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NASA NTRS2008

Chamber for Aerosol Deposition of Bioparticles

Laboratory apparatus is depicted that is a chamber for aerosol deposition of bioparticles on surfaces of test coupons. It is designed for primary use in inoculating both flat and three-dimensional objects with approximately reproducible, uniform dispersions of bacterial spores of the genus Bacillus so that the objects could be used as standards for removal of the spores by quantitative surface sampling and/or cleaning processes. The apparatus is also designed for deposition of particles other than bacterial spores, including fungal spores, viruses, bacteriophages, and standard micron-sized beads. The novelty of the apparatus lies in the combination of a controllable nebulization system with a settling chamber large enough to contain a significant number of test coupons. Several companies market other nebulizer systems, but none are known to include chambers for deposition of bioparticles to mimic the natural fallout of bioparticles. The nebulization system is an expanded and improved version of commercially available aerosol generators that include nebulizers and drying columns. In comparison with a typical commercial aerosol generator, this system includes additional, higher-resolution flowmeters and an additional pressure regulator. Also, unlike a typical commercial aerosol generator, it includes stopcocks for separately controlling flows of gases to the nebulizer and drying column. To maximize the degree of uniformity of dispersion of bioaerosol, the chamber is shaped as an axisymmetrical cylinder and the aerosol generator is positioned centrally within the chamber and aimed upward like a fountain. In order to minimize electric charge associated with the aerosol particles, the drying column is made of aluminum, the drying column is in direct contact with an aluminum base plate, and three equally spaced Po-210 antistatic strips are located at the exit end of the drying column. The sides and top of the chamber are made of an acrylic polymer; to prevent accumulation of electric charge on them, they are spray-coated with an anti-static material. During use, the base plate and the sides and top of the chamber are grounded as a further measure to minimize the buildup of electric charge.

Kern, Roger↗

NASA NTRS2010

Multi-Sensor Mud Detection

Robust mud detection is a critical perception requirement for Unmanned Ground Vehicle (UGV) autonomous offroad navigation. A military UGV stuck in a mud body during a mission may have to be sacrificed or rescued, both of which are unattractive options. There are several characteristics of mud that may be detectable with appropriate UGV-mounted sensors. For example, mud only occurs on the ground surface, is cooler than surrounding dry soil during the daytime under nominal weather conditions, is generally darker than surrounding dry soil in visible imagery, and is highly polarized. However, none of these cues are definitive on their own. Dry soil also occurs on the ground surface, shadows, snow, ice, and water can also be cooler than surrounding dry soil, shadows are also darker than surrounding dry soil in visible imagery, and cars, water, and some vegetation are also highly polarized. Shadows, snow, ice, water, cars, and vegetation can all be disambiguated from mud by using a suite of sensors that span multiple bands in the electromagnetic spectrum. Because there are military operations when it is imperative for UGV's to operate without emitting strong, detectable electromagnetic signals, passive sensors are desirable. JPL has developed a daytime mud detection capability using multiple passive imaging sensors. Cues for mud from multiple passive imaging sensors are fused into a single mud detection image using a rule base, and the resultant mud detection is localized in a terrain map using range data generated from a stereo pair of color cameras.

Rankin, Arturo L.↗

NASA NTRS2010

Reevaluating the Role of Saharan Air Layer in Atlantic Tropical Cyclogenesis and Evolution

