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At least 523 records · Page 29

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NASA NTRS1976

Flutter suppression by active control and its benefits

A general discussion of the airplane applications of active flutter suppression systems is presented with focus on supersonic cruise aircraft configurations. Topics addressed include a brief historical review; benefits, risks, and concerns; methods of application; and applicable configurations. Results are presented where the direct operating costs and performance benefits of an arrow wing supersonic cruise vehicle equipped with an active flutter suppression system are compared with corresponding costs and performance of the same baseline airplane where the flutter deficiency was corrected by passive methods (increases in structural stiffness). The design, synthesis, and conceptual mechanization of the active flutter suppression system are discussed. The results show that a substantial weight savings can be accomplished by using the active system. For the same payload and range, airplane direct operating costs are reduced by using the active system. The results also indicate that the weight savings translates into increased range or payload.

Doggett, R. V., Jr.↗

NASA NTRS1979

Stellar model chromospheres. IX - Chromospheric activity in dwarf stars

High-resolution Ca II K line profiles are used to model the upper photospheres and lower chromospheres of eight main-sequence stars ranging in spectral type from F0 to M0 and exhibiting different degrees of chromospheric activity. The model chromospheres are studied as a function of spectral type and activity for stars of similar spectral type in order to obtain evidence of enhanced nonradiative heating in the upper-photospheric models and in the ratio of minimum temperature at the base of the chromosphere to effective temperature, a correlation between activity and temperature in the lower chromospheres, and a correlation of the width at the base of the K-line emission core and at the K2 features with activity. Chromospheric radiative losses are estimated for the modelled stars and other previously analyzed main-sequence stars. The results obtained strengthen the argument that dMe flare stars exhibit fundamentally solar-type activity but on an increased scale.

Kelch, W. L.↗

NASA NTRS1979

X-ray emission associated with filament activity

The temporal and spatial relationships of activated filaments, soft X-ray production, and H-alpha flares are investigated. The events chosen for study are from a sample of 114 hours of the very best, high-resolution H-alpha records of active regions gleaned from about 150 days of observations of active regions by Big Bear Solar Observatory, all with simultaneous mapping X-ray heliometer coverage. In the final data set, 20 flares are chosen for detailed study (10 significant flares and 10 smaller flarelike events). The data are examined for preflare filament activation and preflare X-ray enhancements with a view to discover a link between the two phenomena. To the limits set by the data, no convincing evidence for consistent preflare effects in H-alpha or X-rays is found. Aside from the 'disparition brusque', it seems clear that filament activity is not directly responsible for any dramatic effects in X-rays, and even there, the enhancement comes after the filament has disappeared.

Acton, L. W.↗

NASA NTRS1979

A review of short-term flare forecasting activities at Toyokawa

Short-term forecasting of solar activity conducted at Toyokawa is briefly reviewed. The forecasts are based on microwave observations of the slowly varying component of solar radiation associated with active regions. It was found that for proton flares which take place in intense active regions, it is possible to predict their occurrence with certain accuracy, but for a certain class of proton flares which occur in a small active region or which are associated with an active region, which evolves very rapidly, or for whose which occur behind the limb, it is almost impossible to forecast their occurrence.

Enome, S.↗

NASA NTRS1980

Effects of motor patterns on water-soluble and membrane proteins and cholinesterase activity in subcellular fractions of rat brain tissue

Albino rats were kept for a year under conditions of daily motor load or constant hypokinesia. An increase in motor activity results in a rise in the acetylcholinesterase activity determined in the synaptosomal and purified mitochondrial fractions while hypokinesia induces a pronounced decrease in this enzyme activity. The butyrylcholinesterase activity somewhat decreases in the synaptosomal fraction after hypokinesia but does not change under the motor load pattern. Motor load causes an increase in the amount of synaptosomal water-soluble proteins possessing an intermediate electrophoretic mobility and seem to correspond to the brain-specific protein 14-3-2. In the synaptosomal fraction the amount of membrane proteins with a low electrophoretic mobility and with the cholinesterase activity rises. Hypokinesia, on the contrary, decreases the amount of these membrane proteins.

Pevzner, L. Z.↗

NASA NTRS1980

Solar activity during the past 10,000 years from radionuclides in lunar samples

The radionuclides Ar-37, Ar-39, H-3, and C-14 in lunar samples are related to solar activity during time periods corresponding to their mean lives. The Ar-37 activities at shallow depths vary with each Apollo mission according to the intensities of the large solar flares preceding the mission. At large depths, the Ar-37 activities are independent of solar flares and decrease with an attenuation length that is in accord with the energy spectrum of the galactic cosmic rays. The Ar-39 depth-profile differs somewhat from galactic cosmic-ray expectation; the difference may be caused by solar modulation during Maunder Minima periods. The H-3 and C-14 activities at shallow depths are considerably higher than expected from galactic cosmic rays. The high H-3 is explained by solar-flare interactions during the past 60 years. The high C-14 activities at shallow depths are caused in part by solar-flare interactions during the past 10,000 years and in part by solar-wind implantations. Solar wind-implanted C-14 is indicated by the grain-size and temperature-release dependence of C-14 in surface soil.

