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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

ELF wave production by an electron beam emitting rocket system and its suppression on auroral field lines - Evidence for Alfven and drift waves

Orthogonal probes on a free-flying plasma diagnostics payload are used to study ELF electric disturbances in the auroral ionosphere that are due to the injection of powerful electron beams. Frequency spectrograms are presented for various pitch angles, pulsing characteristics, and other properties of the injected beams; the large scale DC ionospheric convection electric field is measured, together with auroral particle precipitation, visual auroral forms, and ionospheric parameters. In view of the experimental results obtained, it is postulated that the observed ELF waves are in the Alfven and drift modes, and are generated by the positive vehicle potential during beam injection.

Winckler, J. R.↗
NASA NTRS1985

Rotary-balance experiments on a modern fighter aircraft configuration at high Reynolds numbers

NASA Ames Research Center's research program to investigate high-angle-of-attack aerodynamic phenomena associated with high-performance aircraft includes the development and use of rotary balance apparatuses for wind balance apparatuses for wind tunnel tests of airplane models in a coning motion. A large scale apparatus, developed for testing models at high Reynolds numbers in the Ames 12-Foot Pressure Wind Tunnel, was recently tested with an 0.05-scale F-15 fighter model. Measurements were made at low subsonic Mach numbers and chord Reynolds numbers of 1 to 5.5 million, with angles of attack from 0 to 90 deg and sideslip angles from -15 to +15 deg. Effects of Reynolds number, spin-rate parameter, model attitude, presence of a nose boom, and model/sting mounting angle were investigated.

Malcolm, G. N.↗
NASA NTRS1985

Recent developments in rotary-balance testing of fighter aircraft configurations at NASA Ames Research Center

Two rotary balance apparatuses were developed for testing airplane models in a coning motion. A large scale apparatus, developed for use in the 12-foot Pressure Wind Tunnel primarily to permit testing at high Reynolds numbers, was recently used to investigate the aerodynamics of 0.05-scale model of the F-15 fighter aircraft. Effects of Reynolds number, spin rate parameter, model attitude, presence of a nose boom, and model/sting mounting angle were investigated. A smaller apparatus, which investigates the aerodynamics of bodies of revolution in a coning motion, was used in the 6-by-6 foot Supersonic Wind Tunnel to investigate the aerodynamic behavior of a simple representation of a modern fighter, the Standard Dynamic Model (SDM). Effects of spin rate parameter and model attitude were investigated. A description of the two rigs and a discussion of some of the results obtained in the respective tests are presented.

Malcolm, G. N.↗
NASA NTRS1985

Objectives and design of the Echo 6 electron beam experiment - Large ionospheric perturbations and energetic particle patterns

The data from the March 30, 1983 launching of Echo 6 are presented. Echo 6 contained duplex accelerators and a system of four throw away detectors to detect and analyze conjugate electron echoes. The model used to calculate the proper trajectory of the rocket and the reason for not detecting echoes are discussed. The components of the plasma diagnostic package which was used to study the electron beam interactions with the ionospheric plasma, and the functions of the two controllable electron guns and the two sets of orthogonal electric probes are described. The signal-mode potentials between each probe and the plasma diagnostic payload are investigated. The signals produced by the gun pulses are analyzed and the interpretation of the electric field probe response is examined.

Winckler, J. R.↗
NASA NTRS1987

Coma-Compensated Telescope With Vertex Chopping

New design for chopped-infrared astronomical telescope reduces coma to increase image quality. Coma introduced by tilting cancelled by shaping of secondary mirror to introduce equal but opposite amount of coma independent of tilt angle. Because of this measure, telescope performance on axis remains limited mainly by diffraction.

Macfarlane, Malcolm J.↗
NASA NTRS1986

Water facilities in retrospect and prospect: An illuminating tool for vehicle design

Water facilities play a fundamental role in the design of air, ground, and marine vehicles by providing a qualitative, and sometimes quantitative, description of complex flow phenomena. Water tunnels, channels, and tow tanks used as flow-diagnostic tools have experienced a renaissance in recent years in response to the increased complexity of designs suitable for advanced technology vehicles. These vehicles are frequently characterized by large regions of steady and unsteady three-dimensional flow separation and ensuing vortical flows. The visualization and interpretation of the complicated fluid motions about isolated vehicle components and complete configurations in a time and cost effective manner in hydrodynamic test facilities is a key element in the development of flow control concepts, and, hence, improved vehicle designs. A historical perspective of the role of water facilities in the vehicle design process is presented. The application of water facilities to specific aerodynamic and hydrodynamic flow problems is discussed, and the strengths and limitations of these important experimental tools are emphasized.

