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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 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Neutron measurements in space.

The experimental measurements of the neutron flux and energy spectrum in space since 1964 are reviewed and related to the theoretical predictions. A discussion of the neutron sources is presented. The difficulties associated with neutron measurements of both the atmospheric neutron leakage flux and solar neutrons are included. Particular emphasis is placed upon the neutron leakage flux and energy measurements at energies greater than about 1 MeV. The possibilities of CRAND as a source for the energetic trapped protons are discussed in light of recent measurements of the 10- to 100-MeV neutron flux. The current status of the solar neutron flux observations is also presented. An attempt is made to interpret and discuss recent neutron measurements. In order to understand these results, the theoretical predictions of the neutron fluxes and energy spectra from possible neutron sources are briefly presented.

Lockwood, J. A.↗
NASA NTRS1973

Ultraminiature X-ray fluorescence spectrometer for in-situ geochemical analysis on Mars.

A spectrometer based upon the X-ray fluorescence method of elemental analysis has been developed in an ultraminiature, rugged form suitable for a spacecraft mission to Mars. The instrument employs two radioisotope sources (Fe-55 and Cd-109) which irradiate adjacent areas on a regolith sample. Fluorescent X rays emitted by the sample are detected by four thin-window proportional counters. Using pulse-height discrimination, the energy spectra are determined. Virtually all elements above sodium in the periodic table are detected if present at sufficient levels. Minimum detection limits range from 30 ppm to 2% depending upon the element and the matrix. For most elements, they are below 0.5%. Accuracies also depend upon the matrix, but are generally better than plus or minus 0.5% for all elements of atomic number greater than 14. Elements below sodium are also detected, but as a single group. Ambiguities of identification of the elements producing the observed spectra are minimal.

Clark, B. C.↗
NASA NTRS1973

Surface pressure fluctuations in hypersonic turbulent boundary layers.

The surface pressure fluctuations on a flat-plate model at hypersonic Mach numbers of 5.2, 7.4, and 10.4 with an attached turbulent boundary layer were measured using flush-mounted small piezoelectric sensors. A high-frequency resolution of the pressure field was achieved using specially designed small piezoelectric sensors. The rms pressures and nondimensional energy spectra for all above Mach numbers are presented. The convective velocities, obtained from space-time correlation considerations are equal to 0.7 of the free-stream velocity. The results indicate that the rms pressures vary from 5 to 25% of the mean static pressures. The ratios of rms pressure to dynamic pressure are less than the universally accepted subsonic value of .006. The ratio decreases in value as the Mach number or the dynamic pressure is increased.

Raman, K. R.↗
NASA NTRS1973

Experiments for the study of cosmic gamma-ray bursts

Several experiments are outlined which are designed for investigating cosmic gamma ray bursts; they form a research program that includes balloon experiments currently under development and satellite experiments proposed for future missions. The satellite proposals, in most cases, are either suggested for payloads that are presently defined as to experimental complement, or are for hypothetical spacecraft. Thus, these proposals at present serve to indicate, at least, the possible usefulness of various space missions for cosmic gamma-ray burst studies. Taken as a whole, this program of gamma ray burst experiments should improve on the present observations of the temporal variations, size spectrum, energy spectra, polarizations, directional locations and distribution of source directions, each by several orders of magnitude of improved resolution or of dynamic range.

Cline, T. L.↗
NASA NTRS1973

Ultra-high energy gamma rays

The production of ultrahigh energy gamma rays by proton interactions with relicit radiation, propagation of gamma rays through the universe, and proton cascading in the presence and absence of galactic magnetic fields is discussed. Detailed data are given on proton spectrum link, gamma ray intensity, and energy spectra of gamma rays on production.

