Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Trigger”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

A rocket borne instrument to measure electric fields inside electrified clouds

The development of a rocket borne instrument to measure electric fields in thunderstorms is described. Corona currents from a sharp needle atop a small rocket are used to sense the electric field. A high ohm resistor in series with the corona needle linearizes the relationship between corona current and electric field. The corona current feeds a relaxation oscillator, whose pulses trigger a transmitter which operates in the 395 to 410 MHz meteorological band. The instrument senses fields between 5 kV/m and 100 kV/m.

Ruhnke, L. H.↗
NASA NTRS1971

Balloon measurements of the energy spectrum of cosmic electrons between 1 GeV and 25 GeV

During three balloon flights made in 1966 and 1967, cosmic electrons were investigated with the aid of a hodoscope detector which provided extensive and detailed information on each cosmic ray event triggering the apparatus. Similar information obtained during calibration exposures to protons and pions as well as to electrons was used to provide identification of cosmic electrons and to determine their energies. Differential primary electron intensities measured in the range from 1 GeV to 25 GeV were substantially larger than some earlier measurements. Taken in conjunction with existing measurements at energies above 100 GeV, this indicates that the energy spectrum of cosmic electrons is steeper than that of cosmic-ray nuclei and, consequently, suggests that Compton/synchrotron energy loss plays a significant role in shaping the electron spectrum.

Earl, J. A.↗
NASA NTRS1970

Fundamental ignition study for material fire safety improvement, part 1

The investigation of preignition, ignition, and combustion characteristics of Delrin (acetate terminated polyformaldehyde) and Teflon (polytetrafluoroethylene) resins in air and oxygen are presented. The determination of ignition limits and their dependence on temperature and the oxidizing media, as well as the analyses of the volatiles produced, were studied. Tests were conducted in argon, an inert medium in which only purely pyrolytic reactions can take place, using the stagnation burner arrangement designed and constructed for this purpose. A theoretical treatment of the ignition and combination phenomena was devised. In the case of Delrin the ignition and ignition delays are apparently independent of the gas (air, oxygen) temperatures. The results indicate that hydrogen is the ignition triggering agent. Teflon ignition limits were established in oxygen only.

Paciorek, K. L.↗
NASA NTRS1972

Galaxy formation from annihilation-generated supersonic turbulence in the baryon-symmetric big-bang cosmology and the gamma ray background spectrum

Following the big-bang baryon symmetric cosmology of Omnes, the redshift was calculated to be on the order of 500-600. It is show that, at these redshifts, annihilation pressure at the boundaries between regions of matter and antimatter drives large scale supersonic turbulence which can trigger galaxy formation. This picture is consistent with the gamma-ray background observations discussed previously. Gravitational binding of galaxies then occurs at a redshift of about 70, at which time vortical turbulent velocities of about 3 x 10 to the 7th power cm/s lead to angular momenta for galaxies comparable with measured values.

Stecker, F. W.↗
NASA NTRS1971

Sub-nanosecond ranging possibilities of optical radar at various signal levels and transmitted pulse widths

The behavior of the photomultiplier is considered, as well as the method of derivation of the photomultiplier output pulse and its relation to the reflected light pulse width and amplitude, and the calibration of range precision and accuracy. Pulsed laser radars with light pulse widths of 30, 3, and 0.1 nanosec a considered, with the 0.1 nanosec system capable of highest precision in several modes of operation, including a high repetition rate, single photoelectron reception mode. An alternate calibration scheme using a fast, triggerable light pulser is described in detail.

Poultney, S. K.↗
NASA NTRS1972

Frequency response of a vaporization process to distorted acoustic disturbances

The open-loop response properties expressed as the mass vaporized in phase and out of phase with the pressure oscillations were numerically evaluated for a vaporizing n-heptane droplet. The evaluation includes the frequency dependence introduced by periodic oscillation in droplet mass and temperature. A given response was achieved over a much broader range of frequency with harmonically distorted disturbances than with sinusoidal disturbances. The results infer that distortion increases the probability of incurring spontaneous and triggered instability in any rocket engine combustor by broadening the frequency range over which the vaporization process can support an instability.

