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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

A measurement of the cosmic-ray H-2 and He-3 spectra and H-2/He-4 and He-3/He-4 ratios in 1989

The energy spectra of H-2 and H-3 nuclei up to energies of 450 and 800 MeV nucleon, respectively, were measured during a balloon flight of the NASA/NMSU Balloon Borne Magnet Facility on September 5, 1989. These isotopes were cleanly resolved from the more abundant H-1 and He-4 using a measurement of rigidity versus velocity as measured in a high-resolution scintillation counter. After correction for atmospheric secondaries the measured H-2/He-4 and He-3/He-4 ratios are both consistent with the production expected if H-1 and He-4 have the same path length in the galaxy as heavier cosmic-ray nuclei such as C and Fe, to within about 20 percent. Solar modulation effects play an important role in this uncertainty. This result favors a generally similar propagation history, along with similar types of sources for H-1 and He-4 and the heavier cosmic-ray nuclei.

Webber, W. R.↗
NASA NTRS1992

The molecular core in G34.3 + 0.2 - Millimeter interferometric observations of HCO(+), H(C-13)N, H(C-15)N, and SO

This study presents high-resolution observations of the molecular core in the star-forming region G34.3 + 0.2. Maps at 6-arcsec resolution of emission and absorption of the J = 1 - 0 transitions of HCO(+), H (C-13)N, H(C-15)N, and of the 2(2) - 1(1) transition of SO were obtained in addition to a map of the 3.4-mm continuum emission from the compact H II component. The HCL(+) emission toward G34.3 + 0.2 traces a warm molecular core about 0.9 pc in size. Emission from H (C-13)N is detected over about 0.3 pc. The cometary H II region lies near the edge of the molecular core. The blueshift of the radio recombination lines with respect to the molecular emission suggests that gas from the H II region is accelerated in a champagne flow caused by a steep gradient in the ambient gas density.

Carral, Patricia↗
NASA NTRS2026

The Evolution in Coma Molecular Composition of Comet C/2017 K2 (PanSTARRS) Across the H 2 O Sublimation Zone: ALMA Imaging of an H 2 O-Dominated Coma

We report a survey of molecular emission from cometary volatiles using the Atacama Large Millimeter/Submillimeter Array (ALMA) toward comet C/2017 K2 (PanSTARRS) carried out on UT 2022 September 21, 22, and 23 at a heliocentric distance r H 3 OH, and H 2 CO (along with continuum emission from dust) sampled molecular chemistry in C/2017 K2 at the inner edge of the H 2 O sublimation zone, the region from r H 2 O begins vigorously subliming and increasingly dominating comet activity, discerning parent from daughter or extended source species. This work presents spectrally integrated flux maps, production rates, and parent scale lengths for each molecule. CH 3 OH, CO, and HCN were produced within ~250 km of the nucleus, potentially including contributions from sublimation of icy grains. CS was consistent with production from CS 2 photolysis, and H 2 CO required production from extended sources in the coma. An ortho-to-para ratio of 2.9 ± 0.4 for H 2 CO was derived from simultaneously measured transitions of each spin species. The continuum was extended and spatially resolved, consistent with thermal emission from dust in the coma. Analysis of the continuum visibilities provided an upper limit on the nucleus diameter d <6.6 km and coma dust masses of (1.2-2.4) times10 11 kg.

Nathan X Roth↗
NASA NTRS1989

Electron cyclotron resonance deposition and plasma diagnostics of a-Si:H and a-C:H films

Amorphous silicon (a-Si:H) and amorphous carbon (a-C:H) films deposited by electron cyclotron resonance (ECR) microwave plasma-enhanced chemical vapor deposition are discussed. It is shown that the ECR microwave plasma deposition technique can produce a-Si:H films with material qualities similar to and with a deposition rate one order of magnitude higher than for films deposited by radio-frequency glow discharge. The ECR-deposited a-C:H films are characterized by fluorescence, IR, and Raman spectroscopy. In situ optical emission spectroscopy plasma diagnostics indicates that ECR plasmas have a strong emission at 434 nm, which indicates a higher chemical reactivity than radio-frequency glow discharge plasmas. The radio frequency bias to the substrate is found to play a critical role in determining the film structure and the carbon bonding configuration of ECR-deposited a-C:H films.

