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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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NASA NTRS1974

Observation of soft X-ray emission from a region near Per X-1

Soft X-ray emission from the X-ray source Per X-1 was observed in the 0.4-2 keV energy interval from a rocket-borne X-ray detector. Spectral analysis of the data indicates that in the 0.4-2 keV band the X-ray emission from Per X-1 can be fitted either with a power law or a steep thermal bremsstrahlung spectrum. This steep spectrum is inconsistent with the spectrum measured above 2 keV. The measured flux in 0.4-2 keV band corresponds to X-ray luminosity of 3 times 10 to the 45th ergs per second for Per X-1.

Agrawal, P. C.↗
NASA NTRS1974

SAS-2 observations of celestial diffuse gamma radiation above 30 MeV

The small astronomy satellite, SAS-2, used a 32-deck magnetic core digitized spark chamber to study gamma rays with energies above 30 MeV. Data for four regions of the sky away from the galactic plane were analyzed. These regions show a finite, diffuse flux of gamma rays with a steep energy spectrum, and the flux is uniform over all the regions. Represented by a power law, the differential energy spectrum shows an index of 2.5 + or - 0.4. The steep SAS-2 spectrum and the lower energy data are reasonably consistent with a neutral pion gamma-ray spectrum which was red-shifted (such as that proposed by some cosmological theories). It is concluded that the diffuse celestial gamma ray spectrum observed presents the possibility of cosmological studies and possible evidence for a residual cosmic ray density, and supports the galactic superclusters of matter and antimatter remaining from baryon-symmetric big bang.

Thompson, D. J.↗
NASA NTRS1974

A proposed origin of the Olympus Mons escarpment

Olympus Mons (Nix Olympica) on Mars is delimited by a unique steep, nearly circular scarp. A pyroclastic model is proposed for the construct's origin. It is postulated that the Olympus Mons plateau is constructed predominantly of numerous ash-flow tuffs which were erupted from central sources over an extended period of time. Lava flows may be intercalated with the tuffs. A schematic radial profile incorporating the inferred compaction zones for an ash sheet is proposed. Following emplacement, eolian (and possibly fluvial) erosion and abrasion during dust storms would act on the ash sheets. Interior portions of the sheets would spall and slump following eolian erosion, generating steep, relatively smooth boundary scarps. The scarp would be circular due to symmetrical distribution of compaction zones. The model implies further that the Olympus Mons plateau rests on a more resistant rock substrate.

King, J. S.↗
NASA NTRS1976

The log N-log S curve for 3CR radio galaxies and the problem of identifying faint radio galaxies

The log N-log S slope of optically identified galaxies in the 3CR catalog is analyzed for galaxies with flux levels greater than 10 Jy and located at galactic latitudes greater than 7 deg. For the 86 galaxies with known redshifts, the slope is found to be about 1.16; for all 119 galaxies, the slope is found to be about 1.50. If the 113 unidentified sources are included, the slope steepens to about 1.81. It is shown that this steepness is caused by the unidentified sources. Assuming that the slope is due to evolution at redshifts of 1 to 3 and that the unidentified sources are bright ellipticals, the mean redshifts and apparent brightnesses of these galaxies are calculated. The results indicate that it is impossible to observe the unidentified sources with existing ground-based telescopes, implying that it is presently impossible to establish directly that evolution is responsible for the steep log N-log S curve of the 3CR galaxies.

Burbidge, G. R.↗
NASA NTRS1977

SAS-2 observations of the diffuse gamma radiation in the galactic latitude interval 10 deg absolute b or equal to 90 deg

An analysis of all of the second small astronomy satellite gamma-ray data for galactic latitudes with the absolute value of b 10 deg has shown that the intensity varies with galactic latitude, being larger near 10 deg than 90 deg. For energies above 100 MeV the gamma-ray data are consistent with a latitude distribution of the form I(b) = C sub 1 + C sub 2/sin b, with the second term being dominant. This result suggests that the radiation above 100 MeV is coming largely from local regions of the galactic disk. Between 35 and 100 MeV, a similar equation is also a good representation of the data, but here the two terms are comparable. These results indicate that the diffuse radiation above 35 MeV consists of two parts, one with a relatively hard galactic component and the other an isotropic, steep spectral component which extrapolates back well to the low energy diffuse radiation. The steepness of the diffuse isotropic component places significant constraints on possible theoretical models of this radiation.

