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At least 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Internship Tasks Associated With CIF Icy Regolith Excavation and Volatile Capture Under Vacuum Conditions

Understanding the surface and atmosphere of Mars is critical to current and future development of exploration systems. Dealing with the Martian regolith-the top layer of soil-remains a significant challenge, and much research is still needed. Addressing this need, the Cryogenics Test Lab and Granular Mechanics and Regolith Operations Lab at NASA's Kennedy Space Center are partnering to develop an apparatus that utilizes simulated Martian regolith in an analogous atmospheric environment to gather data about how the material behaves when exposed to water vapor. Martian surface temperatures range from 128 K (-145 C) to 308 K (35 C), and the average pressure is approximately 4.5 Torr; which presents an environment where water can potentially exist in vapor, solid or liquid form. And based on prior Mars missions such as the Phoenix Lander, it is known that water-ice exists just below the surface. This test apparatus will attempt to recreate the conditions that contributed to the Martian ice deposits by exposing a sample to water vapor at low pressure and temperature; thereby forming ice inside the simulant via diffusion. From this, we can better understand the properties and behavior of the regolith, and have more knowledge concerning its ability to store water-and subsequently, how to dig up and extract that water-which will be crucial to sample gathering when the first manned Mars mission takes place.

Thermal-Vacuum Testing↗
NASA NTRS1982

A detailed treatment of two-dimensional, starved lubrication in the vicinity of two counter-rotating cylinders

The problem of starved lubrication in the inlet region for the case of line contact between two nondeforming, equal radii cylinders rotating in opposite directions with equal surface speeds is considered. The lubricant is assumed to be a constant density, isoviscous, Newtonian fluid. The usual approach, which involves the use of Reynolds equation everywhere, is not followed. Instead, the situation is restricted to one in which the lubricant enters the contact region in thin films which adhere to the cylinders. Using Reynolds equation only at the line of centers and a suitable thin film approximation far from that point, the intervening region is treated as a general creeping flow region. Solutions, incorporating complete free surface boundary conditions, are obtained numerically. The hitherto unobtained results due to this approach include the existence of a unique free surface location for a fixed set of operating conditions.

Medrow, R. A.↗
NASA NTRS1975

Utilization of satellite data for inventorying prairie ponds and lakes. LANDSAT-1 data were used to discriminate ponds and lakes for waterfowl management

The author has identified the following significant results. The mapping of open water as an indicator of waterfowl habitat quality was carried out by using two different recognition techniques, a single waveband thresholding approach and a multiple waveband approach termed proportion estimation. The single waveband technique has proven simple to implement. Its computer algorithm was rapid and accurately recognized prairie lakes and large ponds. The resultant products of this processing technique were thematic maps and statistical tabulations describing open surface water conditions. The maps served to portray visually the location and frequency of surface water bodies but usually necessitated additional interpretation.

Gilmer, D. S.↗
NASA NTRS2015

Robotic Reconnaissance Missions to Small Bodies and Their Potential Contributions to Human Exploration