Shing, Y. H.↗
NASA NTRS1991

Material properties and device evaluations of ECR-deposited a-Si:H and a-SiC:H films

Device-quality a-Si:H and a-SiC:H films have been deposited using electron cyclotron resonance (ECR) microwave plasmas of SiH4, CH4, and H2 mixtures. Typical material properties of ECR-deposited, photosensitive a-Si:H films are: (1) high photosensitivity up to 2 x 106 with a photoconductivity of 10 exp -5 to 10 exp -4/(Ohm-cm), (2) a Tauc gap of 1.75 to 1.85 eV, (3) an Urbach slope of 50-60 meV determined by the constant photocurrent method, and (4) an integrated defect density of 1-2 x 10 exp 16/cu cm determined by junction capacitance measurements. Highly conductive, p-type a-SiC:H films have been produced by ECR plasmas with a conductivity of 0.2/(Ohm-cm).

Shing, Y. H.↗
NASA NTRS1989

H(2)- and H(infinity)-design tools for linear time-invariant systems

Recent advances in optimal control have brought design techniques based on optimization of H(2) and H(infinity) norm criteria, closer to be attractive alternatives to single-loop design methods for linear time-variant systems. Significant steps forward in this technology are the deeper understanding of performance and robustness issues of these design procedures and means to perform design trade-offs. However acceptance of the technology is hindered by the lack of convenient design tools to exercise these powerful multivariable techniques, while still allowing single-loop design formulation. Presented is a unique computer tool for designing arbitrary low-order linear time-invarient controllers than encompasses both performance and robustness issues via the familiar H(2) and H(infinity) norm optimization. Application to disturbance rejection design for a commercial transport is demonstrated.

Ly, Uy-Loi↗
NASA NTRS1987

Utilization of potatoes for life support systems in space. III - Productivity at successive harvest dates under 12-h and 24-h photoperiods

Efficient crop production for controlled ecological life support systems requires near-optimal growing conditions with harvests taken when production per unit area per unit time is maximum. This maximum for potato was determined using data on Norland plants which were grown in walk-in growth rooms under 12-h and 24-h photoperiods at 16 C. Results show that high tuber production can be obtained from potatoes grown under a continuous light regime. The dry weights (dwt) of tuber and of the entire plants were found to increase under both photoperiods until the final harvest date (148 days), reaching 5732 g tuber dwt and 704 g total dwt under 12-h, and 791 g tuber dwt and 972 g total dwt under 24-h.

Wheeler, Raymond M.↗
NASA NTRS1993

Breakup and structure of an H-chondrite parent body - The H-chondrite flux over the last million years

Two distinct groups of H chondrites are identified which have respectively induced thermoluminescence peak temperatures above 190 C (AC) and below 190 C (BC). Metallographic cooling rate determinations confirm that the AC group cools at very high rates relative to the latter group. The AC group members have cosmic ray exposure ages of about 8 Myr. Antarctic meteorite of the BC group have cosmic ray exposure ages greater than 20 Myr. Modern H-chondrite falls, which are all of the BC group, have cosmic ray exposure ages of 8 and above 20 Myr. The data show that the abundance of the AC group is directly related to terrestrial age. It is suggested that both the AC group and part of BC group were produced by an impact event at approximately 8 Myr and that the small sizes of the AC group made them prone to destruction, allowing the BC group to dominate the modern H-chondrite flux.

Benoit, Paul H.↗
NASA NTRS1991

Electron cyclotron resonance microwave plasma deposition of a-Si:H and a-SiC:H films

The paper reports electron cyclotron resonance (ECR) deposition of a-Si:H and a-SiC:H thin films using SiH4, CH4, and hydrogen mixed gas plasmas. The ECR deposition conditions were investigated in the pressure region of 0.1 to 100 mtorr, and the film properties were characterized by light and dark conductivity measurements, XRD, Raman spectroscopy, optical transmission, and IR spectroscopy. In addition, the hydrogen dilution effect on ECR-deposited a-SiC:H was investigated.

