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NASA NTRS1988

Dehumidification via membrane separation for space-based applications

The paper describes the development of a membrane-based dehumidification process for space-based applications, such as spacecraft cabins and EVA space suits. Results presented are from: (1) screening tests conducted to determine the efficacy of various membranes to separate water vapor from air, and (2) parametric and long-term tests of membranes operated at conditions that simulate the range of environmental conditions (e.g., temperature and relative humidity) expected in the planned Space Station. Also included in this paper is a discussion of preliminary designs of membrane-based dehumidification processes for the Space Station and EVA space suits. These designs result in compact and energy-efficient systems that offer significant advantages over conventional dehumidification processes.

Gienger, Jane Kucera↗

NASA NTRS1997

Convection in an Infinite Vertical Cylinder in the Presence of a Horizontal Magnetic Field

The use of a magnetic field to suppress convection in low gravity materials processing is an area of active research. This study aims to investigate some of the basic features of an verse magnetic field on convective motion in electrically conducting melts. The geometry considered is in infinite vertical column of liquid metal with an axial temperature gradient and an imposed transverse magnetic field. The incipience and azimuthal orientation of convective roM is investigated. The governing transport equations are nondimensionalized, linearized and the eigen value problem is solved to determine the most physically significant states. The analysis shows that the initial degeneracy (with no magnetic field) is removed by the presence of a magnetic field and the primary convection roll aligns itself so that its plane is perpendicular to the applied magnetic field. A cross over to another mode is also found when the strength of the magnetic field is increased. Velocity distributions are presented corresponding to the lowest modes and the system behavior within limit s of non-linearity is discussed.

Mazuruk, Konstantin↗

NASA NTRS1999

Identification of Gravity-Related Effects on Crystal Growth From Melts With an Immiscibility Gap

This work involves an experimental-numerical approach to study the effects of natural and Marangoni convections on solidification of single crystals from a silicate melt with a liquid-liquid immiscibility gap. Industrial use of crystals grown from silicate melts is becoming increasingly important in electronic, optical, and high temperature structural applications. Even the simplest silicate systems like Al203-SiO2 have had, and will continue to have, a significant role in the development of traditional and advanced ceramics. A unique feature of crystals grown from the silicate systems is their outstanding linear electro-optic properties. They also exhibit exceptionally high optical rotativity. As a result, these crystals are attractive materials for dielectric, optical, and microwave applications. Experimental work in our laboratory has indicated that directional solidification of a single crystal mullite appears to be preceded by liquid-liquid phase separation in the melt. Disruption of the immiscible state results in crystallization of a two phase structure. There is also evidence that mixing in the melt caused by density-driven convection can significantly affect the stability of the immiscible liquid layers and result in poly-crystalline growth. On earth, the immiscible state has only been observed for small diameter crystals grown in float zone systems where natural convection is almost negligible. Therefore, it is anticipated that growth of large single crystals from silicate melts would benefit from microgravity conditions because of the reduction of the natural convective mixing. The main objective of this research is to determine the effects of transport processes on the phase separation in the melt during growth of a single crystal while addressing the following issues: (1) When do the immiscible layers form and are they real?; (2) What are the main physical characteristics of the immiscible liquids?; and (3) How mixing by natural or Marangoni convection affects the stability of the phase separated melt.

Kassemi, M.↗

NASA NTRS2019

A Numerical and Experimental Approach for Modeling Porosity Due to Entrapped Air and Volatiles Off-Gassing During Manufacturing of Composite Structures

High performance composite structures have strict requirements regarding acceptable levels of porosity. The impact can be significant on mechanical performance and mitigating the growth of voids can be a challenge given the complexity of the problem. The evolution of porosity can be summarized as a balance between sources and sinks which determine void growth or shrinkage. The primary sources of void growth include bag leaks, entrapped air in the system, off-gassing of volatiles, and cure shrinkage. Mechanisms which mitigate porosity include removal of air from the system and maintaining sufficient resin pressure during the process to keep volatiles in solution. In this paper, an approach for modeling the evolution of voids due to entrapped air and volatiles is presented. It has been shown in previous experimental studies that decreases in local resin pressure are linked to a higher likelihood of porosity formation. Results of the study are compared to experiments in which the local resin pressure was measured and micrographs of the panels were taken to characterize the porosity.