The existence of the Saharan air layer (SAL), a layer of warm, dry, dusty air that frequently moves westward off of the Saharan desert of Africa and over the tropical Atlantic Ocean, has long been appreciated. As air moves over the desert, it is strongly heated from below, producing a very hot air mass at low levels. Because there is no moisture source over the Sahara, the rise in temperature causes a sharp drop in relative humidity, thus drying the air. In addition, the warm air produces a very strong jet of easterly flow in the middle troposphere called the African easterly jet that is thought to play a critical role in hurricane formation. In recent years, there has been an increased focus on the impact that the SAL has on the formation and evolution of hurricanes in the Atlantic. However, the nature of its impact remains unclear, with some researchers arguing that the SAL amplifies hurricane development and with others arguing that it inhibits it. The argument for positively influencing hurricane development is based upon the fact that the African easterly jet provides an energy source for the waves that eventually form hurricanes and that it leads to rising motion south of the jet that favors the development of deep thunderstorm clouds. The potential negative impacts of the SAL include 1) low-level vertical wind shear associated with the African easterly jet; 2) warm SAL air aloft, which increases thermodynamic stability and suppresses cloud development; and 3) dry air, which produces cold downdrafts in precipitating regions, thereby removing energy needed for storm development. As part of this recent focus on the SAL and hurricanes (which motivated a 2006 NASA field experiment), there has been little emphasis on the SAL s potential positive influences and almost complete emphasis on its possible negative influences, almost to the point of claims that the SAL is the major suppressing influence on hurricanes in the Atlantic. In this study, multiple NASA satellite data sets (TRMM, MODIS, CALIPSO, and AIRS/AMSU) and National Centers for Environmental Prediction global analyses are used to see if the proposed negative influences deserve all of the attention they have recently received. The results show that storms generally form on the southern side of the African jet, where favorable background rotation is high. The jet often helps to form the northern side of the storms and is typically stronger in storms that intensify than those that weaken, suggesting that jet-induced vertical wind shear is not a negative influence on developing storms. Warm SAL air is confined to regions north of the jet and generally does not impact the tropical cyclone precipitation south of the jet. A comparison of the environments of strongly strengthening storms and of weakening storms shows no differences in SAL structure, indicating that the SAL has little influence on whether storms weaken or intensify. The large-scale flow at upper levels above the SAL was found to be most important, with the environment of strengthening storms having very little vertical wind shear and also favoring more expansive outflow from the storm. The SAL is shown to occur in a large-scale environment that is already characteristically dry as a result of large-scale subsidence (sinking air motions). Strong surface heating and deep dry convective mixing enhance dryness at low levels, but moisten the air at midlevels. Therefore, mid-to-upper-level dryness is not a defining characteristic of the SAL, but is instead a signature of subsidence. As a result, we conclude that the SAL is not the major negative influence on hurricanes that recent studies have emphasized. It is just one of many possible influences and can be both positive and negative.

Braun, Scott A.↗

NASA NTRS2015

Integration of Product, Package, Process, and Environment: A Food System Optimization

The food systems slated for future NASA missions must meet crew nutritional needs, be acceptable for consumption, and use resources efficiently. Although the current food system of prepackaged, moderately stabilized food items works well for International Space Station (ISS) missions, many of the current space menu items do not maintain acceptability and/or nutritive value beyond 2 years. Longer space missions require that the food system can sustain the crew for 3 to 5 years without replenishment. The task "Integration of Product, Package, Process, and Environment: A Food System Optimization" has the objective of optimizing food-product shelf life for the space-food system through product recipe adjustments, new packaging and processing technologies, and modified storage conditions. Two emergent food processing technologies were examined to identify a pathway to stable, wet-pack foods without the detrimental color and texture effects. Both microwave-assisted thermal sterilization (MATS) and pressure-assisted thermal stabilization (PATS) were evaluated against traditional retort processing to determine if lower heat inputs during processing would produce a product with higher micronutrient quality and longer shelf life. While MATS products did have brighter color and better texture initially, the advantages were not sustained. The non-metallized packaging film used in the process likely provided inadequate oxygen barrier. No difference in vitamin stability was evident between MATS and retort processed foods. Similarly, fruit products produced using PATS showed improved color and texture through 3 years of storage compared to retort fruit, but the vitamin stability was not improved. The final processing study involved freeze drying. Five processing factors were tested in factorial design to assess potential impact of each to the quality of freeze-dried food, including the integrity of the microstructure. The initial freezing rate and primary freeze drying temperature and pressure were linked to final product quality in freeze-dried corn, indicating processing modifications that could lead to improved product shelf life. Storage temperatures and packaging systems were also assessed for the impact to food quality. Reduced temperature storage had inconclusive impact to the progression of rancidity in butter cookies. Frozen storage was detrimental to fruit and vegetable textural attributes but refrigerated storage helped to sustain color and organoleptic ratings for plant-based foods. With regard to packaging systems, the metallized film overwrap significantly decreased the progression of the rancidity of butter cookies as compared to the highest barrier non-metallized film. The inclusion of oxygen scavengers resulted in noticeable moisture gains in butter cookies over time, independent of packaging film systems. Neither emergent processing technology nor the freeze dry optimization resulted in compelling quality differences from current space food provisions such that a five-year shelf life is likely with these processing changes alone. Using a combination of refrigeration and PATS processing is expected to result in organoleptically-acceptable fruit quality for most fruits through five years. The vitamin degradation will be aided somewhat by the cold temperatures but, given the labile nature of vitamin C, a more stable fortification method, such as encapsulation, should also be investigated to ensure vitamin delivery throughout the product life. Similarly, significant improvement to the packaging film used in the MATS processing, optimization of formulation for dielectric properties, vitamin fortification, and reduced temperature storage should be investigated as a hurdle approach to reach a five year shelf life in wet-pack entrees and soups. Baked goods and other environmentally-sensitive spaceflight foods will require an almost impenetrable barrier to protect the foods from oxygen and moisture ingress but scavengers and reduced storage temperature did not improve baked good shelf life and are not recommended at this time for these foods.

