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Mckay, David S.

Publications and source records attributed to Mckay, David S..

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

On using a pyroclastic deposit as a manned lunar base site

Hawke et al. (1990) suggest that ilmenite found in Apollo 17-type pyroclastic glass may provide feedstock for the hydrogen reduction of ilmenite process for producing lunar oxygen. They also suggest that the ilmenite may help retain solar wind hydrogen and helium which can be extracted for use at a lunar outpost or even transported back to Earth for fusion fuel in the case of helium-3. Therefore, they suggest that ilmenite-rich material may be the best candidate. Here, researchers propose a somewhat different approach. They propose that the pyroclastic glass can be reduced directly to produce oxygen and one or more metals. Sulfur would be another important byproduct of the processing. This process would eliminate the need for having specific minerals such as ilmenite or for doing any mineral concentration. The bulk pyroclastic would provide the feedstock. Some recent experiments at the Johnson Space Center suggest that an iron-rich composition would be the most suitable for this direct feedstock reduction and that the titanium content may not be important. Also, the lunar pyroclastic deposits would be extremely useful in constructing and supporting a lunar base.

Coombs, Cassandra R.↗
NASA NTRS1991

Experimental reduction of simulated lunar glass by carbon and hydrogen and implications for lunar base oxygen production

The most abundant element in lunar rocks and soils is oxygen which makes up approximately 45 percent by weight of the typical lunar samples returned during the Apollo missions. This oxygen is not present as a gas but is tightly bound to other elements in mineral or glass. When people return to the Moon to explore and live, the extraction of this oxygen at a lunar outpost may be a major goal during the early years of operation. Among the most studied processes for oxygen extraction is the reduction of ilmenite by hydrogen gas to form metallic iron, titanium oxide, and oxygen. A related process is proposed which overcomes some of the disadvantages of ilmenite reduction. It is proposed that oxygen can be extracted by direct reduction of native lunar pyroclactic glass using either carbon, carbon monoxide, or hydrogen. In order to evaluate the feasibility of this proposed process a series of experiments on synthetic lunar glass are presented. The results and a discussion of the experiments are presented.

Mckay, David S.↗
NASA NTRS1991

The violent side of mare volcanism

In the past 15 years it has become increasingly evident that lunar pyroclastic volcanism played an important role in the formation and resurfacing of portions of the Moon. Located on mare/highland boundaries, many of these deposits formed in association with mare volcanism. Based on recently acquired geologic and remote sensing data, two generally distinct types of pyroclastic mantling deposits have been identified: regional and localized. Both the regional dark mantling deposits (RDMD) and localized dark mantling deposits (LDMD) are widely distributed across the lunar nearside. The larger RDMD are typically located in lunar highland areas adjacent to many of the major lunar maria, while the smaller LDMD are found on the floors of pre-Imbrian and Inbrian craters. Both deposits are basaltic in composition and are presumed to have originated at great depth (approx. 300 km). The composition, geometry, and vent morphology of the pyroclastic deposits have been used to infer the eruption mechanisms and emplacement styles for both types of deposits.

Coombs, Cassandra R.↗
NASA NTRS1991

The origin of amorphous rims on lunar plagioclase grains: Solar wind damage or vapor condensates

A distinctive feature of micron sized plagioclase grains from mature lunar soils is a thin (20 to 100 nm) amorphous rim surrounding the grains. These rims were originally described from high voltage electron microscope observations of lunar plagioclase grains by Dran et al., who observed rims up to 100 nm thick on plagioclase grains from Apollo 11 and 12 soils. These rims are believed to be the product of solar wind damage. The amorphous rims were studied on micron sized plagioclase grains from a mature Apollo 16 soil using a JEOL 200FX transmission electron microscope equipped with an energy dispersive x ray spectrometer. It was found that the amorphous rims are compositionally distinct from the interior plagioclase and it is proposed that a major component of vapor condensates is present in the rims.

Keller, Lindsay P.↗
NASA NTRS1991

Transmission electron microscopy of an interplanetary dust particle with links to CI chondrites

The majority of hydrated interplanetary dust particles (IDPs) have compositions that resemble CI and CM chondrites, however, their mineralogies are most similar to the fine grained material in certain altered type-3 carbonaceous and ordinary chondrites. During the transmission electron microscope studies of hydrated IDPs, a unique particle was discovered whose mineralogy is very similar to that reported from CI chondrites. W7013F5 is the first IDP whose mineralogy and chemistry approximates that of CI chondrites. The similarity in mineralogy and mineral chemistry suggests that W7013F5 was altered under conditions similar to those that existed on the CI parent bodies.

Keller, Lindsay P.↗
NASA NTRS1991

Using space resources

The topics covered include the following: reducing the cost of space exploration; the high cost of shipping; lunar raw materials; some useful space products; energy from the moon; ceramic, glass, and concrete construction materials; mars atmosphere resources; relationship to the Space Exploration Initiative (SEI); an evolutionary approach to using space resources; technology development; and oxygen and metal coproduction.

