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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 NTRS1985

Satellite Module Design

The tethered satellite system (TSS) satellite is a multimission vehicle able to carry scientific payloads aways from the shuttle orbiter in the range of 130 to 330 km in altitude. The multimission capability is obtained adopting a modular concept of the satellite such to allow for: easy reconfiguration, easy refurbishment, and cost and schedule minimization. The modular concept is realized with: a payload module (PM), a service module (SM), and an auxiliary propulsion module (APM). The satellite configuration for the electrodynamic and atmospheric missions is described as well as its mechanized capabilities. Payload dedicated electrical facilities, satellite position determination accuracy; attitude control and measurement accuracy and attitude oscillation characteristics are summarized.

Vignoli, M.↗
NASA NTRS1984

Copernicus observations of Iota Herculis velocity variations

Observations of Iota Her at 109.61-109.67 nm obtained with the U1 channel of the Copernicus spectrophotometer at resolution 5 pm during 3.6 days in May, 1979, are reported. Radial-velocity variations are detected and analyzed as the sum of two sinusoids with frequencies 0.660 and 0.618 cycles/day and amplitudes 9.18 and 8.11 km/s, respectively. Weak evidence supporting the 13.9-h periodicity seen in line-profile variations by Smith (1978) is found.

Rogerson, J. B., Jr.↗
NASA NTRS1984

Diamagnetism and charge transfer in graphite intercalation compounds

The magnetic susceptibilities at 300 K of the acceptor-type intercalation compounds of graphite with Br2 and ICl are calculated; the results are compared with published experimental measurements in graphs; and the charge-transfer parameter f is inferred using a rigid-band model (Loughin et al., 1978; Weinberger et al., 1978; Mattix et al., 1983). Assuming a screening length of 200 pm, the values determined are f = 0.3 for C(8N)Br2 and f = 0.09 for C(13N)ICl.

Tsang, T.↗
NASA NTRS1985

The Mars Observer Mission

The Mars Observer Mission is to be the first in a series of modest-cost inner-planet missions. Launch is planned for the August/September 1990 Mars opportunity with arrival at Mars one year later. The geoscience/climatology objectives are to be met during a mapping mission over the course of one Mars year (687 days). The mapping orbit will be near-polar (93 degree orbital inclination), sun-synchronous (2 PM sunward equator crossing), and near-circular (350 km orbit altitude, 116 minute period). The spacecraft, to be selected in late 1985, will be a modified version of an existing commercial design which, in the mapping orbit, will maintain a nadir orientation. Experiments and instruments will be selected through an Announcement of Opportunity (AO) process with release of the AO in April 1985, and selection in early 1986. A description of current planning for this mission, with emphasis on climatology, is presented here.

Palluconi, F. D.↗
NASA NTRS1983

Calculation of high-pressure phase transitions in solid N2 and the pressure dependence of intramolecular mode frequencies

A calculation that minimizes the energy of solid N2 with respect to a rhombohedral distortion of the Pm 3n structure shows that a low-temperature phase transition occurs into the R 3c calcite structure at P = 19.2 kbar with a volume change of 0.125 cu cm/mole. This transition agrees with recent Raman scattering measurements. Another transition from R 3c into R3(bar)m is predicted at P = 67.5 kbar, with a volume change of 0.1 cu cm/mole. The pressure dependence of the intramolecular mode frequencies for the R 3c structure are in reasonably good agreement with the two main branches observed experimentally.

Chandrasekharan, V.↗
NASA NTRS1985

Laboratory simulation of meteoritic noble gases. II - Sorption of xenon on carbon: Etching and heating experiments

The release of trapped Xe from amorphous-C phases of meteorites is simulated experimentally by HNO3 etching of carbon-black and pyrolyzed polyvinylidene chloride samples exposed to Xe-127 for 0.5-240 h at 100-1000 C and then degassed for 9 h or more at the same temperatures, as reported by Wacker et al. (1985). The results are presented in tables and graphs and characterized in detail. Samples exposed at 100-200 C are found to lose most of their Xe after etching to a depth of only about 20 pm, while those exposed at 800-1000 C exhibit a second more tightly bound component extending to a depth of 3 nm, indicative of diffusion of Xe during exposure and resembling planetary Xe. The higher noble-gas concentrations measured in meteorites are attributed to rate-controlled Xe uptake over a long period in the solar nebula.

Zadnik, M. G.↗
NASA NTRS1986

Low-Cobalt Powder-Metallurgy Superalloy

Highly-stressed jet-engine parts made with less cobalt. Udimet 700* (or equivalent) is common nickel-based superalloy used in hot sections of jet engines for many years. This alloy, while normally used in wrought condition, also gas-atomized into prealloyed powder-metallurgy (PM) product. Product can be consolidated by hot isostatically pressing (HIPPM condition) and formed into parts such as turbine disk. Such jet-engine disks "see" both high stresses and temperatures to 1,400 degrees F (760 degrees C).