Fichtel, C. E.↗
NASA NTRS1977

SAS-2 observations of the diffuse gamma radiation in the galactic latitude interval from 10 to 90 deg in both hemispheres

An analysis of all the second Small Astronomy Satellite (SAS-2) gamma-ray data for galactic latitudes higher than 10 deg in both hemispheres has shown that the intensity varies with galactic latitude, being larger near 10 deg than 90 deg. For energies above 100 MeV the gamma-ray data are consistent with a latitude distribution of the form I(b) = C1 + C2/sin b, with the second term being dominant. This result suggests that the radiation above 100 MeV is coming largely from local regions of the galactic disk. Between 35 and 100 MeV, a similar equation is also a good representation of the data, but here the two terms are comparable. These results indicate that the diffuse radiation above 35 MeV consists of two parts, one with a relatively hard galactic component and the other an isotropic steep spectral component which extrapolates back well to the low-energy (less than 10 MeV) diffuse radiation. The steepness of the diffuse isotropic component places significant constraints on possible theoretical models of this radiation.

Fichtel, C. E.↗
NASA NTRS1979

Radial deformation of the solar current sheet as a cause of geomagnetic storms

It is suggested that the solar current sheet, extending from a coronal streamer, develops a large-scale radial deformation, at times with a very steep gradient at the earth's distance. The associated magnetic field lines (namely, the interplanetary magnetic field (IMF) lines) are expected to have also a large gradient in the vicinity of the current sheet. It is also suggested that some of the major geomagnetic storms occur when the earth is located in the region where IMF field lines have a large dip angle with respect to the ecliptic plane for an extended period (6-48 h), as a result of a steep radial deformation of the current sheet.

Akasofu, S.-I.↗
NASA NTRS1980

Technique of electrical stimulation of the vestibular analyzer under clinical conditions

Vestibular reactions appear under the action of direct current (dc) on the labyrinth of man and animals. A decrease of the stimulation effect of dc on the extralabyrinthine nervous formations in the suggested method is achieved by the use of electric pulses with steep front and back parts, as well as by previous anesthetization of the skin in the electrode application area by means of novocain solution electrophoresis. For this purpose a pulse producer giving trapezoid pulses with smoothly changing fronts and duration was constructed. With the help of an interrupter it is possible to stop the current increase instantly, and stimulation is performed at the level of the pulse 'plateau'. To induce vestibular reactions under monopolar stimulation, it is necessary to apply the current twice as high as that with bipolar electrode position. The use of short pulses with steep front and back parts for electrode stimulation of the vestibular analyzer is considered to be inexpedient.

Khechinashvili, S. N.↗
NASA NTRS1979

Martian channel morphology - Maja and Kasei Valles

Detailed geomorphic mapping from Viking imagery of selected portions of Kasei Vallis, Maja Vallis, and vicinity reveals numerous similarities of channel morphology to erosional and depositional features of the Channeled Scabland. Characteristic scabland landforms which occur in Kasei and Maja Valles include erosional grooves, streamlined uplands and hills, scour zones around flow obstacles, inner channels with erosional head cuts, breached ridges and basin (crater) rims, pendant forms (bars), erosional terracing of streamlined hills and channel margins, and possible midchannel bars. These features constitute an assemblage of landforms which on earth is most characteristic of catastrophic flood channeling in jointed bedrock. Prominent mass wastage and sapping features are associated with the high-wall relief in lower Kasei Vallis. Many cliffs along the channel margins exhibit steep upper slopes and gentler lower talus slopes which form the spur-and-gully topography that has also been described along chasma walls in the Valles Marineris. Landslides, debris fans, and debris cones can also be recognized. Much less wall modification occurs in the shallower Maja Vallis. Probably, the steep escarpments of Kasei were created by tectonic processes and subsequent channel incision. These escarpments later receded by mass wasting and sapping.

