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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 235 records · Page 13
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NASA NTRS1972

Brightness of forbidden O I lines and properties of shadow bands during the eclipse of 7 March 1970.

Results of two types of measurements made at a site in the center of the eclipse track during the total eclipse of Mar. 7, 1970. The O I forbidden 5577-A and 6300-A lines were measured looking vertically through the eclipse shadow. The intensities were approximately 1 kR, essentially the values obtained in recent rocket measurements of normal day airglow at altitudes above 100 km. This is consistent with the hypothesis that these lines originate primarily at altitudes well above the shadow from mechanisms which are not appreciably perturbed by the approaching shadow. Measurements were also made of the time variation of intensity of incident light during the shadow-band period before second contact. There are saw-tooth fluctuations with steep leading edges, as well as many high-frequency components of smaller amplitude. This time variation does not appear to be obviously related in a simple way to current theories of their production mechanisms, or to the visual appearance of shadow bands.

Kerr, D. E.↗
NASA NTRS1972

Electron loss coefficients for the D-region of the ionosphere from rocket measurements during the eclipses of March 1970 and November 1966.

Observation that recombination-like electron loss coefficients measured during the March 1970 eclipse coincide with those from the November 1966 eclipse and range from 2 x 10 to the minus 7th power cu cm/sec at Z sub zero + 6 km to 0.00005 cu cm/sec at Z sub zero -2 km, where Z sub zero is the altitude of the steep gradient of electron concentration. During totality, Z sub zero was 82.5 km in 1970, and 86.8 km in 1966. For full-sun conditions, Z sub zero was 84 km on both eclipse days. Attachment-like electron loss coefficients from both eclipses are in good agreement below Z sub zero, and have a nearly constant value of about 0.008 per sec. Below Z sub zero, attachment-like loss rates agree with production rates - i.e., electron concentration is proportional to electron production.

Mechtly, E. A.↗
NASA NTRS1972

Lunar rilles and Hawaiian volcanic features - Possible analogues.

Study of the origin and development of lava conduits in terrestrial volcanic regions and the possible association of two important classes of lunar morphological features - i.e., channels and the sinuous rilles on the lunar maria - with stages in the evolution of lava conduits. The study was motivated by observations of some Hawaiian active volcanic regions. The origin of apparent flow channels on steep slopes on the moon is also considered.

Cruikshank, D. P.↗
NASA NTRS1972

Plasma waves in the dayside polar cusp. I - Magnetospheric observations.

General survey of the Ogo 5 plasma-wave measurements for the dayside polar-cusp encounters of Nov. 1, 1968, and detailed analysis of the observations at the low-altitude (r approximately 3 to 5 earth radii) cusp boundaries. The survey section contains an overall discussion of the ULF magnetic-field wave levels and the VLF electric-field amplitude ranges measured from perigee out to 9 earth radii on Nov. 1, 1968. These cusp-associated observations are compared with those made on Oct. 27 and Nov. 6, 1968, when Ogo 5 traversed the dayside magnetosphere without encountering the cusp. It is shown that at the November 1 low-altitude cusp boundaries intense wave levels were detected over a broad spectral region at the steep gradients in cusp plasma density and thermal energy. The results are interpreted in terms of drift instabilities for low-beta plasmas with hot ions, and associated wave-particle and wave-wave interactions are briefly discussed.

Scarf, F. L.↗
NASA NTRS1972

Observed heights of EUV lines formed in the transition zone and corona.

The heights of formation of a number of extreme ultraviolet lines in active regions have been measured from OSO-IV spectroheliograms. Using the Lyman continuum at 2000 km above the white light limb as a reference, we find heights for He I, He II, C III, N III, O IV, O VI, Ne VIII, Mg X, Si XII, Fe XV and Fe XVI that are in approximate agreement with models based on analysis of EUV emission intensities. The height of C II is anomalously high. The accuracy of measurement is typically about 2000 km. The data suggest that the transition zone is less steep than calculated from EUV emission intensities; however, higher resolution observations are necessary to resolve the discrepancy.

Simon, G. W.↗
NASA NTRS1972

A new transient source observed by Uhuru.

A strong X-ray source appeared sometime between March 25 and August 17, 1971. On August 23, its intensity, as observed by the Uhuru satellite, was about twice that of the Crab Nebula, corresponding to about 3 times 10 to the -8th power ergs per sq cm per sec, in the range 2-6 keV. On December 20, 1971, its intensity had declined to one-tenth of that value in the same energy range. Its spectrum was quite steep, and fit a power law with an average energy spectral index of 3.0. The variation of X-ray intensity over a 5-month period shows qualitative differences from the previously observed transient X-ray sources, Cen XR-2 and Cen XR-4.

Matilsky, T. A.↗
NASA NTRS1972

Trapping boundary and field-line motion during geomagnetic storms.

