Search NASA⌕ Search

SEARCH · Search NASA

Results for “V”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Effects of thermal annealing on the deep-level defects and I-V characteristics of 200 keV proton irradiated AlGaAs-GaAs solar cells

Detailed characterization of deep-level defects and analysis of dark I-V data in 200 keV proton irradiated AlGaAs-GaAs solar cells have been carried out for several proton fluences (5 x 10 to the 11th, 10 to the 12th, and 10 to the 13th P/sq cm), using DLTS, C-V, and I-V measurement techniques. To study the effect of low temperature thermal annealing on the deep-level defect properties, these irradiated samples were annealed in vacuum at 300 C for one hour. Comparison was then made on the measured defect parameters (i.e., defect energy levels and densities) and the dark I-V characteristics for both the annealed and unannealed samples.

Li, S. S.↗
NASA NTRS1981

Method of making V-MOS field effect transistors utilizing a two-step anisotropic etching and ion implantation

A method of making V-MOS field effect transistors is disclosed wherein a masking layer is first formed over a surface of a crystalline substrate. An aperture is then formed in the masking layer to expose the surface of the substrate. An anisotropic etchant is applied to the exposed surface so that a groove having a decreasing width within increasing depth is formed. However, the etch is not allowed to go to completion with the result that a partially formed V-shaped groove is formed. Ions are accelerated through the aperture for implantation in the crystalline substrate in the lower portion of the partially formed V-shaped groove. Thereafter, an anisotropic etchant is reapplied to the partially formed V-shaped groove, and the etch is allowed to go to completion.

Jhabvala, M. D.↗
NASA NTRS1979

IUE ultraviolet spectra of V Sagittae

Ultraviolet spectra obtained by the IUE of the short-period, intrinsically variable, double-lined spectroscopic and eclipsing close binary V Sagittae are discussed. The 18 spectra measured between 1150 and 1950 A and 1850 and 3300 A over an interval of 179 days are shown to be dominated by emission features, with only Lyman alpha absorption apparent. Examination of the smooth continuum inferred for each spectrum results in a B-V color index of 0.20. The observed V magnitudes do not show a phase-locked or typical eclipsing light curve, due to intrinsic variability in the UV as well as the visible. The calibrated, reddening-corrected UV fluxes are used in an attempt to determine system temperature, but it is found that the continuum is most likely composite and variable, and thus a unique temperature assignment is impossible. The V Sge system is interpreted as possibly consisting of a primary early A, near-main-sequence star with an effective temperature of 10,000 K and a secondary thick, hot disk (temperature 17,000-300,000 K) embedding a white dwarf.

Koch, R. H.↗
NASA NTRS1981

Solar observations and atomic data for the 3s2 1s0-3s3p 3P1 transition in S v

High resolution solar observations of the S v intersystem line at 1199.18 A are available from Skylab. This line is potentially useful as a density diagnostic for high density plasmas expected in solar flares. S v lines are also prominent in solar spectra at wavelengths below 1000 A. Collision strengths and radiative decay rates are calculated for levels of the configurations 3 s2, 3s3p, 3p2, and 3s3d. Level populations for the five lowest energy levels have been calculated as a function of electron density. These calculations are carried out assuming the temperature at which S v is most abundant in solar plasmas. The calculated population of the 3s3p 3P1 level reaches a pseudo-Boltzmann equilibrium at a density which is about five times higher than is derived from solar spectra and previous density determinations. It is believed that the discrepancy is due to a significant contribution from resonances to the 3s2-3s3p 3P excitation rate coefficient. It is suggested that the contribution of the resonances to the S v excitation rate coefficient can be estimated from a comparison of the experimental results and the theoretical calculations.