Strong, A. W.↗
NASA NTRS1974

Surface pressure fluctuations in hypersonic turbulent boundary layers

The surface pressure fluctuations on a flat plate model at hypersonic Mach numbers of 5.2, 7.4 and 10.4 with an attached turbulent boundary layer were measured using flush mounted small piezoelectric sensors. A high frequency resolution of the pressure field was achieved using specially designed small piezoelectric sensors that had a good frequency response well above 300 KHz. The RMS pressures and non-dimensional energy spectra for all above Mach numbers are presented. The convective velocities, obtained from space time correlation considerations are equal to 0.7 U sub infinity. The results indicate the RMS pressures vary from 5 to 25 percent of the mean static pressures. The ratios of RMS pressure to dynamic pressure are less than the universally accepted subsonic value of 6 x 10/3. The ratio decreases in value as the Mach number or the dynamic pressure is increased. The ratio of RMS pressure to wall shear for Mach number 7.4 satisfies one smaller than or equal to p/tau sub w smaller than or equal to three.

Raman, K. R.↗
NASA NTRS1974

A new component of cosmic rays of unknown origin at a few MeV per nucleon

Recently discovered anomalies in the abundances and energy spectra of quiet time, extraterrestrial hydrogen, helium, carbon, nitrogen, and oxygen require serious revisions of origin theories to account for this new component of cosmic radiation. Abnormally large O/C and N/C ratios, long term intensity variations with time, and radial gradient measurements indicate a non-solar origin for these 2 to 30 MeV/nucleon particles. Ideas suggested to explain these measurements range from acceleration of galactic source material having an unusual composition to local acceleration of particles within the solar cavity. Observations are at present insufficient to choose between these alternate origin models.

Gloecker, G.↗
NASA NTRS1974

Energetic particles in the Jovian magnetosphere

A detailed account of the Pioneer 10 encounter with Jupiter is presented. Flux time histories of electrons and protons are given over a wide energy band. Proton and electron energy spectra are given at various Jovicentric distances. Proton spectra are shown to transform from a power law with indices in the 3-4.2 range to more nearly exponential forms in the inner regions. Extensive data are presented on the angular distributions of protons and electrons at various locations in the Jovicentric magnetosphere. In addition, a harmonic analysis of 1-2 MeV proton angular distributions was performed. Alpha/proton ratios are given as a function of Jovian radius and are compared to the earth and solar wind values.

Trainor, J. H.↗
NASA NTRS1974

An interpretation of the carbon-oxygen to iron ratio

Data from recent measurements on the composition of primary cosmic rays above 1 GeV/nucleon are critically reviewed for information pertaining to selection of suitable energy-dependent composition models. Areas where crucial experimental information may result in selection of a suitable model are pointed out. In particular, the study of the energy distribution of VVH nuclei, and the derivation of more accurate energy spectra of 10 less than or equal to Z less than or equal to 14, 15 less than or equal to Z less than or equal to 23 and Z greater than 24 would contribute to discriminate between models which rely on interstellar propagation and those that ascribe a different source mechanism for Fe group nuclei.

Balasubrahmanyan, V. K.↗
NASA NTRS1974

On the charge state of low energy Fe nuclei accelerated by solar flares

Using sounding rockets, the differential energy spectra of Fe in three solar flares between 0.3 and 50 MeV/nuc were measured. In one of these flares, the geomagnetic field was undisturbed, and the Fe spectrum showed a peak at approximately 2 MeV/nuc. Interpreting this observation with the established quiet time geomagnetic cutoffs, it was calculated that the charge of 2 MeV/nuc Fe is 22 plus or minus 1 instead of the equilibrium value of about 16 for Fe in neutral matter. This nonequilibrium state of ionization imposes a constraint on the flare mechanism and suggests the importance of the flash-phase flare plasma for ionizing heavy nuclei prior to acceleration.

Sullivan, J. D.↗
NASA NTRS1974

Measurements of the Jovian radiation belts

The University of California at San Diego trapped radiation detector measured proton and electron fluxes, angular distributions, and energy spectra throughout the Pioneer 10 fly by of Jupiter in December 1973. The instrumentation and calibrations are described, and good values for particle fluxes in the inner and outer regions are presented. The major features of the Jovian radiation belts are described, with preliminary discussions of their meanings.