Observation that the high-latitude trapping boundary for 20-keV electrons and 100-keV protons became very thin in the early morning hours during two intense substorms. The gradients were too steep to be maintained by drifting particles, so they must have been produced locally over the nightside of the earth. The flux gradient is seen to move at speeds in excess of 100 km/sec. Plasma appears to move away from the tail and around the earth at these high speeds during the sudden expansion phases of the substorms. The rapid plasma motion requires the presence of fluctuating electric fields that sometimes exceed 50 to 100 mV/m at a geomagnetic latitude of 30 deg on the L = 5 field line. These observations fit best into a model that contains two field-aligned sheet currents. The high electric fields that accompany the rapid plasma flow can produce nonadiabatic acceleration of 0.1- to 1-MeV electrons and protons.

Kaufmann, R. L.↗
NASA NTRS1972

Universal instability associated with the plasmapause and its role in geomagnetic micropulsations.

The observed close correlation between the plasmapause and micropulsations is explained on the basis of a universal instability model. Both theoretical and experimental studies of a nonhomogeneous magnetoplasma indicate that a steep plasma density gradient at the plasmapause is likely the origin of the universal instability in the magnetosphere. Drift waves excited at the plasmapause may be unstable in the direction of the electron drift and propagate eastward nearly perpendicularly to the magnetic field. The drift waves, however, tend to convert very quickly to ion sound or Alfven waves with a much larger phase velocity parallel to the magnetic field. This may be a possible source mechanism for rather regular geomagnetic micropulsations, and specific mechanisms are identified for the long- and short-period cases.

Kikuchi, H.↗
NASA NTRS1972

Influence of contraction section shape and inlet flow direction on supersonic nozzle flow and performance.

Wall static pressure measurements and performance parameters are presented for axisymmetric supersonic nozzles with relatively steep convergent sections and comparatively small radius-of-curvature throats. The nozzle walls were essentially adiabatic. These results are compared with those obtained in other nozzles tested previously to appraise the influence of contraction shape on performance. Both the flow coefficient and the thrust were less than the corresponding values for one-dimensional, isentropic, plane flow for both the axial and radial inflow nozzles considered, but the specific impulse, the most important performance parameter, was found to be relatively unchanged. The thrust decrement for the axial inflow nozzles was established primarily by the shape of the contraction section, and could be estimated reasonably well from a conical sink flow consideration. The radial inflow nozzle has a potential advantage from a cooling point of view if used in a rocket engine.

Back, L. H.↗
NASA NTRS1972

STOL research at NASA.

Review of the overall goals, individual objects of ongoing and proposed programs, target dates, and fund requests of NASA's STOL research effort. The realization of a separate STOL short-haul transportation system with a 2000-foot field length capability is shown likely to reduce airport acreage requirements to less than one tenth, approach speed to nearly one half, and airspace required for terminal maneuvering to less than 10% of what conventional high-performance jet aircraft necessitate, and to promise terminal congestion alleviation in areas of high traffic density, improved safety in steep approach, noise abatement, and community annoyance reduction. NASA's described programs will provide the technical foundation upon which industry can base the design and development of aircraft and avionics for the new STOL systems in the latter 1970s, and upon which the government can establish criteria for the certification and regulation of such systems.

Kayton, G. G.↗
NASA NTRS1972

An experimental investigation of STOL longitudinal flying qualities in the landing approach using the variable stability X-22A aircraft.

The first in-flight flying qualities experiment using the variable stability X-22A aircraft investigated longitudinal flying qualities requirements for STOL aircraft in terminal area operations. Emphasis was placed on defining minimum requirements for the short-term response in VFR and IFR landing approaches at representative steep STOL approach conditions of 65 and 80 knots. Evaluation flights were conducted in negligible and moderate turbulence for a wide range of short-term frequencies and dampings. The results were compared with the short-term requirements of MIL-F-83300. The specified Level 1 and 2 VFR boundaries were found to be approximately valid in moderate turbulence for both VFR and IFR flight conditions. In negligible turbulence, the specified VFR Level 2 boundary was also approximately valid but the Level 1 boundary was found to be too stringent. Pilot rating gradients with damping were more apparent than with frequency for the range investigated.

Schuler, J. M.↗
NASA NTRS1972

Response of convectively controlled burning to nonlinear disturbances.

A process where energy release rate is proportional to the square root of the Reynolds number of a burning particle or surface is used to demonstrate some distinctive dynamic properties of a disturbed convectively controlled burning process. The instantaneous energy release rates caused by assumed periodic flow field disturbances are numerically evaluated and examined. Correlation coefficients which express the energy released in-phase with the pressure disturbance are evaluated and analytical solutions for these coefficients are derived. The response of the process is shown to be highly sensitive to the harmonic distortion of the disturbance. For some disturbances the energy released in-phase with the pressure disturbance is an order of magnitude larger than that for linear (sinusoidal) disturbances. The results show that harmonic distortion increases the coupling between the burning process and the flow field. This amplifying effect of harmonic distortion is suppressed when a disturbance becomes steep-fronted; therefore, steepening can act to limit the equilibrium amplitudes in disturbed systems. Amplification is also suppressed when the velocity disturbance is phase shifted with respect to the pressure disturbance or when the process is exposed to a high steady velocity.