Hickmott, Curtis↗

NASA NTRS2009

Understanding how molecular hydrogen impacts the total dose and dose rate response of linear bipolar circuits

Recent Enhanced Low Dose Rate Sensitivity (ELDRS) investigations carried out by RLP Research, Arizona State University (ASU) and Jet Propulsion Laboratory (JPL) have shown significant differences in the degradation of bipolar micro-circuits with total dose in the presence of molecular hydrogen (H2) in packages. This has a significant impact on radiation hardness assurance and opens up opportunities to improve device performance. The general objectives of this program are to: 1. Determine the extent to which hydrogen contamination affects the total dose and dose rate response of linear bipolar circuits; 2. Develop a model that will enable the prediction of high dose rate (HDR) and low dose rate (LDR) response asymptotes and transition dose rates as a function of total dose, temperature, pressurized hydrogen, defect precursors, and other process dependent variables; 3. Explore the possibility of an accelerated hardness assurance method and possible hardening approaches; and 4. Extend the work to other technologies that have total dose response affected by hydrogen contamination.In this document, we xperimentally demonstrate with test transistors and circuits that hydrogen is correlated with ELDRS in bipolar linear circuits. We show that the amount of hydrogen determines: 1) the total dose response versus dose rate and 2) the transition dose rates between the high and low dose rate responses. The experimental results are supported with a steady state drift/diffusion analytical model as well as modeling calculations using COMSOL Multiphysics.

Pease, Ron↗

NASA NTRS1997

Role of Thyroxine in Space-Developed Jellyfish

The Aurelia Metamorphosis Test System was previously used to determine the effects of the space environment on the development and behavior of tiny (1-2 mm) jellyfish ephyrae during the SLS-1 and IML-2 missions. Results from the SLS-1 experiment included the discovery that statolith numbers were significantly reduced in Earth-formed ephyrae flown for nine days in space as compared with ground-based controls. In addition, upon return to Earth, six times more ephyrae which had developed in space than those developed on Earth had pulsing abnormalities, indicating that either these animals did not form their neuromuscular structures normally while in space or they were unable to adapt to the Ig environment upon return to Earth. The metamorphosis process, which enables the formation of ephyrae from polyps is influenced by a hormone, Jf-T4 Oellyfish thyroxine) which is synthesized following iodine administration. Two groups of polyps in space, however, formed ephyrae without iodine administration indicating that Jf-T4 synthesis, utilization, or excretion was different in. the ephyrae. Increased synthesis or build-up in the media of the hormone may also be linked to the increased demineralization of statoliths found in space-exposed ephyrae. In previous experiments, we found that externally administered thyroxine causes increased demineralization of statoliths on Earth. Abnormal pulsina in ephyrae following return to Earth during the SLS-1 mission may also be traced to increased Jf-T4 levels. Thyroxine is known to be important to the normal development and function of the nervous system, heart, and skeletal muscles in higher animals. For this third Jellyfish-in-Space experiment, we proposed to quantitate the levels of Jf- T4 and of T4 receptors in space-developed ephyrae and media and to compare these levels with those of animals developing and at Ig in space and on Earth. We expected to be able to determine whether Jf-T4 synthesis and/or secretion is different in space-flownjellyfish than in controls and to determine which cells (nerve, muscle, lithocytes, etc.)may have enhanced Jf-T4 levels. However, NASA deselected this experiment in August, 1997.

Spangenberg, Dorothy B.↗

NASA NTRS1972

Low cost fabrication of ablative heat shields

A material and process study was performed using subscale panels in an attempt to reduce the cost of fabricating ablative heat shield panels. Although no improvements were made in the material formulation, a significant improvement was obtained in the processing methods compared to those employed in the previous work. The principal feature of the new method is the press filling and curing of the ablation material in a single step with the bonding and curing of the face sheet. This method was chosen to replace the hand troweling and autoclave curing procedure used previously. Double-curvature panels of the same size as the flat panels were fabricated to investigate fabrication problems. It was determined that the same materials and processes used for flat panels can be used to produce the curved panels. A design with severe curvatures consisting of radii of 24 x 48 inches was employed for evaluation. Ten low-density and ten high-density panels were fabricated. With the exception of difficulties related to short run non-optimum tooling, excellent panel filling and density uniformity were obtained.