Cooper, Maya R.↗

NASA NTRS2014

Cleaning Process Development for Metallic Additively Manufactured Parts

Additive Manufacturing of metallic components for aerospace applications offers many advantages over traditional manufacturing techniques. As a new technology, many aspects of its widespread utilization remain open to investigation. Among these are the cleaning processes that can be used for post finishing of parts and measurements to verify effectiveness of the cleaning processes. Many cleaning and drying processes and measurement methods that have been used for parts manufactured using conventional techniques are candidates that may be considered for cleaning and verification of additively manufactured parts. Among these are vapor degreasing, ultrasonic immersion and spray cleaning, followed by hot air drying, vacuum baking and solvent displacement drying. Differences in porosity, density, and surface finish of additively manufactured versus conventionally manufactured parts may introduce new considerations in the selection of cleaning and drying processes or the method used to verify their effectiveness. This presentation will review the relative strengths and weaknesses of different candidate cleaning and drying processes as they may apply to additively manufactured metal parts for aerospace applications. An ultrasonic cleaning technique for exploring the cleanability of parts will be presented along with an example using additively manufactured Inconel 718 test specimens to illustrate its use. The data analysis shows that this ultrasonic cleaning approach results in a well-behaved ultrasonic cleaning/extraction behavior. That is, it does not show signs of accelerated cavitation erosion of the base material, which was later confirmed by neutron imaging. In addition, the analysis indicated that complete cleaning would be achieved by ultrasonic immersion cleaning at approximately 5 minutes, which was verified by subsequent cleaning of additional parts.

Tramel, Terri L.↗

NASA NTRS2017

Regenerative Gas Dryer for In-Situ Propellant Production

Rocket propellant can be produced anywhere that water is found by splitting it into hydrogen and oxygen, potentially saving several tons of mass per mission and enabling the long term presence of humans in space beyond LEO. When water is split into hydrogen and oxygen, the gaseous products can be very humid (several thousand ppm). Propellant-grade gases need to be extremely dry before being converted into cryogenic liquids (less than 26 ppm water for grade B Oxygen). The primary objective of this project is to design, build and test a regenerative gas drying system that can take humid gas from a water electrolysis system and provide dry gas (less than 26ppm water) to the inlet of a liquefaction system for long durations. State of the art work in this area attempted to use vacuum as a means to regenerate desiccant, but it was observed that water would migrate to the dry zone without a sweep gas present to direct the desorbed vapor. Further work attempted to use CO2 as a sweep gas, but this resulted in a corrosive carbonic acid. In order for in-situ propellant production to work, we need a way to continuously dry humid gas that addresses these issues.

