Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “surface modifications”

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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Geologic Mapping of the Olympus Mons Volcano, Mars

We are in the third year of a three-year Mars Data Analysis Program project to map the morphology of the Olympus Mons volcano, Mars, using ArcGIS by ESRI. The final product of this project is to be a 1:1,000,000-scale geologic map. The scientific questions upon which this mapping project is based include understanding the volcanic development and modification by structural, aeolian, and possibly glacial processes. The project s scientific objectives are based upon preliminary mapping by Bleacher et al. [1] along a approx.80-km-wide north-south swath of the volcano corresponding to High Resolution Stereo Camera (HRSC) image h0037. The preliminary project, which covered approx.20% of the volcano s surface, resulted in several significant findings, including: 1) channel-fed lava flow surfaces are areally more abundant than tube-fed surfaces by a ratio of 5:1, 2) channel-fed flows consistently embay tube-fed flows, 3) lava fans appear to be linked to tube-fed flows, 4) no volcanic vents were identified within the map region, and 5) a Hummocky unit surrounds the summit and is likely a combination of non-channelized flows, dust, ash, and/or frozen volatiles. These results led to the suggestion that the volcano had experienced a transition from long-lived tube-forming eruptions to more sporadic and shorter-lived, channel-forming eruptions, as seen at Hawaiian volcanoes between the tholeiitic shield building phase (Kilauea to Mauna Loa) and alkalic capping phase (Hualalai and Mauna Kea).

Bleacher, J. E.↗
NASA NTRS1988

Evaluation of vegetation effects on the generation and modification of mesoscale circulations

The effects of the presence of vegetation cover on modifying sea breeze and thermally induced upslope flows during daytime were investigated, and the possibility of the generation of mesoscale circulations due to nonuniform vegetation cover was evaluated. Scale analysis and numerical model simulations were used to provide quantitative evaluations of the circulations involved in the two vagetation effects, using several illustrative cases. The cases considered demonstrate that the impact of vegetated surfaces is highly dependent on the environmental conditions as well as vegetation characteristics.

Segal, M.↗
NASA NTRS1991

Combined Backscatter Moessbauer Spectrometer and X Ray Fluorescence analyzer (BaMS/XRF) for planetary surface materials

A backscatter Moessbauer spectrometer (BaMS) with included x ray fluorescence (XRF) capability for the Mars Environment Survey (MESUR) Mission, which has been proposed by NASA for 1998, is being developed. The instrument will also be suitable for other planetary missions such as those to the Moon, asteroids, and other solid solar-system objects. The BaMS would be unique for MESUR in providing information about iron mineralogy in rocks, clays, and other surface materials, including relative proportions of iron-bearing minerals. It requires no sample preparation and can identify all the normal oxidation states of iron (3+, 2+, 0). Thus, BaMS is diagnostic for weathering and other soil-forming processes. Backscatter design allows the addition of XRF elemental analysis with little or no modification. The BaMS/XRF instrument complements the thermal analyzer with evolved gas analyzer (TA-EGA) and the alpha-proton x-ray spectrometer (APXS) proposed (along with BaMS) for geochemical analysis on MESUR.

Agresti, D. G.↗
NASA NTRS1995

The 1994 TIMS airborne calibration experiment: Castaic Lake, California

This summary describes the 9 March 1994 Thermal Infrared Multispectral Scanner (TIMS) airborne calibration experiment conducted at Castaic Lake, California. This experiment was a collaborative effort between the TIMS and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) science teams at the Jet Propulsion Laboratory (JPL). TIMS was flown on the NASA/Ames Research Center C130 with the new retractable air fence installed in the TIMS instrument bay. The purpose of this experiment was to determine if the fence would reduce the air turbulence in the TIMS instrument bay, thereby reducing the errors in calibration caused by wind-blast cooling of the blackbody reference sources internal to TIMS. Previous experiments have indicated that the wind blast effect could cause TIMS to over-estimate surface temperatures by more than 10 C. We have examined the TIMS data from twelve lines flown over Castaic Lake. Four of the lines were flown at an altitude of approximately 2.5 km (MSL), four at an altitude of approximately 6.7 km, and four at approximately 8.3 km. At each altitude there were flights with northern and southern headings, with the aircraft level and at a positive pitch (nose-up attitude). The suite of twelve flights was designed to subject the TIMS/air fence system to different wind conditions and air temperatures. The TIMS flights were supported by a ground-truth team, who measured lake surface temperatures from a boat, and an atmosphere characterization team, who launched an airsonde and measured solar irradiance with a Reagan Sun Photometer. The Reagan measurements were used to construct a time-series of estimates of the total abundance of water vapor in the atmospheric column. These estimates were used to constrain modifications of the airsonde water vapor profile measurements made when processing the TIMS data with a customized version of the MODTRAN radiative transfer code.