Introduction: Robotic reconnaissance missions to small bodies will directly address aspects of NASA's Asteroid Initiative and will contribute to future human exploration. The NASA Asteroid Initiative is comprised of two major components: the Grand Challenge and the Asteroid Mission. The first component, the Grand Challenge, focuses on protecting Earth's population from asteroid impacts by detecting potentially hazardous objects with enough warning time to either prevent them from impacting the planet, or to implement civil defense procedures. The Asteroid Mission involves sending astronauts to study and sample a near- Earth asteroid (NEA) prior to conducting exploration missions of the Martian system, which includes Phobos and Deimos. The science and technical data obtained from robotic precursor missions that investigate the surface and interior physical characteristics of an object will help identify the pertinent physical properties that will maximize operational efficiency and reduce mission risk for both robotic assets and crew operating in close proximity to, or at the surface of, a small body. These data will help fill crucial strategic knowledge gaps (SKGs) concerning asteroid physical characteristics that are relevant for human exploration considerations at similar small body destinations. Small Body Strategic Knowledge Gaps: For the past several years NASA has been interested in identifying the key SKGs related to future human destinations. These SKGs highlight the various unknowns and/or data gaps of targets that the science and engineering communities would like to have filled in prior to committing crews to explore the Solar System. An action team from the Small Bodies Assessment Group (SBAG) was formed specifically to identify the small body SKGs under the direction of the Human Exploration and Operations Missions Directorate (HEOMD), given NASA's recent interest in NEAs and the Martian moons as potential human destinations [1]. The action team organized the SKGs into four broad themes: 1) Identify human mission targets; 2) Understand how to work on and interact with the small body surface; 3) Understand the small body environment and its potential risk/benefit to crew, systems, and operational assets; and 4) Understand the small body resource potential. Each of these themes were then further subdivided into categories to address specific SKG issues. Robotic Precursor Contributions to SKGs: Robotic reconnaissance missions should be able to address specific aspects related to SKG themes 1 through 4. Theme 1 deals with the identification of human mission targets within the NEA population. The current guideline indicates that human missions to fastspinning, tumbling, or binary asteroids may be too risky to conduct successfully from an operational perspective. However, no spacecraft mission has been to any of these types of NEAs before. Theme 2 addresses the concerns about interacting on the small body surface under microgravity conditions, and how the surface and/or sub-surface properties affect or restrict the interaction for human exploration. The combination of remote sensing instruments and in situ payloads will provide good insight into the asteroid's surface and subsurface properties. SKG theme 3 deals with the environment in and around the small body that may present a nuisance or hazard to any assets operating in close proximity. Impact and surface experiments will help address issues related to particle size, particle longevity, internal structure, and the near-surface mechanical stability of the asteroid. Understanding or constraining these physical characteristics are important for mission planning. Theme 4 addresses the resource potential of the small body. This is a particularly important aspect of human exploration since the identification and utilization of resources is a key aspect for deep space mission architectures to the Martian system (i.e., Phobos and Deimos). Conclusions: Robotic reconnaissance of small bodies can provide a wealth of information relevant to the science and planetary defense of NEAs. However, such missions to investigate NEAs can also provide key insights into small body strategic knowledge gaps and contribute to the overall success for human exploration missions to asteroids.

Abell, P. A.↗
NASA NTRSDate not supplied

Enabling more routine monitoring of volcanic CO2 degassing from space

“Volcanic aerosol impacts on satellite trace gas retrievals: enabling volcanic emission plume composition measurements to track evolving sub-surface magmatic conditions” ROSES 2019 IDS (Interdisciplinary Science), 2020-2023 (S. Broccardo, PI) Main hypothesis: Space-based observations of the CO2, SO2, and H2O emissions of passively degassing volcanoes, and the derived mass fluxes and their ratios, can be used to constrain a physical model of the pre-eruptive conditions of magmatic reservoirs and thereby improve our understanding of sub-surface processes.

Enabling↗
DOE OSTI2025

Self-consistent modeling of tokamak edge plasma transport with lithium sources

Magnetic confinement fusion devices require effective heat and particle exhaust solutions on the divertor plates to operate sustainably, especially under reactor-relevant conditions. Liquid lithium divertors have been proposed to address two major challenges: control of excessive heat flux to plasma-facing components through vapor shielding and minimization of core plasma contamination from impurities. The National Spherical Torus Experiment-Upgrade (NSTX-U) will explore lithium as a divertor material due to its potential to meet both objectives. We present a self-consistent coupling framework between the plasma boundary transport code UEDGE and the lithium wall transport code Wall–Li to evaluate the feasibility and operational limits of lithium-based divertors. The model aims to optimize lithium sourcing levels to prevent core plasma contamination via fuel dilution while ensuring divertor protection through vapor shielding. This integrated framework, applicable to any tokamak with lithium sources, dynamically adjusts lithium sourcing based on local plasma conditions and surface temperature. The coupled model is tested using NSTX-like geometry and plasma conditions to assess its performance and reliability. Wall–Li calculates lithium fluxes from plasma-facing components, incorporating physical sputtering, thermally enhanced sputtering, and evaporation driven by surface temperature and ion flux. These fluxes are reintroduced into UEDGE as neutral lithium atoms, enabling simulation of their transport and distribution within the plasma. UEDGE computes plasma and neutral transport, surface heat flux, and iteratively feeds this information back to Wall–Li. A small time step is employed to ensure numerical stability and convergence, enabling accurate simulations over typical tokamak discharge durations. This integrated modeling approach provides a robust tool for identifying operational regimes that balance effective lithium sourcing with minimal core plasma contamination, offering critical insights for optimizing lithium-based divertor systems in current and future fusion devices.

