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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 127 records · Page 7

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NASA NTRS1989

A multiflare horn with 1-megawatt power handling capability

The design and testing of the prototype horn for the proposed 1-megawatt radar are described. The unique features of this square horn include a multiflare design in which flare angle changes rather than corrugations are used to generate the required higher-order modes. A five-port combining section is used at the input. The design of this section and the multiflare section are described. Measured radiation patterns are in good agreement with theoretical patterns.

Hoppe, D. J.↗

NASA NTRS1989

Thermal measurements of microwave transmitter feedhorn window

Thermal measurements of microwave transmitter feedhorn windows were performed using an imaging infrared radiometer. The measurement technique is described and results are presented for windows made of 0.001-in. Kapton (trademark of Dupont Chemical Co.) and 0.1-in. HTP-6 (Space Shuttle tile material). Measured and calculated temperatures agree well.

Perez, R. M.↗

NASA NTRS1989

EISCAT observations during MAC/SINE and MAC/Epsilon

The EISCAT incoherent scatter radar facility in Tromsoe, Norway was operated during the MAC/SINE campaign for 78 hours in the period 10 June to 17 July 1987, and during the MAC/Epsilon campaign for 90 hours in the period 15 October to 5 November 1987. The VHF (224 MHz) radar operations during MAC/SINE yielded most interesting observations of strong coherent echoes from the mesopause region. Characteristic data of these polar mesospheric summer echoes are presented. The UHF (933 MHz) radar operations during MAC/Epsilon were done with 18 deg off zenith beam and allows the deduction of meridonal and horizontal wind components as well as radial velocity spectra in addition to the usual electron density profiles in the D and lower E regions. Some results from the VHF and UHF radars indicating the presence of gravity waves are examined.

Roettger, J.↗

NASA NTRS1988

Studies of high latitude mesospheric turbulence by radar and rocket. II - Measurements of small scale turbulence

Measurements of mesospheric small scale turbulence and associated larger scale wave structures were obtained from rocket probe flights during equinox in spring 1985. The measurements were verified by data from the mesosphere-stratosphere-troposphere radar at Poker Flat, Alaska. Electron density irregularities down to an altitude of about 62 km and fluctuations in positive ion density in the altitude region from 50 to 90 km were measured. Turbulence in the inertial subrange was observed at heights where the fluctuations generally were largest. Measurement of background electron density exhibited gradients relative to the monotonically increasing density profile, suggesting the presence of large amplitude wave motions transporting the plasma by mixing. The radar detected the occurrence of 1-3 km wavelike perturbations superimposed on a 7-km wave in the wind velocity field. It is suggested that the 1-3 km waves are more important in the transport of energy and momentum and in the production of turbulence in the lower mesosphere.

Blood, S. P.↗

NASA NTRS1989

Meteoritic silicon carbide and its stellar sources - Implications for galactic chemical evolution

Interstellar silicon carbide grains in meteorites provide a novel means for studying the carbon-star population of about 5 x 10 to the 9th years ago. Their C-12/C-13 ratios differ greatly from the solar value but resemble those of present-day csrbon stars, implying little change in the galactic C-13 inventory. Isotope data on nitrogen and silicon suggest that the silicon carbide grains come mainly from red giants, with small contributions from novae.

Ming, Tang↗

NASA NTRS1990

Directional Couplers For Detecting Circular Waveguide Modes

Samples of TE11 and TE12 modes coupled selectively out of circular waveguide. Report presents additional details of theory, construction, and measured operating characteristics of directional couplers described in "Microwave Transmitter With Multimode Output Section" (NPO-16826). Couplers consist of tapered rectangular-cross-section waveguides fastened lengthwise to outside of circular waveguide, with uniformly-lengthwise-spaced round coupling holes between each rectangular waveguide and circular waveguide.

