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At least 37 records · Page 2

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NASA NTRS1977

The use of twin screw extruders for feeding coal against pressures of up to 1500 PSI

Recent tests with a twin-screw, co-rotating extruder which was successfully used to convey and feed coal against pressures of up to 1500 psi are described. Intermeshing and self-wiping, co-rotating twin-screws give greatly improved conveying and pressure built-up capabilities and avoid hangup and eventual decomposition of coal particles in the screw flights. The conveying action of intermeshing, self-wiping, co-rotating extruder systems approaches that of a positive displacement pump. With this feature, it is possible to maintain very accurate control over all aspects of product conveyance in the extruder, i.e., intake, conveyance and pressure buildup.

Wiedmann, W.↗

NASA NTRS1989

Contamination removal using various solvents and methodologies

Critical and non-critical bonding surfaces must be kept free of contamination that may cause potential unbonds. For example, an aft-dome section of a redesigned solid rocket motor that had been contaminated with hydraulic oil did not appear to be sufficiently cleaned when inspected by the optically stimulated electron emission process (Con Scan) after it had been cleaned using a hand double wipe cleaning method. As a result, current and new cleaning methodologies as well as solvent capability in removing various contaminant materials were reviewed and testing was performed. Bonding studies were also done to verify that the cleaning methods used in removing contaminants provide an acceptable bonding surface. The removal of contaminants from a metal surface and the strength of subsequent bonds were tested using the Martin Marietta and double-wipe cleaning methods. Results are reported.

Jeppsen, J. C.↗

NASA NTRS1997

Space Shuttle Reusable Solid Rocket Motor (RSRM) Hand Cleaning Solvent Replacement at Kennedy Space Center (KSC)

At Kennedy Space Center (KSC), Thiokol Corporation provides the engineering to assemble and prepare the Space Shuttle Reusable Solid Rocket Motor (RSRM) for launch. This requires hand cleaning over 86 surfaces including metals, adhesives, rubber and electrical insulations, various painted surfaces and thermal protective materials. Due to the phase-out of certain ozone depleting chemical (ODC) solvents, all RSRM hand wipe operations being performed at KSC using l,l,1-trichloroethane (TCA) were eliminated. This presentation summarizes the approach used and the data gathered in the effort to eliminate TCA from KSC hand wipe operations.

Keen, Jill M.↗

NASA NTRS2004

Evaluation of various cleaning methods to remove bacillus spores from spacecraft hardware materials

A detailed study was made of the biological cleaning effectiveness, defined in terms of the ability to remove bacterial spores, of a number of methods used to clean hardware surfaces. Aluminum (Al 6061) and titanium (Ti 6Al-4V) were chosen for the study as they were deemed the two materials most likely to be used in spacecraft extraterrestrial sampler construction. Metal coupons (1 cm x 2.5 cm) were precleaned and inoculated with 5.8 x 10(3) cultivable Bacillus subtilis spores, which are commonly found on spacecraft surfaces and in the assembly environments. The inoculated coupons were subsequently cleaned using: (1) 70% isopropyl alcohol wipe; (2) water wipe; (3) multiple-solvent flight-hardware cleaning procedures used at the Jet Propulsion Laboratory (JPL); (4) Johnson Space Center-developed ultrapure water rinse; and (5) a commercial, semi-aqueous, multiple-solvent (SAMS) cleaning process. The biological cleaning effectiveness was measured by agar plate assay, sterility test (growing in liquid media), and epifluorescent microscopy. None of the cleaning protocols tested completely removed viable spores from the surface of the aluminum. In contrast, titanium was capable of being cleaned to sterility by two methods, the JPL standard and the commercial SAMS cleaning process. Further investigation showed that the passivation step employed in the JPL standard method is an effective surface sterilant on both metals but not compatible with aluminum. It is recommended that titanium (Ti 6Al-4V) be considered superior to aluminum (Al 6061) for use in spacecraft sampling hardware, both for its potential to be cleaned to sterilization and for its ability to withstand the most effective cleaning protocols.

