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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

A Spaceflight Experiment to Determine the Effect of Chamfered Sample Holders on Atomic Oxygen Erosion

The exteriors of low Earth orbit (LEO) spacecraft are subjected to many environmental threats that can cause the surface materials to degrade. One of these threats is atomic oxygen (AO), which is formed by photo dissociation of molecular oxygen by energetic UV radiation. Atomic oxygen exposure can result in oxidative erosion of polymers leading to structural or thermal failure of spacecraft components. The amount of AO erosion expected during a mission can be calculated by knowing the AO erosion yield (Ey, volume loss per incident atom) of the material and the AO fluence expected for the mission. The Ey can be determined through dehydrated mass loss measurements of test samples if one knows the AO fluence, density, and exposure area. Such measurements have been made as part of flight experiments, including the Materials International Space Station Experiment 2 (MISSE 2) Polymers Experiment. The MISSE 2 Polymers Experiment sample holders had chamfered circular apertures that controlled the exposure area, but also allowed some additional AO to scatter from the chamfered edges onto the samples thus causing some samples to erode thru and peel at their perimeter due to this scattering effect. By modeling the scattered AO flux one can predict the actual total AO fluence, and hence more accurate sample Ey. Sample holders with different chamfered-perimeter to exposed-area ratios have been designed for future spaceflight experiments that allow a more accurate determination of the Ey for large area polymers, representative of their use on spacecraft surfaces.

Earth Orbital Environments↗
NASA NTRS1993

Helium-3 inventory of lunar samples: A potential future energy resource for mankind?

Recent public concern over the safety, cost, and environmental impact of the worldwide fission reactors has focused the attention of scientists and engineers towards perfecting fusion technology because it promises a much more environmentally acceptable 'clean' energy supply. The fusion reaction D-2 + He-3 yields p(14.7 MeV) + He-4(3.6 MeV) has long been recognized as an ideal candidate for producing commercially 'safer and cleaner' fusion power. Naturally occurring He-3 is scarce on earth; however, lunar regolith is a potential ore for He-3 because the high He-3 in solar wind has been implanted in the lunar regolith for more than 4 x 10(exp 9) years, along with other volatile species. The helium abundance in lunar soils is dependent not only on the maturity of soils (I(sub S)/FeO) but also on their mineralogy. The titanium-rich (ilmenite) lunar soils are important repositories for volatiles, which may be released by heating these soils up to approximately 700 C.

Murali, A. V.↗
NASA NTRS2013

The Regolith Biters: A Divide-And-Conquer Architecture for Sample-Return Missions

The collective interaction of simple systems can be leveraged to attain complex goals. Based on this principle, we envision space system architectures where the core functional components are decoupled, autonomous, and cooperative. We aim to pursue this vision in the context of small-body sample-return missions. After all, no experimental study sheds more light into our understanding of the origin and evolution of the Solar System than the analysis of samples from asteroids and comets. We also believe that their study is important from a strategic perspective: meteorite impacts pose a direct and credible threat to life on Earth, and the development of contingency small-body deflection missions presupposes some knowledge of the target body. The current architectural paradigm for sample-return missions is centered around a design where spacecraft and sampling device are merged into a single, complex system. We argue that this monolithic approach couples the navigation and sample-collection problems, making both more difficult. In contrast, we propose a decoupled system based on the coordinated interaction between a spacecraft and a collective of small, simple devices - the Regolith Biters (RBs). A spacecraft carrying a number of RBs would travel to the vicinity of a small body. From a favorable vantage point, and while remaining within a safe distance in a non-colliding trajectory, it would release the RBs towards the target body. Upon encountering the body, they would bite the regolith (thus retaining a sample), and eject back to orbit. The spacecraft, being endowed with appropriate navigation and tracking capabilities, would rendezvous with and collect those RBs within its reach, and bring them back to Earth. Separating the navigation and sampling concerns removes the need for proximity operations with the small body-the stage in current architectures that carries the most challenges and risks. Eliminating the need for proximity operations brings back to the discussion the exploration of exciting prospects, like highly active comets, fast-rotating bodies, and binary systems. Distributing the sampling problem among a collective of agents provides the opportunity to sample multiple regions in a single mission. It also provides robustness to various environmental conditions, and may enable the distributed, in situ characterization of the body. In the search for reliability, current architectures rely on complexity: an elaborate system should succeed at once. We rely on numbers: a given agent may fail at any stage, but success is attained by the collective.

