Search NASA⌕ Search

SEARCH · Search NASA

Results for “Resurgence”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Solvent-Producing Clostridia Revisited

The review provides an overview of the current status of the solvent-producing clostridia. The origin and development of industrial clostridial species, as well as the history of the industrial Acetone Butanol Ethanol fermentation process, is reexamined, and the recent resurgence of interest in the production of biobutanol is reviewed. Over 300 fully sequenced genomes for solvent-producing and closely related clostridial species are currently available in public databases. These include 270 genomes sourced from the David Jones culture collection. These genomes were allocated arbitrary DJ codes, and a conversion table to identify the species and strains has now been provided. The expanded genomic database facilitated new comparative genomic and phylogenetic analysis. A synopsis of the common features, molecular taxonomy, and phylogeny of solvent-producing clostridia and the application of comparative phylogenomics are evaluated. A survey and analysis of resident prophages in solvent-producing clostridia are discussed, and the discovery, occurrence, and role of novel R-type tailocins are reported. Prophage genomes with R-type tailocin-like features were detected in all 12 species investigated. The widespread occurrence of tailocins in Gram-negative species is well documented; this survey has indicated that they may also be widespread in clostridia.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1972

Thermal history and early magmatism in the moon.

Lunar heat-flow calculations are carried out for a model moon in which (1) near-surface initial temperatures are very high (as the occurrence of a surface anorthositic layer seems to require), and (2) heat-generating radionuclides are transported upward when melting occurs. Near-surface regions are found to cool and then experience a resurgence of high temperature, as radionuclide-rich magmas from the lunar interior accumulate near the surface. This peaking of near-surface temperature can be brought into correspondence with the episode of vulcanism that gave rise to the basalts represented in the Apollo samples, if we assume relatively high lunar temperatures in early times (due to high initial temperatures, or a high content of radioactive elements, or both).

Wood, J. A.↗
NASA NTRS1974

Mars - Clearing of the 1971 dust storm

A semiquantitative analysis of clearing in the 1971 great dust storm on Mars is presented as a function of time and altitude, using Mariner 9 orange- and visual-light photos. Steady settling of dust approximately accounts for the decline of the storm after Dec. 22, 1971. Continuous settling cannot be invoked prior to that date; injection of dust into the atmosphere, i.e., a storm resurgence, occurred in mid-December 1971. Theoretical models of optical depth vs time are developed for various distributions of particles in the atmosphere. By interpreting settling in terms of Stokes' law, estimates of the maximum radii of dust particles throughout the atmosphere have been obtained. Models which best account for the dust-storm decline indicate particles less than 5 microns in diameter high in the atmosphere, with a concentration of larger particles near the ground in the lowest parts of Mars.

Hartmann, W. K.↗
NASA NTRS1975

Solar heating and cooling of buildings

Solar energy has been used for space heating and water heating for many years. A less common application, although technically feasible, is solar cooling. This paper describes the techniques employed in the heating and cooling of buildings, and in water heating. The potential for solar energy to displace conventional energy sources is discussed. Water heating for new apartments appears to have some features which could make it a place to begin the resurgence of solar energy applications in the United States. A project to investigate apartment solar water heating, currently in the pilot plant construction phase, is described.

Bourke, R. D.↗
NASA NTRS1975

Modification of premare impact craters by volcanism and tectonism

Many lunar craters greater than 10 km in diameter exhibit a variety of morphological characteristics which are not produced by meteorite impact or meteorite erosion. Most such craters are located in or near the margins of the maria. Although some could have resulted from processes such as cauldron resurgence, caldera formation, or ring dike emplacement, most have formed by modification of impact craters by endogenic processes including erosion by flowing lava, fissure volcanism, plutonism, and uplift of crater floors along ring fractures of impact origin.