Fireman, E. L.↗

NASA NTRS1981

Special activity utilization of GDSCC antennas during 1980

In addition to direct spacecraft project support, the GDSCC antennas also support special activities. These activities can be categorized as advanced system program, crustal dynamics program, and radio astronomy program activities. The goals of these types of activities that received tracking support at Goldstone are discussed. All Goldstone stations (DSSs 11, 12, 13, and 14) provided a total of 2814.5 tracking hours to special activities during the period January through December 1980.

Jackson, E. B.↗

NASA NTRS1979

Accelerated development and flight evaluation of active controls concepts for subsonic transport aircraft. Volume 1: Load alleviation/extended span development and flight tests

Active wing load alleviation to extend the wing span by 5.8 percent, giving a 3 percent reduction in cruise drag is covered. The active wing load alleviation used symmetric motions of the outboard ailerons for maneuver load control (MLC) and elastic mode suppression (EMS), and stabilizer motions for gust load alleviation (GLA). Slow maneuvers verified the MLC, and open and closed-loop flight frequency response tests verified the aircraft dynamic response to symmetric aileron and stabilizer drives as well as the active system performance. Flight tests in turbulence verified the effectiveness of the active controls in reducing gust-induced wing loads. It is concluded that active wing load alleviation/extended span is proven in the L-1011 and is ready for application to airline service; it is a very practical way to obtain the increased efficiency of a higher aspect ratio wing with minimum structural impact.

Johnston, J. F.↗

NASA NTRS1983

An H-alpha survey of southern hemisphere active chromosphere stars

Because of the variety of extraordinary phenomena exhibited by active chromosphere objects, discovery of new, bright surface-active stars is of considerable importance. Ca II emission is a well-known signature of chromospheric activity, serving even as one of the points of definition of the class of RS CVn binary stars. In connection with the present investigation, spectroscopic observations of 27 Ca II emission stars have been conducted. The observations make it possible to identify unambiguously the most chromospherically active stars in the sample. By observing the H-alpha line, rather than H and K, it is possible to distinguish nine of these stars which are likely to be observational targets as interesting as the extremely surface active objects V711 Tau or FK Com. Of the 27 stars surveyed, two (HD 86005, HD 204128) showed H-alpha as an emission feature above continuum, with estimated equivalent width 1-2 A.

Bopp, B. W.↗

NASA NTRS1983

Studies of Neutron and Proton Nuclear Activation in Low-Earth Orbit 2

The study of neutron and proton nuclear activation in low-Earth orbit reported in NASA CR-162051 has been continued with increasing emphasis given to primary and secondary neutron activation. The previously reported activation due to protons has been modified to include: (1) flux attenuation caused by all inelastic reactions; (2) the modification of the proton flux distribution caused by sample covering material; and (3) the activation of the sample as a function of the distance into the sample from the surface of incidence. A method has been developed for including the effects on the activation of the finite width and length of the samples. The reactant product spectra produced by proton-induced reactions has been studied. Cross sections needed for neutron induced reactions leading to long-lived (half-life 1 day) radioisotopes have been identified and, in some cases, compiled.

Laird, C. E.↗

NASA NTRS1983

Experimental and analytical investigation of active loads control for aircraft landing gear

A series hydraulic, active loads control main landing gear from a light, twin-engine civil aircraft was investigated. Tests included landing impact and traversal of simulated runway roughness. It is shown that the active gear is feasible and very effective in reducing the force transmitted to the airframe. Preliminary validation of a multidegree of freedom active gear flexible airframe takeoff and landing analysis computer program, which may be used as a design tool for active gear systems, is accomplished by comparing experimental and computed data for the passive and active gears.

Morris, D. L.↗

NASA NTRS1984

An aeroelastician's perspective of wind tunnel and flight experiences with active control of structural response and stability

Active controls technology is assessed based on a review of most of the wind-tunnel and flight tests and actual applications of active control concepts since the late sixties. The distinction is made between so-called ""rigid-body'' active control functions and those that involve significant modification of structural elastic response or stability. Both areas are reviewed although the focus is on the latter area. The basic goals and major results of the various studies or applications are summarized, and the anticipated use of active controls on current and near-future research and demonstration aircraft is discussed. Some of the ""holes'' remaining in the feasbility/benefits demonstration of active controls technology are examined.

