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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 NTRS1984

The appearance of magnetic flux on the surfaces of the early main-sequence F stars

Available chromospheric, transition region, and coronal observations of the early main-sequence F stars are examined in order to find that while these objects exhibit enhanced levels of magnetic field-related radiative emissions, significant inhomogeneities in surface activity are not present. This phenomenon is discussed within the context of the calculations published by Schmitt and Rosner (1983) for the production of flux ropes of various spatial scales at a given rotation rate at the bottom of a stellar convection zone. It is found that the spatial scales and area contrast of emergent magnetic flux in these stars that, as a class, are characterized by rapid rotation and thin convection zones are substantially reduced relative to that of the sun.

Giampapa, M. S.↗
NASA NTRS1985

Bottomside sinusoidal irregularities in the equatorial F region. II - Cross-correlation and spectral analysis

Equatorial bottomside sinusoidal (BSS) irregularities have been studied by applying techniques of cross-correlation and spectral analysis to the Atmosphere Explorer data set. The phase of the cross-correlations of the plasma number density is discussed and the two drift velocity components observed using the retarding potential analyzer and ion drift meter on the satellite are discussed. Morphology is addressed, presenting the geographical distributions of the occurrence of BSS events for the equinoxes and solstices. Physical processes including the ion Larmor flux, interhemispheric plasma flows, and variations in the lower F region Pedersen conductivity are invoked to explain the findings.

Cragin, B. L.↗
NASA NTRS1985

The lithium isotope ratio in five F or G dwarfs

Observations of the 6707-A LiI doublet obtained at high resolution and photometric precision are reported for two F dwarfs and three G dwarfs known to have narrow lines and strong 6707-A absorption. Adjacent lines of Ca 1 and Fe 1 are used to predetermine accurately the position and the broadening of theoretical LiI profiles fitted to the observed ones, leaving the abundances of Li-6 and Li-7 as the only adjustable parameters of the calculated profiles. Upper limits R = (Li-6)/(Li-7) less than 0.1 are obtained for four of the stars, while R is less than about 0.1 for Xi UMa A. The total Li/H abundances range from 3 x 10 to the -10th to 10 x 10 to the -10th, with uncertainties probably not exceeding a factor of 2.

Hobbs, L. M.↗
NASA NTRS1985

A theoretical study of the global F region for June solstice, solar maximum, and low magnetic activity

A time-dependent, three-dimensional, multi-ion model of the ionospheric F region at 120-800 km altitude is presented. Account is taken of field-aligned diffusion, cross-field electrodynamic drifts in equatorial and high latitude regions, interhemispheric flow, thermospheric winds, polar wind escape, energy-dependent chemical reactions and neutral composition changes. Attention is also given to the effects of ion production by solar EUV radiation and auroral precipitation, thermal conduction, diffusion-thermal heat flow, local heating and cooling processes, offsets between the geomagnetic and geographic poles, and bending of field lines near the magnetic equator. The model incorporates all phenomena described by previous models and can be applied to tracing magnetic storm and substorm disturbances from high to low latitudes on a global scale. Sample results are provided for ionospheric features during a June solstice, the solar maximum and in a period of low geomagnetic activity. The model will eventually be used to study coupled ionosphere-thermosphere activity.

Sojka, J. J.↗
NASA NTRS1985

Observations of E and F region Mg(+) from Spacelab 1

Images of airglow at 2800 A were taken on the Spacelab 1 Shuttle mission and have been interpreted to be solar resonant emission of magnesium ions. On two orbital passes, observations were made near the magnetic equator while observing in the 2800-A channel. The observations were made near the sunset terminator (approximately 1800 LT), in winter (1983, day 335). Three separate emission clouds were observed, all of which extended well into the F region. The location of the clouds in horizontal space is shown. The processed images have been pseudocolored to highlight the intensity distribution in the clouds. Observations included clouds with apparent magnetic-field aligned striations. Bright emissions were observed at the magnetic equator, at 12-deg north magnetic latitude, and at 12-deg south magnentic latitude. Cloud-center brightnesses varied between 680 rayleighs and 1700 rayleighs.