Feldman, U.↗
NASA NTRS1982

STRAP V - Higher accuracy, lower drift attitude control system

The STRAP V system was developed to provide higher accuracy and lower limit cycle fine pointing (+ or - 7 arcseconds) in all three axes at targets which cannot be tracked by startrackers or solar trackers. The system provides an increase in pointing performance over that obtainable with the STRAP IV (1) Attitude Control System (ACS). The STRAP IV concept of third axis updates is utilized to reduce pointing errors, using the flight-proven STRAP III (2) system as a first stage. Flight aspect photographs and telemetry records show that the STRAP V objectives have been met. The STRAP IV major error contributors have been significantly reduced and the tracking flexibility has been increased with only minor error contributions. Attention is given to the basic STRAP III control modes, major STRAP IV system error sources, tuned restrained inertial gyros (TRIGs), the programmable sequence timer, the STRAP V control box, third axis update, system gyro alignments, and STRAP V operational capabilities.

Budney, T. J.↗
NASA NTRS1983

Determinations of S III, O IV, and Ne V abundances in planetary nebulae from infrared lines

Twelve planetary nebulae have been subjected to airborne observations of the S III (18.71 microns), Ne V (24.28 microns) and O IV (25.87 microns) IR forbidden lines, of which one or more lines were detected in seven of the nebulae. These results are insensitive to nebula temperatures, in contrast to optical or UV lines, although density estimates from the latter were required to obtain abundances. The Ne V electron temperature of 11,200 + 2000 or - 1100 K temperature obtained overlaps O III temperature measurements. Since the ionization potential of Ne IV is much greater than that of O II, the electron temperature of Ne V should be much greater than that of O III. This discrepancy may indicate inaccuracies in currently available atomic parameters for Ne V.

Shure, M. A.↗
NASA NTRS1985

Near-conjugate observations of inverted-V electron precipitation using DE 1 and DE 2

A major focus of auroral research has been related to the inverted-V electron precipitation event, distinguished by the 'inverted-V' variation of peak energy flux in an energy-time spectrogram. Thieman and Hoffman (1984), in an examination of plasma data from near-conjugate DE 1/2 passes in the southern hemisphere, have found that some inverted-V events remain reasonably stable over a time span of up to 18 min, while other events change over shorter time periods. The present investigation has the objective to study quantitatively the energization of inverted-V electron fluxes and to compare the results with predictions from adiabatic acceleration by an electrostatic field. The obtained results suggest that the turbulent processes might contirbute minimally to the energy flux of secondary electrons for some events, but significantly for others.

Lin, C. S.↗
NASA NTRS1985

V-378A: A modified bismaleimide for advanced composites

Addition polyimides cure with no evolution of gaseous by-products at relatively low temperatures and may be cured at low pressures to yield composites with excellent hot-wet strength retention. These properaties have made them excellent candidates as matrix resins for advanced composites. However, commercially available bismaleimides are solids and difficult to handle in preimpregnated form. V-378A is an addition polyimide composed of a mixture of bismaleimides and other reactive ingredients formulated to provide good prepreg properties and handling, facile cure and excellent composite mechanical properties. Several curing mechanisms are utilized to provide the characteristics exhibited by V-378A. Part of the mechanism is free radial and takes place at ambient temperature and above. Other mechanisms are principally Diels-Alder in nature. V-378A prepregs are tacky at ambient temperature, but do not have long tacky outlife similar to some epoxies. V-378A yields composites which exhibit hot-wet strength retention which is superior to that provided by epoxy resin systems.

Street, S. W.↗
NASA NTRS1984

Secular solution for delta-V during spin rate change maneuvers of rigid body spacecraft

Analytic expressions have been found for Euler's Equations of Motion and for the Eulerian Angles for both symmetric and near symmetric rigid bodies under the influence of arbitrary constant body-fixed torques. These solutions have been used to solve for the secular terms in the translational delta-V equations in inertial space. This secular delta-V solution is of interest in application to spinning spacecraft in that it describes the average direction of the delta-V of the spacecraft during a spin-up maneuver. Numerical integration of the governing differential equations has verified that the secular delta-V solution is valid for large time and is accurate in many physical situations including spin-up maneuvers of the Galileo spacecraft.

