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At least 991 records · Page 55

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NASA NTRS1984

Flight service evaluation of Kevlar-49 epoxy composite panels in wide-bodied commercial transport aircraft

Kevlar-49 fairing panels, installed as flight service components on three L-1011s, were inspected after 10 years of service. There are six Kevlar-49 panels on each aircraft: a left-hand and right-hand set of a wing-body sandwich fairing; a solid laminate under-wing fillet panel; and a 422 K (300 F) service aft engine fairing. The three L-1011s include one each in service with Eastern, Air Canada, and TWA. The fairings have accumulated a total of 79,568 hours, with one ship set having nearly 28,000 hours service. The inspections were conducted at the airlines' major maintenance bases with the participation of Lockheed Engineering. The Kevlar-49 components were found to be performing satisfactorily in service with no major problems, or any condition requiring corrective action. The only defects noted were minor impact damage, a few minor disbonds and a minor degree of fastener hole fraying and elongation. These are for the most part comparable to damage noted on fiberglass fairings. The service history obtained in this program indicates that Kevlar-49 epoxy composite materials have satisfactory service characteristics for use in aircraft secondary structure.

Stone, R. H.↗

NASA NTRS1983

Surface studies with (clean) supported metal particles and clusters

Small particles are ideal for combined studies with surface analytical and electron microscopy/diffraction methods. In this way crystallography, microstructure, morphology, physical stability, and electronic structure can be correlated directly with chemical reactivity. Various integrated experimental approaches for conducting model studies with UHV-evaporated particles have been successfully developed; they entail the use of TPD, AES, XPS, and work function measurements on one hand and standard TEM/TED, in-situ TEM/TED, and in-situ STED/TEM techniques on the other hand. The essential features of four particular experimental approaches are discussed and a selection of representative results is presented to illustrate the potential usefulness of such studies in the field of catalysis.

Poppa, H. R.↗

NASA NTRS1984

Voyager observations of Jovian millisecond radio bursts

Voyager Planetary Radio Astronomy data collected over 30-day intervals centered on the two close encounters with Jupiter were utilized to study the characteristics of millisecond-duration radio bursts (s-bursts) at frequencies between 5 and 15 MHz. In this frequency range, s-bursts are found to occur almost independently of Central Meridian Longitude and to depend entirely on the phase of Io with respect to the observer's planetocentric line of sight. Individual bursts typically cover a total frequency range of about 1.5 to 3 MHz, and they are usually strongly circularly polarized. Most bursts in a particular s-burst storm will exhibit the same polarization sense (either right-hand or left-hand), and there is some evidence for a systematic pattern in which one polarizations sense is preferred over the other as a function of Io phase and Central Meridian Longitude. These data are all suggestive of a radio source that is located along the instantaneous Io flux tube and that extends over a linear dimension of 5000 km along the field lines in both the Northern and Southern Hemispheres. Previously announced in STAR as N84-17109

Alexander, J. K.↗

NASA NTRS1984

Analysis of Diabatic Heating During FGGE

The objective is to examine the maintenance of momentum and thermal fields in the Southern Hemisphere and the diabatic heating and generation of available potential energy of the entire global atmosphere. The data generated by the Goddard Laboratory for Atmospheric Sciences First GARP Global Experiment (FGGE) III-b analysis for SOP1 and SOP2 are used for this effort. It is observed that the atmospheric circulation of the Southern Hemisphere exhibits a double jet structure (subtropical jet and polar jet) in winter and a single jet in summer during the FGGE year. The geographic distribution of standard deviation in the height field at 500 mb indicates that the major eddy activities occur in the downstream side of the polar jet and poleward side of the subtropic jet in winter. However, the major eddy activites go hand-in-hand with the jet stream in summer. The momentum transport is essentially carried out by the transient eddies in both seasons. The distribution of the temperature field is more axisymmetric in the Southern Hemisphere than in the Northern Hemisphere. The sensible heat is mainly transported poleward by transient eddies along the strong baroclinic zone where the jet streams are located. In other seasons, it is shown from the geographic distribution of the divergence of transient eddy sensible heat flux that the Antarctic continent acts as a heat sink to consume the sensible heat converged toward the polar area from the middle and low latitudes.

