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At least 379 records · Page 21

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NASA NTRS1959

Hydrodynamic Impact-Load Alleviation with a Penetrating Hydro-Ski

A penetrating hydro-ski was mounted below a model tested previously in the study reported in NACA Technical Note 4401, and a series of impacts were made in the Langley impact basin to determine load alleviation with this type of hydro-ski. The hydro-ski was designed to penetrate through seaway irregularities with a minimum of drag and with small impact loads. The penetrating hydro-ski was small (beam-loading coefficient of 111) and of a streamline shape with the bottom designed for flush retraction into the main model. A series of impacts at fixed trim angles of 8, 16, and 30 deg were made in smooth water and at a fixed trim angle of 8 deg in rough water. The loads and motions of the model were recorded, and photographic observations of the flow and cavities generated in the water by the penetrating hydro-ski were made. The data are presented and the maximum impact loads and maximum drafts of the model with the penetrating hydro-ski are compared with those of the model obtained without the penetrating hydro-ski. Maximum load reductions of 30 to 70 percent in smooth water and of 50 to 80 percent in rough water are indicated. Cavity and flow generation by the penetrating hydro-ski are discussed, and it is indicated that the penetrating hydro-ski moved smoothly through the water and generated deep cavities which are shown by stereophotographs.

Edge, Philip M., Jr.↗

NASA NTRS2018

Robust Bonding Through Process Control

Process control has been proven to be the most reliable means of safeguarding the quality of adhesive bonds according to Federal Aviation Administration (FAA). A method for implementing process control for reduction in risk in a bonded joint fabrication process is demonstrated in this study using a selected bonding system. The stepwise method included risk analysis to identify defects with the highest impact and likelihood to occur, evaluation of various pre-bond surface analysis tools to monitor for the selected defects, and demonstration of the benefits of in-process monitoring utilizing threshold limits determined from bond performance tests. The bonded system selected for investigation was an aerospace carbon fiber epoxy composite substrate surface prepared with random orbital sanding using 180 grit aluminum oxide sand paper. A series of portable, pre-bond surface analysis tools were investigated for their ability to be used for in-line bond process control. Results and threshold limits are presented from roughness, ballistic water contact angle (WCA), color, gloss, and Fourier transform infrared spectroscopy (FTIR) surface analysis tools. Results demonstrated how in-process inspection methods can be used to ensure quality of a surface preparation for a selected bonding system. A framework is provided for implementation of bond process control for robust bonding.

Kutscha, Eileen O.↗

NASA NTRS2021

Land Surface Modeling Over the Dry Chaco: The Impact of Model Structures, and Soil, Vegetation and Land Cover Parameters

In this study, we tested the impact of a revised set of soil, vegetation and land cover parameters on the performance of three different state-of-the-art land surface models (LSMs) within the NASA Land Information System (LIS). The impact of this revision was tested over the South American Dry Chaco, an ecoregion characterized by deforestation and forest degradation since the 1980s. Most large-scale LSMs may lack the ability to correctly represent the ongoing deforestation processes in this region, because most LSMs use climatological vegetation indices and static land cover information. The default LIS parameters were revised with improved soil parameters, satellite-based interannually varying vegetation indices (leaf area index and green vegetation fraction) instead of climatological vegetation indices, and yearly land cover information instead of static land cover. A relative comparison in terms of water budget components and “efficiency space” for various baseline and revised experiments showed that large regional and long-term differences in the simulated water budget partitioning relate to different LSM structures, whereas smaller local differences resulted from updated soil, vegetation and land cover parameters. Furthermore, the different LSM structures redistributed water differently in response to these parameter updates. A time-series comparison of the simulations to independent satellite-based estimates of evapotranspiration and brightness temperature (Tb) showed that no LSM setup significantly outperformed another for the entire region and that not all LSM simulations improved with updated parameter values. However, the revised soil parameters generally reduced the bias between simulated surface soil moisture and pixel-scale in situ observations and the bias between simulated Tb and regional Soil Moisture Ocean Salinity (SMOS) observations. Our results suggest that the different hydrological responses of various LSMs to vegetation changes may need further attention to gain benefits from vegetation data assimilation.