Realmuto, Vincent J.↗
NASA NTRS1994

Summertime tropospheric ozone distributions over central and eastern Canada

Ozone measurements were obtained between the surface and the 6-km altitude on aircraft flights over central and eastern Canada during the summer 1990 NASA Global Tropospheric Experiment Arctic Boundary Layer Expedition (GTE/ABLE 3B). Tropospheric O3 budgets for these regions were observed to be highly variable and significantly impacted by long-range transport and regional scale air mass modification processes. For example, integrated O3 abundance below 5-km altitude averaged 40% and 30% greater in air masses influenced by anthropogenic sources and biomass burning, respectively, than in background (polar) air. Conversely, aged air transported from subtropical areas of the Pacific at times reduced O3 abundance in this height interval by up to 20%. Though intrusion of anthropogenic air was infrequent during the experiment period, the influence of biomass-burning emissions was particularly notable as two thirds of the flights sampled air influenced by plumes from fires burning in Alaska and western Canada. The impinging pollution, both natural and anthropogenic, not only elevated O3 levels directly but also was a source of reactive nitrogen (and nonmethane hydrocarbons) which generally increases the tropospheric lifetime of O3 via moderation of photochemical destruction rates.

Anderson, B. E.↗
NASA NTRS2007

Joint Test Report for Validation of Alternative Low-Emission Surface Preparation/Depainting Technologies for Structural Steel

Headquarters National Aeronautics and Space Administration (NASA) chartered the NASA Acquisition Pollution Prevention (AP2) Office to coordinate agency activities affecting pollution prevention issues identified during system and component acquisition and sustainment processes. The primary objectives of the AP2 Office are to: (1) Reduce or eliminate the use of hazardous materials or hazardous processes at manufacturing, remanufacturing, and sustainment locations. (2) Avoid duplication of effort in actions required to reduce or eliminate hazardous materials through joint center cooperation and technology sharing. The objective of this project was to qualify candidate alternative Low-Emission Surface Preparation/Depainting Technologies for Structural Steel applications at NASA facilities. This project compares the surface preparation/depainting performance of the proposed alternatives to existing surface preparation/depainting systems or standards. This Joint Test Report (JTR) contains the results of testing as per the outlines of the Joint Test Protocol (JTP), Joint Test Protocol for Validation of Alternative Low-Emission Surface Preparation/Depainting Technologies for Structural Steel, and the Field Test Plan (FTP), Field Evaluations Test Plan for Validation of Alternative Low-Emission Surface Preparation/Depainting Technologies for Structural Steel, for critical requirements and tests necessary to qualify alternatives for coating removal systems. These tests were derived from engineering, performance, and operational impact (supportability) requirements defined by a consensus of government and industry participants. This JTR documents the results of the testing as well as any test modifications made during the execution of the project. This JTR is made available as a reference for future pollution prevention endeavors by other NASA Centers, the Department of Defense and commercial users to minimize duplication of effort. The current coating removal processes identified herein are for polyurethane, epoxy and other paint systems applied by conventional wet-spray processes. A table summarizes the target hazardous materials, processes and materials, applications, affected programs, and candidate substrates.