Asteroids↗
NASA NTRS1992

Durability evaluation of photovoltaic blanket materials exposed on LDEF tray S1003

Several candidate protective coatings on Kapton and uncoated Kapton were exposed to the low Earth orbital (LEO) environment on the Long Duration Exposure Facility (LDEF) to determine if the coatings could be used to protect polymeric substrates from degradation in the LEO environment. The coatings that were evaluated were 700 A of aluminum oxide, 650 A of silicon dioxide, and 650 A of a 4 percent polytetrafluoroethylene-96 percent silicon dioxide mixed coating. All of the coatings evaluated were ion beam sputter deposited. These materials were exposed to a very low atomic oxygen fluence (4.8 x 10 exp 19 atoms/sq. cm) as a result of the experiment tray being located 98 degrees from the ram direction. As a result of the low atomic oxygen fluence, determination of a change in mass was not possible for any of the samples including the uncoated Kapton. There was no evidence of spalling of any of the coatings after the approximately 33,600 thermal cycles recorded for LDEF. The surface of the uncoated Kapton, however, did show evidence of grazing incidence texturing. There was a 7-8 percent increase in solar absorptance for the silicon dioxide and aluminum oxide coated Kapton and only a 4 percent increase for the mixed coating. It appears that the addition of a small amount of fluoropolymer may reduce the magnitude of absorptance increase due to environmental exposure. Thermal emittance did not change significantly for any of the exposed samples. Scanning electron microscopy revealed few micrometeoroid or debris impacts, but the impact sites found indicated that the extent of damage or cracking of the coating around the defect site did not extend beyond a factor of three of the impact crater diameter. This limiting of impact damage is of great significance for the durability of thin film coatings used for protection against the LEO environment.

Sharon K Rutledge↗
NASA NTRS2015

2014 ISS Potable Water Characterization and Continuation of the DMSD Chronicle

During 2014 the crews from Expeditions 38-41 were resident on the International Space Station (ISS). In addition to the U.S. potable water reclaimed from humidity condensate and urine, the other water supplies available for their use were Russian potable water reclaimed from condensate and Russian ground-supplied potable water. Beginning in June of 2014, and for the fourth time since 2010, the product water from the U.S. Water Processor Assembly (WPA) experienced a rise in the total organic carbon (TOC) level due to organic contaminants breaking through the water treatment process. Results from ground analyses of ISS archival water samples returned on Soyuz 38 confirmed that dimethylsilanediol (DMSD) was once again the contaminant responsible for the rise. With this confirmation in hand and based upon the low toxicity of DMSD, a waiver was approved to allow the crew to continue to consume the water after the TOC level exceeded the U.S. Segment limit of 3 mg/L. Several weeks after the WPA multifiltration beds were replaced, as anticipated based upon experience from previous rises, the TOC levels returned to below the method detection limit of the onboard TOC analyzer (TOCA). This paper presents and discusses the chemical analysis results for the ISS archival potable water samples returned in 2014 and analyzed by the Johnson Space Center's Toxicology and Environmental Chemistry laboratory. These results showed compliance with ISS potable water quality standards and indicated that the potable water supplies were acceptable for crew consumption. Although DMSD levels were at times elevated they remained well below the 35 mg/L health limit, so continued consumption of the U.S potable water was considered a low risk to crew health and safety. Excellent agreement between inflight and archival sample TOC data confirmed that the TOCA performed optimally and it continued to serve as a vital tool for monitoring organic breakthrough and planning remediation action.

