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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 361 records · Page 20

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NASA NTRS1971

Height-depth ratios of lunar and terrestrial craters.

Quantitative analysis of Gilbert's (1893) observation regarding the surface geometry of lunar craters and terrestrial calderas. Topographic measurements were made using the ratio of exterior rim height to interior crater depth, and then extended to other types of crater. The morphometric data obtained as well as those presented elsewhere (Murray et al., 1970; Guest and Murray, 1969) verify Gilbert's contention that terrestrial calderas and most rimmed lunar craters are entirely unrelated phenomena. Auxiliary characteristics previously interpreted in terms of primary volcanic cratering on the moon are either of nonendogenic origin or are secondary endogenic features superposed on initial impact landforms (Pike, 1967).

Pike, R. J.↗

NASA NTRS1972

Effects of vaporization and condensation on Apollo 11 glass spherules - Implications for cooling rates.

Fourteen of 40 glass spherules present in a section of the Apollo 11 microbreccia 10019,22 were found to exhibit steep concentration gradients at their rims; the oxides of the relatively volatile elements Na, K, and P increase by, respectively, factors of up to 67, 16, and greater than 54 at the spherule rims in comparison to the homogeneous centers. These gradients usually extend over 25-30 microns. Furthermore, the natural surfaces of 11 unpolished glass spherules separated from the fines 10084,97, in 60-80% of all cases, show higher concentrations in Na2O, K2O, and P2O5 than the averages for the central portions of 45 independently analyzed glass spherules. It is suggested that the concentration gradients observed are diffusion gradients and are the result of the impact event which produced the glasses; in the impact melting process, splash drops of melt formed that lost volatiles by vaporization. A procedure is described to determine the cooling rate of a spherule from measured concentration gradients, provided the diffusion coefficients are known for the particular glass compositions in question.

Kurat, G.↗

NASA NTRS1973

Lunar cinder cones.

Data on terrestrial eruptions of pyroclastic material and ballistic considerations suggest that in the lunar environment (vacuum and reduced gravity) low-rimmed pyroclastic rings are formed rather than the high-rimmed cinder cones so abundant on the earth. Dark blanketing deposits in the Taurus-Littrow region (Apollo 17 landing area) are interpreted as being at least partly composed of lunar counterparts of terrestrial cinder cones.

Mcgetchin, T. R.↗

NASA NTRS1974

The use of ERTS-1 images in the search for large sulfide deposits in the Chagai District, Pakistan

The author has identified the following significant results. Visual examination of color composites was tested under relatively ideal conditions for direct detection of large hydrothermal sulfide deposits at the low-grade porphyry copper deposit at Saindak, western Chagai District, Pakistan. The Saindak deposit is characterized by an elongate zone of easily eroded sulfide-rich rock surrounded by a resistant rim of hornfels and propylitically altered rock. The geomorphic features related to the Saindak deposit are easily distinguished on ERTS-1 images. Attempts to detect a color anomaly using false-color composites were not successful. About 36,000 square km of the western Chagai District were examined on false-color composites for direct evidence of large sulfide deposits. New geologic information acquired from the images was used in conjunction with the known geology to evaluate two previously known proposed areas and to suggest seven additional targets for field checking, one of which is proposed on the basis of tonal anomaly alone. The study also showed that Saindak-type deposits are not likely to be present in some extensive areas of the Chagai District; and also that a rim like that at Saindak does not form if regional metamorphism has increased the resistance of the country rock to erosion.

Schmidt, R. G.↗

NASA NTRS1973

Observations of Mare Serenitatis from lunar orbit and their interpretation

Visual observations of color differences of Serenitatis mare materials from orbit complement photography and other remotely sensed data. The light tan gray inner fill of the Serenitatis Basin is younger than the dark blue gray annulus; the latter continues into and appears to be contemporaneous with the fill of Mare Tranquillitatis. Mare ridges occur in both the inner basin fill and the dark annulus of Serenitatis. Ridges are interpreted as the result of structural deformation and up-doming after the solidification of the basaltic lavas. On the southeastern rim of the Serenitatis Basin is the darkest blue gray unit within which Apollo 17 landed. Highland massifs surrounding this unit have unstable slopes which are believed to be the result of localized tectonic activity. On the southwest rim of the basin are the dark tan to brown gray mantling materials of the Sulpicius Gallus Formation.

El-Baz, F.↗

NASA NTRS1975

Analysis of the effects on life of leading-edge holes in an airfoil subjected to arbitrary spanwise and chordwise temperature distributions

The effects of temperature gradients, cooling-hole rim and bulk metal temperatures, and mechanical stress were investigated by using a finite-element structural analysis of a symmetrical airfoil with and without leading-edge holes. The results indicate that leading-edge film cooling is beneficial when large chordwise temperature gradients exist and if the cooling-hole rim temperatures are above the bulk metal temperature. The effects of film cooling at other locations on the airfoil were not considered, and the relative merits of convection or film cooling at the leading edge, in terms of allowable turbine inlet temperature or coolant flow requirements, were not evaluated.