Lewis, Pattie↗
NASA NTRS1995

Intelligent automated surface grid generation

The goal of our research is to produce a flexible, general grid generator for automated use by other programs, such as numerical optimizers. The current trend in the gridding field is toward interactive gridding. Interactive gridding more readily taps into the spatial reasoning abilities of the human user through the use of a graphical interface with a mouse. However, a sometimes fruitful approach to generating new designs is to apply an optimizer with shape modification operators to improve an initial design. In order for this approach to be useful, the optimizer must be able to automatically grid and evaluate the candidate designs. This paper describes and intelligent gridder that is capable of analyzing the topology of the spatial domain and predicting approximate physical behaviors based on the geometry of the spatial domain to automatically generate grids for computational fluid dynamics simulators. Typically gridding programs are given a partitioning of the spatial domain to assist the gridder. Our gridder is capable of performing this partitioning. This enables the gridder to automatically grid spatial domains of wide range of configurations.

Yao, Ke-Thia↗
NASA NTRS1974

Io - A surface evaporite deposit

A model is suggested for Io's surface composition involving evaporite salt deposits, rich in sodium and sulfur. According to this model, these deposits were produced as a result of the migration of salt-saturated aqueous solutions to Io's surface from a warm or hot interior followed by loss of the water to space. This model satisfies cosmochemical constraints based on Io's initial composition, current density, and thermal history. Salt-rich assemblages are easily derivable from the leaching of carbonaceous chondritic material. The chemical and optical properties of such deposits, after modification by irradiation, can be used to explain Io's overall albedo and spectral reflectance, its dark reddish poles, and the observed sodium emission as well as or better than other currently suggested materials.

Fanale, F. P.↗
NASA NTRS1990

Project summaries

Lunar base projects, including a reconfigurable lunar cargo launcher, a thermal and micrometeorite protection system, a versatile lifting machine with robotic capabilities, a cargo transport system, the design of a road construction system for a lunar base, and the design of a device for removing lunar dust from material surfaces, are discussed. The emphasis on the Gulf of Mexico project was on the development of a computer simulation model for predicting vessel station keeping requirements. An existing code, used in predicting station keeping requirements for oil drilling platforms operating in North Shore (Alaska) waters was used as a basis for the computer simulation. Modifications were made to the existing code. The input into the model consists of satellite altimeter readings and water velocity readings from buoys stationed in the Gulf of Mexico. The satellite data consists of altimeter readings (wave height) taken during the spring of 1989. The simulation model predicts water velocity and direction, and wind velocity.

Source record↗
NASA NTRS1993

The Influence of Swirl Brakes and a Tip Discharge Orifice on the Rotordynamic Forces Generated by Discharge-to-Suction Leakage Flows in Shrouded Centrifugal Pumps

Recent experiments conducted in the Rotor Force Test Facility at the California Institute of Technology have examined the effects of a tip leakage restriction and swirl brakes on the rotordynamic forces due to leakage flows on an impeller undergoing a prescribed circular whirl. The experiments simulate the leakage flow conditions and geometry of the Alternate Turbopump Design (ATD) of the Space Shuttle High Pressure Oxygen Turbopump and are critical to evaluating the pump's rotordynamic instability problems. Previous experimental and analytical results have shown that discharge-to-suction leakage flows in the annulus of a shrouded centrifugal pump contribute substantially to the fluid induced rotordynamic forces. Also, previous experiments have shown that leakage inlet (pump discharge) swirl can increase the cross-coupled stiffness coefficient and hence increase the range of positive whirl for which the tangential force is destabilizing. In recent experimental work, the present authors demonstrated that when the swirl velocity within the leakage path is reduced by the introduction of ribs or swirl brakes, then a substantial decrease in both the destabilizing normal and tangential forces could be achieved. Motivation for the present research is that previous experiments have shown that restrictions such as wear rings or orifices at pump inlets affect the leakage forces. Recent pump designs such as the Space Shuttle Alternate Turbopump Design (ATD) utilize tip orifices at discharge for the purpose of establishing axial thrust balance. The ATD has experienced rotordynamic instability problems and one may surmise that these tip discharge orifices may also have an important effect on the normal and tangential forces in the plane of impeller rotation. The present study determines if such tip leakage restrictions contribute to undesirable rotordynamic forces. Additional motivation for the present study is that the widening of the leakage path annular clearance and the installation of swirl brakes in the ATD has been proposed to solve its instability problems. The present study assesses the effect of such a design modification on the rotordynamic forces. The experimental apparatus consists of a solid or dummy impeller, a housing instrumented for pressure measurements, a rotating dynamometer and an eccentric whirl mechanism. The solid impeller is used so that leakage flow contributions to the forces are measured, but the main throughflow contributions are not experienced. The inner surface of the housing has been modified to accommodate meridional ribs or swirl brakes within the leakage annulus. In addition, the housing has been modified to accommodate a discharge orifice that qualitatively simulates one side of the balance piston orifice of the Space Shuttle ATD. Results indicate the detrimental effects of a discharge orifice and the beneficial effects of brakes. Plots of the tangential and normal forces versus whirl ratio show a substantial increase in these forces along with destabilizing resonances at some positive whirl ratios when a discharge orifice is added. When brakes are added, some of the detrimental effects of the orifice are reduced. For the tangential force, a plot versus whirl ratio shows a significant reduction and a destabilizing resonance appears to be eliminated. For the normal force, although the overall force is not reduced, again a destabilizing resonance appears to be eliminated.