Erickson, G. E.↗
NASA NTRS1986

A study of radar cross section measurement techniques

Past, present, and proposed future technologies for the measurement of radar cross section were studied. The purpose was to determine which method(s) could most advantageously be implemented in the large microwave anechoic chamber facility which is operated at the antenna test range site. The progression toward performing radar cross section measurements of space vehicles with which the Orbital Maneuvering Vehicle will be called upon to rendezvous and dock is a natural outgrowth of previous work conducted in recent years of developing a high accuracy range and velocity sensing radar system. The radar system was designed to support the rendezvous and docking of the Orbital Maneuvering Vehicle with various other space vehicles. The measurement of radar cross sections of space vehicles will be necessary in order to plan properly for Orbital Maneuvering Vehicle rendezvous and docking assignments. The methods which were studied include: standard far-field measurements; reflector-type compact range measurements; lens-type compact range measurement; near field/far field transformations; and computer predictive modeling. The feasibility of each approach is examined.

Mcdonald, Malcolm W.↗
NASA NTRS1987

Color postprocessing for 3-dimensional finite element mesh quality evaluation and evolving graphical workstation

Three general tasks on general-purpose, interactive color graphics postprocessing for three-dimensional computational mechanics were accomplished. First, the existing program (POSTPRO3D) is ported to a high-resolution device. In the course of this transfer, numerous enhancements are implemented in the program. The performance of the hardware was evaluated from the point of view of engineering postprocessing, and the characteristics of future hardware were discussed. Second, interactive graphical tools implemented to facilitate qualitative mesh evaluation from a single analysis. The literature was surveyed and a bibliography compiled. Qualitative mesh sensors were examined, and the use of two-dimensional plots of unaveraged responses on the surface of three-dimensional continua was emphasized in an interactive color raster graphics environment. Finally, a postprocessing environment was designed for state-of-the-art workstation technology. Modularity, personalization of the environment, integration of the engineering design processes, and the development and use of high-level graphics tools are some of the features of the intended environment.

Panthaki, Malcolm J.↗
NASA NTRS1986

Self indexing latch system

A self-latching jaw assembly is described which includes a pair of jaws for latching a fitting of an associated structure such as the keel fitting of a space telescope. The jaw assembly automatically locates the fitting received on a positioning pedestal and latches it in its original location on the pedestal without need of precision alignment. The first jaw is actuated and moved to the right whereupon a reciprocating plunger, extended from the nose of the jaw senses the hub of the spool. A jaw position responsive switch is then actuated to terminate the drive motor of the jaw. The astronaut will then actuate the drive motor of the jaw and the jaw will move to the left, whereupon the standoff will engage the face of the jaw in a latching position. In the latching position, the noses of the jaws will be under the flanges of the spool.

John C Gibson↗
NASA NTRS1987

High pressure cosmochemistry of major planetary interiors: Laboratory studies of the water-rich region of the system ammonia-water

Several studies relative to high pressure cosmochemistry of major planetary interiors are summarized. The behavior of gas-ice mixtures at very high pressures, studies of the phase diagram of (NH3) sub x (H2O) sub 1-x at pressures to 5GPa and temperatures from 240 to 370 K, single crystal growth of ammonia dihydrate at room temperature in order to determine their structures by x-ray diffraction, spectroscopy of chemical reactions during shock compression in order to evaluate how the reactions affect the interpretation of equation of state data obtained by shock methods, and temperature and x-ray diffraction measurements made on resistively heated wire in diamond anvil cells in order to obtain phase and structural data relevant to the interiors of terrestrial planets are among the studies discussed.

Nicol, Malcolm↗
NASA NTRS1986

Plasma structures in Comet Halley

Large-scale plasma phenomena based on results of spacecraft probing of comets Halley and Giacobini-Zinner and on International Halley Watch are discussed. The data show that: the basic mechanism for the comets' interaction with the solar wind (Alfven, 1957) is correct; that the turn-on and turn-off of plasma activity follows the description of Mendis and Flammer (1984); and that disconnection events are associated with sector boundary crossings and an essential element in the morphology of developed plasma tails (Niedner and Brandt, 1978).

Brandt, John C.↗
NASA NTRS1986

Plasma-tail activity at the time of the Vega encounters

Physical associations are sought between Halley's plasma tail activity seen in ground-based imagery and near-comet, solar wind/IMF measurements obtained by the Vega spacecraft. Disconnection Events (DE's) and the sector boundary/frontside magnetic reconnection model (Niedner and Brandt, 1978) of their origin are discussed. Strong support for the model comes from 2 DE's: a major event whose onset, on March 7 to 8, is strongly correlated with a reversal of the comet's magnetic barrier observed by Vega-1 and Vega-2 and with an IMF sector boundary observed by Vega-1; and a minor event on March 7 which may be associated with the two-polarity (possibly reconnecting) magnetic barrier seen by Vega-1 on March 6, when the solar-wind density was low.