Heidmann, M. F.↗
NASA NTRS1971

The reduction of a ""safety catastrophic'' potential hazard: A case history

A worst case analysis is reported on the safety of time watch movements for triggering explosive packages on the lunar surface in an experiment to investigate physical lunar structural characteristics through induced seismic energy waves. Considered are the combined effects of low pressure, low temperature, lunar gravity, gear train error, and position. Control measures constitute a seal control cavity and design requirements to prevent overbanking in the mainspring torque curve. Thus, the potential hazard is reduced to safety negligible.

Joseph P. Jones↗
NASA NTRS1972

Measurements in atmospheric electricity designed to improve launch safety during the Apollo series

Ground test measurements were made during the launches of Apollo 13 and 14 in an effort to better define the electrical characteristics of a large launch vehicle. Of particular concern was the effective electrical length of the vehicle and plume since this parameter markedly affects the likelihood of a lightning stroke being triggered by a launch during disturbed weather conditions. Since no instrumentation could be carried aboard the launch vehicle, the experiments were confined to LF radio noise and electrostatic-field measurements on the ground in the vicinity of the launch pad. The philosophy of the experiment and the instrumentation and layout are described. From the results of the experiment it is concluded that the rocket and exhaust do not produce large-scale shorting of the earth's field out to distances of thousands of feet from the launch pad. There is evidence, however, that the plume does add substantially to the electrical length of the rocket. On this basis, it was recommended that there be no relaxation of launch rules for launches during disturbed weather.

Nanevicz, J. E.↗
NASA NTRS1972

Atmospheric electricity criteria guidelines for use in aerospace vehicle development

Lightning has always been of concern for aerospace vehicle ground activities. The unexpected triggering of lightning discharges by the Apollo 12 space vehicle shortly after launch and the more recent repeated lightning strikes to the launch umbilical tower while the Apollo 15 space vehicle was being readied for launch have renewed interest in studies of atmospheric electricity as it relates to space vehicle missions. The material presented reflects some of the results of these studies with regard to updating the current criteria guidelines.

Daniels, G. E.↗
NASA NTRS1971

The stability of sunspot magnetic fields and the origin of solar flares.

The steady motion in sunspot magnetic regions is considered for both current-free and force-free configurations. The sufficient condition for stability is obtained in the presence of both external current-free and force-free magnetic fields and a steady motion. It is shown that the pattern of such steady motion is most important in triggering an instability of sunspot magnetic fields, both for the current-free and force-free configuration. When there is no steady motion, the current-free configuration of sunspot magnetic fields is always stable, whereas the stability in the case of force-free magnetic fields is connected with the configuration. The onset of a solar flare seems to be associated with an instability connected to the steady motion within the sunspot magnetic regions.

Sakurai, K.↗
NASA NTRS1971

Moonquakes.

Although the average rate of seismic energy release within the moon appears to be far below that of the earth, over 100 events believed to be moonquakes have been recorded by the two seismic stations installed on the lunar surface during Apollo missions 12 and 14. With few exceptions, the moonquakes occur at monthly intervals near times of perigee and apogee and show correlations with the longer-term (7-month) lunar gravity variations. The repeating moonquakes are believed to occur at not less than 10 different locations. However, a single focal zone accounts for 80 per cent of the total seismic energy detected. This active zone appears to be 600 kilometers south-southwest of the Apollo 12 and 14 sites and deep within the moon. Each focal zone must be small (less than 10 kilometers in linear dimension) and fixed in location over a 14-month period. Cumulative strain at each location is inferred. Thus, the moonquakes appear to be releasing internal strain of unknown origin, the release being triggered by tidal stresses.

Latham, G.↗
NASA NTRS1971

A note on the acceleration phase of high-energy particles in the solar flare on 7 July, 1966.

The acceleration phase of solar cosmic rays and relativistic electrons is studied on the basis of the observational data available on the optical, radio, X-ray, and particle events associated with the solar flare that occurred on July 7, 1966. The generating process of hydromagnetic shock waves which excited the type-II radio burst detected at a frequency below about 100 MHz is also discussed. The results of the study suggest that no secondary acceleration process after the explosive phase can contribute much to the generation of high energy particles. The ejection of solar cosmic rays and relativistic electrons seems to be related to the expansion of the magnetic bulge which can trap accelerated electrons from the triggering region of solar flares.