Sivo, Joseph M.↗
NASA NTRS1998

A Simulation of Biological Prosesses in the Equatorial Pacific Warm Pool at 165 deg E

A nine-year simulation (1984-1992) of biological processes in the equatorial Pacific Warm Pool is presented. A modified version of the 4-component (phytoplankton, zooplankton, nitrate and ammonium) ecosystem model by McClain et al. (1996) is used. Modifications include use of a spectral model for computation of PAR and inclusion of fecal pellet remineralization and ammonium nitrification. The physical parameters (horizontal and vertical velocities and temperature) required by the ecosystem model were derived from an improved version of the Gent and Cane (1990) ocean general circulation model (Murtugudde and Busalacchi, 1997). Surface downwelling spectral irradiance was estimated using the clear-sky models of Frouin et al. (1989) and Gregg and Carder (1990) and cloud cover information from the International Satellite Cloud Climatology Project (ISCCP). The simulations indicate considerable variability on interannual time scales in all four ecosystem components. In particular, surface chlorophyll concentrations varied by an order of magnitude with maximum values exceeding 0.30 mg/cu m in 1988, 1989, and 1990, and pronounced minimums during 1987 and 1992. The deep chlorophyll maximum ranged between 75 and 125 meters with values occasionally exceeding 0.40 mg/cu m. With the exception of the last half of 1988, surface nitrate was always near depletion. Ammonium exhibited a subsurface maximum just below the DCM with concentrations as high as 0.5 mg-atN/cu m . Total integrated annual primary production varied between 40 and 250 gC/sq m/yr with an annual average of 140 gC/sq m/yr. Finally, the model is used to estimate the mean irradiance at the base of the mixed layer, i.e., the penetration irradiance, which was 18 Watts/sq m over the nine year period. The average mixed layer depth was 42 m.

McClain, Charles R.↗
NASA NTRS2010

A Study of Parallels Between Antarctica South Pole Traverse Equipment and Lunar/Mars Surface Systems

The parallels between an actual Antarctica South Pole re-supply traverse conducted by the National Science Foundation (NSF) Office of Polar Programs in 2009 have been studied with respect to the latest mission architecture concepts being generated by the United States National Aeronautics and Space Administration (NASA) for lunar and Mars surface systems scenarios. The challenges faced by both endeavors are similar since they must both deliver equipment and supplies to support operations in an extreme environment with little margin for error in order to be successful. By carefully and closely monitoring the manifesting and operational support equipment lists which will enable this South Pole traverse, functional areas have been identified. The equipment required to support these functions will be listed with relevant properties such as mass, volume, spare parts and maintenance schedules. This equipment will be compared to space systems currently in use and projected to be required to support equivalent and parallel functions in Lunar and Mars missions in order to provide a level of realistic benchmarking. Space operations have historically required significant amounts of support equipment and tools to operate and maintain the space systems that are the primary focus of the mission. By gaining insight and expertise in Antarctic South Pole traverses, space missions can use the experience gained over the last half century of Antarctic operations in order to design for operations, maintenance, dual use, robustness and safety which will result in a more cost effective, user friendly, and lower risk surface system on the Moon and Mars. It is anticipated that the U.S Antarctic Program (USAP) will also realize benefits for this interaction with NASA in at least two areas: an understanding of how NASA plans and carries out its missions and possible improved efficiency through factors such as weight savings, alternative technologies, or modifications in training and operations.