Spores, Bacterial/metabolism↗

NASA NTRS2006

Preventing Ice Before it Forms

In the late 1990s, a team of engineers at Ames Research Center invented an anti-icing fluid to keep ice from building up on airplane wings. Ice on wings can be a serious safety hazard, especially during takeoff, when a sheet of ice the thickness of a compact disc can reduce lift by 25 percent or more. The typical approach to clearing off the ice is to use a deicing solution once the ice has built up. The fluid created by the Ames team, though, when applied to a dry surface, prevents the ice from even forming a surface bond, which saves deicing time and money, while also preventing excessive use of chemical solvents. If, however, the solution is not applied before ice forms, it also serves as a traditional deicing formula. The formula contains propylene glycol, which has a very low freezing point, and a thickener, which helps the fluid adhere to the surface. Ice gathers on top of the formula, and then it can be wiped off with little effort. This thickening agent, a pseudo-plastic, sprays on as a liquid, like lemonade, gels like a lemon sherbet, turns back to a liquid when wiped, and then gels again into its sherbet consistency when left to solidify. The sherbet-gel stage is especially important when the formula is sprayed onto a vertical or steeped surface, as it clings better than a liquid would.

Source record↗

NASA NTRS2007

Center Director's Discretionary Fund 2005 Annual Report

The FY 2005 CDDF projects were selected from the following spaceport and range technology and science areas: fluid system technologies; spaceport structures and materials; command, control, and monitoring technologies; and biological sciences (including support for environmental stewardship). The FY 2005 CDDF research projects involved development of the following: a) Capacitance-based moisture sensors to optimize plant growth in reduced gravity; b) Commodity-free calibration methods; c) Application of atmospheric plasma glow discharge to alter the surface properties of polymers for improved electrostatic dissipation characteristics; d) A wipe-on, wipe-off chemical process to remove lead oxides found in paint; e) A robust metabolite profiling platform for better understanding the "law" of biological regulation; f) An explanation of the excavation processes that occur when a jet of gas impinges on a bed of sand; g) "Smart coatings" to detect and control corrosion at an early stage to prevent further corrosion h) A model that can produce a reliable diagnosis of the quality of a software product; i) The formulation of advanced materials to meet system safety needs to minimize electrostatic charges, flammability, and radiation exposure; j) A lab-based instrument that uses the electro-optic Pockels effect to make static electric fields visible; k) A passive volatile organic compound (VOC) cartridge to filter, identify, and quantify VOCs flowing into or emanating from plant flight experiments.

Nurge, Mark↗

NASA NTRSDate not supplied

Evaluation of Contact Separation Force Testing as a Screening Methodology for Electrical Socket Contacts

During system level testing intermittent and permanent open circuit failures of mated, crimp removable, electrical contact pairs were experienced. The root cause of the failures was determined to be low (but not zero) contact forces applied by the socket contact tines against the engaging pin. The low contact force reduces the effectiveness of the wiping action of the socket tines against the pin. The observed failure mode may be produced when insufficient wiping during mate, demate and small relative movement in use allows for the accumulation of debris or insulating films that electrically separate the contact pair. The investigation identified at least three manufacturing process control problems associated with the socket contacts that enabled shipment of contacts susceptible to developing low contact forces: (1) Improper heat treatment of the socket tines resulting in plastic rather than elastic behavior; (2) Overly thinned socket tines at their base resulting in reduced pin retention forces; (3) Insufficient screening tests to identify parts susceptible to the aforementioned failure mechanisms. The results from an extensive screening program of socket contacts utilizing the industry standard contact separation force test procedures are described herein. The investigation shows this method to be capable of identifying initially weak sockets. However, sockets whose contact retention forces may degrade during use may not be screened out by pin retention testing alone. Further investigations are required to correlate low contact retention forces with increased electrical contact resistance in the presence of insulating films that may accumulate in the use environment.

Christopher Green↗

NASA NTRS2012

The Evolution of Friction Stir Welding Theory at Marshall Space Flight Center

From 1995 to the present the friction stir welding (FSW) process has been under study at Marshall Space Flight Center (MSFC). This is an account of the progressive emergence of a set of conceptual tools beginning with the discovery of the shear surface, wiping metal transfer, and the invention of a kinematic model and making possible a treatment of both metallurgical structure formation and process dynamics in friction stir welding from a unified point of view. It is generally observed that the bulk of the deformation of weld metal around the FSW pin takes place in a very narrow, almost discontinuous zone with high deformation rates characteristic of metal cutting. By 1999 it was realized that this zone could be treated as a shear surface like that in simple metal cutting models. At the shear surface the seam is drawn out and compressed and pressure and flow conditions determine whether or not a sound weld is produced. The discovery of the shear surface was followed by the synthesis of a simple 3- flow kinematic model of the FSW process. Relative to the tool the flow components are: (1) an approaching translational flow at weld speed V, (2) a rotating cylindrical plug flow with the angular velocity of the tool , and (3) a relatively slow ring vortex flow (like a smoke ring) encircling the tool and driven by shoulder scrolls and pin threads. The rotating plug flow picks up an element of weld metal, rotates it around with the tool, and deposits it behind the tool ( wiping metal transfer ); it forms plan section loops in tracers cut through by the tool. Radially inward flow from the ring vortex component retains metal longer in the rotating plug and outward flow expels metal earlier; this interaction forms the looping weld seam trace and the tongue and groove bimetallic weld contour. The radial components of the translational and ring vortex flows introduce parent metal intrusions into the small grained nugget material close to the tool shoulder; if this feature is pronounced, nugget collapse may result. Certain weld features, in particular internal banding seen in transverse section as onion rings and associated surface ridges called tool marks , have long implied an oscillation flow component, but have only recently been attributed in the literature to tool eccentricity. Rotating plug shape, typically a hollow cylinder flared at the end where it sticks to the shoulder, varies as pressure distribution on the tool determines where sticking occurs. Simplified power input estimates balanced against heat loss estimates give reasonable temperature estimates, explain why the power requirement changes hardly at all over a wide range of RPM s, and yield isotherms that seem to fall along boundaries of parameter windows of operation.

