Electric flight systems
Materials used to illustrate a presentation on the development of electric flight systems are presented. Systems concepts are outlined.
Clay, C. W.↗
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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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Energetic ion mass spectrometer
A new type of spectrometer for space application has been developed to measure separately mass/charge and the three-dimensional velocity distribution of incident ions. The instrument has relatively high resolution and allows rapid measurement of the four-dimensional set of mass/charge, speed, elevation angle, and azimuth angle. The instrument includes a sector magnet, an electrostatic deflector, microchannel plate detectors with position sensitive readout, and a set of grids with variable applied voltage.
Neugebauer, M.↗
An analysis of prop-fan/airframe aerodynamic integration
An approach to aerodynamic integration of turboprops and airframes, with emphasis placed upon wing mounted installations is addressed. Potential flow analytical techniques were employed to study aerodynamic integration of the prop fan propulsion concept with advanced, subsonic, commercial transport airframes. Three basic configurations were defined and analyzed: wing mounted prop fan at a cruise Mach number of 0.8, wing mounted prop fan in a low speed configuration, and aft mounted prop fan at a cruise Mach number of 0.8.
Boctor, M. L.↗
Ion mass spectrometer
An ion mass spectrometer is described which detects and indicates the characteristics of ions received over a wide angle, and which indicates the mass to charge ratio, the energy, and the direction of each detected ion. The spectrometer includes a magnetic analyzer having a sector magnet that passes ions received over a wide angle, and an electrostatic analyzer positioned to receive ions passing through the magnetic analyzer. The electrostatic analyzer includes a two dimensional ion sensor at one wall of the analyzer chamber, that senses not only the lengthwise position of the detected ion to indicate its mass to charge ratio, but also detects the ion position along the width of the chamber to indicate the direction in which the ion was traveling.
Neugebauer, M.↗
A reexamination of rotational and tangential discontinuities in the solar wind
An analysis is made of interplanetary tangential and rotational solar wind discontinuities (TD and RD) and comparisons are made between the features of RDs and TDs. An ISEE 3 field and positive ion data set from 1978 includes high time resolution magnetometer data and is used for the comparisons, as are data from a positive ion analyzer. The field magnitude of RDs remains constant as the field rotates, while that of a TD passes through a local minimum. First and second adiabatic invariants for protons and He abundances are usually also conserved for RDs but not for TDs. The velocity change for an RD across a discontinuity is smaller than that predicted by MHD theory. Finally, plasma conditions at a discontinuity more closely resemble RDs than TDs.
Neugebauer, M.↗
Observation of gamma-rays from LMC X-4 above 10(16) eV
Data from the University of Adelaide air shower array at Buckland Park taken over a three year period have been analyzed to search for evidence of ultra high energy gamma-ray emission from neutron star binary X-ray sources having known orbital periods. The detection of UHE gamma-rays from LMC X-4 above 10 to the 16th power eV, is reported; the first extragalactic object to be positively detected at these energies.
Protheroe, R. J.↗
EAS Cerenkov measurements of the composition of the cosmic ray flux around 10 to the 16th power eV
Information can be obtained about the nature of a primary cosmic ray by looking at the way in which an extensive air shower (EAS) develops in the atmosphere. Heavy nuclei give rise to showers that develop high in the atmosphere and the depth of maximum development is subjected to much smaller fluctuations than is the case for showers originating from protons. This development is followed by optical methods based on the observations of Cerenkov light or fluorescence light. The Cerenkov observations have two complementary techniques: measurement of the time profile of the Cerenkov pulse with resolution of a few nanoseconds and measurement of the lateral distribution of the Cerenkov light. In each case the measured quantities must be related to some characteristic development parameters.
Dawson, B. R.↗
Search for bursts in air shower data
There have been reports in recent years of the possible observation of bursts in air shower data. If such events are truly of an astrophysical nature then, they represent an important new class of phemonenon since no other bursts have been observed above the MeV level. The spectra of conventional gamma ray bursts are unknown at higher energies but their observed spectra at MeV energies appear generally to exhibit a steepening in the higher MeV range and are thus unlikely to extrapolate to measurable fluxes at air shower energies. An attempt has been made to look for deviations from randomness in the arrival times of air showers above approx. 10 to the 14th power eV with a number of systems and results so far are presented here. This work will be continued for a substantial period of ime with a system capable of recording bursts with multiple events down to a spacing of 4 microns. Earlier data have also been searched for the possible association of air shower events with a glitch of the Vela pulsar.