Mueller, Robert P.↗
NASA NTRS2011

The Effect of Different Operations Modes on Science Capabilities During the 2010 Desert-RATS Test: Insights from the Geologist Crewmembers

The 2010 Desert RATS field test utilized two Space Exploration Vehicles (prototype planetary rovers) and four crewmembers (2 per rover) to conduct a geologic traverse across northern Arizona while testing continuous and twice-per-day communications paired with operation modes of separating and exploring individually (Divide & Conquer) and exploring together (Lead & Follow), respectively. This report provides qualitative conclusions from the geologist crewmembers involved in this test as to how these modes of communications and operations affected our ability to conduct field geology. Each mode of communication and operation provided beneficial capabilities that might be further explored for future Human Spaceflight Missions to other solar system objects. We find that more frequent interactions between crews and an Apollo-style Science Team on the Earth best enables scientific progress during human exploration. However, during multiple vehicle missions, this communication with an Earth-based team of scientists, who represent "more minds on the problem", should not come at the exclusion of (or significantly decrease) communication between the crewmembers in different vehicles who have the "eyes on the ground". Inter-crew communications improved when discussions with a backroom were infrequent. Both aspects are critical and cannot be mutually exclusive. Increased vehicle separation distances best enable encounters with multiple geologic units. However, seemingly redundant visits by multiple vehicles to the same feature can be utilized to provide improved process-related observations about the development and modification of the local terrain. We consider the value of data management, transfer, and accessibility to be the most important lesson learned. Crews and backrooms should have access to all data and related interpretations within the mission in as close to real-time conditions as possible. This ensures that while on another planetary surface, crewmembers are as educated as possible with respect to the observations and data they will need to collect at any moment.

Bleacher, Jacob E.↗
NASA NTRS2017

Thermally-Conductive Metallic Coatings and Applications for Heat Removal on In-Space Cryogenic Vehicles

For large in-space cryogenic upper stages, substantial axial heat removal from a forward skirt by vapor-based heat interception may not be achieved by simple attachment methods unless sufficient thermal conductance from the skirt to the cooling fluid can be achieved. Preferable methods would allow for the addition of the cooling system to existing structure with minimal impact on the structure. Otherwise, significant modification to the basic structural design andor novel and complex attachment mechanisms with high effective thermal conductance are likely to be required. The approach being pursued by evolvable Cryogenics (eCryo) is to increase the thermal performance of a relatively simple attachment system by applying metallic or other thermally conductive material coatings to the mating surface area of the fluid channel where it is attached the skirt wall. The expectation of candidate materials is that the dramatic increase in conductivity of pure metals at temperatures close to liquid hydrogen vapor temperature will compensate for the reduced actual contact area typical of mechanical joints. Basic contact conductance data at low temperatures for candidate interface materials is required to enable the test approach. A test rig was designed at NASA Glenn Research Center to provide thermal contact resistance testing between small sample coupons coated with conductive material via electron beam evaporation, a low-temperature option that will not affect physical properties of base materials. Average coating thicknesses were 10 k. The test fixture was designed to mount directly to a cryocooler cold head within a vacuum test chamber. The purpose of this test was to determine qualitative contact conductance between various test samples. Results from this effort will be implemented in a sub-scale vapor-based heat interception test, where the applicability for increased heat removal on large structural skirts will be considered.

