers is recorded as photon counts in 1 microsec bins. The results of a number of laser shots are summed together to provide atmospheric returns which have acceptable signal to noise characteristics. Measurements of the Raman nitrogen return were acquired up to an altitude in excess of 20 km. Temperature profiles were retrieved from the attenuation corrected Raman nitrogen return assuming the atmosphere to be in hydrostatic equilibrium and using the ideal gas law. Retrieved temperature profiles are shown compared with independent temperature measurements.

Melfi, S. H.↗
NASA NTRS1986

Laser heterodyne system for obtaining height profiles of minor species in the atmosphere

An infrared laser heterodyne system for obtaining height profiles of minor constituents of the atmosphere was developed and erected. A brief discription of the system is given. The system consists of a tunable CO2 waveguide laser in the 9 to 11 micrometer band, that is used as a local oscillator and a heliostat that follows the sun and brings in solar radiation, that is mixed with the laser beam in a high speed liquid nitrogen cooled mercury cadmium telluride detector. The detected signal is analysed in a RF spectrum analyser that allows tracing absorption line profiles. Absorption lines of a number of minor constituents in the troposphere and stratosphere, such as O3, NH3, H2O, SO2, ClO, N2O, are in the 9 to 11 micrometer band and overlap with that of CO2 laser range. The experimental system has been made operational and trial observations taken. Current measurements are limited to ozone height profiles. Results are presented.

Jain, S. L.↗
NASA NTRS1986

Wind profiler data in a mesoscale experiment from a meteorological perspective

During May and June of 1985, the Oklahoma-Kansas Preliminary Regional Experiment of STORM-Central (OK PRE-STORM) was carried out, with the major objectives of learning more about mesoscale convective systems (MCSs) and gaining experience in the use of new sensing systems and measurement strategies that will improve the design of STORM-Central. Three 50-MHz wind profilers were employed in a triangular array with sides about 275 km. It is far too soon to report any results of this effort, for it has barely begun. The purpose here is to show some examples of the data, some of the surrounding conventional data, and to discuss some of the issues important to meteorologists in evaluating the contribution of the profiler data. The case of 10 to 11 June 1985, featuring a major squall line system which crossed the dense observing network from northwest to southeast, passing the Liberal site about 2230 GMT/10 June, the McPherson site about 0100 GMT/11 June, and Wichita about 0300 GMT/11 June is discussed. Radar and satellite data show that the system was growing rapidly when it passed Liberal, and was large and mature when it passed through McPherson and Wichita. The radar depiction of the system during this stage is given, with the McPherson site in the intense convective echoes near the leading edge at 01 GMT and in the stratiform precipitation at 03 GMT. The profiler wind data for a 9-hour period encompassing the squall line passage at each site are given.

Zipser, E. J.↗
NASA NTRS1986

Colorado wind profilers

The Wave Propagation Laboratory (WPL) has operated a network of wind profiling radars in Colorado. The current configuration of the network is described. All radars operate continuously and unattended to supply hourly-averaged wind profiles to a central computer in Boulder in real time. The hardware and software changes made to improve reliability are discussed. This research network will continue to be used to provide wind profiles for operational and research meteorologists and the performance of various wavelength systems will be evaluated.

Strauch, R. G.↗
NASA NTRS1986

Wind profiler demonstration system

The National Oceanic and Atmospheric Administration (NOAA) has started procurement of a 30-station demonstration network of Doppler radar wind profilers to be deployed in the central United States by 1989. The purposes of this demonstration network are: (1) to assess the impact of a large wind profiler network on meteorological forecasting; (2) to test wind profiler hardware designed specifically for commercial production and widespread deployment; and (3) to provide wind data for research programs involving weather phenomena in the central United States.

Chadwick, R. B.↗
NASA NTRS1986

Fe II emission line profiles in spectra of high luminosity non-coronal stars

The results of a program to study the winds of noncoronal late-type giant and supergiant stars with IUE are presented. The primary data for this study are profiles, fluxes, and velocities of the Fe II emission lines which occur throughout the 2200 to 3230 A region of the IUE long wavelength spectrographs. The apparent dependence of the Fe II profiles on stellar luminosity (surface gravity) and intrinsic line strength is discussed. The discovery of significant changes in the Fe II profiles in spectra of Gamma Crucis (M3 III), during the period 1978 to 1985, that suggest a substantial change in its outer atmosphere is noted.

Carpenter, Kenneth G.↗
NASA NTRS1986

Comet Halley neutral gas density profile along the Vega 1 trajectory measured by NGE

Data from the Vega 1 permitted the determination of the total neutral gas density profile along the spacecraft trajectory. Discounting small fluctuations, the field ionization source instrument measured a density profile which varied approximately as the inverse radial distance squared. Data from the electron impact ionization instrument yielded a series of calibration points; e.g., the neutral density at 100,000 km is 10,000/cc. The combined data provide a calibrated total density profile, and imply a neutral production rate of 10 to the 30th power molecules/sec.

Curtis, C. C.↗