Harf, F. H.↗
NASA NTRS1986

Analysis of effective radiant temperatures in a Pacific Northwest forest using Thermal Infrared Multispectral Scanner data

Analysis of Thermal Infrared Multispectral Scanner data collected over H. J. Andrews experimental forest in western Oregon indicated that aspect and slope gradient had a greater effect on the thermal emission of younger reforested clearcuts than of older stands. Older forest stands (older than 25 years) with greater amounts of green biomass and closed canopies, had lower effective radiant temperatures than younger, less dense stands. Aspect and slope had little effect on the effective radiant temperature of these older stands. Canopy temperature recorded at approximately 1:30 pm local time July 29, 1983 were nearly equal to maximum daily air temperature recorded at eight reference stands. The investigation provided some insights into the utility of the thermal sensor for detecting surface temperature differences related to forest composition and green biomass amounts in mountain terrain.

Sader, S. A.↗
NASA NTRS1987

Advanced powder metallurgy aluminum alloys via rapid solidification technology, phase 2

Marko's rapid solidification technology was applied to processing high strength aluminum alloys. Four classes of alloys, namely, Al-Li based (class 1), 2124 type (class 2), high temperature Al-Fe-Mo (class 3), and PM X7091 type (class 4) alloy, were produced as melt-spun ribbons. The ribbons were pulverized, cold compacted, hot-degassed, and consolidated through single or double stage extrusion. The mechanical properties of all four classes of alloys were measured at room and elevated temperatures and their microstructures were investigated optically and through electron microscopy. The microstructure of class 1 Al-Li-Mg alloy was predominantly unrecrystallized due to Zr addition. Yield strengths to the order of 50 Ksi were obtained, but tensile elongation in most cases remained below 2 percent. The class 2 alloys were modified composition of 2124 aluminum alloy, through addition of 0.6 weight percent Zr and 1 weight percent Ni. Nickel addition gave rise to a fine dispersion of intermetallic particles resisting coarsening during elevated temperature exposure. The class 2 alloy showed good combination of tensile strength and ductility and retained high strength after 1000 hour exposure at 177 C. The class 3 Al-Fe-Mo alloy showed high strength and good ductility both at room and high temperatures. The yield and tensile strength of class 4 alloy exceeded those of the commercial 7075 aluminum alloy.

Ray, Ranjan↗
NASA NTRS1986

Pulsed injection control of a titanium-doped sapphire laser

Injection control of a tunable Ti:sapphire laser using a narrow-bandwidth pulsed dye laser operating at a wavelength removed from the peak of the Ti:sapphire-laser gain curve is reported. The free-running Ti:sapphire laser had broadband laser emission from 750 to 790 nm. Injection at 727 nm resulted in essentially complete energy extraction at that wavelength in a 2.5-pm bandwidth matching the injection source.

Brockman, Philip↗
NASA NTRS1987

'Marginal' BY Draconis stars

Spectroscopic observations of 52 dK-dM stars, obtained at 640-665 nm (with spectral resolution 70-90 pm) using CCD detectors on the coude-feed telescope at KPNO since 1982, are reported. Data for four stars found to have diluted absorption or weak emission above continuum at H-alpha are presented in tables and spectra and discussed in detail. These objects (Gliese numbers 256, 425A, 900, and 907.1) are shown to be 'marginal' BY Dra stars, single objects of age 2.5-3 Gyr with activity and rotational velocity (3-5 km/s) between those of normal dM stars and those of true BY Dra stars. An explanation based on evolution from the BY Dra stage through marginal BY Dra to inactive dM is proposed.

Bopp, Bernard W.↗
NASA NTRS1986

A 20 GHz, high efficiency dual mode TWT for the ACTS program

The development of a 50 W/10 W dual mode K-band downlink TWT is examined, and its performance is evaluated. The designs of the electron gun, RF circuit, and collector for the TWT, which is enclosed in a capsule, are described. It is observed that the high power mode (HPM) power output is at 50 GHz and the low power mode (LPM) output is at 12 GHz; the saturated gain is 52.5 dB for HPM and 3 dB for LPM; the AM-PM is 4.2 dB; the HPM dc power output is 104 W; and the LPM dc output is 42 W; and the efficiency is 45 percent for the HPM and 28.6 percent for the LPM.