Sullivan, Thomas A.↗
NASA NTRS1991

In-Situ Resource Utilization (ISRU): Surface systems program area of the exploration technology program

The topics presented are covered in viewgraph form and include the following: (1) utilization of Lunar and Mars resources; (2) oxygen - an example of cost savings; (3) In Space Resource Utilization (ISRU); (4) basic resource processing methods; (5) planetary mining; (6) raw materials preparation; (7) validation, testbeds, and flight experiments; (8) mission readiness schedule; and (9) ISRU budget guideline.

Mckay, David S.↗
NASA NTRS1990

An assessment of the meteoritic contribution to the Martian soil

The flux of meteoritic material at Mars was assessed and the perturbations to the indigenous soil produced by the addition of meteoritic material to the Martian soil was determined. Using the measured mass influx at earth and the estimates of the Mars/earth flux ratio, the planet-wide mateoritic mass influx on Mars was found to be between 2700 and 59,000 t/yr. Assuming a uniform distribution into a soil with a mean planetary production rate of 1 m/b.y., it is estimated that this mass influx would produce a meteoritic concentration in the Mars soil ranging from 2 to 29 percent by mass. Experimental measurements which a Mars lander spacecraft could make to determine the fraction of meteoritic material in the soils are suggested.

Flynn, George J.↗
NASA NTRS1990

Results from returned spacecraft surfaces

Meteoroid and space debris impact data obtained from space exposed spacecraft parts or meteoroid experiments is analyzed. The returned space exposed surfaces considered include spacecraft windows, meteoroid experiments exposed on space flights, and samples of opportunity such as foil wrapped around a cosmic ray package. The debris flux is found to exceed the meteoroid flux in creating impact craters smaller than 20 microns in diameter, and may again exceed it for impact structures larger than a few mm in diameter. For impact structures between 100 microns and 1 mm in diameter, the debris flux is found to be several times less than the meteoroid flux. Determining more accurately the meteoroid or orbital debris mass that makes a given crater or hole size remains is considered to be the main remaining problem.

Zook, Herbert A.↗
NASA NTRS1989

Microparticle impacts in space: Results from Solar Max and shuttle witness plate inspections

The Solar Maximum Satellite developed electronic problems after operating successfully in space for several years. Astronauts on Space Shuttle mission STS-41C retrieved the satellite into the orbiter cargo bay, replaced defective components, and re-deployed the repaired satellite into orbit. The defective components were returned to Earth for study. The space-exposed surfaces were examined. The approach and objectives were to: document morphology of impact; find and analyze projectile residue; classify impact by origin; determine flux distribution; and determine implications for space exposure. The purpose of the shuttle witness plate experiment was to detect impacts from PAM D2 solid rocket motor; determine flux and size distribution of particles; and determine abrasion effects on various conditions. Results are given for aluminum surfaces, copper surfaces, stainless steel surfaces, Inconel surfaces, and quartz glass surfaces.

Mckay, David S.↗
NASA NTRS1989

A tenfold increase in the abundance of large solid particles in the stratosphere, as measured over the period 1976-1984

Representative chemical, structural, and morphological analyses of the large (greater than 1 micron diameter) solid particles from three impaction collection surfaces have been performed. These collections sampled the stratosphere at approximately 17-19 km in altitude during 1976, 1981, and 1984. For these sampling periods, the stratospheric solid-particle number densities have been determined to be 0.089, 0.16, and 1.7 particles/cu m of air, respectively, for particles of greater than 1 micron diameter. This rise in solid-particle number density for the stratosphere over the collection period is likely due to the influx of solid rocket exhaust and rocket and satellite debris into the atmosphere in increasingly larger amounts with time. Some of this material is shed from spacecraft during ascent through the atmosphere, but the majority is probably provided during the descent of material from earth's growing belt of debris in low-earth orbit.

Zolensky, Michael E.↗
NASA NTRS1989

Mineralogical and chemical properties of the lunar regolith

The composition of lunar regolith and its attendant properties are discussed. Tables are provided listing lunar minerals, the abundance of plagioclase feldspar, pyroxene, olivine, and ilmenite in lunar materials, typical compositions of common lunar minerals, and cumulative grain-size distribution for a large number of lunar soils. Also provided are charts on the chemistry of breccias, the chemistry of lunar glass, and the comparative chemistry of surface soils for the Apollo sites. Lunar agglutinates, constructional particles made of lithic, mineral, and glass fragments welded together by a glassy matrix containing extremely fine-grained metallic iron and formed by micrometeoric impacts at the lunar surface, are discussed. Crystalline, igneous rock fragments, breccias, and lunar glass are examined. Volatiles implanted in lunar materials and regolith maturity are also addressed.