Michiel Maertens↗

DOE OSTI2026

VIC-Global Parameter Dataset Sensitivity with the Variable Infiltration Capacity Model: Evaluating the importance of dynamic land surface parameters when using the VIC-Global parameter dataset

Accurate prediction of runoff is essential to water resources management, flood risk assessment, and ecosystem protection. However, many hydrological models still have relatively substantial limitations when representing the influence of land use and land cover (LULC) on runoff generation and routing. Changes in LULC, such as deforestation, urban expansion, agricultural intensification, and wetland loss, have been shown to alter the water balance at the land surface through fundamental hydrologic processes (e.g., interception, infiltration, evapotranspiration, and soil storage). However, it remains an open question what the exact magnitude and timing of these impacts are for the spatial and temporal scales commonly used in engineering applications. In this analysis we focus on one aspect of recent LULC change for assessing human impacts, which is urbanization. Specifically we seek to determine the impacts of urbanization on the magnitude and timing of surface runoff and baseflow in HUC-12 basins in Clark County, Nevada which has experienced rapid urbanization. We use the Variable Infiltration Capacity (VIC) hydrology model with a widely used off-the-shelf dataset of land surface parameters, VIC-Global, both of which have been commonly used in the past for water and energy balance modeling for large scale hydrologic studies. We examine two scenarios where the first scenario removes all urbanized land cover and parameterizes those areas of the basins as barren or open shrubland. The second scenario tests the opposite case where all areas of the basins are classified as urban regardless of their present classification. The results from the VIC model show there is a low sensitivity for daily surface runoff between scenarios. The daily baseflow values indicate similar low sensitivity to the classification change during specific periods, but then have substantial differences during other period when large precipitation events are occurring. This is likely due to the assumed parameter values for the urban land cover classification made by the VIC-Global dataset. Using a static land cover parameterization is reasonable for large domain hydrology models that are being used for near-term planning horizons (<30 years). However, longer planning horizons where feedbacks between the atmosphere and land surface are important, especially in transient climate situations, considerations for how to update land surface parameters should be incorporated.

42 ENGINEERING↗

NASA NTRS2007

Partitioning Evapotranspiration in Semiarid Grassland and Shrubland Ecosystems Using Diurnal Surface Temperature Variation

The encroachment of woody plants in grasslands across the Western U.S. will affect soil water availability by altering the contributions of evaporation (E) and transpiration (T) to total evapotranspiration (ET). To study this phenomenon, a network of flux stations is in place to measure ET in grass- and shrub-dominated ecosystems throughout the Western U.S. A method is described and tested here to partition the daily measurements of ET into E and T based on diurnal surface temperature variations of the soil and standard energy balance theory. The difference between the mid-afternoon and pre-dawn soil surface temperature, termed Apparent Thermal Inertia (I(sub A)), was used to identify days when E was negligible, and thus, ET=T. For other days, a three-step procedure based on energy balance equations was used to estimate Qe contributions of daily E and T to total daily ET. The method was tested at Walnut Gulch Experimental Watershed in southeast Arizona based on Bowen ratio estimates of ET and continuous measurements of surface temperature with an infrared thermometer (IRT) from 2004- 2005, and a second dataset of Bowen ratio, IRT and stem-flow gage measurements in 2003. Results showed that reasonable estimates of daily T were obtained for a multi-year period with ease of operation and minimal cost. With known season-long daily T, E and ET, it is possible to determine the soil water availability associated with grass- and shrub-dominated sites and better understand the hydrologic impact of regional woody plant encroachment.

Moran, M. Susan↗

NASA NTRS2013

Impact of AIRS Thermodynamic Profiles on Precipitation Forecasts for Atmospheric River Cases Affecting the Western United States

This project is a collaborative activity between the NASA Short-term Prediction Research and Transition (SPoRT) Center and the NOAA Hydrometeorology Testbed (HMT) to evaluate a SPoRT Advanced Infrared Sounding Radiometer (AIRS: Aumann et al. 2003) enhanced moisture analysis product. We test the impact of assimilating AIRS temperature and humidity profiles above clouds and in partly cloudy regions, using the three-dimensional variational Gridpoint Statistical Interpolation (GSI) data assimilation (DA) system (Developmental Testbed Center 2012) to produce a new analysis. Forecasts of the Weather Research and Forecasting (WRF) model initialized from the new analysis are compared to control forecasts without the additional AIRS data. We focus on some cases where atmospheric rivers caused heavy precipitation on the US West Coast. We verify the forecasts by comparison with dropsondes and the Cooperative Institute for Research in the Atmosphere (CIRA) Blended Total Precipitable Water product.