Magnetic confinement fusion↗
NASA NTRS1995

Remote sounding of surface radiative fluxes in cirrus cloudy conditions

It has been long recognized that radiation and radiation perturbations play a critical role in the climate system. Surface radiative fluxes are useful parameters for monitoring global change, for understanding of the effects of clouds on the radiation field, and for improving parameterization of surface sensible and latent heat fluxes. Monitoring of the radiation budget at the top of the atmosphere has been one of the prime satellite programs for the last 30 years. However, monitoring radiative fluxes at the surface over the globe from space cannot be performed in a direct way at the present time. In particular, since clouds are the prime regulators of the radiative fluxes, uncertainties in the retrieved cloud parameters, which are inputs to radiative transfer models, can introduce significant errors in the computed radiative fluxes. Thus, remote sounding of surface radiative fluxes in cloudy conditions requires the development of both satellite cloud retrieval scheme and radiation models. In this paper, we present results of computed surface radiative fluxes in cirrus cloudy conditions using a cirrus cloud retrieval scheme and a detailed radiative transfer program. Comparisons have been made between the computed surface radiative fluxes and the ground-based radiometer measurements obtained during FIRE-II-IFO, which was carried out near Coffeyville, Kansas, during November and December, 1991.

Ou, S. C.↗
NASA NTRS2021

Assimilation of SMAP Brightness Temperature Observations in the GEOS Land–Atmosphere Data Assimilation System

Errors in soil moisture adversely impact the modeling of land–atmosphere water and energy fluxes and, consequently, near-surface atmospheric conditions in atmospheric data assimilation systems (ADAS). To mitigate such errors, a land surface analysis is included in many such systems, although not yet in the currently operational NASA Goddard Earth Observing System (GEOS) ADAS. This article investigates the assimilation of L-band brightness temperature (Tb) observations from the Soil Moisture Active Passive (SMAP) mission in the GEOS weakly coupled land–atmosphere data assimilation system (LADAS) during boreal summer 2017. The SMAP Tb analysis improves the correlation of LADAS surface and root-zone soil moisture versus in situ measurements by ∼0.1–0.26 over that of ADAS estimates; the unbiased root-mean-square error of LADAS soil moisture is reduced by 0.002–0.008 m^3 /m^3 from that of ADAS. Furthermore, the global land average RMSE versus in situ measurements of screen-level air specific humidity (q2m) and daily maximum temperature (T2m_max ) is reduced by 0.05 g/kg and 0.04 K, respectively, for LADAS compared to ADAS estimates. Regionally, the RMSE of LADAS q2m and T2m_max is improved by up to 0.4 g/kg and 0.3 K, respectively. Improvement in LADAS specific humidity extends into the lower troposphere (below ∼700 mb), with relative improvements in bias of 15–25%, although LADAS air temperature bias slightly increases relative to that of ADAS. Finally, the root mean square of the LADAS Tb observation-minus-forecast residuals is smaller by up to ∼0.1 K than in a land-only assimilation system, corroborating the positive impact of the Tb analysis on the modeled land–atmosphere coupling.

microwave remote sensing↗
NASA NTRS1989

Land-surface temperature measurement from space - Physical principles and inverse modeling

To apply the multiple-wavelength (split-window) method used for satellite measurement of sea-surface temperature from thermal-infrared data to land-surface temperatures, the authors statistically analyze simulations using an atmospheric radiative transfer model. The range of atmospheric conditions and surface temperatures simulated is wide enough to cover variations in clear atmospheric properties and surface temperatures, both of which are larger over land than over sea. Surface elevation is also included in the simulation as the most important topographic effect. Land covers characterized by measured or modeled spectral emissivities include snow, clay, sands, and tree leaf samples. The empirical inverse model can estimate the surface temperature with a standard deviation less than 0.3 K and a maximum error less than 1 K, for viewing angles up to 40 degrees from nadir under cloud-free conditions, given satellite measurements in three infrared channels. A band in the region from 10.2 to 11.0 microns will usually give the most reliable single-band estimate of surface temperature. In addition, a band in either the 3.5-4.0-micron region or in the 11.5-12.6-micron region must be included for accurate atmospheric correction, and a band below the ozone absorption feature at 9.6 microns (e.g., 8.2-8.8 microns) will increase the accuracy of the estimate of surface temperature.