small scale testing↗
NASA NTRS2011

Atmospheric Chemistry Over Southern Africa

During the southern African dry season, regional haze from mixed industrial pollution, biomass burning aerosol and gases from domestic and grassland fires, and biogenic sources from plants and soils is worsened by a semi-permanent atmosphere gyre over the subcontinent. These factors were a driver of several major international field campaigns in the 1990s and early 2000s, and attracted many scientists to the region. Some researchers were interested in understanding fundamental processes governing chemistry of the atmosphere and interaction with climate change. Others found favorable conditions for evaluating satellite-derived measurements of atmospheric properties and a changing land surface. With that background in mind a workshop on atmospheric chemistry was held in South Africa. Sponsored by the International Commission for Atmospheric Chemistry and Global Pollution (ICACGP; http://www.icacgp.org/), the workshop received generous support from the South African power utility, Eskom, and the Climatology Research Group of the University of the Witwatersrand, Johannesburg, South Africa. The purpose of the workshop was to review some earlier findings as well as more recent findings on southern African climate vulnerability, chemical changes due to urbanization, land-use modification, and how these factors interact. Originally proposed by John Burrows, president of ICACGP, the workshop was the first ICACGP regional workshop to study the interaction of air pollution with global chemical and climate change. Organized locally by the University of the Witwatersrand, the workshop attracted more than 60 delegates from South Africa, Mozambique, Botswana, Zimbabwe, France, Germany, Canada, and the United States. More than 30 presentations were given, exploring both retrospective and prospective aspects of the science. In several talks, attention was focused on southern African chemistry, atmospheric pollution monitoring, and climate processes as they were studied in the field campaigns such as Transport and Atmospheric Chemistry Near the Equator-Atlantic (TRACE-A), Southern African Fire-Atmosphere Research Initiative (SAFARI-92), and Southern African Regional Science Initiative (SAFARI 2000). Since those large international efforts, satellites have matured enough to enable quantifiable measurements of regional land surface, atmosphere, and ocean. In addition, global and chemical transport models have also been advanced to incorporate various data. Thus, the timing of the workshop was right for a full-fledged re-assessment of the chemistry, physics, and socio-economical impacts caused by pollution in the region, including a characterization of sources, deposition, and feedbacks with climate change.

Gatebe, Charles K.↗
NASA NTRS1982

Nucleation theory - Is replacement free energy needed?

It has been suggested that the classical theory of nucleation of liquid from its vapor as developed by Volmer and Weber (1926) needs modification with a factor referred to as the replacement free energy and that the capillary approximation underlying the classical theory is in error. Here, the classical nucleation equation is derived from fluctuation theory, Gibb's result for the reversible work to form a critical nucleus, and the rate of collision of gas molecules with a surface. The capillary approximation is not used in the derivation. The chemical potential of small drops is then considered, and it is shown that the capillary approximation can be derived from thermodynamic equations. The results show that no corrections to Volmer's equation are needed.

Doremus, R. H.↗
NASA NTRS1978

An investigation into the role of plastic failure in crater modification

The mechanical stability of an impact crater is analyzed in this paper via a quasi-static, axisymmetric slip line theory of plasticity. The yield model incorporated is Mohr-Coulomb and a simplified rectangular profile is used for the transient cavity. The degree of stability (or instability) is described as a function of internal friction angle, depth/diameter ratio, and a dimensionless parameter. To match the observed slumping of large lunar craters the cohesion strength of the lunar surface material must be low (less than 20 bars) and the angle of internal friction must be less than 2 deg. It is not implausible that these failure strength characteristics are realized by freshly shocked rock.

Mckinnon, W. B.↗
NASA NTRS1980

Stratospheric aerosol modification by supersonic transport and space shuttle operations - Climate implications

The potential effects on stratospheric aerosols of supersonic transport emissions of sulfur dioxide gas and submicron soot granules, and space shuttle rocket emissions of aluminum oxide particulates are estimated. An interactive particle-gas model of the stratospheric aerosol layer is used to calculate changes due to exhaust emissions, and an accurate radiation transport model is employed to compute the effect of aerosol changes on the earth's average surface temperature. It is concluded that the release of large numbers of small particles (soot or aluminum oxide) into the stratosphere should not lead to a corresponding significant increase in the concentration of large, optically active aerosols, but that the increase in large particles is severely limited by the total mass of sulfate available to make large particles in situ, and by the rapid loss of small seed particles via coagulation. We find that a fleet of several hundred advanced supersonic aircraft operating daily at 20 km, or the launch of one space shuttle rocket per week, could produce roughly a 20% increase in the large-particle concentration of the stratosphere. We find, in addition, that aerosol increases of this magnitude would reduce the global surface temperature by less than 0.01 K.

Turco, R. P.↗