Zavodsky, Bradley T.↗

DOE OSTI2024

How dry is dead? Evaluating the impact of desiccation on the viability of the invasive species Cissus quadrangularis

Abstract Cissus quadrangularis is a succulent vine that degrades forests where it is not native by growing over trees and causing them to break or by impeding regeneration. Methods for its control have been tried but no satisfactory approach has been found yet. We carried out an experiment to analyze how much desiccation Cissus can endure before losing its ability to grow when rehydrated, using fragments of 0.5, 1, 2, and 3 internodes to test if desiccation tolerance was affected by fragment length. We found that Cissus remains viable after losing up to 80% of its weight, with shorter fragments losing viability (capacity to grow) at 70% weight loss. No fragments sustained viability at 90% water loss, establishing a critical threshold for Cissus desiccation tolerance. Our study also showed that shorter fragments (0.5 internodes) were less viable compared to longer ones (1, 2 or 3 internodes). Cissus has a remarkable tolerance to desiccation. Therefore, management strategies should ensure complete dehydration of Cissus fragments to prevent its regrowth. Reducing fragments to smaller sizes could amplify the effectiveness of control measures by reducing their viability, but risks of increasing propagule numbers should be considered.

Mondragón‐Botero, Ariadna↗

NASA NTRS1997

Evaluation of a Human Modeling Software Tool in the Prediction of Extra Vehicular Activity Tasks for an International Space Station Assembly Mission

The difficulty of accomplishing work in extravehicular activity (EVA) is well documented. It arises as a result of motion constraints imposed by a pressurized spacesuit in a near-vacuum and of the frictionless environment induced in microgravity. The appropriate placement of foot restraints is crucial to ensuring that astronauts can remove and drive bolts, mate and demate connectors, and actuate levers. The location on structural members of the foot restraint sockets, to which the portable foot restraint is attached, must provide for an orientation of the restraint that affords the astronaut adequate visual and reach envelopes. Previously, the initial location of these sockets was dependent upon the experienced designer's ability to estimate placement. The design was tested in a simulated zero-gravity environment; spacesuited astronauts performed the tasks with mockups while submerged in water. Crew evaluation of the tasks based on these designs often indicated the bolt or other structure to which force needed to be applied was not within an acceptable work envelope, resulting in redesign. The development of improved methods for location of crew aids prior to testing would result in savings to the design effort for EVA hardware. Such an effort to streamline EVA design is especially relevant to International Space Station construction and maintenance. Assembly operations alone are expected to require in excess of four hundred hours of EVA. Thus, techniques which conserve design resources for assembly missions can have significant impact. We describe an effort to implement a human modelling application in the design effort for an International Space Station Assembly Mission. On Assembly Flight 6A, the Canadian-built Space Station Remote Manipulator System will be delivered to the U.S. Laboratory. It will be released from its launch restraints by astronauts in EVA. The design of the placement of foot restraint sockets was carried out using the human model Jack, and the modelling results were compared with actual underwater test results. The predicted locations of the sockets was found to be acceptable for 94% of the tasks attempted by the astronauts, This effort provides confidence in the capabilities of this package to accurately model tasks. It therefore increases assurance that the tool maybe used early in the design process.

Dischinger, H. Charles↗

NASA NTRS2004

Total Water Measurements Using In Situ UV Fragment Fluorescence Spectroscopy in Support of CRYSTAL-FACE

Given both the powerful diagnostic importance of the condensed phases of water for dynamics and the impact of phase changes in water on the radiation field, the accurate, in situ observation of total water is of central importance to CRYSTAL-FACE. This is clear both from the defined scientific objectives of the NRA and from developments in the coupled fields of stratosphere/troposphere exchange, cirrus cloud formation/removal and mechanisms for the distribution of water vapor in the middle/upper troposphere. Accordingly, we were funded under NASA Grant NAG5-115487 to perform the following tasks for the CRYSTAL-FACE mission that took place in Key West, Florida, during July 2001: 1) Prepare the Total Water instrument for integration into the WB57F and test flights scheduled for Spring 2002. 2) Calibrate and prepare the Total Water instrument for the Summer 2002 CRYSTAL-FACE science flights based in Jacksonville, Florida. 3) Provide both science and engineering support for the above-mentioned efforts. 4) Analyze and interpret the CRYSTAL-FACE data in collaboration with the other mission scientists. 5) Attend the proposed science workshop in Spring 2003. 6) Publish the data and analysis in peer-reviewed journals.