Mckay, David S.↗
NASA NTRS1988

Lunar hydrogen: A resource for future use at lunar bases and space activities

Hydrogen abundances were determined for grain size separates of five lunar soils and one soil breccia. The hydrogen abundance studies have provided important baseline information for engineering models undergoing study at the present time. From the studies is appears that there is sufficient hydrogen present in selected lunar materials which could be recovered to support future space activities. It is well known that hydrogen can be extracted from lunar soils by heating between 400 and 800 C. Recovery of hydrogen for regolith materials would involve heating with solar mirrors and collecting the released hydrogen. Current baseline models for the lunar base are requiring the production of 1000 metric tons of oxygen per year. From this requirement it follows that around 117 metric tons per year of hydrogen would be required for the production of water. The ability to obtain hydrogen from the lunar regolith would assist in lowering the operating costs of any lunar base.

Gibson, Everett K., Jr.↗
NASA NTRS1988

Glasses in ancient and young Apollo 16 regolith breccias - Populations and ultra Mg-prime glass

Electron microprobe analysis was used to determine the major element compositions of glass spheres and fragments in seven possibly ancient (about 4 Gyr) and three young (less than 4 Gyr) Apollo 16 regolith breccias. It is found that mare glasses are extremely rare in the ancient regolith breccias, and silica-poor gabbroic anorthosite and high-alumina silica-poor glasses are not present in ancient breccias. Ultra Mg-prime glasses are unique to the Apollo 16 regolith breccias and are most common in the ancient breccias. It is suggested that the presence of ultra Mg-prime glasses could indicate the presence of previously unsampled crustal or volcanic rock types on the moon.

Wentworth, Susan J.↗
NASA NTRS1988

Petrology and provenance of Apollo 15 drive tube 15007/8

The petrology of submillimeter fractions of soils from 13 levels of Apollo 15 drive tube 15007/8 have been studied through grain size analysis, modal analysis of the 90-150 micron sieve fraction, and electron probe microanalysis of monomineralic fragments of olivine, pyroxene, and plagioclase from the soils. It is shown that core 15007/8 does not contain distinct lithologic units and probably contains soils of mixed maturity in which mixing has greatly dominated in situ reworking. No petrologic layering is found in the core. Abundances of KREEP basalts correlate with mare basalts and not with anorthosite, norite, and troctolite components from the Apennine Front. Some olivine and pyroxene fragments with mare basalt affinity are found to be optically and chemically unzoned, suggesting that they may have been derived from unusual source rocks.

Basu, Abhijit↗
NASA NTRS1987

Analytical electron microscopy of fine-grained phases in primitive interplanetary dust particles and carbonaceous chondrites

In order to describe the total mineralogical diversity within primitive extraterrestrial materials, individual interplanetary dust particles (IDPs) collected from the stratosphere as part of the JSC Cosmic Dust Curatorial Program were analyzed using a variety of AEM techniques. Identification of over 250 individual grains within one chondritic porous (CP) IDP shows that most phases could be formed by low temperature processes and that heating of the IDP during atmospheric entry is minimal and less than 600 C. In a review of the mineralogy of IDPs, it was suggested that the occurrence of other silicates such as enstatite whiskers is consistent with the formation in an early turbulent period of the solar nebula. Experimental confirmation of fundamental chemical and physical processes in a stellar environment, such as vapor phase condensation, nucleation, and growth by annealing, is an important aspect of astrophysical models for the evolution of the Solar System. A detailed comparison of chondritic IDP and carbonaceous chondrite mineralogies shows significant differences between the types of silicate minerals as well as the predominant oxides.

Mackinnon, Ian D. R.↗
NASA NTRS1986

Chemical zoning and homogenization of olivines in ordinary chondrites and implications for thermal histories of chondrules

The extent and degree of homogenization of chemical zoning of olivines in type 3 ordinary chondrites is studied in order to obtain some constraints on cooling histories of chondrites. Based on Mg-Fe and CaO zoning, olivines in type 3 chondrites are classified into four types. A single chondrule usually contains olivines with the same type of zoning. Microporphyritic olivines show all four zoning types. Barred olivines usually show almost homogenized chemical zoning. The cooling rates or burial depths needed to homogenize the chemical zoning are calculated by solving the diffusion equation, using the zoning profiles as an initial condition. Mg-Fe zoning of olivine may be altered during initial cooling, whereas CaO zoning is hardly changed. Barred olivines may be homogenized during initial cooling because their size is relatively small. To simulated microporphyritic olivine chondrules, cooling from just below the liquidus at moderately high rates is preferable to cooling from above the liquidus at low rates. For postaccumulation metamorphism of type 3 chondrites to keep Mg-Fe zoning unaltered, the maximum metamorphic temperature must be less than about 400 C if cooling rates based on Fe-Ni data are assumed. Calculated cooling rates for both Fa and CaO homogenization are consistent with those by Fe-Ni data for type 4 chondrites. A hot ejecta blanket several tens of meters thick on the surface of a parent body is sufficient to homogenize Mg-Fe zoning if the temperature of the blanket is 600-700 C. Burial depths for petrologic types of ordinary chondrites in a parent body heated by Al-26 are broadly consistent with those previously proposed.

Miyamoto, Masamichi↗