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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

A 12 GHz satellite video receiver: Low noise, low cost prototype model for TV reception from broadcast satellites

A 12-channel synchronous phase lock video receiver consisting of an outdoor downconverter unit and an indoor demodulator unit was developed to provide both low noise performance and low cost in production quantities of 1000 units. The prototype receiver can be mass produced at a cost under $1540 without sacrificing system performance. The receiver also has the capability of selecting any of the twelve assigned satellite broadcast channels in the frequency range 11.7 to 12.2 GHz.

Hreha, M. A.↗
NASA NTRS1980

Reactivity of stratospheric aerosols to small amounts of ammonia in the laboratory environment

Trace ammonia in laboratory air reacts easily with sulfuric acid aerosol samples to form crystalline ammonium sulfate. Argon atmospheres, however, protect sampling surfaces from ammonia contamination. It is found that atmospheric aerosols treated in this way contain only sulfuric acid. After an hour exposed to laboratory air, these same samples convert to ammonium sulfate. Aerosol particles have been collected, using argon control, to determine if the absence of crystalline sulfate is common. But so far there is no evidence that aerosols are neutralized by ammonia in the stratosphere.

Hayes, D.↗
NASA NTRS1981

Size distributions and mineralogy of ash particles in the stratosphere from eruptions of Mount St. Helens

Samples from the stratosphere obtained by U-2 aircraft after the first three major eruptions of Mount St. Helens contained large globules of liquid acid and ash. Because of their large size, these globules had disappeared from the lower stratosphere by late June 1980, leaving behind only smaller acid droplets. Particle size distributions and mineralogy of the stratospheric ash grains demonstrate inhomogeneity in the eruption clouds.

Farlow, N. H.↗
NASA NTRS1981

Comparison of stratospheric aerosol measurements over Poker Flat, Alaska, July, 1979

Stratospheric aerosols were collected at Poker Flat, Alaska, in July, 1979, to determine particle properties, confirm coincident satellite SAGE measurements, and compare similar results obtained with different airborne samplers. Because of the steep slopes in size-distribution curves for larger particles, it is found that properties such as concentrations, aerosol mass, and optical extinction are very sensitive to small errors in radii. It is calculated that the concentration measurements agree with photoelectric particle counter results when a 16% radius change is introduced. An 8% radius change matches our calculated sulfate mass with filter mass measurements. And a 13% radius change results in agreement between the calculated optical extinction and coincident SAGE satellite results. Recognizing that different instruments can produce 10-20% differences in measured sizes, it is believed the results of these comparative measurements of SAGE and in situ instruments are essentially in agreement.

Farlow, N. H.↗
NASA NTRS1981

A study of stratospheric aerosol maturity

A sampling and analysis technique that uses the binomial distribution to characterize stratospheric aerosol populations at the 95% level of confidence is described. Particle samples obtained over Alaska during July 15-19, 1979, are used; the results show the presence of more small particles at lower altitude than at high altitudes. Calculations of the surface area and volume distributions for all aerosol samples collected are given. Evidence from these data suggests either that Aitken nuclei are injected or diffused across the tropopause and rise into the stratosphere, where they mature into larger particles, or nuclei form in the lower stratosphere and become mature aerosols at high altitude. Samples obtained at another site give the same results, supporting the view that the process of injection or nucleation and maturing of aerosols with altitude may be global and need not occur only in locations exhibiting unique meteorologic features.

Oberbeck, V. R.↗
NASA NTRS1981

Structural studies on HCN oligomers

NMR spectral studies on the HCN oligomers suggest the presence of carboxamide and urea groupings. The release of CO2, H2O, HCN, CH3CN, HCONH2 and pyridine on pyrolysis is consistent with the presence of these groupings as well as carboxylic acid groups. No basic primary amine groupings could be detected with fluorescamine. Hydrazinolysis of the HCN oligomers releases 10% of the amino acids normally released by acid hydrolysis. The oligomers give a positive biuret test but this is not due to the presence of peptide bonds. There is no conclusive evidence for the presence of peptide bonds in the HCN oligomers. No diglycine was detected on partial hydrolysis of the HCN oligomers at pH 8.5 suggesting that HCN oligomers were not a source of prebiotic peptides.

Ferris, J. P.↗
NASA NTRS1982

Automatic Calibration Systems

A continuous requirement exists for calibration and environmental testing of instruments in use at multitude of test facilities at Langley Research Center. Brief summarizes several automated systems available for calibration of research instruments to include: six-component balance, multimeter, amplifier, pyrometer, voltage-controlled oscillator, pressure transducer and accelerometer.