Shing, Y. H.↗
NASA NTRS1979

H-alpha and H-beta emission in quiescent prominences

High-resolution H-alpha and H-beta line profiles in a number of quiescent prominences were measured at positions of weak to moderate brightness (for H-alpha integrated intensity of not less than 1.35 x 10 to the 5th ergs/sq cm/s/sr). Those profiles that appear to originate primarily in a single physical element can be accurately fitted with a two-component model, each component being characterized by a temperature, a Gaussian microturbulence distribution, and a constant source function. The various values of integrated intensity, optical thickness, and Doppler width are compared with previous measurements and recent theoretical calculations; several discrepancies are noted and discussed.

Landman, D. A.↗
NASA NTRS1983

A search for H-2, H-3, and He-3 in large solar flares

The results of a new study of solar flare H and He isotopes imply that earlier observations have significantly overestimated the abundances of H-2, H-3, and He-3 in large solar flares. No evidence is found that solar flare nuclei have suffered any significant amount of fragmentation before escaping from the sun.

Mewaldt, R. A.↗
NASA NTRS1986

H-alpha scans of the intergalactic H I cloud in Leo

Scans of H-alpha were obtained for two fields within the large, intergalactic H I cloud in Leo. The data provide a conservative upper limit of 1.7 x 10 to the -7th ergs/sq cm/s/sr on the H-alpha surface brightness of the cloud. This limit corresponds to an emission measure of less than 2 cm exp -6 pc for gas at a temperature of 10,000 K and implies an ionized hydrogen mass of less than 9 x 10 to the 9th f exp 1/2 solar mass within the cloud, where f is the filling fraction of the gas. This intensity may have important implications for possible sources of the ionization.

Reynolds, R. J.↗
NASA NTRS1989

Theoretical characterization of the potential energy surface for H + O2 yields HO2(asterisk) yields HO + O. II - The potential for H atom exchange in HO2

The results of CASSCF multireference contracted CI calculations with large ANO basis sets are presented for the exchange region of the HO2 potential-energy surface. The saddle point for H atom exchange is about 13 kcal/mol below the energy of H + O2; therefore, this region of the surface should be accessible during H + O2 recombination and methathesis reactions.

Walch, Stephen P.↗
NASA NTRS1994

A New Global Potential Energy Surface for the Hydroperoxyl Radical, HO2: Reaction Coefficients for H + O2 and Vibrational Splittings for H Atom Transfer

A new analytic global potential energy surface describing the hydroperoxyl radical system H((sup 2)S) + O2(X (sup 3)Sigma((sup -)(sub g))) (reversible reaction) HO2 ((X-tilde) (sup 2)A'') (reversible reaction) O((sup 3)P) + O H (X (sup 2)Pi) has been fitted using the ab initio complete active space SCF (self-consistent-field)/externally contracted configuration interaction (CASSCF/CCI) energy calculations of Walch and Duchovic. Results of quasiclassical trajectory studies to determine the rate coefficients of the forward and reverse reactions at combustion temperatures will be presented. In addition, vibrational energy levels were calculated using the quantum DVR-DGB (discrete variable representation-distributed Gaussian basis) method and the splitting due to H atom migration is investigated. The material of the proposed presentation was reviewed and the technical content will not reveal any information not already in the public domain and will not give any foreign industry or government a competitive advantage.

Dateo, Christopher E.↗
NASA NTRS1997

Differentiating Between H and F or H and CN on C(III) or Si(III) Surfaces

A Sc tipped probe molecule yields a larger difference for the probe-H vs probe-F interaction energies than our previously studied, electron-rich pyridine (C5H5N) and (CH3)3PO probes. However, the electron-deficient Sc tipped probe does not eliminate the probe-nearest data neighbor interaction problem associated with the C(III) surface. The difference in the probe-H and probe-F interaction energies is smaller for Si(III) than C(III), making it more difficult to differentiate between these two atoms on Si(III). The larger lattice constant for Si(III) significantly reduces the data atom-data atom interaction energy as well as the probe-neighbor interaction energies. This means that the H/CN system which is not practical for C(III) due to the CN-CN repulsion, is possible for Si(III). The difference in the probe-H and probe-CN interaction energies is very large for the H/CN data storage system, making this the best system studied to date. This system could be used on C(III) if a hydrogen 'fence' is built around each data site, which corresponds to using only one quarter of the surface sites for data storage.

Bauschlicher, Charles W.↗