Chen, T. C.↗

NASA NTRS1984

The Effect of Part-simulation of Weightlessness on Human Control of Bilateral Teleoperation: Neuromotor Considerations

The effect of weightlessness on the human operator's performance in force reflecting position control of remote manipulators was investigated. A gravity compensation system was developed to simulate the effect of weightlessness on the operator's arm. A universal force reflecting hand controller (FRHC) and task simulation software were employed. Two experiments were performed because of anticipated disturbances in neuromotor control specification on the human operator in an orbital control environment to investigate: (1) the effect of controller stiffness on the attainment of a learned terminal position in the three dimensional controller space, and (2) the effect of controller stiffness and damping on force tracking of the contour of a simulated three dimensional cube using the part simulation of weightless conditions. The results support the extension of neuromotor control models, which postulate a stiffness balance encoding of terminal position, to three dimensional motion of a multilink system, confirm the existence of a disturbance in human manual control performance under gravity compensated conditions, and suggest techniques for compensation of weightlessness induced performance decrement through appropriate specification of hand controller response characteristics. These techniques are based on the human control model.

Corker, K.↗

NASA NTRS1984

The Representation of Action Plans in Long Term Memory

A sequence of experiments conducted on a two hand chord typewriter, to compare the efficiency of different coding principles employed to associate letters with their chord productions is described. This keyboard represents an effort to identify effective alternatives to the existing typewriter. It consists of two seperate 5-key panels (one for each hand), and letters are entered by typing chords composed of one to five fingers. Each panel is capable of producing the full alphabet. One group of experiments was designed to separate between perceptual and motor factors in the acivation of single letter chords. The results underline the importance of perceptual factors in the activation of motor plans. The complexity of the patterns employed to represent letters was shown to account for 50 percent of variance in the typing speeds of single letters. The theoretical implications of these results are discussed in relation to a vision based theory of action plans.

Fussfeld, G. N.↗

NASA NTRS1984

What Pilots like (and Don't Like) About the New Cockpit Technology

Pilot's perceptions of the new cockpit technology in the B-767 are discussed. Although the data reported were taken from the introductory experience of the B-767, it is felt that similar, if not identical, results would be obtained with any other new cockpit technology aircraft, i.e., the A310. The following conclusions were drawn from the information collected thus far: A large majority of the pilots enjoy flying the B-767 more than the older airplanes. The pilots accept the new cockpit technology, and they choose to use it because they find it useful. The pilots are aware of the possible loss of flying skill with the presence of automation, and they hand fly (usually with flight director) to prevent this loss. There is no evidence of loss of skills from the data collected. The primary points of confusion or surprise were autothrottle/autopilot interactions; the autopilot during the wrong way or not capturing the course; and achieving desired results with the Flight Management System/Control Display Unit (FMS/CDU). The pilots felt training for the FMS/CDU could be improved, and they especially wanted more hands on experience.

Curry, R. E.↗

NASA NTRS1984

Translational control of a graphically simulated robot arm by kinematic rate equations that overcome elbow joint singularity

An operator commands a robot hand to move in a certain direction relative to its own axis system by specifying a velocity in that direction. This velocity command is then resolved into individual joint rotational velocities in the robot arm to effect the motion. However, the usual resolved-rate equations become singular when the robot arm is straightened. To overcome this elbow joint singularity, equations were developed which allow continued translational control of the robot hand even though the robot arm is (or is nearly) fully extended. A feature of the equations near full arm extension is that an operator simply extends and retracts the robot arm to reverse the direction of the elbow bend (difficult maneuver for the usual resolved-rate equations). Results show successful movement of a graphically simulated robot arm.