Cecka, A. M.↗

NASA NTRS1982

Determining spacecraft angular position with Delta VLBI - The Voyager demonstration

A demonstration of a new VLBI-based radio metric data type for interplanetary navigation has been conducted using the Voyager spacecraft on their approach to Saturn. Pseudo-range measurements from stations on intercontinental baselines were employed, in conjunction with interferometric observations of quasars, to obtain a precise measure of the spacecraft angular position. In addition to its high accuracy this technique requires significantly less station time than conventional range and Doppler and can be used in a downlink only mode. The paper describes the data type, acquisition system, and processing procedures. Anticipated measurement accuracy is established by analysis of various system error sources. Results obtained from Voyager observations are given to show that the system performance is in accordance with expectations.

Border, J. S.↗

NASA NTRS1983

Analysis of defect structure in silicon. Characterization of SEMIX material. Silicon sheet growth development for the large area silicon sheet task of the low-cost solar array project

Statistically significant quantitative structural imperfection measurements were made on samples from ubiquitous crystalline process (UCP) Ingot 5848 - 13C. Important correlation was obtained between defect densities, cell efficiency, and diffusion length. Grain boundary substructure displayed a strong influence on the conversion efficiency of solar cells from Semix material. Quantitative microscopy measurements gave statistically significant information compared to other microanalytical techniques. A surface preparation technique to obtain proper contrast of structural defects suitable for quantimet quantitative image analyzer (QTM) analysis was perfected and is used routinely. The relationships between hole mobility and grain boundary density was determined. Mobility was measured using the van der Pauw technique, and grain boundary density was measured using quantitative microscopy technique. Mobility was found to decrease with increasing grain boundary density.

Natesh, R.↗

NASA NTRS1985

Undercooling and solidification behavior in the InSb-Sb system

Use of the droplet emulsion technique has been successful in studying the undercooling and crystallization behavior of Sb, InSb, and an InSb-Sb eutectic alloy. Both droplet size and imposed cooling rate were influential in controlling the extent of liquid undercooling. The droplet surface coating was of significant importance in determining the resultant solidification product structure through its effect on nucleation kinetics. The maximum undercooling for pure Sb was extended from 0.08 to 0.23 T sub m. While simple crushing techniques provided a dramatic increase in droplet undercooling over the bulk material, emulsification treatments both enhanced this undercooling and allowed successful formation of a metastable simple cubic Sb phase. This phase was stable to temperatures approaching the melting point. The simple cubic phase was detected in droplet samples processed using DTA, air and water quenching, and drop tube processing under a helium gas atmosphere. A deviation in the InSb parent ingot composition limited interpretation of the line compound results, however, emulsification techniques extended the undercooling of this material to 0.17 T sub L and provided a stable, protective surface coating for the droplets. Emulsification of the eutectic alloy was effective at producing various levels of undercooling from 0.1 to 0.2 T sub E. Microstructural examination revealed a normal-type eutectic structure in the undercooled droplets indicating that solidification occurred within the coupled zone and that this zone is somewhat symmetric about the eutectic composition.

Graves, J. A.↗

NASA NTRS1993

Optimization of 15 parameters influencing the long-term survival of bacteria in aquatic systems

NASA is presently engaged in the design and development of a water reclamation system for the future space station. A major concern in processing water is the control of microbial contamination. As a means of developing an optimal microbial control strategy, studies were undertaken to determine the type and amount of contamination which could be expected in these systems under a variety of changing environmental conditions. A laboratory-based Taguchi optimization experiment was conducted to determine the ideal settings for 15 parameters which influence the survival of six bacterial species in aquatic systems. The experiment demonstrated that the bacterial survival period could be decreased significantly by optimizing environmental conditions.

Obenhuber, D. C.↗

NASA NTRS1993

Extraction of stability and control derivatives from orbiter flight data

The Space Shuttle Orbiter has provided unique and important information on aircraft flight dynamics. This information has provided the opportunity to assess the flight-derived stability and control derivatives for maneuvering flight in the hypersonic regime. In the case of the Space Shuttle Orbiter, these derivatives are required to determine if certain configuration placards (limitations on the flight envelope) can be modified. These placards were determined on the basis of preflight predictions and the associated uncertainties. As flight-determined derivatives are obtained, the placards are reassessed, and some of them are removed or modified. Extraction of the stability and control derivatives was justified by operational considerations and not by research considerations. Using flight results to update the predicted database of the orbiter is one of the most completely documented processes for a flight vehicle. This process followed from the requirement for analysis of flight data for control system updates and for expansion of the operational flight envelope. These results show significant changes in many important stability and control derivatives from the preflight database. This paper presents some of the stability and control derivative results obtained from Space Shuttle flights. Some of the limitations of this information are also examined.