Sakurai, K.↗
NASA NTRS1971

Techniques for gamma rays.

The detecting systems used in high energy astrophysics are generally more similar to particle detectors than to optical devices. The basic design of the gamma ray instrument depends on whether the energy range is below about 10 MeV and therefore in the region where the Compton effect predominates in the absorption of the gamma-rays, or above that energy where electron-positron pair production is most important. The most usual approach to the detector system in the lower of the two energy intervals is to use a scintillation counter in the center of the detector system to absorb the photons and permit a measure of their energy, and to surround it by another detector which is employed as an active anticoincidence shield to discriminate against charged particles. In the gamma-ray interval above about 10 MeV, the very low flux of gamma rays and the high particle background has directed the development of high energy gamma-ray telescopes towards complicated techniques and large detector arrays. As a result, several investigators have now turned to the spark chamber as the heart of a detector system. Generally, it is surrounded by an anticoincidence system and is triggered by a counter telescope.

Fichtel, C. E.↗
NASA NTRS1972

Balloon measurements of the energy spectrum of cosmic electrons between 1 and 25 GeV.

During three balloon flights made in 1966 and 1967, cosmic electrons were investigated with the aid of a hodoscope detector that provided extensive and detailed information on each cosmic-ray event triggering the apparatus. Similar information obtained during calibration exposures to protons and pions as well as to electrons was used to provide identification of cosmic electrons and to determine their energies. Differential primary electron intensities measured in the range from 1 to 25 GeV were substantially larger than some earlier measurements. In conjunction with existing measurements at energies above 100 GeV, this finding indicates that the energy spectrum of cosmic electrons is steeper than that of cosmic-ray nuclei and consequently suggests that Compton/synchrotron energy loss plays a significant role in shaping the electron spectrum.

Earl, J. A.↗
NASA NTRS1972

Feedback in sequential machine realizations.

A method is described for determining the realizability of a sequential machine with trigger or set-reset flip-flop memory elements when the feedback of the machine is given by a Boolean function. Feedbacks in several types of sequential machines with different memory elements are compared, showing the memory specifications allowing the realization of such machines.

Harlow, C. A.↗
NASA NTRS1972

The Lick Observatory image-dissector scanner.

A scanner that uses an image dissector to scan the output screen of an image tube has proven to be a sensitive and linear detector for faint astronomical spectra. The image-tube phosphor screen acts as a short-term storage element and allows the system to approach the performance of an ideal multichannel photon counter. Pulses resulting from individual photons, emitted from the output phosphor and detected by the image dissector, trigger an amplifier-discriminator and are counted in a 24-bit, 4096-word circulating memory. Aspects of system performance are discussed, giving attention to linearity, dynamic range, sensitivity, stability, and scattered light properties.

Robinson, L. B.↗
NASA NTRS1972

A versatile pulse programmer for pulsed nuclear magnetic resonance spectroscopy.

A digital pulse programmer producing the standard pulse sequences required for pulsed nuclear magnetic resonance spectroscopy is described. In addition, a 'saturation burst' sequence, useful in the measurement of long relaxation times in solids, is provided. Both positive and negative 4 V trigger pulses are produced that are fully synchronous with a crystal-controlled time base, and the pulse programmer may be phase-locked with a maximum pulse jitter of 3 ns to the oscillator of a coherent pulse spectrometer. Medium speed TTL integrated circuits are used throughout.

Tarr, C. E.↗
NASA NTRS1972

Noise suppression by time exposure oscilloscope photography.

We describe a simple and inexpensive means of enhancing repetitive signals obscured by noise with roughly equal amplitude. The signal and noise are displayed on an oscilloscope, and we perform a time average over many traces by time exposure photography. If the oscilloscope triggering is synchronous with the signal, the result is a significant suppression of the offending noise.

Huchital, G. S.↗