Klumpe, E. W.↗
NASA NTRS1985

Prediction of stable crack growth and instability using the V sub R-curve method

A methodology is presented for predicting stable crack growth and instability of cracked structural components from results of laboratory tests on metallic materials under plane-stress conditions. The methodology is based on the displacement V sub R at the tip of a stably tearing crack. Basically, the V sub R-curve method is a resistance curve approach, such as K sub R and J sub R, except that the 'crack drive' is written in terms of crack-tip displacement instead of K or J. The relationship between crack-tip-opening displacement, crack length, specimen type, and tensile properties is derived from the Dugdale model for the cracked structure of interest. This report describes the laboratory test procedure and calculations used to obtain the V sub R resistance curve from fracture tests of compact or of middle-crack tension (formally center-crack) specimens. The analysis procedure used to predict stable crack growth and instability of any through-the-thickness crack configuration made of the same material and thickness, and tested under the same environmental conditions, is presented. The various limitations of the present V sub R curve method are given. Four example calculations and predictions are shown.

Newman, J. C., Jr.↗
NASA NTRS1988

Application of the V(R) resistance curve method to fracture of various crack configurations

The fracture resistance curve method of Newman (1985), based on the crack-tip-opening displacement, V(R), for a 'stationary' crack, was applied to various crack configurations in 2024-T351 and 7075-T651 aluminum alloys tested at room temperature. Using a stationary crack solution, the crack-tip-displacement was calculated at the current crack length for the crack configurations which included compact, middle-crack, single-edge-crack, and three-hole-crack tension specimens. The results showed that the V(R) resistance curves are insensitive to crack length, specimen width, and specimen type up to maximum load. After the maximum load is reached, the V(R) remains nearly constant; this constant depends only on specimen type, specimen width, and crack length. The V(R) resistance curve method can be used with the strip-yield analyses to accurately predict stable crack growth and instability of cracked metallic materials.

Newman, J. C., Jr.↗
NASA NTRS1988

ETS-V propagation experiments in Japan

Propagation experiments on ship, aircraft, and land mobile earth stations were carried out using the Engineering Test Satellite-V (ETS-V), which was launched in August 1987. The propagation experiments are one of the missions of the Experimental Mobile Satellite System (EMSS). Initial experimental results of ETS-V/EMSS on propagation using ship, aircraft, and land mobiles with ETS-V are given.

Ohmori, Shingo↗
NASA NTRS1989

V, Cr, and Mn in the earth, moon, EPB, and SPB and the origin of the moon - Experimental studies

The abundances of V, Cr, and Mn inferred for the mantles of the earth and moon decrease in that order and are similar in both mantles (but distinct from those in the mantles of the Eucrite Parent Body and Shergottite Parent Body), suggesting a common origin for the mantles of the earth and the moon. This hypothesis was investigated on the basis of a comparison between the depletions of V, Cr, and Mn in the mantles of the earth and the moon, and the metal/silicate partition coefficients of these elements at 1260 C and 1 bar pressure among a S-bearing metallic liquid, a silicate melt, and a FeNi alloy. It was found that the earth and the moon depletions of V, Cr, and Mn are not correlated with metal/silicate partition coefficients; the V and Cr partitioned into S-rich metallic liquids under reducing conditions more strongly than Mn, consistent with the relative volatilities of these elements. This indicates that the depletion patterns of these elements in the mantles of the earth and moon cannot be attributed primarily to terrestrial core formation.

Drake, Michael J.↗
NASA NTRS1993

Double-V block fingers with cruciform recess

In a robot having a gripper including a pair of fingers and a drive motor for driving the fingers toward and away from one another while the fingers remain parallel to each other, the fingers consist of finger pads, which interface with a handle on an object to be grasped, and a shank, which attaches the fingers to the robot gripper. The double-V finger has two orthogonal V-grooves forming in the center of the finger pads and recessed cruciform. The double-V finger is used with a handle on the object to be grasped which is the negative of the finger pads. The handle face consists of V-shaped pads capped with a rectangular cruciform. As the gripper is brought into place near the handle, the finger pads are lined up facing the handle pads. When the finger pad and the handle pad are in proper alignment, the rectangular ridges on the handle fall inside the rectangular grooves on the finger, and the grip is complete.

