Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “H”

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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Infrared studies of H II regions and OH sources

This paper presents the observational results of a high spatial-resolution mapping and photometric study in the wavelength range from 1.65 to 20 microns of four H II regions and seven OH sources. Infrared emission indicative of the presence of heated dust was found from the compact H II condensations in W51, DR21, and NGC7538. Infrared emission was also found from the positions of maser sources in NGC 7538, W75(N) W75(S) and Sharpless 269, but not from that in W51. An extended infrared source was found coincident with the peculiar OH source OH 0739-14.

Wynn-Williams, C. G.↗
NASA NTRS1974

Infrared emission from the southern H II region H2-3

The H II region H2-3 has been found to have a large infrared flux with a luminosity of 100,000 to 200,000 solar luminosity values between 1.65 and 25 microns. Most of this flux comes from a single component with a diameter of 110 sec (2 pc). At 2.2 microns there is an unresolved source which is identified as the exciting star of the nebula; it can provide the required ionization and the total luminosity observed at infrared wavelengths. The 3- to 25 micron radiation is shown to be consistent with dust heated by L-alpha radiation within the nebula, but much of the 40- to 350-micron radiation probably originates from outside the H II region.

Becklin, E. E.↗
NASA NTRS1974

On ionization in H I regions

A comparison is made of the K I, Na I, Ca II, and H I interstellar absorption lines formed in relatively low-density interstellar clouds in H I regions. The data indicate that the fractional ionization (ratio of electron density to hydrogen density) is nearly constant for a range in hydrogen densities covering a factor of 15. If ionization balance exists in the clouds, then ionization of hydrogen by either low-energy cosmic rays or soft X-rays cannot be the principal source of the observed free electrons, and the hydrogen ionization rate is less than 10 to the -16th power per sec for these processes.

Hobbs, L. M.↗
NASA NTRS1974

Radiative transitions involving the /2p2/ 3Pe metastable autodetaching state of H-

A Hylleraas bound-state wave function and 1s-2s-2p close-coupling continuum wave functions are used to calculate the absorption coefficient for the free-bound transition of H(1s) + e + quantum to a H anion in (2p2,3Pe) and the differential emission rate for the inverse process. The absorption and emission spectral maximum is found to be at a photon wavelength of 1219.5 A, an improvement of 2 A on other calculations. This free-bound absorption process appears to be a significant source of continuous ultraviolet opacity.

Jacobs, V. L.↗
NASA NTRS1974

Mission analysis for the interplanetary monitoring platforms IMP-H and -J

IMP-H and -J were launched in September 1972 and October 1973, respectively, and placed into orbits of low eccentricity halfway distant to the moon. IMP-H was required to remain between 30 and 40 earth radii for three years, and IMP-J was to maintain a similar orbit while staying on the opposite side of the earth. In both cases no orbit-adjust capability was provided after firing of a solid-propellant apogee kick motor; so strategy during mission operations depended on advance studies of orbit evolution and sensitivity to pertinent error sources. This is presented in detail along with the launch window study, and comparisons are made between the target and achieved orbits.

Muhonen, D. P.↗
NASA NTRS1974

Measurements of ion-molecule reactions of He/+/, H/+/, and HeH/+/ with H2 and D2

Drift tube-mass spectrometer measurements of several ion-molecule reactions believed to be prominent in the hydrogen-helium upper atmosphere of Jupiter are described. The total rate constant at 300 K of the reaction of He(+) with H2 is about 1.1 x 10 to the neg 13 cu cm/sec. The reaction proceeds mainly by dissociative charge transfer to produce H(+), with a small portion going by charge transfer to H2(+) and by atom rearrangement to HeH(+). The rate coefficient increases slowly with ion mean energy to a value of 2.8 x 10 to the neg 13 at 0.18 eV. The rate of the corresponding reaction with deuterium, He(+) + D2, has the rate coefficient of about 5 x 10 to the neg 14 at 300 K. Measurements of the three-body reaction of H' and the two-body reaction of HeH' with H2 to form H3(+) ions are described.

Johnsen, R.↗
NASA NTRS1974

Far-infrared emission from H II regions. II - Multicolor photometry of selected sources and 2.2 min resolution maps of M42 and NGC 2024

Medium- and broad-bandwidth photometric measurements have been made of seven compact H II regions at wavelengths between 30 and 650 microns. The results are consistent with the hypothesis that the far-infrared flux is continuum radiation from dust grains. Color temperatures range from 33 to 85 K. For most of the sources, the infrared flux is low enough so that the dust could conceivably be mixed with the ionized gas. In at least one case, however, the far-infrared spectrum and luminosity of the source cannot be reconciled with reasonable grain models unless the far-infrared flux comes from a shell surrounding the H II region. M42 (Orion) and NGC 2024 (Orion B) have been mapped at 90 microns with a resolution (half-power beam diameter) of 2.2 min. Although the peak far-infrared brightness in M42 occurs at the position of the Kleinmann-Low infrared nebula, most of the flux originates in a more extended (about 6 x 8 min) source. The energy for the diffuse component could be supplied by the stars in the Trapezium cluster. However, the single early-type star visible in NGC 2024 is not luminous enough to account for either the infrared flux or the observed free-free flux.

Harper, D. A.↗
NASA NTRS1969

Apollo 14 (mission H-3) Baseline Mission Profile

Preliminary Apollo 14 (Mission H-3) trajectory data for the July 1970 launch window are presented in this document. A general mission profile is presented, and approximate variations of selected mission parameters are indicated. Note that the information in this document is preliminary and will be updated in the Apollo 14 (Mission H-3) operational trajectory documents.