Paz, Aaron↗

NASA NTRS2020

Twenty‐First Century Drought Projections in the CMIP6 Forcing Scenarios

There is strong evidence climate change will increase drought risk and severity, but these conclusions depend on the regions, seasons, and drought metrics being considered. We analyze changes in drought across the hydrologic cycle (precipitation, soil moisture, and runoff) in projections from Phase Six of the Coupled Model Intercomparison Project (CMIP6). The multi‐model ensemble shows robust drying in the mean state across many regions and metrics by the end of the 21st century, even following the more aggressive mitigation pathways (SSP1‐2.6 and SSP2‐4.5). Regional hotspots with strong drying include western North America, Central America, Europe and the Mediterranean, the Amazon, southern Africa, China, Southeast Asia, and Australia. Compared to SSP3‐7.0 and SSP5‐8.5, however, the severity of drying in the lower warming scenarios is substantially reduced and further precipitation declines in many regions are avoided. Along with drying in the mean state, the risk of the historically most extreme drought events also increases with warming, by 200–300% in some regions. Soil moisture and runoff drying in CMIP6 is more robust, spatially extensive, and severe than precipitation, indicating an important role for other temperature‐sensitive drought processes, including evapotranspiration and snow. Given the similarity in drought responses between CMIP5 and CMIP6, we speculate both generations of models are subject to similar uncertainties, including vegetation processes, model representations of precipitation, and the degree to which model responses to warming are consistent with observations. These topics should be further explored to evaluate whether CMIP6 models offer reasons to have increased confidence in drought projections.

drought↗

NASA NTRS1991

Use of electron microprobe x-ray analysis for determination of low calcium concentrations across leaves deficient in calcium

An electron microprobe with wavelength-dispersive x-ray spectrometry (WDS) was found to be useful for the determination of Ca concentrations in leaf tissue deficient in Ca. WDS effectively detected Ca concentrations as low as 0.2 mg/g dry wt in the presence of high levels of K and Mg (120 and 50 mg/g dry wt, respectively). Leaf specimens were prepared for analysis by quick-freezing in liquid nitrogen and freeze-drying at -20 degrees C to maintain elemental integrity within the tissue. Because dry material was analyzed, sample preparation was simple and samples could be stored for long periods before analysis. A large beam diameter of 50 gm was used to minimize tissue damage under the beam and analyze mineral concentrations within several cells at one time. Beam penetration was between 50 and 55 microns, approximately one-third of the thickness of the leaf. For analysis of concentrations in interveinal areas, analyses directed into the abaxial epidermis were found most useful. However, because of limited beam penetration, analyses of veinal areas would require use of cross sections [correction of crosssections]. Solid mineral standards were used for instrument standardization. To prevent measurement errors resulting from differences between the matrix of the mineral standards and the analyzed tissue, concentrations in leaves were corrected using gelatin standards prepared and analyzed under the same conditions. WDS was found to be useful for documenting that very low Ca levels occur in specific areas of lettuce leaves exhibiting the Ca deficiency injury termed tipburn.

Non-NASA Center↗

NASA NTRS2023

High-Pressure Oxygen Dryer (HPOD) FY 2023 Trade Study and Market Survey

A reliable source of dry, high-pressure oxygen is needed for future lunar missions to support nominal and contingency operations on the Surface Habitat (SH) and the Pressurized Rover (PR) in future Gateway missions. A High-Pressure Oxygen Dryer (HPOD) is needed to support potential use of primary oxygen generation systems, the High-Pressure Oxygen Generation Assembly (HPOGA) and the Skyre EOC, by drying the wet oxygen exiting the systems. The objective of this paper is to perform an architecture trade study and market survey of options to dry a continuous stream of 45°C, 4000 PSIG oxygen containing ~ 500 ppm H2O (dew point 52°C) down to < 7 ppm H2O (dew point -15°C) for both the 28-day and 365-day timeframe. A total of seven different technologies were identified as potential dryer candidates during the market survey, relying on one of three principles, adsorption, filtration, and cooling. During the sizing and trade study, it was found that several of the technologies aren’t sufficient for the extreme conditions and were eliminated. In the end, a single-use throw away adsorption bed traded the best for single mission use, while a pressure regenerative adsorption bed traded the best for a multiple mission scenario. The results of this analysis are intended to influence future design work for high-pressure oxygen drying applications.