Wan, Zhengming↗
NASA NTRS1985

Free Surface Phenomena Under Low- and Zero-Gravity Conditions

In a low- or zero-gravity environment the free surface of a liquid can behave in striking, unexpected ways. For example, in a partially filled container, a free surface that is well behaved under terrestrial conditions can rise to an arbitrarily large height or even fail to exist when gravity is absent. An answer is sought to the central mathematical questions: Under what conditions can free surfaces exist and what are their properties? -- and experimental questions of what means can be devised to observe and to measure the surfaces quantitatively. Current activity focuses on material selection and the design of optical diagnostic methods for in-space experiments. These experiments will test mathematical predictions of discontinuous transition from existence to nonexistence of capillary free surfaces in certain geometric configurations under zero gravity conditions. Liquids and container materials suitable for achieving the required contact-angle range and optical properties are being investigated, as well as the effects of contaminants and fluid motion on contact angle. The optical diagnostic technique investigation concerns laser-induced fluorescence, including emphasis on data on acquisition, sources and detectors, reliability, data management, and computer control.

Concus, P.↗
NASA NTRS1985

The Martian dust storm of Sol 1742

After nearly five earth years on Mars, the Mutch Memorial Station (Viking Lander 1) finally witnessed a local dust storm that eroded trenches, conical piles, and other disturbed surfaces in the sample field and near the Lander. The event, called the Dust Storm of Sol 1742, occurred late in the third winter of Lander observations between Sols 1728 and 1757. Analyses of tiny new wind tails and movement of materials indicate that the eroding winds were variable but northeasterly than those that had previously shaped the surface. Pebbly residues and movement of 4-5 mm clods suggest drag velocities or friction speeds of the winds were about 2.2-4.0 m/s. Wind speeds at the height of the meteorology boom (1.6 m) were probably about 40-50 m/s. Much of the observed erosion could have occurred in a few to several tens of seconds, but somewhat longer times are suggested by analogy with the erosion of terrestrial soils. Most of the erosion occurred where preexisting equilibrium conditions of surface configurations and surface material properties had been altered by the Lander during landing and during surface-sampler activities, but thin layers of bright fine-grained dust were also removed and redistributed. Surfaces where preexisting equilibrium conditions were unaltered appeared to be uneroded.

Moore, H. J.↗
NASA NTRS1985

The production of glow precursors by oxidative erosion of spacecraft surfaces

Erosion rates of organic materials are measured during a recent flight of the shuttle (STS-8). Several forms of carbon and a variety of thermosetting and thermoplastic polymers are exposed to the ram beam of atomic oxygen. Arrhenius energies of about 1000 to 2000 cal/mole were measured from the rate dependencies on temperature. If some simple assumptions are made about the chemical nature of the desorbed species, the data can be used to estimate production rates at surfaces in orbit under different conditions of temperature, oxygen atom flux, and material surface conditions.

Gregory, J. C.↗
NASA NTRS2002

On the Boundary Condition for Water at a Hydrophobic, Dense Surface

We study the no-slip boundary conditions for water at a hydrophobic (graphite) surface using non-equilibrium molecular-dynamics simulations. For the planar Couette flow, we find a slip length of 64 nm at 1 bar and 300 K, decreasing with increasing system pressure to a value of 31 nm at 1000 bar. Changing the properties of the interface to from hydrophobic to strongly hydrophilic reduces the slip to 14 nm. Finally, we study the flow of water past an array of carbon nanotubes mounted in an inline configuration with a spacing of 16.4 x 16.4 nm. For tube diameters of 1.25 and 2.50 nm we find drag coefficients in good agreement with the macroscopic, Navier-Stokes values. For carbon nanotubes, the no-slip condition is valid to within the definition of the position of the interface.