Niedner, Malcolm B., Jr.↗
NASA NTRS1987

Comet-solar wind interaction as viewed from the International Cometary Explorer Mission (ICE) and from the earth

An overview of large-scale plasma phenomena is presented based on results of the ICE spacecraft probing of comet Giacobini-Zinner and on worldwide submissions to the Large-Scale Phenomena Discipline Specialist Team of the International Halley Watch. Results indicate that the magnetic field capture and draping model, originated by Alfven, is correct. Examples of tail 'turn on' and evolution are presented with emphasis on the observed Disconnection Events (DEs). The sector boundary model of DEs is consistent with the data and a dramatic example of synergism between in situ data from the VEGAs and ground-based imagery for the DE originating March 8.6, 1986 is presented.

Brandt, John C.↗
NASA NTRS1986

Dynamics of cometary plasma tails

Cometary plasma tail data obtained before and after the current appearance of Halley's Comet are reviewed. The relation between the formation of plasma tails and comet/solar-wind interactions is discussed. The ion rays and helical waves of the plasma tail are described. The disconnection events and interaction of bright comets with the IMF, associated with the current appearance of Comet Halley, are examined. Consideration is given to the cometary magnetic barriers observed by the Vega-1 and Vega-2 spacecraft.

Niedner, Malcolm B., Jr.↗
NASA NTRS1986

Chlorine chemistry in the Antarctic stratosphere - Impact of OClO and Cl2O2 and implications for observations

Theories have been proposed to relate the reduction of O3 during Antarctic spring to catalytic cycles involving chlorine and bromine species. A necessary condition for any chlorine-catalyzed scheme is that a large fraction of the chlorine must be in the form of ClO in the lower stratosphere. It has been suggested that these high levels of ClO could be maintained by fast heterogeneous reactions, whose rates are not known at present. Model calculations based on the above mechanisms predict considerable amounts of OClO and Cl2O2, particularly during the night. Results of calculations of the diurnal variations of ClO, OClO, and Cl2O2 during Antarctic spring are presented for different cases. Results from the calculations suggest that coincident measurements of the total column abundance and diurnal variation of ClO and OClO may help constrain key aspects of the proposed chemical mechanisms. Removal of O3 by the catalytic cycle involving Cl2O2 could be as important as that involving BrO for present levels of chlorine, provided that Cl2O2 photolyzes rapidly to yield Cl and ClO2. It is shown that there is no synergy between these two cycles, since they both compete for the available ClO.

Rodriguez, Jose M.↗
NASA NTRS1986

A study of the damping capacity of graphite epoxy composites in a vacuum

The damping properties of a graphite epoxy composite material (used in the construction of the Hubble Space Telescope) are measured under a variety of conditions in a vacuum chamber to simulate conditions in space. An improved method is proposed which utilizes several points of the response curve near a resonance to estimate the damping ratio and the undamped resonance frequency. The damping of a graphite epoxy tube is monitored for four weeks to study moisture desorption and temperature effects. A significant variation is observed in the damping ratio with temperature.

Rao, Mohan D.↗
NASA NTRS1986

Prediction of light aircraft interior sound pressure level from the measured sound power flowing in to the cabin

The validity of the room equation of Crocker and Price (1982) for predicting the cabin interior sound pressure level was experimentally tested using a specially constructed setup for simultaneous measurements of transmitted sound intensity and interior sound pressure levels. Using measured values of the reverberation time and transmitted intensities, the equation was used to predict the space-averaged interior sound pressure level for three different fuselage conditions. The general agreement between the room equation and experimental test data is considered good enough for this equation to be used for preliminary design studies.

Atwal, Mahabir S.↗
NASA NTRS1987

The IHW island network

Early astronomical photography of comets at perihelion encouraged the establishment of an International Halley Watch (IHW) Team for regularly photographing the Comet. The February 1986 period was particularly troublesome due to the limitations of cometary visibility in the Southern Hemisphere. Schmidt cameras were placed on Tahiti, Easter Island, Faraday Station on the Antarctic Peninsula, Reunion Island and in South Africa. Blue- and red-filter B/W images were obtained every night and color prints were occasionally shot. Each night's images were examined before the next night's photography. Several interesting anecdotes are recounted from shipping, manning and operation of the telescopes.

Niedner, Malcolm B., Jr.↗