High Pressure Oxygen↗

NASA NTRSDate not supplied

High-Pressure Oxygen Dryer (HPOD) FY 2023 Trade Study and Market Survey

High Pressure Oxygen↗

NASA NTRSDate not supplied

High-Pressure Oxygen Dryer (HPOD) FY 2023 Trade Study and Market Survey

A reliable source of dry, high-pressure oxygen is needed for future lunar missions to support nominal and contingency operations on the Surface Habitat (SH) and the Pressurized Rover (PR) in future Gateway missions. A High-Pressure Oxygen Dryer (HPOD) is needed to support potential use of primary oxygen generation systems, the High-Pressure Oxygen Generation Assembly (HPOGA) and the Skyre EOC, by drying the wet oxygen exiting the systems. The objective of this paper is to perform an architecture trade study and market survey of options to dry a continuous stream of 45°C, 4000 PSIG oxygen containing ~ 500 ppm H 2 O (dew point 52°C) down to < 7 ppm H 2 O (dew point -15°C) for both the 28-day and 365-day timeframe. A total of seven different technologies were identified as potential dryer candidates during the market survey, relying on one of three principles, adsorption, filtration, and cooling. During the sizing and trade study, it was found that several of the technologies aren’t sufficient for the extreme conditions and were eliminated. In the end, a single-use throw away adsorption bed traded the best for single mission use, while a pressure regenerative adsorption bed traded the best for a multiple mission scenario. The results of this analysis are intended to influence future design work for high-pressure oxygen drying applications.

High Pressure Oxygen↗

NASA NTRS1962

Influence of Tire Tread Pattern and Runway Surface Condition on Braking Friction and Rolling Resistance of a Modern Aircraft Tire

A series of taxiing tests was conducted at the Langley landing loads track with both braked and unbraked (freely rolling) single and tandem wheels equipped with 32x8.8 type VII aircraft tires of different tread designs to obtain data on tire and braking characteristics during operation on dry and on contaminated concrete and asphalt run ways. Contaminants used were water, slush, JP-4 jet fuel, and organic and detergent fire-extinguishing foams. Forward velocities for the tests ranged from approximately 13 to 104 knots. Vertical loads of approximately 9,000 to 22,000 pounds and tire inflation pressures of 85 to 350 pounds per square inch were used. Results indicated that the unbraked tire rolling resistance increased with increasing forward velocity on dry and on contaminated runway surfaces. Peak tire-ground friction coefficients developed during wheel braking decreased rapidly with increasing velocity on contaminated runways but remained relatively unchanged on dry runways as the forward velocity was increased. Dry-runway friction coefficients were found to be relatively insensitive to tire tread pattern. However, the magnitude of the friction coefficients developed by tires on contaminated runways was extremely sensitive to the tire tread pat tern used, with circumferential-groove treads developing the highest values of friction coefficient, and smooth and dimple treads the lowest values for the tread patterns and runway conditions investigated.

Horne, Walter B.↗

NASA NTRS1977

Performance evaluation of two black nickel and two black chrome solar collectors

The test program was based on the evaluation of four unique solar collectors described below: (1) black nickel collector surface with a desiccant drying bed, (2) black nickel collector surface without a desiccant drying bed, (3) black chrome collector surface with a dessicant drying bed, and (4) black chrome collector surface without a desiccant drying bed. The test program included three distinct phases: Initial performance evaluation, natural environmental aging, and post-aging performance evaluation. Results of Phase III testing conclusively indicated a higher normalized efficiency for Black Chrome surfaces when compared to Black Nickel.