Brennan, W. J.↗
NASA NTRS1980

Mars Tharsis region - Volcanotectonic events in the stratigraphic record

It is pointed out that the most recent volcanism and much of the oldest tectonic activity on Mars have apparently occurred within the Tharsis region. Detailed geologic mapping from Viking images has provided new information on the evolutionary history of the region. The eruptive sequence and areal extent of lava flows in the Tharsis region have been defined by stratigraphic studies and crater counts made on individual flow units. Faults and fractures transecting these units provide a record of changing tectonic intensity during the period of high volcanic activity. Volcanism began with the resurfacing of basement rocks early in the history of the region and continued without large interruptions through nine major eruptive episodes. Volcanic centers shifted from place to place but resurgent activity occurred at several volcanoes. Volcanism culminated during the foration of large shield volcanoes along Tharsis Montes and thereafter appears to have gradually declined.

Scott, D. H.↗
NASA NTRS1984

Missions and Vehicle Concepts for Modern, Propelled, Lighter-Than-Air Vehicles

The results of studies conducted over the last 15 years to assess missions and vehicle concepts for modern, propelled, lighter-than-air vehicles (airships) were surveyed. Rigid and non-rigid airship concepts are considered. The use of airships for ocean patrol and surveillance is discussed along with vertical heavy lift airships. Military and civilian needs for high altitude platforms are addressed. Around 1970 a resurgence of interest about lighter-than-air vehicles (airships) occurred in both the public at large and in certain isolated elements of the aerospace industry. Such renewals of airship enthusiasm are not new and have, in fact, occurred regularly since the days of the Hindenburg and other large rigid airships. However, the interest that developed in the early 1970's has been particularly strong and self-sustaining for a number of good reasons. The first is the rapid increase in fuel prices over the last decade and the common belief (usually true) that airships are the most fuel efficient means of air transportation. Second, a number of new mission needs have arisen, particularly in surveillance and patrol and in vertical heavy-lift, which would seem to be well-suited to airship capabilities. The third reason is the recent proposal of many new and innovative airship concepts. Finally, there is the prospect of adapting to airships the tremendous amount of new aeronautical technology which has been developed in the past few decades thereby obtaining dramatic new airship capabilities. The primary purpose of this volume is to survey the results of studies, conducted over the last 15 years, to assess missions and vehicle concepts for modern propelled lighter-than-air vehicles.

Ardema, M. D.↗
NASA NTRS1986

Geophysical characteristics and crustal structure of greenstone terranes: Canadian Shield

Geophysical studies in the Canadian Shield have provided some insights into the tectonic setting of greenstone belts. Greenstone belts are not rooted in deep crustal structures. Geophysical techniques consistently indicate that greenstones are restricted to the uppermost 10 km or so of crust and are underlain by geophysically normal crust. Gravity models suggest that granitic elements are similarly restricted, although magnetic modelling suggests possible downward extension to the intermediate discontinuity around approx. 18 km. Seismic evidence demonstrates that steeply-dipping structure, which can be associated with the belts in the upper crust, is not present in the lower crust. Horizontal intermediate discontinuities mapped under adjacent greenstone and granitic components are not noticeably disrupted in the boundary zone. Geophysical evidence points to the presence of discontinuities between greenhouse-granite and adjacent metasedimentary erranes. Measured stratigraphic thicknesses of greenstone belts are often twice or more the vertical thicknesses determined from gravity modelling. Explantations advanced for the discrepancy include stratigraphy repeated by thrust faulting and/or listric normal faulting, mechanisms which are consistent with certain aspects of conceptual models of greenstone development. Where repetition is not a factor the gravity evidence points to removal of the root zones of greenstone belts. For one region, this has been attributed to magmatic stopping during resurgent caldera activity.

Thomas, M. D.↗
NASA NTRS1987

Resonant Alfven waves on auroral field lines

It is shown that resonant Alfven waves on dipole magnetic field geometry and plasma distributions suitable for auroral field lines can be conventiently treated in the theory of Mathieu functions. Resurgent interest in invoking large-scale Alfven waves to structure some elements of auroral electrodynamics calls for interpretation of measured perpendicular electric and magnetic disturbance fields in terms of Alfven waves. The ability to express the resonant eigenmodes in closed form in terms of Mathieu functions allows for convenient tests of the Alfven wave structuring hypothesis. Implications for current vector electric and magnetic disturbance measurements are discussed.