Nunes, Arthur C.↗

NASA NTRS2013

Microbiological Sampling Methods and Sanitation of Edible Plants Grown on ISS

Pathogenic microbes on the surfaces of salad crops and growth chambers pose a threat to the health of crew on International Space Station. For astronauts to safely consume spacegrown vegetables produced in NASA's new vegetable production unit, VEGGIE, three technical challenges must be overcome: real-time sampling, microbiological analysis, and sanitation. Raphanus sativus cultivar Cherry Bomb II and Latuca sativa cultivar Outredgeous, two saled crops to be grown in VEGGIE, were inoculated with Salmonella enterica serovar Typhimurium (S. Typhimurium), a bacterium known to cause food-borne illness~ Tape- and swab-based sampling techniques were optimized for use in microgravity and assessed for effectiveness in recovery of bacteria from crop surfaces: Rapid pathogen detection and molecular analyses were performed via quantitative real-time polymerase chain reactiop using LightCycler® 480 and RAZOR® EX, a scaled-down instrument that is undergoing evaluation and testing for future flight hardware. These methods were compared with conventional, culture-based methods for the recovery of S. Typhimurium colonies. A sterile wipe saturated with a citric acid-based, food-grade sanitizer was applied to two different surface materials used in VEGGIE flight hardware that had been contaminated with the bacterium Pseudomonas aeruginosa,. another known human pathogen. To sanitize surfaces, wipes were saturated with either the sanitizer or sterile deionized water and applied to each surface. Colony forming units of P. aeruginosa grown on tryptic soy agar plates were enumerated from surface samples after sanitization treatments. Depending on the VEGGIE hardware material, 2- to 4.5-log10 reductions in colony-forming units were observed after sanitization. The difference in recovery of S. Typhimurium between tape- and swab- based sampling techniques was insignificant. RAZOR® EX rapidly detected S. Typhimurium present in both raw culture and extracted DNA samples.

Parrish, Charles H. II↗

NASA NTRS2013

Characterization of Heat Melt Compactor (HMC) Product Water

The Heat Melt Compactor (HMC) is designed to sterilize and process wastes produced during space missions. Benefits of the HMC include reduction of biohazards to the crew, reduction in volume of wastes that would otherwise require storage, production of radiation shielding tiles, and recovery of water and other resources. Water reuse is critical onboard spacecrafts; it reduces the need for resupply missions and saves valuable storage space. The main sources of water in HMC batches are food, beverages, shampoo, disinfecting wipes, toothpaste, and diapers. Water reclaimed by the HMC was analyzed for concentrations of Na+, NH4+, K+, Mg2+, Ca2+, Cl-‐, NO2-‐, Br-‐, NO3-‐, PO43-‐, SO42-‐, total organic carbon (TOC), total inorganic carbon (TIC), % total solids, and pH. The data are discussed in relation to the current water input characteristics established for the International Space Station Water Processor Assembly system. Batches with higher than average amounts of food produced HMC product water with higher sulfate content, and batches with higher proportions of disinfectant wipes and food yielded HMC product water with higher ammonium concentration. We also compared theoretical chemical composition of HMC product water based on food labels and literature values to experimental results.