Straub, John E., II↗
NASA NTRS2001

Canaveral National Seashore Water Quality and Aquatic Resource Inventory

Mosquito Lagoon is a shallow, bar-built estuary located on the east central Florida Coast, primarily within the KSC boundary. The lagoon and watershed cover approximately 327 sq km (79422 acres) .The Lagoon occupies 159 sq km (37853 acres). Water depths average approximately 1m. The lagoon volume is approximately 1.6 x 10(exp 8)cu m. Water quality in Mosquito Lagoon is good. Salinity data typically range between 20 ppt and 35 ppt. The lowest value recorded was 4.5 ppt and the highest value was 37 ppt. Water temperatures fluctuate 2 - 3 C over a 24 h period. Cold front passage can rapidly alter water temperatures by 5 - 10 C or more in a short period of time. The highest temperature was 33.4 C and the lowest temperature was 8.8 C after a winter storm. Dissolved oxygen concentrations ranged from a low of 0.4 mg/l to a high of 15.3 mg/l. Extended periods of measurements below the Florida Department of Environmental Protection criteria of 4.0 mg/l were observed in fall and spring months suggesting high system respiration and oxygen demand. Metals such as antimony, arsenic, molybdenum and mercury were report as below detection limits for all samples. Cadmium, copper, chromium, silver, and zinc were found to be periodically above the Florida Department of Environmental Protection criteria for Class II and Class III surface waters.

Hall, C. R.↗
NASA NTRS2015

2014 ISS Potable Water Characterization and Continuation of the Dimethylsilanediol Chronicle

During 2014 the crews from Expeditions 38-41 were in residence on the International Space Station (ISS). In addition to the U.S. potable water reclaimed from humidity condensate and urine, the other water supplies available for their use were Russian potable water reclaimed from condensate and Russian ground-supplied potable water. Beginning in June of 2014 and for the fourth time since 2010, the product water from the U.S. water processor assembly (WPA) experienced a rise in the total organic carbon (TOC) level due to organic contaminants breaking through the water treatment process. Results from ground analyses of ISS archival water samples returned on Soyuz 38 confirmed that dimethylsilanediol was once again the contaminant responsible for the rise. With this confirmation in hand and based upon the low toxicity of dimethylsilanediol, a waiver was approved to allow the crew to continue to consume the water after the TOC level exceeded the U.S. Segment limit of 3 mg/L. Several weeks after the WPA multifiltration beds were replaced, the TOC levels returned to below the method detection limit of the onboard TOC analyzer (TOCA) as anticipated based upon experience from previous rises. This paper presents and discusses the chemical analysis results for the ISS archival potable-water samples returned in 2014 and analyzed by the Johnson Space Center's Toxicology and Environmental Chemistry laboratory. These results showed compliance with ISS potable water quality standards and indicated that the potable-water supplies were acceptable for crew consumption. Although dimethylsilanediol levels were at times elevated, they remained well below the 35 mg/L health limit so the continued consumption of the U.S. potable water was considered a low risk to crew health and safety. Excellent agreement between in-flight and archival sample TOC data confirmed that the TOCA performed optimally and continued to serve as a vital tool for monitoring organic breakthrough and planning remediation action.

Straub, John E., II↗
NASA NTRS2024

Per- and Polyfluoroalkyl Substances Confirmatory Sampling Report, South Repeater Building (SWMU 121), Kennedy Space Center, Florida

This Per- and Polyfluoroalkyl Substances (PFAS) Confirmatory Sampling (CS) Report was prepared by AECOM Technical Services, Inc. (AECOM) for the National Aeronautics and Space Administration (NASA) under Contract 80KSC019D0010, Task Order 80KSC021F0096. The purpose of this report is to document CS activities at the South Repeater Building, Solid Waste Management Unit (SWMU) 121, formerly known as the Area 3 Repeater Building (A3RB). A Phase I SWMU Assessment and Confirmatory Sampling Report (NASA 2019) and a Phase II and III SWMU Assessment and Confirmatory Sampling Report (NASA 2022b) were previously submitted detailing Center-Wide assessment activities performed at the John F. Kennedy Space Center (KSC) in Florida that identified 33 locations of concern and 19 areas of potential concern at KSC associated with the storage, use, or release of materials containing PFAS. A review of the analytical results from investigation derived waste samples collected in 2020 from the South Repeater Building area indicated concentrations of perfluorooctanesulfonic acid (PFOS) were above Florida Department of Environmental Protection (FDEP) provisional Groundwater Cleanup Target Levels of 70 nanograms per liter (ng/L) at a concentration of 1,750 ng/L. Following this review, the KSC Fire Chief was contacted; the Chief recalled fighting a brush fire in 1998 in the area, during which an unknown volume of aqueous film-forming foam was used to extinguish the fire. The Phase II and Phase III SWMU Assessment Report recommended this area proceed to CS. Historical results in this area are provided in Appendix A . PFAS CS activities were contracted at the South Repeater Building. Initial CS activities were conducted in accordance with the PFAS Assessment and Mitigation Work Plan (AECOM 2022), which was submitted to the NASA Remediation Project Management team and accepted by the team on November 1 and 8, 2021. The objectives of the PFAS CS were to: - - Confirm and begin to assess the extent of PFAS affected media in the South Repeater Building area. - - Identify locations for groundwater, soil, surface water, and soil core sampling. - - Qualitatively characterize the migration potential of released PFAS to environmental media (soil, groundwater, and surface water). The following activities were completed to meet the PFAS CS objectives: - - Installation of monitoring wells via direct push technology (DPT) and rotosonic techniques - - Groundwater, soil, and surface water sampling - - Collection of soil cores to evaluate site lithology - - Development of initial PFAS plume characterization