Losey, R.↗

NASA NTRS1978

Mechanisms of deterioration of nutrients

Methods for improving the quality of freeze-dried foods were investigated. Areas discussed include: (1) microstructure of freeze-dried systems, (2) structural changes in freeze-dried systems, (3) artificial food matrices, and (4) osmotic preconcentration to yield improved freeze-dried products.

Karel, M.↗

NASA NTRS1984

Binder for Carbon-Fiber Coating

Insoluble, even coating formed by soaking in polyacrylic acid. Carbon fiber material prepared by soaking in solution of 20 percent polyacrylic acid in water. Material blotted and dried at 120 degrees C for at least 2 hours. Dried material reacted with boiling aqueous solution of calcium acetate. Treated material removed from boiling solution, blotted, dried at 120 degrees C, washed with distilled water, and dried again.

Dowler, W. L.↗

NASA NTRS1984

Forced convection heat transfer to air/water vapor mixtures

Heat transfer coefficients were measured using both dry and humid air in the same forced convection cooling scheme and were compared using appropriate nondimensional parameters (Nusselt, Prandtl and Reynolds numbers). A forced convection scheme with a complex flow field, two dimensional arrays of circular jets with crossflow, was utilized with humidity ratios (mass ratio of water vapor to air) up to 0.23. The dynamic viscosity, thermal conductivity and specific heat of air, steam and air/steam mixtures are examined. Methods for determining gaseous mixture properties from the properties of their pure components are reviewed as well as methods for determining these properties with good confidence. The need for more experimentally determined property data for humid air is discussed. It is concluded that dimensionless forms of forced convection heat transfer data and empirical correlations based on measurements with dry air may be applied to conditions involving humid air with the same confidence as for the dry air case itself, provided that the thermophysical properties of the humid air mixtures are known with the same confidence as their dry air counterparts.

Richards, D. R.↗

NASA NTRS1986

Wheat response to CO2 enrichment: CO2 exchanges transpiration and mineral uptakes

When simulating canopies planted in varied densities, researchers were able to demonstrate that increase of dry matter production by enhancing CO2 quickly becomes independant of increase of leaf area, especially above leaf area index of 2; dry matter gain results mainly from photosynthesis stimulation per unit of surface (primary CO2 effect). When crop density is low (the plants remaining alone a longer time), the effects of increasing leaf surface (tillering, leaf elongation here, branching for other plants etc.) was noticeable and dry matter simulation factor reached 1.65. This area effect decreased when canopy was closed in, as the effect of different surfaces no longer worked. The stimulation of photosynthesis reached to the primary CO2 effect. The accumulation in dry matter which was fast during that phase made the original weight advantage more and more neglectible. Comparison with short term measurements showed that first order long term effect of CO2 in wheat is predictible with short term experiment, from the effect of CO2 on photosynthesis measured on reference sample.

Andre, M.↗

NASA NTRS1986

Effect of water immersion on cardiopulmonary physiology at high gravity (+Gz)

The cardiopulmonary responses of eight male subject between 21-31 years exposed to 1, 2, and 3 Gz during immersion at 35 + or - 0.5 C to heart level and during control dry rides are studied. Ventilation, O2 consumption, the end-tidal pressure of CO2, heart frequency, cardiac output, functional residual capacity, and the arterial pressure of CO2 were measured. It is observed that as Gz increases ventilation, heart frequency, and O2 consumption increase, and the end-tidal and arterial pressures of CO2 decrease during dry rides, but are not altered during immersion. It is detected that the functional residual capacity is lower during immersion and decreases in both the dry and immersed state as Gz increases, and cardiac output decreases as Gz increases in dry rides. It is noted that changes produced by acceleration in a Gz direction are due to the effect on the systemic circulation rather than to the effect on the lungs.

Arieli, R.↗