Iliff, Kenneth W.↗

NASA NTRS2001

The Continuing Evolution of Land Surface Parameterizations

Land surface models (LSMs) play a critical role in the simulation of climate, for they determine the character of a large fraction of the atmosphere's lower boundary. The LSM partitions the net radiative energy at the land surface into sensible heat, latent heat, and energy storage, and it partitions incident precipitation water into evaporation, runoff, and water storage. Numerous modeling experiments and the existing (though very scant) observational evidence suggest that variations in these partitionings can feed back on the atmospheric processes that induce them. This land-atmosphere feedback can in turn have a significant impact on the generation of continental precipitation. For this and other reasons (including the role of the land surface in converting various atmospheric quantities, such as precipitation, into quantities of perhaps higher societal relevance, such as runoff), many modeling groups are placing a high emphasis on improving the treatment of land surface processes in their models. LSMs have evolved substantially from the original bucket model of Manabe et al. This evolution, which is still ongoing, has been documented considerably. The present paper also takes a look at the evolution of LSMs. The perspective here, though, is different - the evolution is considered strictly in terms of the 'balance' between the formulations of evaporation and runoff processes. The paper will argue that a proper balance is currently missing, largely due to difficulties in treating subgrid variability in soil moisture and its impact on the generation of runoff.

Koster, Randal↗

NASA NTRS2012

The NASA X-Ray Mission Concepts Study

The 2010 Astrophysics Decadal Survey recommended a significant technology development program towards realizing the scientific goals of the International X-ray Observatory (IXO). NASA has undertaken an X-ray mission concepts study to determine alternative approaches to accomplishing IXO's high ranking scientific objectives over the next decade given the budget realities, which make a flagship mission challenging to implement. The goal of the study is to determine the degree to which missions in various cost ranges from $300M to $2B could fulfill these objectives. The study process involved several steps. NASA released a Request for Information in October 2011, seeking mission concepts and enabling technology ideas from the community. The responses included a total of 14 mission concepts and 13 enabling technologies. NASA also solicited membership for and selected a Community Science Team (CST) to guide the process. A workshop was held in December 2011 in which the mission concepts and technology were presented and discussed. Based on the RFI responses and the workshop, the CST then chose a small group of notional mission concepts, representing a range of cost points, for further study. These notional missions concepts were developed through mission design laboratory activities in early 2012. The results of all these activities were captured in the final X-ray mission concepts study report, submitted to NASA in July 2012. In this presentation, we summarize the outcome of the study. We discuss background, methodology, the notional missions, and the conclusions of the study report.

Petre, Robert↗

NASA NTRS1990

Aeolian Removal of Dust Types from Photovoltaic Surfaces on Mars

Dust elevated in local or global dust storms on the Martian surface could settle on photovoltaic (PV) surfaces and seriously hamper their performance. Using a recently developed technique to apply a uniform dust layer, PV surface materials were subjected to simulated Martian winds in an attempt to determine whether natural Aeolian processes on Mars would sweep off the settled dust. Three different types of dust were used; an optical polishing powder, basaltic "trap rock", and iron (III) oxide crystals. The effects of wind velocity, angle of attack, height above the Martian surface, and surface coating material were investigated. It was found that arrays mounted with an angle of attack approaching 45 degrees show the most efficient clearing. Although the angular dependence is not sharp, horizontally mounted arrays required significantly higher wind velocities to clear off the dust. From this test it appears that the arrays may be erected quite near the ground, but previous studies have suggested that saltation effects can be expected to cause such arrays to be covered by soil if they are set up less than about a meter from the ground. Particle size effects appear to dominate over surface chemistry in these experiments, but additional tests are required to confirm this. Providing that the surface chemistry of Martian dusts is not drastically different from simulated dust and that gravity differences have only minor effects, the materials used for protective coatings for photovoltaic arrays may be optimized for other considerations such as transparency, and chemical or abrasion resistance. The static threshold velocity is low enough that there are regions on Mars which experience winds strong enough to clear off a photovoltaic array if it is properly oriented. Turbulence fences proved to be an ineffective strategy to keep dust cleared from the photovoltaic surfaces.