Kaufman, A.↗

NASA NTRS1974

Metal-olivine associations and Ni-Co contents in two Apollo 12 mare basalts

Olivine crystals in mare basalts 12004,8 and 12022,12 are normally zoned with Cr-poor rims. The Ni content of rare 2- to 10-micron metal inclusions in olivine decreases markedly as Fe/Mg in their immediate olivine hosts increases. Each metal grain appears to have been enclosed by late olivine almost immediately after it crystallized. The fractionation trend for the olivine and metal contrasts with the subsolidus equilibration trend for pallasites. For the basalts, not even local equilibrium of Fe, Ni and Co at metal/olivine interfaces can be detected by microprobe. Ni and Co concentrations range from about 300 ppm in olivine cores to about 70 ppm in rims. The limits of detection, at 95% confidence, are 36 ppm (Ni) and 25 ppm (Co). The distribution of Ni and Co in olivine, like that of Mg and Cr, records the depletion of these elements in the melt.

Hewins, R. H.↗

NASA NTRS1975

The Annular Suspension and Pointing (ASP) system for space experiments and predicted pointing accuracies

An annular suspension and pointing system consisting of pointing assemblies for coarse and vernier pointing is described. The first assembly is attached to a carrier spacecraft (e.g., the space shuttle) and consists of an azimuth gimbal and an elevation gimbal which provide 'coarse' pointing. The second or vernier pointing assembly is made up of magnetic actuators of suspension and fine pointing, roll motor segments, and an instrument or experiment mounting plate around which is attached a continuous annular rim similar to that used in the annular momentum control device. The rim provides appropriate magnetic circuits for the actuators and the roll motor segments for any instrument roll position. The results of a study to determine the pointing accuracy of the system in the presence of crew motion disturbances are presented. Typical 3 sigma worst-case errors are found to be of the order of 0.001 arc-second.

Anderson, W. W.↗

NASA NTRS1975

Calcium-aluminum-rich inclusions in the Allende meteorite - Evidence for a liquid origin

We have made a detailed examination of the mineralogy, textures, and assemblages of six calcium-aluminum-rich inclusions (CAI) in the Allende meteorite. They can be classified into four types - hibonite-bearing, fassaite- and olivine-bearing, feldspathoid-bearing and fassaite-bearing CAI that are hibonite and olivine free. Examples of each type appear to have crystallized from a liquid rather than by agglomeration of solid nebular condensates. Some lines of evidence for a liquid origin are the presence of spherical and ovoid shapes and rims containing minerals that are more refractory than minerals inside the inclusion. Thermodynamic calculations and comparisons with liquidus phase diagrams indicate that the CAI could have been produced by direct condensation to metastable subcooled liquids that subsequently crystallized or by remelting of an equilibrium high-temperature condensate by impact. The diopside rims in some hibonite-bearing CAI and the paucity of metal in fassaite-olivine-bearing CAI are more consistent with direct condensation of a liquid.

Blander, M.↗

NASA NTRS1977

First-order torques and solid-body spinning velocities in intense sound fields

The letter reports an observation of first-order nonzero time-averaged torques and solid-body spinning velocities in intense acoustic fields. The experimental apparatus consisted of a vertical cylindrical rod supported on an air bearing and passing through a box with two loudspeakers centered on adjoining vertical sides. The rim velocity of the cylinder and the torque on the cylinder are measured as functions of air-particle velocity and the phase difference between the x and y components of the particle velocity. It is found that both rim velocity and torque are linear functions of particle velocity. Difficulties in constructing a proper theoretical description of the observed effects are discussed.

Wang, T. G.↗

NASA NTRS1976

High-explosive cratering analogs for bowl-shaped, central uplift, and multiring impact craters

The paper describes six experimental explosion craters in terms of their basic morphology, subsurface structural deformation, and surrounding ejecta blanket. These craters exhibit one or more of the following features: bowl shapes with underlying breccia lens, central uplifts, multirings, terraced walls, rim strata, zones of concentric rim deformation, inner continuous ground cover of ejecta blankets formed by overturned flaps, secondary cratering, and fused alluvium. These craters were formed by large shock wave energy transfers at or near zero heights-of-burst, and it is possible that impact craters with analogous morphologic and structural features may have formed under similar surface energy transfer conditions.

Roddy, D. J.↗

NASA NTRS1977

The nature of the gravity anomalies associated with large young lunar craters

The negative Bouguer anomalies (i.e., mass deficiencies) associated with four young lunar craters are analyzed. Model calculations based on generalizations made from studies of terrestrial impact structures suggest that the major contribution to the Bouguer anomaly for these lunar craters is due to a lens of brecciated material confined within the present crater rim crest and extending vertically to at least a depth of one-third the crater rim diameter. Calculations also reveal a systematic variation in the magnitude of the mass deficiencies with the cube of the crater diameter.