PFAS↗
NASA NTRS2023

Morpheus Test Area SWMU #119 Per- and Polyfluoroalkyl Substances (PFAS) Site Assessment Work Plan

This Work Plan documents the proposed field sampling activities for a per- and polyfluoroalkyl substances (PFAS) Site Assessment at the Morpheus Test Area (MTA) at Kennedy Space Center (KSC). The Work Plan provides a background of the historical activities that occurred at the MTA, and the limited environmental investigations performed at the MTA. The proposed Site Assessment activities at MTA includes the collection of soil samples from seven locations, the installation of a staff gauge in site surface water, the installation of four monitoring wells, perform direct push groundwater sampling at ten locations, and collect one surface water sample. Sampling details, depths, and locations are presented in the Work Plan. The Work Plan was presented to the KSC Remediation Team in the form of an Advance Data Package in February 2023. Following STRIVES approval, the SLF FRB PFAS Site Assessment Work Plan will be formally submitted to the Florida Department of Environmental Protection.

Howard Franklin Fowler↗
NASA NTRS1980

A Continuation of Base-line Studies for Environmentally Monitoring Space Transportation Systems at John F. Kennedy Space Center: Chemical Studies of Rainfall and Soil Analysis - Volume 2

The results of a study which was designed to monitor, characterize, and evaluate the chemical composition of precipitation (rain) which fell at the Kennedy Space Center, Florida (KSC) during the period July 1977 to March 1979 are reported. Results which were obtained from a soil sampling and associated chemical analysis are discussed. The purpose of these studies was to determine the environmental perturbations which might be caused by NASA space activities.

Madsen, B. C.↗
NASA NTRS1976

Fluidic hydrogen detector production prototype development

A hydrogen gas sensor that can replace catalytic combustion sensors used to detect leaks in the liquid hydrogen transfer systems at Kennedy Space Center was developed. A fluidic sensor concept, based on the principle that the frequency of a fluidic oscillator is proportional to the square root of the molecular weight of its operating fluid, was utilized. To minimize sensitivity to pressure and temperature fluctuations, and to make the sensor specific for hydrogen, two oscillators are used. One oscillator operates on sample gas containing hydrogen, while the other operates on sample gas with the hydrogen converted to steam. The conversion is accomplished with a small catalytic converter. The frequency difference is taken, and the hydrogen concentration computed with a simple digital processing circuit. The output from the sensor is an analog signal proportional to hydrogen content. The sensor is shown to be accurate and insensitive to severe environmental disturbances. It is also specific for hydrogen, even with large helium concentrations in the sample gas.