Ferris, A. T.↗
NASA NTRS1982

Mount St. Helens aerosol evolution

Stratospheric aerosol samples were collected using a wire impactor during the year following the eruption of Mount St. Helens. Analysis of samples shows that aerosol volume increased for 6 months due to gas-to-particle conversion and then decreased to background levels in the following 6 months.

Oberbeck, V. R.↗
NASA NTRS1981

Irradiation of NH3-CH4 mixtures as a model of photochemical processes in the Jovian planets and Titan

The reactions occurring upon the ultraviolet irradiation of ammonia-methane mixtures are investigated in a simulation of the atmospheric chemistry of the Jovian planets and Titan. Gas mixtures were irradiated at 185 nm at temperatures from 156-298 K, and product and reactant concentrations were determined by means of gas chromatography. The ratio of the moles of CH4 lost per mole of NH3 decomposed is found to be 0.25, with the extent of CH4 decomposition independent of temperature. The absence of a temperature effect suggests that nonthermal atoms, probably hydrogen, initiate CH4 decomposition by the extraction of a hydrogen atom. A decrease in CH4 loss with increasing pressure or the addition of other gases to the photolysis mixture, and the lack of an increase in NH3 photolysis with CH4 pressure support this mechanism. Major reaction products obtained include C2H2, C3H8 or CH3NH2, and C4H10. Considerations of atmospheric concentrations of H2 and He indicate that NH3 photolysis does not contribute to CH4 decomposition on Jupiter, Saturn, Uranus, and Neptune, although it may have had a role in the formation of the Titan atmosphere.

Ferris, J. P.↗
NASA NTRS1981

Photolysis of CH4-NH3 mixtures and PH3 as models for the photochemical transformations on the primitive earth and Jupiter

Methane, ammonia and phosphine are some of the possible constituents of the atmospheres of the Jovian planets and their satellites. Photolysis of NH3 in the presence of CH4 at 185 nm in the temperature range of 25 C to -100 C results in the decomposition of CH4. The reaction is inhibited by added H2 or SF6. These findings are consistent with the reaction of hot hydrogen atoms with CH4 to give the CH3 radical. P2H4 is the initial product formed by the photolysis of PH3 at 206 nm. Kinetic studies established that it is the intermediate in the formation of P4 from PH3. The potential significance of these reactions to the atmospheric photochemistry of the Jovian planets and moons is discussed.

Ferris, J. P.↗
NASA NTRS1981

Clay-mediated reactions of HCN oligomers - The effect of the oxidation state of the clay

Montmorillonite clays which contain Fe(III) inhibit the oligomerization of aqueous solutions of HCN. The inhibitory effect is due to the rapid oxidation of diaminomaleonitrile, a key intermediate in HCN oligomerization, by the Fe(III) incorporated into the aluminosilicate lattice of the clay. The Fe(III) oxidizes diaminomaleonitrile to diiminosuccinonitrile, a compound which is rapidly hydrolyzed to HCN and oxalic acid derivatives. Diaminomaleonitrile is not oxidized when Fe(III) in the montmorillonite is reduced with hydrazine. The oxidation state of the clay is an important variable in experiments designed to simulate clay catalysis on the primitive earth.

Ferris, J. P.↗
NASA NTRS1982

Altitude variations in stratospheric aerosols of a tropical region

To investigate the possibility that significant amounts of tropical tropospheric air may be convectively introduced into the stratosphere, aerosol samplings over Panama were made at various altitudes using a wire impactor collector. The percentage of particle sizes less than the mean mode decreases with height above the tropopause, suggesting depletion of small particles, possibly due to coagulation. Larger aerosols (greater than 0.3 micron in diam.) are more abundant farther above the tropopause, indicating growth, mainly by condensation. The total particle concentration decreases with increasing height above the tropopause, and also with increasing temperature. Aerosols containing smaller-size particles are thus found closer to the tropopause, and larger-size, more-evolved aerosols occur at higher altitudes. These data indicate that convective activity at the Intertropical Convergence Zone may be a source mechanism for stratospheric aerosols.