Bruce, T. E. G.↗
Anisotropy and the knee of the energy spectrum
The measured cosmic ray energy spectrum exhibits clear structure (the knee) at approx 3 x 10 to the 15th power eV (sea level shower size approx 3 x 10 to the 5th power particles). Additionally, at energies in this general region, there occur apparent changes in shower development such that the observed characteristics of showers at this energy appear different to those characteristics observed at somewhat higher energies. At energies just below this region, the cosmic ray anisotropy amplitude apparently begins a progressive increase with energy. The latter effect does not clearly fit with the first two since there appears to be no significant change exactly at the knee. However, the phase of the first harmonic of the anisotropy appears to show a substantial change just where the energy spectrum shows structure and in the middle of the shower development changes. The first harmonic phase appears to change from approx. 18 hours R.A. to approx. 5 hours R.A. as the energy of observation moves through the knee. In this paper the latter change is examined in some detail by taking into account information contained in the second harmonic of the anisotropy.
Clay, R. W.↗
The Buckland Park air shower array
The new Buckland Park Air Shower Array has been producing analyzed shower data since July 1984. The array is described and some preliminary performance figures are presented.
Clay, R. W.↗
The longitudinal thickness of air-shower fronts
Linsely (1983) has proposed a technique for the detection and analysis of air showers at large distances from the shower axis based on a measurement of the shower front thickness and the assumption that this thickness is closely related to the core distance. Some of the problems involved with realizing such a technique were investigated, and some related observations are reported. The practical problems of how consistent the measurements of the shower front would be, how one would use the measurement, and how the rate of triggered events would depend on the minimum pulse width required are studied.
Clay, R. W.↗
A transient digitiser for fast air shower events
Air shower structure are often measured on time scales of a few nanoseconds. Longitudinal disk structure near the core is of the order of meters in dimension, air Cerenkov pulses have full widths at half maximum of the order of tens of nanoseconds, and fast timing over typical arrays is usually measured to nanosecond accuracy. oscilloscopes can be used but have very limited dynamic range and are expensive if measurements down to a few nanoseconds are to be made. For the fast Cerenkov work, an instrument with better dynamic range than an oscilloscope and with a time resolution sufficient to allow measurements limited only by system risetime of a few nanoseconds is needed. A 16/32 channel, 8 bit, fast transient digitizer was designed and built which runs at sample intervals down to approx. 1 nanosecond per channel.
Wild, N. R.↗
Extensive air showers (HE-4)
Ultra high energy (UHE) gamma ray astronomy is an exciting area which has added a new sense of purpose to ground based array work. There is much to be done before UHE gamma ray showers can be understood properly and it is important to remain conservative with claims while the properties of such showers are still not clear. The muon content is only one of the properties that needs to be clarified. It remains to be seen how well progress occurs on the second order problem of detailed interaction parameters once the gross features are clarified. The shower disk thickness has become an area of intense study with interest in Linsley's technique for measuremnts of giant showers and in the study of structure near the core for improving fast timing and studying delayed subshowers. Perhaps the most significant area of promise for the future is individual shower develpments with Cerenkov and, particularly, air fluorescence techniques. The importance and potential of having relatively complete information on a complete set of individual showers can hardly be overestimated. A complete understanding of the observation process is needed to determine whether or not the recorded data set is complete at a given energy, apparent core distance, and zenith angle.
Clay, R. W.↗
Rust Inhibitor And Fungicide For Cooling Systems
Mixture of benzotriazole, benzoic acid, and fungicide prevents growth of rust and fungus. Water-based cooling mixture made from readily available materials prevents formation of metallic oxides and growth of fungi in metallic pipes. Coolant remains clear and does not develop thick sludge tending to collect in low points in cooling systems with many commercial rust inhibitors. Coolant compatible with iron, copper, aluminum, and stainless steel. Cannot be used with cadmium or cadmium-plated pipes.
Adams, James F.↗
Analysis of the plugging of the systems autonomy demonstration project brassboard filters
A fine gray powder was clogging the brassboard filters. The powder appeared to be residue from a galvanic corrosive attack by ammonia of the aluminum and stainless steel components in the system. The corrosion was caused by water and chlorine that had entered into the system and combined with the ammonia. This combination made an electrolyte and a corrosive agent of the ammonia that attacked the metals in the system. The corroded material traveled through the system with the ammonia and clogged the filters. Key conclusions are: the debris collecting in the filters is a by-product of galvanic corrosion; the debris is principally corroded aluminum and stainless from the system; and galvanic corrosion occurred from water and chlorine that entered the system during normal and/or extreme operating and servicing conditions. Key recommendations are: use only one metal in the ammonia system-titanium, aluminum, or stainless steel; make the system as air-tight as possible (replace fittings with welded joints); and replace electron paramagnetic resonance (EPR) O-rings with neoprene O-rings, and do not use freon to clean system components.