Heat Melt Compactor↗

NASA NTRS2015

Veggie ISS Validation Test Results and Produce Consumption

The Veggie vegetable production system flew to the International Space Station (ISS) in the spring of 2014. The first set of plants, Outredgeous red romaine lettuce, was grown, harvested, frozen, and returned to Earth in October. Ground control and flight plant tissue was sub-sectioned for microbial analysis, anthocyanin antioxidant phenolic analysis, and elemental analysis. Microbial analysis was also performed on samples swabbed on orbit from plants, Veggie bellows, and plant pillow surfaces, on water samples, and on samples of roots, media, and wick material from two returned plant pillows. Microbial levels of plants were comparable to ground controls, with some differences in community composition. The range in aerobic bacterial plate counts between individual plants was much greater in the ground controls than in flight plants. No pathogens were found. Anthocyanin concentrations were the same between ground and flight plants, while antioxidant and phenolic levels were slightly higher in flight plants. Elements varied, but key target elements for astronaut nutrition were similar between ground and flight plants. Aerobic plate counts of the flight plant pillow components were significantly higher than ground controls. Surface swab samples showed low microbial counts, with most below detection limits. Flight plant microbial levels were less than bacterial guidelines set for non-thermostabalized food and near or below those for fungi. These guidelines are not for fresh produce but are the closest approximate standards. Forward work includes the development of standards for space-grown produce. A produce consumption strategy for Veggie on ISS includes pre-flight assessments of all crops to down select candidates, wiping flight-grown plants with sanitizing food wipes, and regular Veggie hardware cleaning and microbial monitoring. Produce then could be consumed by astronauts, however some plant material would be reserved and returned for analysis. Implementation of this plan is a step toward developing pick-and-eat food production to supplement the packaged diet on ISS and for future exploration missions where plants could make up a larger portion of the diet. Supported by NASA Space Biology Program.

Food Safety↗

NASA NTRS2017

Solvent Replacement for Hydrochlorofluorocarbon-225 for Cleaning Oxygen System Components

This Technical Memorandum is the result of a 2-year project funded by the Defense Logistics Agency-Aviation, Hazardous Minimization and Green Products Branch, to identify and test two candidate solvents to replace hydrochlorofluorocarbon-225 (HCFC-225) for cleaning oxygen systems. The solvents were also compared to a second solvent composed predominantly of perfluorobutyl iodide (PFBI), which had received limited approval by the United States Air Force (USAF) for hand wipe cleaning of components for aviators’ breathing oxygen systems. The tests performed for this study were based on those reported in AFRL-ML-WP-TR-2003-4040, “The Wipe Solvent Program,” the test program used to qualify Ikon® Solvent P for USAF applications.The study was completed in August 2014, prior to the completion of a more extensive study funded by the NASA Rocket Propulsion Test (RPT) program. The results of the RPT project are reported in NASA/TP-2015-18207, “Replacement of Hydrochlorofluorocarbon–225 Solvent for Cleaning and Verification Sampling of NASA Propulsion Oxygen Systems Hardware, Ground Support Equipment, and Associated Test Systems.” The test methods used in this study for nonvolatile residue (NVR) background, materials compatibility, and cleaning effectiveness were different than those used for the RPT project; a smaller set of materials and contaminants were tested. The tests for this study were complementary to and provided supplementary information for the down-selection process during the course of the test program reported in NASA/TP-2015-218207.

Mitchell, M. A.↗

NASA NTRS2017

FY 2017 Center Innovation Fund Annual Report - Highlights/Abstract section

This project evaluated the feasibility of low pressure cold plasma (CP) for two applications: disinfection of produce grown in space and sterilization of medical equipment in space. Currently there is no ISS capability for disinfecting pick and eat crops, food utensils, food production areas, or medical devices. This deficit is extended to projected long duration missions. Small, portable, cold plasma devices would provide an enhanced benefit to crew health and address issues concerning microbial cross contamination. The technology would contribute to the reduction of solid waste since currently crews utilize benzalkonium chloride wet wipes for cleaning surfaces and might use PRO-SAN wipes for cleaning vegetables. CP cleaning/disinfection/sterilization can work on many surfaces, including all metals, most polymers, and this project evaluated produce. Therefore CP provides a simple system that has many different cleaning application in space: produce, medical equipment, cutlery, miscellaneous tools.

plant growt↗

NASA NTRS2018

Dimethylsilanediol (DMSD) Source Assessment and Mitigation on ISS: Estimated Contributions from Personal Hygiene Products Containing Volatile Methyl Siloxanes (VMS)