Walther, J. H.↗
NASA NTRS2011

Visible and Near-IR Reflectance Spectra of Smectite Acquired Under Dry Conditions for Interpretation of Martian Surface Mineralogy

Visible and near-IR (VNIR) spectra from the MEx OMEGA and the MRO CRISM hyper-spectral imaging instruments have spectral features associated with the H2O molecule and M OH functional groups (M = Mg, Fe, Al, and Si). Mineralogical assignments of martian spectral features are made on the basis of laboratory VNIR spectra, which were often acquired under ambient (humid) conditions. Smectites like nontronite, saponite, and montmorillionite have interlayer H2O that is exchangeable with their environment, and we have acquired smectite reflectance spectra under dry environmental conditions for interpretation of martian surface mineralogy. We also obtained chemical, Moessbauer (MB), powder X-ray diffraction (XRD), and thermogravimetric (TG) data to understand variations in spectral properties. VNIR spectra were recorded in humid lab air at 25-35C, in a dynamic dry N2 atmosphere (50-150 ppmv H2O) after exposing the smectite samples (5 nontronites, 3 montmorillionites, and 1 saponite) to that atmosphere for up to approximately l000 hr each at 25-35C, approximately 105C, and approximately 215C, and after re-exposure to humid lab air. Heating at 105C and 215C for approximately 1000 hr is taken as a surrogate for geologic time scales at lower temperatures. Upon exposure to dry N2, the position and intensity of spectral features associated with M-OH were relatively insensitive to the dry environment, and the spectral features associated with H2O (e.g., approximately 1.90 micrometers) decreased in intensity and are sometimes not detectable by the end of the 215C heating step. The position and intensity of H2O spectral features recovered upon re-exposure to lab air. XRD data show interlayer collapse for the nontronites and Namontmorillionites, with the interlayer remaining collapsed for the latter after re-exposure to lab air. The interlayer did not collapse for the saponite and Ca-montmorillionite. TG data show that the concentration of H2O derived from structural OH was invariant to the dry N2 treatment for saponite and the montmorillionites, but the nontronites had additional structural OH after treatment. Upon exposure to dry N2, the VNIR spectra also acquired a red slope with decreasing albedo between approximately 0.4 and approximately 2.0 micrometers. The magnitude of the effects covaries with exposure time to dry N2 and heating temperature. Upon re-exposure to lab air, the slope and albedo do not completely recover to pre-exposure values. MB data show that these effects do not result from partial reduction of ferric to ferrous iron, and TG data show they do not result from loss of structural OH. Possible explanations include formation of small clusters of (superparamagnetic) ferric oxide and reduced smectite crystallinity. The difference in spectral properties between spectra acquired in humid lab air and under dry conditions are consequential for interpretation of CRISM and OMEGA spectra. For example, nontronite by itself and not nontronite plus ferrihydrite can account for the red spectral slope in martian spectra where nontronite is indicated by the Fe-OH spectral features.

Morris, Richard V.↗
NASA NTRS1983

Archival of aircraft scatterometer data from AAFE RADSCAT missions

Aircraft scatterometer data obtained over the ocean with the Radiometer-Scatterometer (RADSCAT) instrument is documented. The normalized radar cross section data was obtained at 13.9 GHz for a variety of ocean surface wind conditions, which are also presented. All such valid RADSCAT ocean scatterometer data for which surface truth was obtained are included, except for ice research missions during the last year of RADSCAT's lifetime. Aircraft scatterometer data obtained for the SEASAT underflights were with a second instrument, the Airborne Microwave Scatterometer (AMSCAT). The RADSCAT data are archived on card image computer tapes and on microfiche.

Schroeder, L. C.↗
NASA NTRS1991

An analytic solution of the transient behavior of backscattering thermal protective coatings exposed to combined radiative and convective heating

An analytic solution of the material response to combined radiative and convective heating is presented. The solution includes the equations of radiative transfer (within the material), coupled to a transient energy equation which contains both radiative and convective terms. The analysis allows for unlimited spectral detail, but assumes that within the range of applicability, the various material properties do not vary significantly with temperature. Also, to facilitate development of the analytic solution, it is assumed that scattering within the material dominates absorption, and the material exposed surface does not ablate. The exposed surface boundary condition includes convective heating and spectral radiation, some of which is absorbed by the surface and some which penetrates the surface.

Cornelison, Charles J.↗
NASA NTRS1921

Effects of nature of cooling surface on radiator performance

This report discusses the effects of roughness, smoothness, and cleanness of cooling surfaces on the performance of aeronautic radiators, as shown by experimental work, with different conditions of surface, on (1) heat transfer from a single brass tube and from a radiator; (2) pressure drop in an air stream in a single brass tube and in a radiator; (3) head resistance of a radiator; and (4) flow of air through a radiator. It is shown that while smooth surfaces are better than rough, the surfaces usually found in commercial radiators do not differ enough to show marked effect on performance, provided the surfaces are kept clean.

Parsons, S R↗