Barker, L. K.↗

NASA NTRS1984

The Boot Lake MF imaging radar

The Middle-Atmosphere Imaging Radar is located at the Boot Lake field site, 10 miles east of Brighton, Colorado. It operates at 2.66 MHz with a 50-kW peak pulse power in 30 microsecond pulses. Ten independent coaxial-collinear antennas are used; five are parallel and run east-west, the other five are parallel and run north-south. Each antenna consists of eight half-wave dipoles. All ten antennas or a crossed pair may be used for transmission; all ten are sampled by pairs in rapid sequence for reception. The system is now operating on a campaign basis as a Fourier interferometer by measuring the complex voltages on the ten antennas and Fourier transforming them independently. Multiple scatterers within a single range gate, now sorted by velocity, can be located individually by their phase angles. The transmitted signal cycles through four modes (N-S linear, right-hand circular, E-W linear, and left-hand circular).

Adams, G. W.↗

NASA NTRS1984

The plasma wave environment of an auroral arc. II - ULF waves on an auroral arc boundary

On March 9, 1978, a sounding rocket launched from Poker Flat, Alaska, at 2200 LT, made a four-component measurement of a 0.5 Hz hydromagnetic wave as the payload crossed the poleward boundary of a quiet homogeneous auroral arc. An energy flux of about 10 to the -6th W/sq m was observed propagating upward with a left-handed polarization within the arc, and a flux 6 times greater was observed propagating downward with a right-handed polarization on the arc boundary. The waves were identified as shear mode Alfven waves. Various models for the source of the free energy are discussed with the conclusion that the most likely production mechanism was either the electromagnetic or electrostatic Kelvin-Helmholtz instability.

Gelpi, C. G.↗

NASA NTRS1984

Stability and accuracy analysis of some fully-discrete algorithms for the one-dimensional second-order wave equation

The present investigation is concerned with some basic results for a predictor-multicorrector algorithm applied to the one-dimensional wave equation, giving particular attention to so-called 2-pass explicit schemes in which both lumped and coupled mass matrices are employed. In an assessment of the accuracy and stability properties of the algorithms, use is made of the one-dimensional, second-order wave equation. The maximum stable time step of the lumped right-hand-side mass, 2-pass explicit algorithm is twice that of the 1-pass explicit algorithm. Improved accuracy is obtained by employing higher-order, or consistent, right-hand-side, mass.

Hughes, T. J. R.↗

NASA NTRS1985

Electromagnetic ion beam instabilities - Hot beams at interplanetary shocks

This paper considers Vlasov instabilities driven by a very hot ion beam streaming parallel to a magnetic field. The linear theory of electromagnetic instabilities driven by such a beam in a homogeneous, collisionless, nonrelativistic plasma is used. Numerical solutions of the full linear dispersion equation for bi-Maxwellian distribution functions are presented. If the thermal speed of the beam is greater than its drift speed, the two dominant modes are the right-hand and left-hand resonant ion beam instabilities. The parametric dependencies of the threshold drift speeds and growth rates for both modes are presented. In particular, the thresholds are shown to be sensitive functions of the beam temperature anisotropies. Arguments are presented that these two modes are driven by the suprathermal ion component at interplanetary shocks, and that the growth of these modes is sufficient to account for the amplitudes of MHD-like waves observed at such shocks.

Gary, S. P.↗

NASA NTRS1986

A Rapid Attachment of Strain Gages

Hand-held toroidal gun concentrates heat in localized area. New method for bonding film gages eliminates time-consuming oven curing Hand-held "gun," operates on induction heating to concentrate heat in localized area. Ferritic plate added for low-reluctance or no-reluctance surfaces.

Schott, T. D.↗

NASA NTRS1986

Reliability Research for Photovoltaic Modules

Report describes research approach used to improve reliability of photovoltaic modules. Aimed at raising useful module lifetime to 20 to 30 years. Development of cost-effective solutions to module-lifetime problem requires compromises between degradation rates, failure rates, and lifetimes, on one hand, and costs of initial manufacture, maintenance, and lost energy, on other hand. Life-cycle costing integrates disparate economic terms, allowing cost effectiveness to be quantified, allowing comparison of different design alternatives.