Source record↗
NASA NTRS1974

On the use of Godhavn H-component as an indicator of the interplanetary sector polarity

An objective method of inferring the polarity of the interplanetary magnetic field using the H-component at Godhavn is presented. The objectively inferred polarities are compared with a subjective index inferred earlier. It is concluded that no significant difference exists between the two methods. The inferred polarities derived from Godhavn H is biased by the (slp) sub q signature in the sense that during summer prolonged intervals of geomagnetic calm will result in inferred Away polarity regardless of the actual sector polarity. This bias does not significantly alter the large scale structure of the inferred sector structure.

Svalgaard, L.↗
NASA NTRS1975

H-alpha synoptic charts of solar activity during the first year of solar cycle 20, October 1964 - August 1965

Solar activity during the period October 28, 1964 through August 27, 1965 is presented in the form of charts for each solar rotation constructed from observations made with the chromospheric H-alpha spectra line. These H-alpha synoptic charts are identical in format and method of construction to those published for the period of Skylab observations. The sunspot minimum marking the start of Solar Cycle 20 occurred in October, 1964; therefore, charts represent solar activity during the first year of this solar cycle.

Mcintosh, P. S.↗
NASA NTRS1974

The role of dislocation as sinks for H centers in LiF

The investigation reported shows that the internal friction of compressed LiF crystals which have been irradiated by gamma-rays at liquid nitrogen temperature recovers during isochronal annealing at a low linear rate. An analysis of the annealing process is conducted. It is concluded that the recovery of the internal friction is related to the interaction between dislocations and H centers. The H centers are produced by the gamma-rays.

Yabe, M.↗
NASA NTRS1975

Aperture synthesis observations of galactic H II-regions

Aperture synthesis observations at 2.695 GHz and 8.085 GHz of the H II regions NRAO 591, NGC 6857, NGC 7538, M8, W3 and W49A made with the NRAO interferometer are presented. A set of Gaussian functions is derived to describe the radiation distribution of each H II region at each frequency. Fine structure is found in all regions. With the exception of the extended source in W49A, all previously known sources with high excitation parameters are resolved into smaller sources. The electron densities of individual sources range from 100 per cu cm up to 100,000 per cu cm. In NGC 6857, NGC 7538 and W49A, continuum sources smaller than 4 arc sec and with electron densities exceeding 10,000 per cu cm are found close to the known class II OH emission sources. In M8, we find a ring which seems to be split at the position of the O-star Herschel 36.

Wink, J. E.↗
NASA NTRS1975

Infrared forbidden lines in H II regions and planetary nebulae

Emissivity coefficients are calculated as functions of electron density and temperature for the IR forbidden lines between 2 and 300 microns of the elements and ionization stages most abundant in H II regions and planetary nebulae. The effect of self-absorption is investigated, and a method is presented for estimating when self-absorption may be important. The IR line spectrum of the Orion Nebula is predicted using the emissivity coefficients, and ionic abundances are derived for the Ar III, S IV, and Ne II forbidden lines in a number of planetary nebulae. The sulfur abundance and sulfur/oxygen ratio are discussed for H II regions and planetary nebulae. The average sulfur/oxygen ratio is found to be about 0.05 for gaseous nebulae.

Simpson, J. P.↗
NASA NTRS1975

Calculation of autoionization of He and H/-/ using the projection-operator formalism

Improved calculations are reported for the first several autoionization states of the lower symmetries of He and H(-). Unshifted energies are calculated by diagonalizing QHQ using a Hylleraes basis with more terms than previously used; shifts, widths, and photoabsorption shape parameters are obtained with the additional use of exchange-approximate nonresonant continuum functions. Previous calculations of H(-) resonances are reviewed and slightly augmented by applying various nonresonant continua and correcting small errors. A comparison is made between the calculations and experimental results and is found to be very satisfactory except for the lowest 1P autoionization state of He, which is shown to need a more accurate experimental determination.

Bhatia, A. K.↗
NASA NTRS1975

On the use of Godhavn H component as an indicator of the interplanetary sector polarity

An objective method of inferring the polarity of the interplanetary magnetic field using the H component at Godhavn is presented. The objectively inferred polarities are compared with a subjective index inferred earlier (Svalgaard, 1972b). It is concluded that no significant difference exists between the two methods. The inferred polarities derived from Godhavn H are biased by the Sq-p signature in the sense that during summer, prolonged intervals of geomagnetic calm will result in inferred away polarity regardless of the actual sector polarity. This bias does not significantly alter the large-scale structure of the inferred sector structure.

Svalgaard, L.↗
NASA NTRS1976

H alpha observations of the 12 August 1975 type 3-RS bursts

H alpha filtergram observations of a number of the Type III-RS (reverse slope) bursts that occurred on August 12, 1975 are presented. Solar radio emission was peculiar on that date in that a large number, and proportion, of the usually rare reverse slope bursts were observed. The radio bursts are shown to coincide in time with a homologous set of H alpha flares located at the limbward edge of spot group Mt. Wilson 19598. A model is proposed in which the reverse slope bursts are the downward branches of U bursts, whose upward branches are hidden behind the coronal density enhancement over the spot group.

Labonte, B. J.↗
NASA NTRS1975

Molecular hydrogen in H II region transition zones

Model calculations are performed which demonstrate that H II - H I transition zones with densities between 10 and 100 per cu cm may contain molecular-hydrogen column densities of the order of 10 to the 13th power to 10 to the 15th power per sq cm. Observational data for several stars are presented which confirm the theoretical values. It is concluded that all detectable molecular hydrogen is not necessarily located in cold regions of space.

Hill, J. K.↗