Roe, G. W.↗
NASA NTRS2002

A geostatistical analysis of small-scale spatial variability in bacterial abundance and community structure in salt marsh creek bank sediments

Small-scale variations in bacterial abundance and community structure were examined in salt marsh sediments from Virginia's eastern shore. Samples were collected at 5 cm intervals (horizontally) along a 50 cm elevation gradient, over a 215 cm horizontal transect. For each sample, bacterial abundance was determined using acridine orange direct counts and community structure was analyzed using randomly amplified polymorphic DNA fingerprinting of whole-community DNA extracts. A geostatistical analysis was used to determine the degree of spatial autocorrelation among the samples, for each variable and each direction (horizontal and vertical). The proportion of variance in bacterial abundance that could be accounted for by the spatial model was quite high (vertical: 60%, horizontal: 73%); significant autocorrelation was found among samples separated by 25 cm in the vertical direction and up to 115 cm horizontally. In contrast, most of the variability in community structure was not accounted for by simply considering the spatial separation of samples (vertical: 11%, horizontal: 22%), and must reflect variability from other parameters (e.g., variation at other spatial scales, experimental error, or environmental heterogeneity). Microbial community patch size based upon overall similarity in community structure varied between 17 cm (vertical) and 35 cm (horizontal). Overall, variability due to horizontal position (distance from the creek bank) was much smaller than that due to vertical position (elevation) for both community properties assayed. This suggests that processes more correlated with elevation (e.g., drainage and redox potential) vary at a smaller scale (therefore producing smaller patch sizes) than processes controlled by distance from the creek bank. c2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

Non-NASA Center↗
NASA NTRS1984

Testing of Candidate Batteries for Global Positioning System

Three lithium batteries proposed as candidates for use in the Global Positioning System are studied. The batteries are discharged at several rates and temperatures both before and after environmental testing. Batteries are heated inside a closed chamber until they vent. Samples of the vented gases are analyzed for components which might be toxic. The test results raise concerns about each of the proposed batteries.

Barnes, J. A.↗
NASA NTRS1988

FTIR characterization of thermally cycled PMR-15 composites

Chemical characterization results are presented for a variety of PMR-15/graphite composites, differentiated according to prepreg types and cure cycles, which were subjected to 1000 thermal cycles between 0 and 450 F. Fourier transform IR spectroscopy was used in conjunction with diffuse reflectance sampling to examine whether changes in the matrix resin chemistry due to environmental exposure may have contributed to microcracking. Analysis based on compound spectra revealed behavior associated with the oxidation of methylene groups to carbonyl groups on the composite surface; evidence of crosslinking also emerged, although the two phenomena do not appear to be related.

Young, Philip R.↗
NASA NTRS1994

Inference of subsurface thermohaline structure from fields measurable by satellite

Satellites now provide global measurements of the ocean's surface height and temperature. Ocean climatologies for the northwest Pacific and northwest Atlantic Oceans that relate sea surface height, sea surface temperature, day of the year, latitude, and longitude to temperature and salinity profiles were produced using least-squares regression. These analyses use over 33,000 profiles of historical temperature and salinity data and are considerably streamlined and compacted by expressing each profile in terms of empirical orthogonal functions. Evaluations and error analyses of the climatologies, including a comparison to the navy's Generalized Digital Environmental Model, were performed and differences between the regions are discussed. Two sample vertical sections are shown to be closely reproduced with the climatologies. Climatologies based on surface height and temperature are found to offer considerable improvement over climatologies based only on position.

Carnes, Michael R.↗
NASA NTRS2011

SpaceX Dragon Air Circulation System

The Dragon capsule is a reusable vehicle being developed by Space Exploration Technologies (SpaceX) that will provide commercial cargo transportation to the International Space Station (ISS). Dragon is designed to be a habitable module while it is berthed to ISS. As such, the Dragon Environmental Control System (ECS) consists of pressure control and pressure equalization, air sampling, fire detection, illumination, and an air circulation system. The air circulation system prevents pockets of stagnant air in Dragon that can be hazardous to the ISS crew. In addition, through the inter-module duct, the air circulation system provides fresh air from ISS into Dragon. To utilize the maximum volume of Dragon for cargo packaging, the Dragon ECS air circulation system is designed around cargo rack optimization. At the same time, the air circulation system is designed to meet the National Aeronautics Space Administration (NASA) inter-module and intra-module ventilation requirements and acoustic requirements. A flight like configuration of the Dragon capsule including the air circulation system was recently assembled for testing to assess the design for inter-module and intra-module ventilation and acoustics. The testing included the Dragon capsule, and flight configuration in the pressure section with cargo racks, lockers, all of the air circulation components, and acoustic treatment. The air circulation test was also used to verify the Computational Fluid Dynamics (CFD) model of the Dragon capsule. The CFD model included the same Dragon internal geometry that was assembled for the test. This paper will describe the Dragon air circulation system design which has been verified by testing the system and with CFD analysis.