Ross, Ronald J., Jr.↗

NASA NTRS1986

Two-Arm-Manipulator Controller

Shoulder harness allows wearer to control simultaneously and independently two remote manipulator arms and end effectors. Each manipulator arm would have 7 degrees of freedom. Two arm mechanisms of controller moved by operator's arms and hands. Remote manipulator, located elsewhere, responds to operator's arm and hand movements. Adjustable shoulder straps, waist belt, and leg straps hold harness securely on wearer. Mechanisms and harness allow operator to reach almost normally at control station.

Coryell, S.↗

NASA NTRS1985

Remote sensing of coastal wetlands biomass using Thematic Mapper wavebands

Spectral data, simulating thematic mapper bands 3, 4 and 5 are gathered in salt and brackish marshes using a hand-held radiometer. Simple regression models are developed equating spectral radiance indices with total live biomass for S. alterniflora in a salt marsh and for a variety of plant species in a brackish marsh. Models are then tested using an independent set of data and compared to harvest estimates of biomass. In the salt marsh, biomass estimates from spectral data are similar to harvest biomass estimates during most of the growing season. Estimates of annual net aerial primary productivity calculated from spectral data are within 21% of production estimated from harvest data. During August, biomass estimates from spectral data in the brackish marsh are similar to biomass estimated by harvesting techniques. At other times during the growing season, spectral data estimates of biomass are not always comparable to harvest biomass estimates. Reasonable estimates of wetlands biomass are possible during the peak of the growing season (August) using spectral data similar to thematic mapper bands 3, 4 and 5 gathered with hand-held radiometers.

Hardisky, M. A.↗

NASA NTRS1985

Lithospheric and crustal thinning

In rift zones, both the crust and the lithosphere get thinner. The amplitude and the mechanism of these two thinning situations are different. The lithospheric thinning is a thermal phenomenon produced by an asthenospherical uprising under the rift zone. In some regions its amplitude can exceed 200%. This is observed under the Baikal rift where the crust is directly underlaid by the mantellic asthenosphere. The presence of hot material under rift zones induces a large negative gravity anomaly. A low seismic velocity zone linked to this thermal anomaly is also observed. During the rifting, the magmatic chambers get progressively closer from the ground surface. Simultaneously, the Moho reflector is found at shallow depth under rift zones. This crustal thinning does not exceed 50%. Tectonic stresses and vertical movements result from the two competing effects of the lithospheric and crustal thinning. On the one hand, the deep thermal anomaly induces a large doming and is associated with extensive deviatoric stresses. On the other hand, the crustal thinning involves the formation of a central valley. This subsidence is increased by the sediment loading. The purpose here is to quantify these two phenomena in order to explain the morphological and thermal evolution of rift zones.

Moretti, I.↗

NASA NTRS1986

Support for global science: Remote sensing's challenge

Remote sensing uses a wide variety of techniques and methods. Resulting data are analyzed by man and machine, using both analog and digital technology. The newest and most important initiatives in the U. S. civilian space program currently revolve around the space station complex, which includes the core station as well as co-orbiting and polar satellite platforms. This proposed suite of platforms and support systems offers a unique potential for facilitating long term, multidisciplinary scientific investigations on a truly global scale. Unlike previous generations of satellites, designed for relatively limited constituencies, the space station offers the potential to provide an integrated source of information which recognizes the scientific interest in investigating the dynamic coupling between the oceans, land surface, and atmosphere. Earth scientist already face problems that are truly global in extent. Problems such as the global carbon balance, regional deforestation, and desertification require new approaches, which combine multidisciplinary, multinational research teams, employing advanced technologies to produce a type, quantity, and quality of data not previously available. The challenge before the international scientific community is to continue to develop both the infrastructure and expertise to, on the one hand, develop the science and technology of remote sensing, while on the other hand, develop an integrated understanding of global life support systems, and work toward a quantiative science of the biosphere.

Estes, J. E.↗