Gaier, James R.↗

NASA NTRS2019

Bright Opportunities for Atmospheric Characterization of Small Planets: Masses and Radii of K2-3 b, c, and d and GJ3470 b from Radial Velocity Measurements and Spitzer Transits

We report improved masses, radii, and densities for four planets in two bright M-dwarf systems, K2-3 and GJ3470, derived from a combination of new radial velocity and transit observations. Supplementing K2 photometry with follow-up Spitzer transit observations refined the transit ephemerides of K2-3 b, c, and d by over a factor of 10. We analyze ground-based photometry from the Evryscope and Fairborn Observatory to determine the characteristic stellar activity timescales for our Gaussian Process fit, including the stellar rotation period and activity region decay timescale. The stellar rotation signals for both stars are evident in the radial velocity data and is included in our fit using a Gaussian process trained on the photometry. We find the masses of K2-3 b, K2-3 c, and GJ3470 b to be 6.48(+0.99,-0.93), 2.14(+1.08,-1.28), and 12.58(+1.31,-1.28)Mꚛ, respectively. K2-3 d was not significantly detected and has a 3σ upper limit of 2.80 Mꚛ. These two systems are training cases for future TESS systems; due to the low planet densities (ρ < 3.7 g/cu.cm) and bright host stars (K < 9 mag), they are among the best candidates for transmission spectroscopy in order to characterize the atmospheric compositions of small planets.

Molly R. Kosiarek↗

NASA NTRSDate not supplied

Nutrient Stability in NASA Spaceflight Experiment Rodent Food Bars

Nutrient-upgraded Rodent Food Bars are the standard diet for mice involved in spaceflight experiments aboard the International Space Station as part of NASA’s Rodent Research Project. These Food Bars are a twin-screw extruded AIN-93G based product with nutrient additives to preserve a healthy and complete diet for the animals, and the bar form factor is necessary for use in the microgravity environment. Due to the nature of NASA flight projects and the lengthy production process of these Food Bars, a shelf-life assessment was undertaken to determine nutrient stability over an extended storage time. To assess palatability and stability over an extended duration, a panel of lipid oxidation markers and both fat- and water-soluble vitamins were assessed under various time and temperature conditions via AOAC International standardized methodology. Thiamine was the least stable vitamin at room temperature. Bars that had been continually kept at 4C (t=6, 12, 27 months) showed significantly higher levels of thiamine (via Student’s t-test) compared to all other bars that underwent some degree of ambient temperature storage. This suggests that refrigeration is a key component in maintaining adequate nutrient levels in these relatively high moisture (average 29.3%) food bars. Also of note was the level of Vitamin A in the form of retinol. There was no correlation to storage temperature, but rather the only factor having an effect on retinol levels was time. As low, yet consistent decrease in retinol was observed over the course of the experiment, though at no time did the retinol levels drop below the rodent Nutrient Requirements for Laboratory Animals (NRC). In conclusion, over the 27-month time course, all analyzed vitamins and lipid oxidation factors remained relatively stable and at levels which provide fully sufficient nutrition to rodents during spaceflight. Some groups however, displayed higher-than-expected aerobic and anaerobic bacteria colony forming units, which is believed to stem from a since-revised handling technique.

Food↗

NASA NTRSDate not supplied

Exemplifying the Usability of NASA Earth Observations to Analyze Potential Risk Factors that Predispose Wildfires in the Rural-Urban Areas of Córdoba, Argentina

In recent years, Córdoba, Argentina has experienced intensified wildfire activity, with fires in 2020 alone scorching over 300,000 hectares within the province. Potential causes for the increased burn area include climate change, the expanding wildland-urban interface, and inadequate fire management practices. Previous studies have produced fire frequency maps for the region, but gaps remain in understanding the parameters influencing fire behavior and growth. This project partnered with the Instituto Nacional de Tecnología Agropecuaria to address these gaps by utilizing NASA’s remote sensing capabilities to analyze key wildfire risk factors. Using a combination of data inputs from Soil Moisture Active Passive (SMAP), Shuttle Radar Topography Mission (SRTM), Global Precipitation Measurement (GPM) Integrated Multi-satellite Retrievals for GPM (IMERG), and Aqua/Terra Moderate Resolution Imaging Spectroradiometer (MODIS), a ten-year baseline was created using environmental variables to determine anomalies that influenced the fires of 2020. Of these anomalies, the baseline data were used to calculate the statistical significance of the environmental factors to the wildfires. This study found that the normalized difference vegetation index (NDVI) and precipitation were the strongest indicators for the September 2020 wildfires. Using the environmental risk factors, this project created a wildfire risk map for the province of Córdoba, which can be used to enhance partner’s fire management strategies and decision-making processes.

Chassety Raines↗