Fillius, R. W.↗
NASA NTRS1974

Energetic particles in the Jovian magnetosphere

Detail account of the Pioneer 10 encounter with Jupiter as viewed by the Goddard-University of New Hampshire cosmic ray experiment. Flux time histories of electrons and protons are given over a wide energy band. These show a marked variation with magnetic latitude. Significant removal of low-energy protons by Io is apparent in the inner magnetosphere (less than or equal to 6 Jovian radii). Proton and electron energy spectra are given at various Jovicentric distances. The electron spectra are remarkably hard and constant in slope in the 0.12 to 8.0-MeV interval, the electron spectral index having a value of 1.5 to 2.0 in the region outside 25 Jovian radii. Proton spectra are shown to transform from a power law with indices in the 3 to 4.2 range to more nearly exponential forms in the inner regions (less than or equal to 40 Jovian radii). Extensive data are presented on the angular distributions of protons and electrons at various locations in the Jovicentric magnetosphere.

Trainor, J. H.↗
NASA NTRS1974

Pioneer 10: Observations of energetic electrons in the Jovian magnetosphere

Results are given of a study of the intensities, energy spectra, and angular distribution of energetic particles in the magnetosphere of Jupiter; the heliocentric radial gradient of the intensity of galactic cosmic rays; and the occurrence, intensity, and angular distribution of solar flare particles and their propagation through the interplanetary medium at large heliocentric distances.

Randall, B. A.↗
NASA NTRS1974

Processing electrophysiological signals for the monitoring of alertness

Mathematical techniques are described for processing EEG signals associated with varying states of alertness. Fast algorithms for implementing real-time computations of alertness estimates were developed. A realization of the phase-distortionless digital filter is presented which approaches real-time filtering and a transform for EEG signals. This transform provides information for the alertness estimates and can be performed in real time. A statistical test for stationarity in EEG signals is being developed that will provide a method for determining the duration of the EEG signals necessary for estimating the short-time power or energy spectra for nonstationary analysis of EEG signals.

Lai, D. C.↗
NASA NTRS1974

Jupiter radiation belt models (July 1974)

Flux profiles which were derived from data returned by Pioneer 10 during Jupiter encounter, form the basis for a new set of numerical models for the energy spectra of electrons and protons in Jupiter's inner magnetosphere.

Divine, N.↗
NASA NTRS1975

An analysis of space environment effects on performance and missions of a Solar Electric Propulsion Stage (SEPS)

The development of an analysis which addresses the problems of degrading space environmental effects on the performance and missions of a Solar Electric Propulsion Stage (SEPS) is reported. A detailed study concerning the degrading effects of the Van Allen Belt charged-particle radiation on specific spacecraft subsystems is included, along with some of the thermal problems caused by electromagnetic radiation from the sun. The analytical methods used require the integration of two distinct analyses. The first, is a low-thrust trajectory analysis which uses analytical approximations to optimum steering for orbit raising, including three-dimensional plane change cases. The second is the conversion of the Vette time-averaged differential energy spectra for protons and electrons into a 1-MeV electron equivalent environment as a function of spatial position and thickness of various shielding materials and solar-cell cover slides.

Mcglathery, D. M.↗
NASA NTRS1974

Substorm injection boundaries

An improved magnetospheric electric field model is used to compute the initial locations of particles injected by several substorms. Trajectories are traced from the time of their encounter with the ATS-5 satellite backwards to the onset time given by ground-based magnetometers. A spiral shaped inner boundary of injection is found which is quite similar to that found by a statistical analysis. This injection boundary is shown to move in an energy dependent fashion which can explain the soft energy spectra observed at the inner edge of the electrons plasma sheet.

Mcilwain, C. E.↗
NASA NTRS1975

Photoelectron escape from the ionosphere of Jupiter

Photoelectron escape fluxes and ambient electron heating from the Jovian ionosphere are computed as a function of local time and latitude. Several differences for the fluxes expected from a hydrogen atmosphere, rather than a terrestrial type of atmosphere, are described, including an increase in structure in the energy spectra due to the paucity of ionic states entering the photo-ionization processes and lower escape fluxes above 10 eV than were expected from a simple scaling of earth fluxes.

Swartz, W. E.↗