Chiu, Y. T.↗
NASA NTRS1986

Review of convectively cooled structures for hypersonic flight

Resurgent interest in development of Aerospace Plane and Orient Express type vehicles promises to stretch structural technology for hypersonic flight vehicles to the uppermost limits. Significant portions of the structure may require active cooling of some type to survive hostile environments. Despite a lack of recent research activity for cooled structures, a significant body of unclassified knowledge exists concerning such structures. Contractual and in-house research conducted mainly by NASA's Langley Research Center during the 60's and 70's on vehicles very similar to the proposed Orient Express has provided a substantial data base for convectively cooled hypersonic flight structures. Specifically, results are presented for regeneratively cooled structural concepts which have a relatively high heat flux capability and use the hydrogen fuel directly as a coolant; and for structural concepts which use a secondary coolant loop to absorb incident heating and then transfer the absorbed heat to the liquid hydrogen fuel as it flows to the engines. Results are presented to indicate application regions in terms of heat flux capability for various concepts and benefits for each concept. Experience gained and costs are discussed in terms of heat flux capability for various concepts and benefits for each concept. Additionally, experience gained and cost involved with design, fabrication, and testing of full-scale convectively cooled structures are discussed.

Shore, Charles P.↗
NASA NTRS1988

The effect of the near earth micrometeoroid environment on a highly reflective mirror surface

A resurgence of interest in placing large solar concentrator solar dynamic systems in space for power generation has brought up again a concern for maintaining the integrity of the optical properties of highly specular reflecting surfaces in the near earth space environment. One of the environmental hazards needing evaluation is the micrometeoroid environment. It has been shown that highly reflective polished metals and thin film coatings degrade when exposed to simulated micrometeoroids in the lab. At NASA-Lewis, a shock tube was used to simulate the phenomenon of micrometeoroid impact by accelerating micron sized particles to hypervelocities. Any changes in the optical properties of surfaces exposed to this impact were then evaluated. The degradation of optical properties of polished metals and thin metallic films after exposure to simulated micrometeoroids was determined as a function of impacting kinetic energy area of the particles. A calibrated sensor was developed to not only detect the micrometeoroid environment, but also to evaluate the degradation of the optical properties of thin aluminum films in space. Results of the simulation are presented and discussed.

Mirtich, Michael J.↗
NASA NTRS1989

Survey Of Wind Tunnels At Langley Research Center

Report presented at AIAA 14th Aerodynamic Testing Conference on current capabilities and planned improvements at NASA Langley Research Center's major wind tunnels. Focuses on 14 major tunnels, 8 unique in world, 3 unique in country. Covers Langley Spin Tunnel. Includes new National Transonic Facility (NTF). Also surveys Langley Unitary Plan Wind Tunnel (UPWT). Addresses resurgence of inexpensive simple-to-operate research tunnels. Predicts no shortage of tools for aerospace researcher and engineer in next decade or two.

Bower, Robert E.↗
NASA NTRS1989

NASA directions in space propulsion for 2000 and beyond

In his National Space Policy of 1988, President Reagan committed to a goal of expanding human presence and activity in the solar system. This goal has provided the impetus for a resurgence of activity in a broad range of space technology efforts in general and for a number of propulsion technology programs in particular. Building on recommendations from several detailed studies of the U.S. space program, NASA has increased the level of investment in propulsion technology development. The Civil Space Technology Initiative is developing propulsion technology in support of near-Earth operations. These efforts are focused on both main and booster engines and seek to provide design methods and databases to support future developments of low cost, reliable transportation systems. Program elements include turbomachinery, combustion systems, and condition monitoring and diagnostics, and the design methodology developed at component levels will be verified in large scale systems. The Pathfinder program is developing a suite of technologies to enable a broad range of manned and unmanned missions beyond Earth's orbit. These include both chemical and electric propulsion technologies to support potential missions to the moon and Mars.