Muennemann, Frank↗
NASA NTRS1987

The role of fragmentation in interaction of meteoroids with the Earth's atmosphere

As a rule, when analyzing the mechanism of quasi continuous fragmentation (QCF) it is assumed that fragments separated from the parent meteoroid (PM) are of equal initial mass. In reality, this may not be so. A major difficulty is the lack of observational data on the function of the fragment initial mass distribution and so one must resort to theoretical modeling. A discrete distribution is considered which excluded to a certain extent some mathematical difficulties. The calculation results are given and discussed.

Babadjanov, P. B.↗
NASA NTRS1986

Development in tunable solid state lasers with high spectral purity, high efficiency and long lifetime for differential absorption lidar

The paper presents a review of tunable vibronic solid state lasers for DIAL measurements and provides new experimental results for tunable Ti:sapphire lasers, materials development, and spectral bandwidth narrowing through injection control. Pulsed injection control of a Ti:sapphire laser with a 2.5-pm narrow band pulsed dye laser and with another Ti:sapphire laser is demonstrated with nearly complete energy extraction, indicating homogeneous line broadening. The status of tunable solid state lasers in the 1.6-2.3 micron range for DIAL measurements of trace gases, and development trends for lasers with reduced cryogenic cooling needs, are included. The effects of laser gain on optical damage, energy extraction, and amplified spontaneous emission are indicated for several tunable lasers.

Hess, R. V.↗
NASA NTRS1988

Development of a 39.5 GHz Karp traveling wave tube for use in space

A millimeter-wave TWT was developed using a dispersive, high-impedance forward wave interaction structure based on a ladder, with non-space-harmonic interaction, for a tube with high gain per inch and high efficiency. The 'Tunneladder' interaction structure combines ladder properties modified to accommodate Pierce gun beam optics on a radially magnetized PM focusing structure. The development involved the fabrication of chemically milled, shaped ladders diffusion brazed to each ridge of a double ridged waveguide. Cold-test data are presented, representing the omega-Beta and impedance characteristics of the modified ladder circuit These results were used in small and large-signal computer programs to predict TWT gain and efficiency. A laboratory model tube was designed and fabricated, including all major subassemblies.

Jacquez, A.↗
NASA NTRS1988

A Very Large Area Network (VLAN) knowledge-base applied to space communication problems

This paper first describes a hierarchical model for very large area networks (VLAN). Space communication problems whose solution could profit by the model are discussed and then an enhanced version of this model incorporating the knowledge needed for the missile detection-destruction problem is presented. A satellite network or VLAN is a network which includes at least one satellite. Due to the complexity, a compromise between fully centralized and fully distributed network management has been adopted. Network nodes are assigned to a physically localized group, called a partition. Partitions consist of groups of cell nodes with one cell node acting as the organizer or master, called the Group Master (GM). Coordinating the group masters is a Partition Master (PM). Knowledge is also distributed hierarchically existing in at least two nodes. Each satellite node has a back-up earth node. Knowledge must be distributed in such a way so as to minimize information loss when a node fails. Thus the model is hierarchical both physically and informationally.

Zander, Carol S.↗
NASA NTRS1990

Recent results from advanced research on space solar cells at NASA

The NASA program in space photovoltaic research and development encompasses a wide range of emerging options for future space power systems, and includes both cell and array technology development. The long range goals are to develop technology capable of achieving 300 W/kg for planar arrays, and 300 W/sq m for concentrator arrays. InP and GaAs planar and concentrator cell technologies are under investigation for their potential high efficiency and good radiation resistance. The Advanced Photovoltaic Solar Array (APSA) program is a near term effort aimed at demonstrating 130 W/kg beginning of life specific power using thin (62 pm) silicon cells. It is intended to be technology transparent to future high efficiency cells and provides the baseline for development of the 300 W/kg array.

Flood, Dennis J.↗
NASA NTRS1989

A laser spectrometer and wavemeter for pulsed lasers

The design, construction, calibration, and evaluation of a pulsed laser wavemeter and spectral analyzer are described. This instrument, called the Laserscope for its oscilloscope-like display of laser spectral structure, was delivered to NASA Langley Research Center as a prototype of a laboratory instrument. The key component is a multibeam Fizeau wedge interferometer, providing high (0.2 pm) spectral resolution and a linear dispersion of spectral information, ideally suited to linear array photodiode detectors. Even operating alone, with the classic order-number ambiguity of interferometers unresolved, this optical element will provide a fast, real-time display of the spectral structure of a laser output. If precise wavelength information is also desired then additional stages must be provided to obtain a wavelength measurement within the order-number uncertainty, i.e., within the free spectral range of the Fizeau wedge interferometer. A Snyder (single-beam Fizeau) wedge is included to provide this initial wavelength measurement. Difficulties in achieving the required wide-spectrum calibration limit the usefulness of this function.

Mckay, J. A.↗