Anderson, James G.↗

NASA NTRSDate not supplied

TPSAS-NF1676L-23557-DND

The Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) measures both parallel and perpendicular backscatter of linearly polarized 532 nm light from cloud particles in the atmosphere. The perpendicular component of the return signal allows differentiation between cloud layers consisting of spherical water droplets from those with non-spherical ice particles. A two-way distribution of layer-integrated 532 nm total backscatter and the layer-integrated 532 nm depolarization ratio further differentiates between water cloud layers with significant multiple scattering, horizontally-oriented ice particles that cause specular reflections, and randomly-oriented ice particles, as described in Hu et al., 2009. The cloud phase algorithm functions well for the majority of clouds, but there have been some recent changes and improvements that are described in this poster. The impact of the CALIOP viewing angle change from near-nadir (0.3 degrees) to slightly tilted (3.0 degrees) on the optical properties of the various CALIOP cloud particle phases is also shown. A major improvement to the phase algorithm is the limitation of a spatial coherence test for horizontally-oriented ice to cloud layers that have sufficient integrated attenuated backscatter to likely contain HOI. This change reduces a "striping" effect caused by noisiness in the spatial coherence test for thin cloud layers. Additional temperature tests are considered, and the regional and vertical distribution of cloud layers with the various CALIOP cloud phases is shown. Only one cloud particle phase is allowed for each 5 km portion of a cloud layer that is considered by the cloud phase algorithm, so we use in situ aircraft and CloudSat observations to determine how the CALIOP cloud phase algorithm is treating optically and thermally thick clouds, which may be mixed-phase.

Melody Avery↗

NASA NTRSDate not supplied

All-sky Microwave Radiance Assimilation in The GEOS Atmospheric Reanalysis for The Early 21st Century (GEOS-21C)

The Goddard Earth Observing System (GEOS) is used for weather, climate, and air quality forecasts and producing reanalysis datasets. Its atmospheric data assimilation system (ADAS) is a hybrid–4DEnVar system. Various satellite radiance, atmospheric motion vector (winds), aircraft, and convectional data are assimilated by this system to produce global atmospheric states. Satellite data assimilation within GEOS ADAS is enhanced by considering correlated observational errors among infrared radiance observations and assimilating new microwave radiance data in all-sky conditions since the release of the Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2). These new microwave radiance data include brightness temperature measurements made by the Global Precipitation Mission (GPM) microwave imager (GMI) and Advanced Microwave Scanning Radiometer 2 / Global Change Observation Mission 1st – Water (AMSR2/GCOM-W). Historical microwave radiance data made by various Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I) and the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) aboard the Aqua satellite are tested within the all-sky microwave radiance assimilation framework in the preparation of the GEOS enhanced Atmospheric Reanalysis for the early 21st century (GEOS-21C). Assimilation of these data in all-sky conditions enhances use of other satellite data and improves GEOS analysis and forecast. In this talk, we will present the procedures of to assimilate microwave radiance data in all-sky conditions and their impact on atmospheric analysis in the preparation of GEOS-21C.

Jianjun Jin↗

NASA NTRSDate not supplied

Preparation for and Performance of a Pseudomonas aeruginosa Biofilm Experiment On Board the International Space Station