Reck, Gregory M.↗
NASA NTRS1989

Advanced computational techniques for hypersonic propulsion

Computational Fluid Dynamics (CFD) has played a major role in the resurgence of hypersonic flight, on the premise that numerical methods will allow performance of simulations at conditions for which no ground test capability exists. Validation of CFD methods is being established using the experimental data base available, which is below Mach 8. It is important, however, to realize the limitations involved in the extrapolation process as well as the deficiencies that exist in numerical methods at the present time. Current features of CFD codes are examined for application to propulsion system components. The shortcomings in simulation and modeling are identified and discussed.

Povinelli, Louis A.↗
NASA NTRS1988

Thickness and volume of mare deposits in Tsiolkovsky, lunar farside

In the 193-km crater Tsiolkovsky on the lunar far side, dark mare deposits overlie a brighter unit presumed to be impact melt. Craters impacting through the mare materials commonly excavate the underlying impact melt and form a high-albedo ejecta deposit. Apollo metric photographs of Tsiolkovsky were divided into 25-sq-km bins, and within each bin a crater was statistically determined to be the minimum size necessary to excavate underlying impact-melt materials. This 'threshold' crater diameter was measured, and the corresponding depth of excavation was determined based on Maxwell's (1973) Z-model calculations. Crater excavation depths were related to mare thicknesses, and an isopach map was derived that shows an average mare thickness of 22.3 m and a maximum thickness of over 70 m. Based on these data, the most probable average thickness is 116 m with a corresponding mare volume of 1182 cu km. Comparing topographic data to those more accurately determined through impact crater excavation indicates that a possible floor resurgence of up to 95 m may have occurred prior to and during mare emplacement.

Craddock, Robert A.↗
NASA NTRS1988

The effect of the near earth micrometeoroid environment on a highly reflective mirror surface

A resurgence of interest in placing large solar concentrator solar dynamic systems in space for power generation has brought up again a concern for maintaining the integrity of the optical properties of highly specular reflecting surfaces in the near earth space environment. One of the environmental hazards needing evaluation is the micrometeoroid environment. It has been shown that highly reflective polished metals and thin film coatings degrade when exposed to simulated micrometeoroids in the lab. At NASA-Lewis, a shock tube was used to simulate the phenomenon of micrometeoroid impact by accelerating micron sized particles to hypervelocities. Any changes in the optical properties of surfaces exposed to this impact were then evaluated. The degradation of optical properties of polished metals and thin metallic films after exposure to simulated micrometeoroids was determined as a function of impacting kinetic energy area of the particles. A calibrated sensor was developed to not only detect the micrometeoroid environment, but also to evaluate the degradation of the optical properties of thin aluminum films in space. Results of the simulation are presented and discussed.

Mirtich, Michael J.↗
NASA NTRS1989

Late quaternary geomorphology of the Great Salt Lake region, Utah, and other hydrographically closed basins in the western United States: A summary of observations

Attributes of Quaternary lakes and lake basins which are often important in the environmental prehistory of semideserts are discussed. Basin-floor and basin-closure morphometry have set limits on paleolake sizes; lake morphometry and basin drainage patterns have influenced lacustrine processes; and water and sediment loads have influenced basin neotectonics. Information regarding inundated, runoff-producing, and extra-basin spatial domains is acquired directly from the paleolake record, including the littoral morphostratigraphic record, and indirectly by reconstruction. Increasingly detailed hypotheses regarding Lake Bonneville, the largest late Pleistocene paleolake in the Great Basin, are subjects for further testing and refinement. Oscillating transgression of Lake Bonneville began about 28,000 yr B.P.; the highest stage occurred about 15,000 yr B.P., and termination occurred abruptly about 13,000 yr B.P. A final resurgence of perennial lakes probably occurred in many subbasins of the Great Basin between 11,000 and 10,000 yr B.P., when the highest stage of Great Salt Lake (successor to Lake Bonneville) developed the Gilbert shoreline. The highest post-Gilbert stage of Great Salt Lake, which has been one of the few permanent lakes in the Great Basin during Holocene time, probably occurred between 3,000 and 2,000 yr B.P.

Currey, Donald R.↗