Dvorak, J.↗

NASA NTRS1978

Modification of fresh crater landforms - Evidence from the moon and Mercury

The morphology of fresh lunar and Mercurian craters provides insight into processes of crater formation and modification. Measurements determined for Mercurian craters and compared to previously presented lunar data are depth/diameter, central peak and wall-related mass movement frequencies as functions of diameter, crater rim wall width/rim diameter, rim diameter/floor diameter, and central peak height/rim diameter. Two important results are as follows: (1) there is no evidence for direct gravity scaling of crater morphology, although some slight scaling relationship may be indicated, and (2) mass movements are responsible for the change in depth/diameter relationship observed near 2-km depth and 10-km diameter. The latter result is helpful in explaining gravitational and topographic data which suggest low-density regions beneath large fresh craters.

Malin, M. C.↗

NASA NTRS1978

Analysis of a magnetically suspended, high-performance instrument pointing system

This paper describes a highly accurate auxiliary instrument pointing system which can provide fine pointing for a variety of solar-, stellar-, and Earth-viewing scientific instruments during extended space shuttle orbital missions. This system, called the Annular Suspension and Pointing System (ASPS), consists of pointing assemblies for coarse and vernier pointing. The 'coarse' assembly is attached to the spacecraft (e.g., the space shuttle) and consists of an elevation gimbal and a lateral gimbal to provide coarse pointing. The vernier pointing assembly consists of the payload instrument mounted on a plate around which is attached a continuous annular rim. The vernier assembly is suspended in the lateral gimbal using magnetic actuators which provide rim suspension forces and fine pointing torques. A detailed linearized mathematical model is developed for the ASPS/space shuttle system, and control laws and payload attitude state estimators are designed. Statistical pointing performance is predicted in the presence of stochastic disturbances such as crew motion, sensor noise, and actuator noise.

Joshi, S. M.↗

NASA NTRS1975

The petrogenesis of 77115 and its xenocrysts - Description and preliminary interpretation

77115, a fragment-laden feldspathic pigeonite basalt, is one of four hand specimen-size samples collected from a boulder about 2.5 m across at Station 7, Taurus-Littrow. 77115 crystallized rapidly from a melt at or near the lunar surface and contains a population of xenoliths and xenocrysts which must have come from two or more separate sources. Broad reaction rims present in many of the xenocrysts suggest that cooling of the melt may have been very slow initially and rapid in the latter stage to produce the very fine-grained matrix. If the requirement for two cooling rates can be established, this will favor an endogenous igneous origin rather than an impact origin for the melt. Another interpretation is that the matrix crystallized first, followed by subsolidus reaction between xenocrysts and matrix to form the rims. The Apollo 17 feldspathic pigeonite basalts are postulated to be the dominant rock types of the early lunar crust.

Chao, E. C. T.↗

NASA NTRS1979

Digital controller design: Analysis of the annular suspension pointing system

The Annular Suspension and Pointing System (ASPS) is a payload auxiliary pointing device of the Space Shuttle. The ASPS is comprised of two major subassemblies, a vernier and a coarse pointing subsystem. The experiment is attached to a mounting plate/rim combination which is suspended on magnetic bearing/actuators (MBA) strategically located about the rim. Fine pointing is achieved by gimballing the plate/rim within the MBA gaps. Control about the experiment line-of-sight is obtained through the use of a non-contacting rim drive and positioning torquer. All sensors used to close the servo loops on the vernier system are noncontacting elements. Therefore, the experiment is a free-flyer constrained only by the magnetic forces generated by the control loops.

Kuo, B. C.↗

NASA NTRS1979

The terrestrial cratering record. I - Current status of observations

The location, size and principle characteristics of the currently known proven and probable terrestrial impact craters are compiled. A crater is classified as proven if the structure is associated with meteoritic fragments, and probable if shock metamorphic effects are observed in the target rocks. Proven impact structures have been found to be Pleistocene to Recent in age, while probable impact structures range from Precambrian to Pleistocene. Diameter and age relationships are used to show that a 20 km impact structure will be recognizable as a crater for up to 600 million years, and smaller structures will have shorter lifetimes. Depth-diameter relationships for terrestrial craters show them to be intrinsically shallower than their lunar counterparts, and a transition in crater morphology from simple, or bowl-shaped with an uplifted rim, to complex, with an uplifted center and a depressed rim, is observed with increasing diameter. Shock metamorphic studies have lead to the identification of the type of bolide at a number of probable impact craters, supporting meteoritic origins.

Grieve, R. A. F.↗

NASA NTRS1979

Central peaks in lunar craters - Morphology and morphometry

Fresh lunar craters with diameters from 17 to 175 km are found to display a linear relationship between the central peak morphology and morphometry and such critical crater parameters as rim crest diameter, floor diameter, and substrate. Some other previously established linear relationships have been cited as evidence that floor diameter, peak height, and peak ring diameter are related to the kinetic energy of impact. The two new relations derived in the present work would therefore indicate that the central peaks, too, are related to the kinetic energy of impact, and probably begin to form early in the cratering event as suggested by Milton and Roddy (1972) and Head (1978). There seems to be no obvious reason to expect such linear relationships between central peak diameter and rim crest and floor diameter if the peaks are formed by gravity induced failure of the transient cavity, as suggested by Dence et al. (1968).

Hale, W.↗