Heidmann, M. F.↗
NASA NTRS1972

An Analysis of Texture on Lunar Ground Photos

An experiment was performed in an attempt to evaluate autocorrelation as an indicator of texture using five small patches representing varying distances on each of four lunar photos. Each patch was scanned at 50 micron increments on a 64-level gray scale. Several problems were involved in using the ordinary autocorrelation value but a rougher autocorrelation measure, the percentage of neighboring pairs (at a given lag distance) which fell within one graylevel of one another, yielded very encouraging results. As the distance to the feature decreased, initial slope of the graph of percentage against lag increased, and the general level of the graph decreased. When a crestline was present, the graph tended to continue to decrease at higher lags as well, rather than leveling off after the initial steep slope.

Olson, J. M.↗
NASA NTRS1973

Primary cosmic ray electrons above 10 GeV: Evidence for a spectral break

A balloon borne measurement of the cosmic ray electron spectrum from 10 to 200 GeV is reported in which two new techniques have been used to remove proton background contamination. First, the depth of the spectrometer was more than 25 radiation lengths, the equivalent of more than 2 mean free paths of material, enabling hadronically and electromagnetically induced cascades to be differentiated for a subset of the data. Second, electromagnetic cascade starting points were determined to within + or - 0.1 radiation lengths based upon a calibration with electrons from 5.4 to 18 GeV at the Stanford Linear Accelerator, greatly reducing the chances for a proton to simulate an electron. The resulting spectrum, when fitted with a power law, is quite steep, -3.2 + or - 0.1, but the chi-square fit is marginal. A significantly better fit is achieved assuming a transition region model in which the source spectral index is 2.7 with a break occurring at about 50 GeV.

Silverberg, R. F.↗
NASA NTRS1973

Cas A X-ray spectrum: Evidence for iron line emission

A sensitive measurement by rocket borne detectors of the X-ray flux from Cas A has revealed a steep continuum and a broad spectral feature in the region where line radiation from iron nuclei would be expected. The flux in this feature is .0122 plus or minus .0017 photons/sq cm/s: the total energy flux from 2 to 10 KeV is 1.02 x 10 to the minus 9th power ergs/sq cm/s. The presence of broad iron lines is consistent with a model in which approximately 13 MeV/nucleon iron nuclei charge exchange with surrounding interstellar oxygen and other heavy atoms. The model suggests that a substantial fraction of the energy from the outburst has gone into low energy cosmic rays which produce the observed HII region surrounding the remnant.

Serlemitsos, P. J.↗
NASA NTRS1973

Comparative evaluation of ERTS imagery for resource inventory in land use planning

The author has identified the following significant results. Numerous previously unmapped faults in central Oregon have been distinguished on ERTS-1 imagery. Tectonic mapping of fault-controlled linears demonstrates the utility of ERTS-1 imagery as a mean of illustrating and studying the regional tectonics of the state. Soil colors observed on ERTS-1 frame 1075-18150-5 at the eastern end of the Columbia basin correlate very well with those from descriptions of soils from that area. Digital output from frame 1021-18151 has shown the enhanced ability to interpret such features as joint patterns, shadowed landslide blocks, bottomlands, and drainage patterns. Widespread use of wheat-fallow rotation in northern Umatilla County, Oregon, insures that nearly one-half of the cultivated soil is devoid of vegetation much of the time. On ERTS-1 imagery, fallow fields are only slightly darker than fields of wheat stubble at the western end of the transect. Similar climate-related contrasts in soil color are visible on ERTS-1 Imagery from several other portions of the Columbia Basin. Absence of steep topography in the area mentioned, however, minimizes the disturbing effect caused by shadows.

Simonson, G. H.↗
NASA NTRS1973

A manual control theory analysis of vertical situation displays for STOL aircraft

Pilot-vehicle-display systems theory is applied to the analysis of proposed vertical situation displays for manual control in approach-to-landing of a STOL aircraft. The effects of display variables on pilot workload and on total closed-loop system performance was calculated using an optimal-control model for the human operator. The steep approach of an augmentor wing jet STOL aircraft was analyzed. Both random turbulence and mean-wind shears were considered. Linearized perturbation equations were used to describe longitudinal and lateral dynamics of the aircraft. The basic display configuration was one that abstracted the essential status information (including glide-slope and localizer errors) of an EADI display. Proposed flight director displays for both longitudinal and lateral control were also investigated.

Baron, S.↗
NASA NTRS1973

Mars: Fretted and chaotic terrains

Fretted Martian terrain is characterized by smooth, flat, lowland areas separated from a cratered upland by abrupt escarpments of complex planimetric configuration and a maximum estimated height approaching 1 to 2 km. It is the product of some unusual erosive or abstractive process that has created steep escarpments. Chaotic terrain differs from fretted terrain in having a rough floor topography featuring a haphazard jumble of large angular blocks, and by arc-shaped slump blocks on its bounding escarpments. Its existence has now been confirmed by Mariner 9 pictures, and the characteristics, location, and areal extent of chaotic terrain have been more accurately and completely defined.

Sharp, R. P.↗