Hernandez, Brenda↗
NASA NTRS2014

The Nuclear Cryogenic Propulsion Stage

Nuclear Thermal Propulsion (NTP) development efforts in the United States have demonstrated the technical viability and performance potential of NTP systems. For example, Project Rover (1955 - 1973) completed 22 high power rocket reactor tests. Peak performances included operating at an average hydrogen exhaust temperature of 2550 K and a peak fuel power density of 5200 MW/m3 (Pewee test), operating at a thrust of 930 kN (Phoebus-2A test), and operating for 62.7 minutes in a single burn (NRX-A6 test). Results from Project Rover indicated that an NTP system with a high thrust-to-weight ratio and a specific impulse greater than 900 s would be feasible. Excellent results were also obtained by the former Soviet Union. Although historical programs had promising results, many factors would affect the development of a 21st century nuclear thermal rocket (NTR). Test facilities built in the US during Project Rover no longer exist. However, advances in analytical techniques, the ability to utilize or adapt existing facilities and infrastructure, and the ability to develop a limited number of new test facilities may enable affordable development, qualification, and utilization of a Nuclear Cryogenic Propulsion Stage (NCPS). Bead-loaded graphite fuel was utilized throughout the Rover/NERVA program, and coated graphite composite fuel (tested in the Nuclear Furnace) and cermet fuel both show potential for even higher performance than that demonstrated in the Rover/NERVA engine tests.. NASA's NCPS project was initiated in October, 2011, with the goal of assessing the affordability and viability of an NCPS. FY 2014 activities are focused on fabrication and test (non-nuclear) of both coated graphite composite fuel elements and cermet fuel elements. Additional activities include developing a pre-conceptual design of the NCPS stage and evaluating affordable strategies for NCPS development, qualification, and utilization. NCPS stage designs are focused on supporting human Mars missions. The NCPS is being designed to readily integrate with the Space Launch System (SLS). A wide range of strategies for enabling affordable NCPS development, qualification, and utilization should be considered. These include multiple test and demonstration strategies (both ground and in-space), multiple potential test sites, and multiple engine designs. Two potential NCPS fuels are currently under consideration - coated graphite composite fuel and tungsten cermet fuel. During 2014 a representative, partial length (approximately 16") coated graphite composite fuel element with prototypic depleted uranium loading is being fabricated at Oak Ridge National Laboratory (ORNL). In addition, a representative, partial length (approximately 16") cermet fuel element with prototypic depleted uranium loading is being fabricated at Marshall Space Flight Center (MSFC). During the development process small samples (approximately 3" length) will be tested in the Compact Fuel Element Environmental Tester (CFEET) at high temperature (approximately 2800 K) in a hydrogen environment to help ensure that basic fuel design and manufacturing process are adequate and have been performed correctly. Once designs and processes have been developed, longer fuel element segments will be fabricated and tested in the Nuclear Thermal Rocket Element Environmental Simulator (NTREE) at high temperature (approximately 2800 K) and in flowing hydrogen.

Houts, Michael G.↗
NASA NTRS2010

Repetitive Interrogation of 2-Level Quantum Systems

Trapped ion clocks derive information from a reference atomic transition by repetitive interrogations of the same quantum system, either a single ion or ionized gas of many millions of ions. Atomic beam frequency standards, by contrast, measure reference atomic transitions in a continuously replenished "flow through" configuration where initial ensemble atomic coherence is zero. We will describe some issues and problems that can arise when atomic state selection and preparation of the quantum atomic system is not completed, that is, optical pumping has not fully relaxed the coherence and also not fully transferred atoms to the initial state. We present a simple two-level density matrix analysis showing how frequency shifts during the state-selection process can cause frequency shifts of the measured clock transition. Such considerations are very important when a low intensity lamp light source is used for state selection, where there is relatively weak relaxation and re-pumping of ions to an initial state and much weaker 'environmental' relaxation of the atomic coherence set-up in the atomic sample.

Rabi interrogation↗