Voellmer, George M.↗
NASA NTRS1995

Structure of V(H2)n(+) Clusters for n = 1-6

Geometries, vibrational frequencies, spin states, H2 binding energies, and Delta(S) values have been determined for V(H2)n(+), for n = 1-6, using the B3LYP hybrid functional. The binding energies and Delta(S) values are in good agreement with experiment, thus showing that the B3LYP functional offers a reliable approach for optimizing the geometry and determining the H2 binding energies for this system. The calculations show that the increase in the binding energy and entropy associated with the addition of the sixth H2 to V(+) is due to a change in spin state from quintet for the smaller clusters to triplet for V(H2)6(+). The results for V(H2)n(+) are compared with those for CO(H2)n(+).

Maitre, Philippe↗
NASA NTRS2002

Measured and Simulated Dark J-V Characteristics of a-Si:H Single Junction p-i-n Solar Cells Irradiated with 40 keV Electrons

The effect of 40 keV electron irradiation on a-Si:H p-i-n single-junction solar cells was investigated using measured and simulated dark J-V characteristics. EPRI-AMPS and PC-1D simulators were explored for use in the studies. The EPRI-AMPS simulator was employed and simulator parameters selected to produce agreement with measured J-V characteristics. Three current mechanisms were evident in the measured dark J-V characteristics after electron irradiation, namely, injection, shunting and a term of the form CV(sup m). Using a single discrete defect state level at the center of the band gap, good agreement was achieved between measured and simulated J-V characteristics in the forward-bias voltage region where the dark current density was dominated by injection. The current mechanism of the form CV(sup m) was removed by annealing for two hours at 140 C. Subsequent irradiation restored the CV(sup m) current mechanism and it was removed by a second anneal. Some evidence of the CV(sup m) term is present in device simulations with a higher level of discrete density of states located at the center of the bandgap.

Lord, Kenneth↗
NASA NTRS2007

Ares V: Designing the Heavy Lift Capability to Explore the Moon

NASA's Vision for Exploration requires a safe, efficient, reliable, and versatile launch vehicle capable ofplacing large payloads into Earth orbit for transfer to the Moon and destinations beyond. The Ares V Cargo Launch Vehicle (CaLV) will provide this heavy lift capability. The Ares V launch concept is shown. When it stands on the launch pad at Kennedy Space Center late in the next decade, the Ares V stack will be almost 360 feet fall. As currently envisioned, it will lift 136 metric tons (300,000 pounds) to a 30-by-160 nautical mile orbit at 28.5-degrees inclination, or 55 metric tons (120,000 pounds) to trans-lunar injection. This paper will cover the latest developments in the Ares V project in 2007 and discuss future activities.

Sumrall, John P.↗
NASA NTRS2007

Ares V Launch Capability Enables Future Space Telescopes

NASA's Ares V cargo launch vehicle offers the potential to completely change the paradigm of future space science mission architectures. A major finding of the NASA Advanced Telescope and Observatory Capability Roadmap Study was that current launch vehicle mass and volume constraints severely limit future space science missions. And thus, that significant technology development is required to package increasingly larger collecting apertures into existing launch shrouds. The Ares V greatly relaxes these constraints. For example, while a Delta IV has the ability to launch approximate a 4.5 meter diameter payload with a mass of 13,000 kg to L2, the Ares V is projected to have the ability to launch an 8 to 12 meter diameter payload with a mass of 60,000 kg to L2 and 130,000 kg to Low Earth Orbit. This paper summarizes the Ares V payload launch capability and introduces how it might enable new classes of future space telescopes such as 6 to 8 meter class monolithic primary mirror observatories, 15 meter class segmented telescopes, 6 to 8 meter class x-ray telescopes or high-energy particle calorimeters.

Stahl, H. Philip↗