Hoppe, Daniel J.↗

NASA NTRS1990

Computing Scattering Matrices For Circular Waveguides

Scattering Matrix Program for Circular Waveguide Junctions computes scattering matrix for series of circular waveguide sections. Sections must have same axis, but radius and length of each section completely arbitrary. Devices analyzed include simple waveguide step discontinuity like that used in a dual-mode horn, stepped matching section, or corrugated waveguide section with constant or varying slot depth. Certain types of corrugated horns also analyzed with program. Mathematical model used in program accurately predicts reflection and transmission characteristics of such devices, taking into account excitation of modes of higher order as well as multiple reflections and energy stored at each discontinuity. Written in FORTRAN 77.

Hoppe, Daniel J.↗

NASA NTRS1989

A square multiflare horn with 1-megawatt CW power-handling capability

The analysis and low-power testing of a square multiflare horn designed for 1-megawatt CW operation is described. Design considerations for the five-port input section are discussed. The required aperture modes are determined from radiation pattern considerations, and analysis of the multiflare section is carried out using mode matching. Measurements demonstrate that a circularly symmetric beam is produced with relatively low sidelobes.

Hoppe, Dan↗

NASA NTRS1990

Temperature measurements of a high-power microwave feedhorn window

Temperature measurements of a high-power microwave feedhorn window, obtained using an imaging IR radiometer during transmitter operation at 365 kW CW and 8.5 GHz, are discussed. The window under investigation was constructed of HTP-6, a high-thermal-performance material developed to shield the Space Shuttle Orbiter from the heat of reentry. The measurement technique is described, and experimental results are presented. The window performed adequately at 365 kW CW with a center temperature of 475 C. The tests verify that HTP-6 can be used as a window material or a support structure in high-power waveguides at power densities of 1.47 kW/sq cm for extended periods of time, with no change in its mechanical characteristics.

Hoppe, Daniel J.↗

NASA NTRS1991

Megawatt Square Microwave Feed Horn

Prototype multiflare square horn antenna designed to combine phased 8.51-GHz outputs of four 250-kW amplifiers into single 1-MW continuous-wave beam. Main lobe and side lobes reasonably below main lobe obtained by choosing tapers of multiflare horn to couple power from TE(Sub10) mode into three other modes. Intended to illuminate subreflector of 70-m-diameter radar antenna. Nearly duplicates radiation pattern of corrugated round feed horn.

Hoppe, Daniel J.↗

NASA NTRS1991

Calculating Scattering At Circular-Waveguide Junctions

Computer program calculates scattering matrices for circular waveguides including step discontinuities between collinear sections of different radii. Radius and length of each section specified arbitrarily. Examples of devices analyzed with program include waveguides with single step discontinuities, matching sections, corrugated straight sections, and corrugated horns. Sections with smooth tapers and horns with arbitrary profiles approximated by series of small steps.

Hoppe, D. J.↗

NASA NTRS1991

High pressure water jet cutting and stripping

High pressure water cutting techniques have a wide range of applications to the American space effort. Hydroblasting techniques are commonly used during the refurbishment of the reusable solid rocket motors. The process can be controlled to strip a thermal protective ablator without incurring any damage to the painted surface underneath by using a variation of possible parameters. Hydroblasting is a technique which is easily automated. Automation removes personnel from the hostile environment of the high pressure water. Computer controlled robots can perform the same task in a fraction of the time that would be required by manual operation.

Hoppe, David T.↗

NASA NTRS1990

A multiwavelength study of the galaxy UGC 11000

The properties of the galaxy UGC 11,000 were investigated using broad-band and narrow-band CCD images, K-band photometry, long-slit optical spectroscopy, and 21-cm radio observations. Results show that the UGC 11,000 can be classified as belonging to the SB(s)dm IV galaxy type. Its heliocentric velocity was found to be equal to (1398 + or - 15) km/sec, which is about a factor of 4 larger than that assumed previously. Three dominant stellar populations were distinguished in UGC 11,000: (1) a bulge with colors corresponding to early-F main sequence stars; (2) a young disk populaton with median colors of late-A type, associated with the spiral-arm pattern and numerous giant H II regions; and (3) an older population of G to K stars corresponding to the outermost regions of the galaxy. The giant H II regions exhibit high star-forming activity and high oxygen abundance. The bulge and the outer disk are free of ionized gas and contain red stars.