Hanson, P. W.↗

NASA NTRS1984

Temporal Variations of Solar UV Spectral Irradiance Caused by Solar Rotation and Active Region Evolution

Variations in the solar 100 to 400 nm UV spectral irradiance caused by solar rotation and active region evolution, are discussed as a function of UV wavelength, CMD dependence, and in relation to the temporal variations in the total solar irradiance, 10.7 cm radio flux, sunspot number and Ca K plage data. Active region radiation at cm wavelengths includes a component proportional to the magnetic field. Active region evolution involves a more rapid growth, peak and decay of sunspots and their strong magnetic fields than the Ca K plages and their related UV enhancements. Major plages often last a rotation or more longer than the active region's sunspots. Large active regions, including those associated with major dips in the total solar irradiance, tend to produce the strongest peaks in 10.7 cm and sunspot numbers on their first rotation, while the Ca K plages and UV enhancements peak on the next rotation and decay more slowly on subsequent rotations. Differences in CMD dependencies cause temporal differences including the stronger presence of 13 day variations in the UV flux.

Donnelly, R. F.↗

NASA NTRS1984

Non-doe-sponsored Domestic Dish Activities

The parabolic dish development activities being undertaken within the private sector of the United States were addressed. The primary emphasis of these non-DOE-sponsored activities is the development of commercial products that can penetrate the market in the near term. The exchange of information between these activities and the complementary DOE-sponsored work directed toward developing advancements in technology is considered to be of major importance. The experiences and problems encountered in the private sector serve as inputs that will help guide in the planning of the DOE program. In turn, a principal objective of the DOE program is the transfer findings of its technological development activities to the private sector. Activities in the private are characterized by their diversity in terms of both product design and marketing approach. The differences in the design concepts and the sizes of the dish concentrators under development are particularly noteworthy.

Fujita, T.↗

NASA NTRS1982

Acid phosphatase and protease activities in immobilized rat skeletal muscles

The effect of hind-limb immobilization on selected Iysosomal enzyme activities was studied in rat hing-limb muscles composed primarily of type 1. 2A, or 2B fibers. Following immobilization, acid protease and acid phosphatase both exhibited signifcant increases in their activity per unit weight in all three fiber types. Acid phosphatase activity increased at day 14 of immobilization in the three muscles and returned to control levels by day 21. Acid protease activity also changed biphasically, displaying a higher and earlier rise than acid phosphatase. The pattern of change in acid protease, but not acid phosphatase, closely parallels observed muscle wasting. The present data therefore demonstrate enhanced proteolytic capacity of all three fiber types early during muscular atrophy. In addition, the data suggest a dependence of basal hydrolytic and proteolytic activities and their adaptive response to immobilization on muscle fiber composition.

Witzmann, F. A.↗

NASA NTRS1985

Active control landing gear for ground load alleviation

Results of analytical and experimental investigations of a series-hydraulic active control landing gear show that such a gear is feasible when using existing hardware and is very effective in reducing loads, relative to those generated by a conventional (passive year) gear, transmitted to the airframe during ground operations. Analytical results obtained from an active gear, flexible aircraft, take-off and landing analysis are in good agreement with experimental data and indicate that the analysis is a valid tool for study and initial design of series-hydraulic active control landing gears. An analytical study of a series-hydraulic active control main landing gear on an operational supersonic airplane shows that the active gear has the potential for improving the dynamic response of the aircraft and significantly reducing structural fatigue damage during ground operations.

Mcgehee, J. R.↗

NASA NTRS1984

Ultraviolet observations of the Be star Mu Centauri during its recent active phase

IUE and Copernicus ultraviolet observations and ground-based image-tube and direct spectrograms of the pole-on Be star Mu Cen have been combined to investigate the nature of this star's activity during its Balmer emission-line episode of 1980-81. Within the uncertainties of the observations, the UV data show no evidence for a wind, a classical-type shell injection, or a region of superionization, either before, during, or after the active phase. This is contrary to current views on how the circumstellar envelopes in Be stars are produced. The only difference between the UV spectra observed during activity and quiescence was that the lines from the more highly ionized species (e.g., Si III, Si IV, Al III) were slightly stronger and broader when Balmer emission was present. Evidence is presented that the activity most likely resides in or near the photosphere, and that during such active periods the photospheric temperature is higher. The recently discovered nonradial pulsations in Mu Cen (Baade, 1984) may supply the energy. The lack of sharp or broad shell lines in the UV suggests that the Balmer emission envelope is at least somewhat flattened.

Peters, G. J.↗

NASA NTRS1984

Homologous flares and the evolution of NOAA Active Region 2372

A detailed record of the evolution of NOAA Active Region 2372 has been compiled by the FBS Homology Study Group. It was one of the most prolific flare-producing regions observed by SMM. The flares occurred in distinct stages which corresponded to particular evolutionary phases in the development of the active region magnetic field. By comparison with a similar but less productive active region, it is found that the activity seems to be related to the magnetic complexity of the region and the amount of shear in the field. Further, the soft X-ray emission in the quiescent active region is related to its flare rate. Within the broader definition of homology adopted, there was a degree of homology between the events within each stage of evolution of AR2372.

Strong, K. T.↗