Baker, V. R.↗
NASA NTRS1980

Numerical techniques for solving nonlinear instability problems in smokeless tactical solid rocket motors

The selection of a satisfactory numerical method for calculating the propagation of steep fronted shock life waveforms in a solid rocket motor combustion chamber is discussed. A number of different numerical schemes were evaluated by comparing the results obtained for three problems: the shock tube problems; the linear wave equation, and nonlinear wave propagation in a closed tube. The most promising method--a combination of the Lax-Wendroff, Hybrid and Artificial Compression techniques, was incorporated into an existing nonlinear instability program. The capability of the modified program to treat steep fronted wave instabilities in low smoke tactical motors was verified by solving a number of motor test cases with disturbance amplitudes as high as 80% of the mean pressure.

Baum, J. D.↗
NASA NTRS1982

Morphology and network patterns of Martian valleys

The erosional origin of Martian valleys is briefly discussed. The absence of streamlined obstacles and interior channels, the steep and rugged walls and flat floors, and the presence of steep-walled, cuspate amphitheater terminations and sparse, open networks, argue against erosion by rainfall and surface flow and in favor of erosion by subsurface water.

Pieri, D. C.↗
NASA NTRS1983

NASA-FAA helicopter Microwave Landing System curved path flight test

An ongoing series of joint NASA/FAA helicopter Microwave Landing System (MLS) flight tests was conducted at Ames Research Center. This paper deals with tests done from the spring through the fall of 1983. This flight test investigated and developed solutions to the problem of manually flying curved-path and steep glide slope approaches into the terminal area using the MLS and flight director guidance. An MLS-equipped Bell UH-1H helicopter flown by NASA test pilots was used to develop approaches and procedures for flying these approaches. The approaches took the form of Straight-in, U-turn, and S-turn flightpaths with glide slopes of 6 deg, 9 deg, and 12 deg. These procedures were evaluated by 18 pilots from various elements of the helicopter community, flying a total of 221 hooded instrument approaches. Flying these curved path and steep glide slopes was found to be operationally acceptable with flight director guidance using the MLS.

Swenson, H. N.↗
NASA NTRS1984

Characterization of macrosegregation in ESR IN-718

Aspects of macrosegregation theory, such as dendrite arm spacing, pool profile and mushy zone depth are beneficial to developing consumable melting process for Ion Nickel IN-718, Electro-Slag Refining, especially ESR. Aspects of microsegregation theory, such as correlation of dendrite arm spacing with heat transfer mechanisms and local solidification time, are used to minimize remnant dendritism in both ESR and Vacuum Arc Remelting VAR IN-718. Specifically, ESR IN-718 must be optimized by developing practices which maximize ingot cooling rate and minimize the steepness of the solidus and liquidus isotherms. The knowledge concerning macrosegregation in consumable melted IN-718 is in the form of correlations. Since the isotherm steepness is undoubtedly involved, investigations which include a microgravity environment might separate microsegregation effects from macrosegregation effects. Accounting for the effects of gravity and density differences between the metal pool and the interdendritic fluid, in combination with the pool and mushy zone profiles, can lead to improved melting solidification practices for IN-718, and allow prediction of macrosegregation tendency to be incorporated into high temperature alloy design.

Domingue, J. A.↗
NASA NTRS1984

Structure of the magnetotail at 220 earth radii and its response to geomagnetic activity

Using plasma electron and magnetic field measurements from ISEE 3, 220 earth radii from earth, it is found that the magnetotail at that distance is a coherent structure that evidently waves about through distances comparable to its own lateral scale size. For about one-third of the time it was inside the magnetotail, ISEE 3 was in the plasma sheet. During quiet times the plasma sheet is apparently quite thin, but in response to geomagnetic activity it expands, becoming filled with hot plasma flowing tailward at speeds sometimes exceeding 1000 km/sec, and forces the magnetotail cross-section itself to expand. The plasma sheet's expansion is delayed typically by about 30 minutes from the onset of the associated geomagnetic activity (often a clearly identified isolated substorm). The magnetic field in the newly-expanded plasma sheet usually exhibits a few-minute steep northward excursion followed by a more prolonged (and often steep) southward excursion. These are believed to be the signatures of arrival of a plasmoid formed and released near the earth at the onset of the corresponding geomagnetic activity. The discreteness of these plasma releases through the magnetotail and their close association with onsets of geomagnetic activity at earth suggest that they are consequences of spontaneous release, probably by magnetic reconnection, of energy and plasma earlier stored in the magnetotail.