Biofilms are a problem on Earth given their ability to degrade the materials upon which they grow and due to their relevance to infections. Remarkably, 65% and 80% of infections and chronic diseases on Earth are associated with biofilms, respectively. In space, these problems' impact is higher because the crew's lives and mission success depend on nominal operation of mechanical systems. Furthermore, the isolated confined environment nature of spaceflight may increase the rates of disease transmission. In the case of the International Space Station (ISS), biofilms are an identified problem on the Environmental Control and Life Support System (ECLSS), namely on the water processor assembly (WPA). In late 2019, the Space Biofilms experiment launched towards ISS to (i) characterize the mass, thickness, morphology, and gene expression of biofilms formed in space with respect to matched Earth controls, (ii) interrogate the expression of antimicrobial resistance genes, and (iii) test novel materials as potential biofilm control strategies for future ECLSS components. For this, 288 bacterial samples were prepared prior to the launch of the Northrop Grumman CRS-12 mission from NASA's Wallops Flight Facility. The samples were integrated into the spaceflight hardware, BioServe's Fluid Processing Apparatus (FPA) packed in sets of eight in Group Activation Packs (GAP). Half of these samples were activated and terminated on orbit by NASA astronauts Jessica Meir and Christina Koch, while the remaining half were processed equivalently on Earth. The spaceflight bacterial samples of Space Biofilms returned on board SpaceX' CRS-19 Dragon spacecraft, in early 2020. We here describe the test campaign implemented to verify the experiment design and confirm it would enable us to achieve the project's scientific goals. This campaign ended with the Experiment Verification Test (EVT), from which we here present example morphology and transcriptomic results. We describe in detail the sample preparation prior to flight, including cleaning and sterilization of the coupons of six materials (SS316, passivated-SS316, lubricant impregnated surface, catheter-grade silicone with and without a nanotopography, and cellulose membrane), loading and integration of growth media, bacterial inoculum, fixative and preservative to enable experiment termination on orbit. Additionally, we describe the performance of the experiment on board the ISS, including crew activities, use of assets, temperature profile, and experiment timeline; all leading to a successful spaceflight experiment.

Pamela Flores↗

NASA NTRSDate not supplied

Plants in Space and Space Crop Production

As astronauts venture farther from Earth, and for longer periods, the space food system will increase in importance. Crop production can supplement a packaged diet to provide additional nutrients and dietary variety for astronauts, and in future missions, bioregenerative approaches may be used to generate a larger percentage of the diet. Plants may also provide behavioural health benefits and assist with other life support functions. Several unique challenges exist for growth of plants in microgravity and on other planetary surfaces like the moon and Mars. Testing with the Veggie and Advanced Plant Habitat (APH) chambers on the International Space Station is allowing us to understand the impacts of gravity and spaceflight on crop growth, nutritional content, acceptability, and the importance of plants to astronauts living and working away from Earth. We are also gaining a better understanding of food safety concerns and the behaviour of space plant microbiomes and plant pathogens. As we transition from research towards operational space crop production to enable human exploration, there are several gaps and challenges of growing crops in space that must be addressed. Research and technology development in key areas such as water and nutrient delivery, plant health monitoring, and crop selection are needed to overcome these challenges. Additionally, there are opportunities for breeding or engineering of custom space crops related to plant growth and development, plant physiology, produce nutrition, organoleptic acceptability, and post-harvest characteristics. Solutions to help ensure food security off-Earth may also translate to better approaches to terrestrial sustainable crop production.

Advanced Plant Habitat↗

NASA NTRS2023

Plants in Space and Space Crop Production

Advanced Plant Habitat↗

DOE OSTI2024

ITER ECH Transmission Line System Design and Status

The electron cyclotron (EC) heating & current drive (H&CD) system on ITER provides plasma heating by generating, transmitting, and launching high-intensity, high-frequency (170 GHz) electromagnetic wave energy steerable across the plasma cross-section. The transmission line (TL) subsystem connects the Matching Optics Unit (MOU) on each of the 24 gyrotrons to the 32 feed points in the four upper launchers and the 24 feed points in the equatorial launcher. Each TL must be able to operate at up to 1.2 MW of input power for up to 1 hour pulse lengths. The TL system contains 50 mm water-cooled corrugated waveguide, 90o miter bends, 140o miter bends, polarizer miter bend pairs, switches, expansion units, pumpouts, DC breaks, MOU-TL adapters, Radio Frequency (RF) loads, and isolation shutter valves. A detailed finite element analysis has been used to verify the thermo-mechanical performance of each component. The microwave performance has been analyzed using a 2-D electromagnetic code combined with a Monte Carlo code. This approach allows the impact of manufacturing and installation tolerances to be assessed and optimized to provide a high probability of achieving the system performance requirements. Prototypes of the waveguide and TL components have been fabricated and tested at high-power. Production contracts are now being issued for fabrication and delivery of the waveguide and components to ITER.