Mende, S. B.↗
NASA NTRS1985

Fault detection and accommodation testing on an F100 engine in an F-15 airplane

The fault detection and accommodation (FDA) methods that can be used for digital engine control systems are presently subjected to a flight test program in the case of the F-15 fighter's F100 engine electronic controls, inducing selected faults and then evaluating the resulting digital engine control responses. In general, flight test results were found to compare well with both ground tests and predictions. It is noted that the inducement of dual-pressure failures was not feasible, since FDA logic was not designed to accommodate them.

Myers, L. P.↗
NASA NTRS1985

The changes in small metal cluster size with adsorption Be13Xn, X = H, O, S, Cl and F

The Be-Be and Be-adsorbate distances are optimized for small Be13Xn clusters,s assuming only two independent degrees of freedom. Results for chemisorption into the three-fold hollows are quite similar to those found for small metal clusters on supports. It is predicted that Cl and F will have the same effect on the metal-metal bond lengths, and so will O and S.

Bauschlicher, C. W., Jr.↗
NASA NTRS1985

Development of control laws for a flight test maneuver autopilot for an F-15 aircraft

An autopilot can be used to provide precise control to meet the demanding requirements of flight research maneuvers with high-performance aircraft. This paper presents the development of control laws within the context of flight test maneuver requirements. The control laws are developed using eigensystem assignment and command generator tracking. The eigenvalues and eigenvectors are chosen to provide the necessary handling qualities, while the command generator tracking enables the tracking of a specified state during the maneuver. The effectiveness of the control laws is illustrated by their application to an F-15 aircraft to ensure acceptable aircraft performance during a maneuver.

Alag, G. S.↗
NASA NTRS1985

Development of a flight test maneuver autopilot for an F-15 aircraft

An autopilot can be used to provide precise control to meet the demanding requirements of flight research maneuvers with high-performance aircraft. This paper presents the development of control laws for a flight test maneuver autopilot for an F-15 aircraft. A linear quadratic regulator approach is used to develop the control laws within the context of flight test maneuver requirements by treating the maneuver as a finite time tracking problem with regulation of state rates. Results are presented to show the effectiveness of the controller in insuring acceptable aircraft performance during a maneuver.

Alag, G. S.↗
NASA NTRS1986

Loads and motions of an F-106B flying through thunderstorms

Data are presented on loads and motions of a NASA F-106B airplane flying inside thunderstorms. No significant differences in piloting techniques were observed among the three pilots involved. It is indicated that airliners in normal operations occasionally encounter turbulence almost as severe as those encountered in these thunderstorm flights.

Winebarger, R. M.↗
NASA NTRS1984

Digital Electronic Engine Control (DEEC) Flight Evaluation in an F-15 Airplane

Flight evaluation in an F-15 aircraft by digital electronic engine control (DEEC) was investigated. Topics discussed include: system description, F100 engine tests, effects of inlet distortion on static pressure probe, flight tests, digital electronic engine control fault detection and accommodation flight evaluation, flight evaluation of a hydromechanical backup control, augmentor transient capability of an F100 engine, investigation of nozzle instability, real time in flight thrust calculation, and control technology for future aircraft propulsion systems. It is shown that the DEEC system is a powerful and flexible controller for the F100 engine.

Source record↗
NASA NTRS1984

Effects of inlet distortion on a static pressure probe mounted on the engine hub in an F-15 airplane

Problems encountered in obtaining good engine face pressure data were studied. A single static measurement located upstream of the engine hub in the stream flow was found to provide a pressure signal suitable for engine control. Two identical probes for measuring fan inlet static (PS2) pressure were designed and mounted on the hub of the left F100-PW-100 turbofan engine installed in the F-15 test aircraft for flight evaluation. The probe is used as a static pressure sensor for a digital engine control system.