Hones, E. W., Jr.↗
NASA NTRS1984

Stability of absorption phenomena in laser-thermal propulsion

The mean flow and stability characteristics of laser absorption phenomena in a choked converging-diverging nozzle are considered. Calculations are presented for a given nozzle geometry and a series of laser intensities. Gas absorptivities corresponding to a hydrogen-cesium mixture are used with different initial temperatures being selected to investigate the effects of changes in the shape of the k-T curve. Both stability and mean flow calculations are limited to the one-dimensional case. The mean flow results show a decrease in mass flow as laser power is increased, along with increasingly steep temperature profiles. Calculations span regions of partial and complete absorption. One region is found where multiple solutions exist. Local stability results indicate the u-c characteristic is the only unstable mode in the unheated case. Laser heat addition makes this mode more unstable and also destabilizes the u-characteristic. Numerical calculations of disturbance propagation show that the instability of the u-c disturbances is counteracted by their reflection to u + c disturbances at the upstream end. The growth of the u-disturbances is localized in regions where the temperature profile is steep and they are damped in other regions. The increasing destabilization that is observed with increased laser power is probably the reason for difficulty in obtaining converged mean flow solutions at high laser intensities.

Merkle, C. L.↗
NASA NTRS1984

Flight tests of the Digital Integrated Automatic Landing System (DIALS)

The design, development, implementation and flight tests of the Digital Integrated Automatic Landing System (DIALS) are discussed. The system was implemented and flight tested on the Transport Systems Research Vehicle (TSRV), a Boeing 737-100. The design uses modern optimal control methods. The direct digital design obtained uses a 10 Hz rate for the sampling of sensors and the control commands. The basic structure of the control law consists of a steady state Kalman filter followed by a control gain matrix. The sensor information used includes Microwave Landing System (MLS) position, attitude, calibrated airspeed, and body accelerations. The phases of the final approach considered are localized and steep glideslope capture (which may be performed simultaneously or independently), localizer and glideslope track, crab/decrab, and flare to touchdown. The system can capture, track, and flare from conventional, as well as steep, glideslopes ranging from 2.5 deg to 5.5 deg. All of the modes of the control law including the Kalman filters were implemented on the TSRV flight computers which use fixed point arithmetic with 16 bit words. The implementation considerations are described as well as an analysis of the flight test results.

Halyo, N.↗
NASA NTRS1985

A Silicic Shield Volcano in Bolivia

Volcan Quemado and its environs provides an excellent site to study the radar signature of a silicic volcanic construct. This feature differs from basaltic terrains primarily by the evidence of explosive eruptions associated with silica-rich magmas. These explosions produced a complex of distinctive craters that are visible on radar because of their steep inner walls and exposed bedrock units. Explosive events also generated surface deposits of fine (1 mm to 10 cm) material that mantles the region around the volcano to a distance of 20 to 30 km from its center. These features are very different from those observed on basaltic flows, which typically lack violet, explosive events. In these terrains, the surface is dominated by radar-rough flows with steep, lobate flow fronts. Craters are less common, although maars are found in some regions. These comparisons suggest that spaceborne radar may be able to distinguish surface characteristics that can be used to identify volcanic eruptive styles on Venus, Mars, and other solar-system bodies.

Christensen, P. R.↗
NASA NTRS1985

High-energy neutrinos from a lunar observatory

The detection of high-energy (HE) cosmic and solar-flare neutrions near the lunar surface would be feasible at energies much lower than for a terrestrial observatory. At these lower energies ( 10 to the 9th eV), the neutrino background is drastically reduced below that generated by cosmic rays in the Earth's atmosphere. Because of the short mean free path ( 1m) of the progenitor pi and K mesons against nuclear interactions in lunar rocks, the neutrino background would be quite low. At 1 GeV, less than 1% of the pions would decay; at 10 GeV, 0.1%. Thus, if the neutrino flux to be observed is intense enough, and its spectrum is steep enough, then the signal-to-noise ratio is very favorable. The observation of HE neutrinos from solar flares would be dramatically enhanced, especially at lower energies, since the flare spectra are very steep. Detection of these neutrinos on Earth does not appear to be feasible. A remarkable feature of solar flares as viewed in HE neutrinos from a lunar base is that the entire surface of the Sun would be visible.

Shapiro, M. M.↗