Hanson, Gregory↗

NASA NTRS2000

Goddard Cumulus Ensemble (GCE) Model: Application for Understanding Preciptation Processes

The global hydrological cycle is central to climate system interactions and the key to understanding their behavior. Rainfall and its associated precipitation processes are a key link in the hydrologic cycle. Fresh water provided by tropical rainfall and its variability can exert a large impact upon the structure of the upper ocean layer. In addition, approximately two-thirds of the global rain falls in the Tropics, while the associated latent heat release accounts for about three-fourths of the total heat energy for the Earth's atmosphere. Precipitation from convective cloud systems comprises a large portion of tropical heating and rainfall. Furthermore, the vertical distribution of convective latent-heat releases modulates large-scale tropical circulations (e.g., the 30-60-day intraseasonal oscillation), which, in turn, impacts midlatitude weather through teleconnection patterns such as those associated with El Nino. Shifts in these global circulations can result in prolonged periods of droughts and floods, thereby exerting a tremendous impact upon the biosphere and human habitation. And yet, monthly rainfall over the tropical oceans is still not known within a factor of two over large (5 degrees latitude by 5 degrees longitude) areas. Hence, the Tropical Rainfall Measuring Mission (TRMM), a joint U.S./Japan space project, can provide a more accurate measurement of rainfall as well as estimate the four-dimensional structure of diabatic heating over the global tropics. The distributions of rainfall and inferred heating can be used to advance our understanding of the global energy and water cycle. In addition, this information can be used for global circulation and climate models for testing and improving their parameterizations.

Tao, Wei-Kuo↗

NASA NTRS1953

Theory and procedure for determining loads and motions in chine-immersed hydrodynamic impacts of prismatic bodies

A theoretical method is derived for the determination of the motions and loads during chine-immersed water landings of prismatic bodies. This method makes use of a variation of two-dimensional deflected water mass over the complete range of immersion, modified by a correction for three-dimensional flow. Equations are simplified through omission of the term proportional to the acceleration of the deflected mass for use in calculation of loads on hulls having moderate and heavy beam loading. The effects of water rise at the keel are included in these equations. In order to make a direct comparison of theory with experiment, a modification of the equations was made to include the effect of finite test-carriage mass. A simple method of computation which can be applied without reading the body of this report is presented as an appendix along with the required theoretical plots for determination of loads and motions in chine-immersed landings.

Schnitzer, Emanuel↗

NASA NTRS1992

Titan: a laboratory for prebiological organic chemistry

When we examine the atmospheres of the Jovian planets (Jupiter, Saturn, Uranus, and Neptune), the satellites in the outer solar system, comets, and even--through microwave and infrared spectroscopy--the cold dilute gas and grains between the stars, we find a rich organic chemistry, presumably abiological, not only in most of the solar system but throughout the Milky Way galaxy. In part because the composition and surface pressure of the Earth's atmosphere 4 x 10(9) years ago are unknown, laboratory experiments on prebiological organic chemistry are at best suggestive; but we can test our understanding by looking more closely at the observed extraterrestrial organic chemistry. The present Account is restricted to atmospheric organic chemistry, primarily on the large moon of Saturn. Titan is a test of our understanding of the organic chemistry of planetary atmospheres. Its atmospheric bulk composition (N2/CH4) is intermediate between the highly reducing (H2/He/CH4/NH3/H2O) atmospheres of the Jovian planets and the more oxidized (N2/CO2/H2O) atmospheres of the terrestrial planets Mars and Venus. It has long been recognized that Titan's organic chemistry may have some relevance to the events that led to the origin of life on Earth. But with Titan surface temperatures approximately equal to 94 K and pressures approximately equal to 1.6 bar, the oceans of the early Earth have no ready analogue on Titan. Nevertheless, tectonic events in the water ice-rich interior or impact melting and slow re-freezing may lead to an episodic availability of liquid water. Indeed, the latter process is the equivalent of a approximately 10(3)-year-duration shallow aqueous sea over the entire surface of Titan.

Non-NASA Center↗