Hughes, D. L.↗
NASA NTRS1984

Real-time in-flight thrust calculation on a digital electronic engine control-equipped F100 engine in an F-15 airplane

Computer algorithms which calculate in-flight engine and aircraft performance real-time are discussed. The first step was completed with the implementation of a real-time thrust calculation program on a digital electronic engine control (DEEC) equiped F100 engine in an F-15 aircraft. The in-flight thrust modifications that allow calculations to be performed in real-time, to compare results to predictions, are presented.

Ray, R. J.↗
NASA NTRS1986

In-flight and wind tunnel leading-edge vortex study on the F-106B airplane

The vapor screen technique was successfully applied to an F-106B fighter aircraft during subsonic and transonic maneuvers. This system has allowed the viewing of multiple vortex systems on the wing upper surface at angles of attack less than 19 deg. In addition, similarities as well as differences were determined to exist between the vortex systems for a full scale semispan model and the flight vehicle at 20 deg incidence. Furthermore, variations in Reynolds number and Mach number were identified as to how they affect vortex system details at flight conditions.

Lamar, J. E.↗
NASA NTRS1986

Flight control system development and flight test experience with the F-111 mission adaptive wing aircraft

The wing on the NASA F-111 transonic aircraft technology airplane was modified to provide flexible leading and trailing edge flaps. This wing is known as the mission adaptive wing (MAW) because aerodynamic efficiency can be maintained at all speeds. Unlike a conventional wing, the MAW has no spoilers, external flap hinges, or fairings to break the smooth contour. The leading edge flaps and three-segment trailing edge flaps are controlled by a redundant fly-by-wire control system that features a dual digital primary system architecture providing roll and symmetric commands to the MAW control surfaces. A segregated analog backup system is provided in the event of a primary system failure. This paper discusses the design, development, testing, qualification, and flight test experience of the MAW primary and backup flight control systems.

Larson, R. R.↗
NASA NTRS1986

Coverage dependent effects on metal surfaces - O, S, F, and Cl on Ni

The c(2 x 2) and p(2 x 2) vibrational frequencies for a rigid Ni lattice are computed for O, S, F, and Cl on Ni(100). It is found that only O/Ni(100) shows a large difference in rigid lattice vibrational frequency. A large shift in rigid lattice vibrational frequency is also found for O/Ni(111) between 0.25 and 0.5 monolayer coverages. Also associated with the change in coverage, is a change in the height above the surface R(perpendicular). This varies from a 0.11 A reduction for O/Ni(100), to an expansion of 0.06 A for F/Ni(100).

Bauschlicher, C. W., Jr.↗
NASA NTRS1986

Scintillations associated with bottomside sinusoidal irregularities in the equatorial F region

Multisatellite scintillation observations and spaced receiver drift measurements are presented for a category of equatorial F region plasma irregularities characterized by nearly sinusoidal waveforms in the ion number density. The observations were made at Huancayo, Peru, and the measurements at Ancon, Peru, associated with irregularities observed by the Atmospheric-Explorer-E satellite on a few nights in December 1979. Utilizing ray paths to various geostationary satellites, it was found that the irregularities grow and decay almost simultaneously in long-lived patches extending at least 1000 km in the east-west direction.

Basu, S.↗
NASA NTRS1986

Mean neutral circulation in the winter polar F region

A description of the mean global-scale circulation in the Northern Hemisphere F region has been synthesized by collating and averaging data from a global network of ground-based Fabry-Perot interferometers and from satellite sensors. An analysis of the results obtained shows that the combination of measurements made from multiple, strategically located ground-based observatories with satellite data provides a powerful technique for specifying the mean dynamic state of the earth's thermosphere. It is also found that a three-dimensional time-dependent numerical model with appropriate inputs for mean ionospheric convection can adequately predict the general characteristics observed in the mean thermospheric circulation.

Killeen, T. L.↗