Schulte-Ladbeck, R. E.↗

NASA NTRS1990

Mean state densities, temperatures and winds during the MAC/SINE and MAC/EPSILON campaigns

Two field campaigns were conducted, primarily in northern Norway, in the summer and late autumn of 1987; these yielded a total of 41 in situ temperature profiles and 67 in situ wind profiles. Simultaneously, ground-based measurements were conducted of OH temperatures and sodium lidar temperatures for 85 and 104 hours, respectively. The summer campaign's mean temperature profile exhibited major deviations from the CIRA (1986) reference atmosphere; the differences between this model and the observations are less pronounced in the autumn. Both the summer and autumn mean wind profiles were in general agreement with the CIRA model.

Luebken, F.-J.↗

NASA NTRS1990

Electric field measurements during the MAC/EPSILON campaign

The MAC/EPSILON observational campaign in northern Norway involved the taking of three-axis electric field measurements of the middle atmosphere by means of five rocketborne payloads during October and November, 1987. Simultaneous horizontal electric field measurements made by two of the rocket flights were in general agreement in their limited overlap region. The more extensive horizontal E-field measurements exhibited a decreasing mapping function with decreasing altitude, thereby indicating the presence of fields from a local auroral patch. Small-scale variations in the horizontal fields of the lights were similar to observed wavelike variations in the neutral wind field.

Croskey, C. L.↗

NASA NTRS1990

Conceptual design of a 1-MW CW X-band transmitter for planetary radar

A proposed conceptual design to increase the output power of an existing X-band planetary radar transmitter used for planetary radar exploration from 365 kW to 1 MW CW is presented. The basic transmitter system requirements as dictated by the specifications for the radar are covered. The characteristics and expected performance of the high-power klystrons are considered, and the transmitter power amplifier system is discussed. Also included is the design of all of the associated high-power microwave components, the feed system, and the phase-stable exciter. The expected performance of the beam supply, heat exchanger, and monitor and control devices is also presented. Finally, an assessment of the state-of-the-art technology needed to meet system requirements is given and possible areas of difficulty are summarized.

Bhanji, A. M.↗

NASA NTRS1991

The dwarf galaxy UGC 5272 and its small companion galaxy

The present study of optical images and spectroscopy of the dwarf irregular galaxy UGC 5272 notes the presence, at 3.6 kpc, of a small neighboring galaxy which is also of irregular type and has a Holmberg diameter of 0.6 kpc. Attention is given to the possibility that the two galaxies, which are resolved into single stars, may form a physical pair. It is suggested that the blue-to-red supergiant ratio of UGC 5272 is high due to its low metallicity. While its extremely blue colors are suggestive of a recent starburst, the structural parameters of the galaxy are surprisingly normal. The gas contribution to total mass is high.

Hopp, U.↗

NASA NTRS1991

Automated carbon dioxide cleaning system

Solidified CO2 pellets are an effective blast media for the cleaning of a variety of materials. CO2 is obtained from the waste gas streams generated from other manufacturing processes and therefore does not contribute to the greenhouse effect, depletion of the ozone layer, or the environmental burden of hazardous waste disposal. The system is capable of removing as much as 90 percent of the contamination from a surface in one pass or to a high cleanliness level after multiple passes. Although the system is packaged and designed for manual hand held cleaning processes, the nozzle can easily be attached to the end effector of a robot for automated cleaning of predefined and known geometries. Specific tailoring of cleaning parameters are required to optimize the process for each individual geometry. Using optimum cleaning parameters the CO2 systems were shown to be capable of cleaning to molecular levels below 0.7 mg/sq ft. The systems were effective for removing a variety of contaminants such as lubricating oils, cutting oils, grease, alcohol residue, biological films, and silicone. The system was effective on steel, aluminum, and carbon phenolic substrates.

Hoppe, David T.↗