Dimethylsilanediol (DMSD) is a small organosilicon compound present in humidity condensate on the International Space Station. Aqueous DMSD originates from volatile methyl siloxane (VMS) compounds in the ISS cabin atmosphere. DMSD is not effectively removed by the WPA (Water Processor Assembly), requiring removal and replacement of both WPA Multifiltration (MF) Beds for an estimated resupply penalty of approximately 70 kg/year. Analyses indicate that WPA can handle DMSD if the concentration in the condensate can by reduced by fifty percent. Personal Hygiene Products (PHPs) used by crew are suspected to be a significant source of VMS. Source removal of VMS will be required to achieve a measurable impact to the DMSD concentration in the condensate. The inventory of total crew provisions for ISS was analyzed to identify silicon containing materials and products used for personal hygiene that emit VMS. Accounting for the wide range in mass of hygiene product applied to skin or hair, the frequency of application, the product selection, the number of crew using a given product, the range in silicon mass fraction of different products, and the potential vaporization of the product, the potential total VMS emissions from personal hygiene products for a crew of six on ISS were estimated. The total daily VMS emissions from PHPs estimate ranges from 261 to 1145 mg-Si per day, compared to total estimated VMS generation rates on ISS of 800 to 1500 mg-Si per day. The main sources of VMS were determined to be antiperspirants (173 to 696 mg-Si per day), skin lotions (63 to 248 mg-Si per day), wipes (25 to 124 mg-Si per day) and hair conditioner (0 to 69 mg-Si per day). Several siloxanes-free options are available for deodorants, wet wipes, lotions, and leave-in conditioners. These products are now being assessed for crew member use in future increments.

Muirhead, Dean L.↗

NASA NTRSDate not supplied

Excavation of Exploration Toilet Fecal Canister from ISS Operations and Future Mission Impacts

Space exploration requires accommodations for crew members similar to survival on Earth including food and water, clothing, and protection from the environment. In addition, allowances for biological processes such as breathing, defecation and urination must be provided. In a micro-gravity environment, these are particularly challenging. Optimizing the consumables needed for these activities is a vital part of the spacecraft design as well as providing mass/volume for science cargo and the crew needs such as food and clothing. NASA has collected use rates for the consumables needed for defecation and urination over the decades of human-rated space travel. Most recently, the exploration toilet demonstration on International Space Station (ISS) provided data on defecation in the form of a returned canister which collected 13 days of fecal deposits, wipes, gloves and compaction plates. The canister was excavated by a dedicated team of engineers at Johnson Space Center (JSC) to provide the latest information on deposit size and weight, number of wipes and gloves used, and compaction efficiency which directly relates to the number of canisters needed. Although this is only one canister, the data found has been directly applied to manifest decisions for the Orion Artemis-2 mission. Future canisters will add to this data set. Details on what was found and how it compares to historical numbers as well as how it will be used for exploration missions will be covered in this paper.

Toilet↗

NASA NTRSDate not supplied

Excavation of Exploration Toilet Fecal Canister From ISS Operations and Future Mission Impacts

Toilet↗

NASA NTRSDate not supplied

Excavation of Exploration Toilet Fecal Canister from ISS Operations and Future Mission Impacts

Toilet↗

NASA NTRSDate not supplied

In-Situ Electrochemical Generation and Utilization of Hydrogen Peroxide for Disinfection

Disinfection needs to meet personal hygiene requirements at the International Space Station (ISS) is currently accomplished through the use of pre-packaged, disposable, wetted wipes, which represent an appreciable carry-along mass and disposal burden. However, as human missions travel further into the solar system the availability of resources to resupply will be diminished. Therefore, next-generation system should use onboard utilities to create on demand disinfectants, thereby reducing the dependence on earth-based supplies and further eliminating storage and disposal problems. Accordingly, we are developing an in-situ approach to electrochemically generate hydrogen peroxide disinfecting solution utilizing onboard life support supplies (Air/Water) to neutralize surface microorganisms present in closed living systems. As discussed within our 2019 and 2021 ICES papers (ICES-2019-38 and ICES-2021-273), we have continued to improve our TRL by scaling the electrochemical generation production process and validating the system in a zero-gravity parabolic loop flight test. In this paper we will demonstrate a system that can achieve over 1 L of >2 w/w% peroxide per day with DI water and air feeds. The hydrogen peroxide solutions generated were sent to NASA for microbial control property characterization. Overall, the electrochemical peroxide generation system offers a more economical and practical alternative, with the disinfectant being generated on demand and in-situ (using available life support materials of Air/Water); and applied to reusable cloths. The specific application of interest to this program is crew contact surfaces in space vehicles, but this technology could be utilized for waste water disinfection, heat exchanger biofouling remediation, and laundry applications. The peroxide generation system will also be able to address Earth-based needs in various settings such as field hospitals, restaurants, military, warehouses, movie theatres, among many others.

hydrogen peroxide↗