Goodman, J.↗
NASA NTRS1982

Chemical evolution. XL - Clay-mediated oxidation of diaminomaleonitrile

The inhibition of the oligomerization of HCN by montmorillonite clays is shown to be caused by oxidation of diaminomaleonitrile (DAMN) by ferric ion in the clay lattice, with ferrous ion and oxalic acid the reaction products. It is demonstrated that diiminosuccinonitrile is the initial reaction product and is rapidly hydrolized to oxalic acid and HCN. The same oxidative transformations are effected by ferric ion bound to Dowex 50, ferric ion in solution, and Ni(NH3)6(2+). The rate of reaction of DAMN indicates no catalytic role for the clay in the oxidation of DAMN, and little reaction of the latter was observed with montmorillonite in which the bulk of the iron was in the divalent state. The possible significance of these redox reactions to chemical evolution is discussed.

Ferris, J. P.↗
NASA NTRS1981

Force instrumentation for cryogenic wind tunnels using one-piece strain-gage balances

Materials and techniques for a transducer capable of obtaining accurate force measurements at cryogenic temperatures (down to 77 K) and high pressures (up to 9 atm) have been determined. Areas of high stress concentration are minimized by balance design, and model and sting attachment methods able to withstand cryogenic temperatures are used. Maraging 200 is the material used for the balances, due to its high impact strength and simple heat treatment procedure. Test results verify that the balances produce reliable, repeatable, and predictable data from 300 K to 110 K under steady state conditions. Techniques have been developed to reduce the temperature-induced bridge output, such as the use of bridges with two gages mounted transverse to the principal stress direction. Under these conditions, the results given by the balances should be equally good during transient temperatures on five of the six components. The work will be used at the National Transonic Facility (NTF) at NASA Langley.

Ferris, A. T.↗
NASA NTRS1982

Mount Saint Helens aerosol evolution

Stratospheric aerosol samples were collected using a wire impactor during the year following the eruption of Mt. St. Helens. Analysis of samples shows that aerosol volume increased for 6 months due to gas-to-particle conversion and then decreased to background levels in the following 6 months.

Oberbeck, V. R.↗
NASA NTRS1973

Wind-tunnel measurements of the chordwise pressure distribution and profile drag of a research airplane model incorporating a 17-percent-thick supercritical wing

The Langley 8-foot transonic pressure tunnel to determine the wing chordwise pressure distribution for a 0.09-scale model of a research airplane incorporating a 17-percent-thick supercritical wing. Airfoil profile drag was determined from wake pressure measurements at the 42-percent-semispan wing station. The investigation was conducted at Mach numbers from 0.30 to 0.80 over an angle-of-attack range sufficient to include buffet onset. The Reynolds number based on the mean geometric chord varied from 2 x 10 to the 6th power at Mach number 0.30 to 3.33 x 10 to the 6th power at Mach number 0.65 and was maintained at a constant value of 3.86 x 10 to the 6th power at Mach numbers from 0.70 to 0.80. Pressure coefficients for four wing semispan stations and wing-section normal-force and pitching-moment coefficients for two semispan stations are presented in tabular form over the Mach number range from 0.30 to 0.80. Plotted chordwise pressure distributions and wake profiles are given for a selected range of section normal-force coefficients over the same Mach number range.

Ferris, J. C.↗
NASA NTRS1972

Static aerodynamic characteristics of a model with a 17 percent thick supercritical wing

The statis stability and control characteristics and air loads on the wing and aileron of a 0.09 scale model of an airplane with a 17 percent thick supercritical wing were investigated. The longitudinal aerodynamic characteristics were determined over a lift coefficient range sufficiently high to induce buffet onset at Mach numbers from 0.30 to 0.80. In addition, the lateral aerodynamic characteristics were determined as a function of sideslip angle and angle of attack at selected Mach numbers.

Ferris, J. C.↗
NASA NTRS1975

Static longitudinal aerodynamic characteristics of a model with a modified 17 percent thick supercritical wing

The static longitudinal stability characteristics of a 0.09 scale model of an airplane with a modified 17 percent thick supercritical wing were investigated. Modifications were made to the wing to reduce a gradual buildup of boundary layer shock loss preceding drag divergence (drag creep) noted in an earlier investigation. The longitudinal aerodynamic characteristics were determined over a Mach number range from 0.30 to 0.76 at angles of attack that generally provided a lift coefficient range from 0 to buffet onset. Results indicate that the modifications to the airfoil essentially eliminated the drag creep associated with the airfoil that occurs between the critical Mach number and the drag divergence Mach number.

Ferris, J. C.↗