Clay, John C.↗
M.I.N.G., Mars Investment for a New Generation: Robotic construction of a permanently manned Mars base
A basic procedure for robotically constructing a manned Mars base is outlined. The research procedure was divided into three areas: environment, robotics, and habitat. The base as designed will consist of these components: two power plants, communication facilities, a habitat complex, and a hangar, a garage, recreation and manufacturing facilities. The power plants will be self-contained nuclear fission reactors placed approx. 1 km from the base for safety considerations. The base communication system will use a combination of orbiting satellites and surface relay stations. This system is necessary for robotic contact with Phobos and any future communication requirements. The habitat complex will consist of six self-contained modules: core, biosphere, science, living quarters, galley/storage, and a sick bay which will be brought from Phobos. The complex will be set into an excavated hole and covered with approximately 0.5 m of sandbags to provide radiation protection for the astronauts. The recreation, hangar, garage, and manufacturing facilities will each be transformed from the four one-way landers. The complete complex will be built by autonomous, artificially intelligent robots. Robots incorporated into the design are as follows: Large Modular Construction Robots with detachable arms capable of large scale construction activities; Small Maneuverable Robotic Servicers capable of performing delicate tasks normally requiring a suited astronaut; and a trailer vehicle with modular type attachments to complete specific tasks; and finally, Mobile Autonomous Rechargeable Transporters capable of transferring air and water from the manufacturing facility to the habitat complex.
Amos, Jeff↗
The inter-outburst behavior of cataclysmic variables
Existing International Ultraviolet Explorer (IUE) and American Association of Variable Star Observers (AAVSO) archive data was used to accomplish a large scale study of what happens to the ultraviolet flux of accretion disk systems during the quiescent intervals between outbursts and how it relates to the preceding outburst characteristics of amplitude and width. The data sample involved multiple IUE observations for 16 dwarf novae and 8 novae along with existing optical coverage. Results indicate that most systems show correlated ultraviolet (UV) flux behavior with interoutburst phase, with 60 percent of the dwarf novae and 50 percent of the novae having decreasing flux trends while 33 percent of the dwarf novae and 38 percent of the novae show rising UV flux during the quiescent interval. All of the dwarf novae with decreasing UV fluxes at 1475A have orbital periods longer than 4.4 hours, while all (except BV Cen) with flat or rising fluxes at 1475A have orbital periods less than two hours. There are not widespread correlations of the UV fluxes with the amplitude of the preceding outburst and no correlations with the width of the outburst. From a small sample (7) that have relatively large quiescent V magnitude changes between the IUE observations, most show a strong correlation between the UV and optical continuum. Interpretation of the results is complicated by not being able to determine how much the white dwarf contributes to the ultraviolet flux. However, it is now evident that noticeable changes are occurring in the hot zones in accreting systems long after the outburst, and not only for systems that are dominated by the white dwarf. Whether these differences are due to different outburst mechanisms or to changes on white dwarfs which provide varying contributions to the UV flux remains to be determined.
Szkody, Paula↗
A critical evaluation of two-equation models for near wall turbulence
A variety of two-equation turbulence models,including several versions of the K-epsilon model as well as the K-omega model, are analyzed critically for near wall turbulent flows from a theoretical and computational standpoint. It is shown that the K-epsilon model has two major problems associated with it: the lack of natural boundary conditions for the dissipation rate and the appearance of higher-order correlations in the balance of terms for the dissipation rate at the wall. In so far as the former problem is concerned, either physically inconsistent boundary conditions have been used or the boundary conditions for the dissipation rate have been tied to higher-order derivatives of the turbulent kinetic energy which leads to numerical stiffness. The K-omega model can alleviate these problems since the asymptotic behavior of omega is known in more detail and since its near wall balance involves only exact viscous terms. However, the modeled form of the omega equation that is used in the literature is incomplete-an exact viscous term is missing which causes the model to behave in an asymptotically inconsistent manner. By including this viscous term and by introducing new wall damping functions with improved asymptotic behavior, a new K-tau model (where tau is identical with 1/omega is turbulent time scale) is developed. It is demonstrated that this new model is computationally robust and yields improved predictions for turbulent boundary layers.
Speziale, Charles G.↗