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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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The purpose of this test was to characterize the Micron 512 GB NAND (MT29F512G08AUCBBH8-6IT:B) flash memory parameter degradation for total dose response. In the test, the device was exposed to high dose rate (HDR) irradiations using gamma radiation. Device parameters such as leakage currents, quantity of upset bits and overall chip and die health were investigated.
The purpose of this test was to characterize the flight lot of Texas Instruments' LM193 (flight part number is 5962-9452601Q2A) for total dose response. This test served as the radiation lot acceptance test (RLAT) for the lot date code (LDC) tested. Low dose rate (LDR) irradiations were performed in this test so that the device susceptibility to enhanced low dose rate sensitivity (ELDRS) was determined.
Modern electrical components are susceptible to damage from high levels of radiation and extreme temperatures found near reactors in terrestrial nuclear power plants and in aerospace applications. Radiation-hardened electronics are being developed, largely for the aerospace industry, but they sometimes rely on application-specific, small-batch semiconductor fabrication processes. These processes tend to be prohibitively expensive to develop and maintain outside major industrial facilities or governmental agencies. Recently, commercially available, nonradiation-rated junction-gate field-effect transistors (JFETs) were shown to maintain their functionality at gamma doses exceeding 1 MGy, suggesting that nonrated, commercially available electrical components could be used to develop systems that are tolerant to ionizing radiation. However, gamma ray survival is not indicative of neutron dose survival, and few studies characterize JFETs under neutron irradiation. To address this knowledge gap, a JFET-based analog multiplexer and optical pulsewidth modulation (PWM) encoder was developed and irradiated using a 252 Cf source to 1.6×10 13 n/cm 2 . The multiplexed optical encoder (MOE) system maintained functionality throughout testing and showed little evidence of radiation effects. These results indicate that circuitry tolerant to fast neutron damage can be developed using low-cost, nonradiation-rated, commercially available JFETs, which could provide a lower production cost alternative to specialized semiconductor processes when designing and building electronics better able to survive neutron irradiation.
An elastomer-toughened epoxy-graphite composite system (CE339/T300) was evaluated for its potential durability in the space radiation environment. The physical and chemical response of this system was characterized following exposure to radiation doses equivalent to 20 to 30 years in geosynchronous orbit using 1 MeV electrons. The results show that electrons generate extensive crosslinking and embrittlement of the matrix. This embrittlement results in chemical and mechanical property changes that would limit the service life of this epoxy system in some space structure applications.
The effects of a simulated space radiation environment on the dimensional stability of an elastomer-toughened epoxy-graphite composite were determined. The response of the material was characterized following exposure to radiation doses equivalent to geosynchronous orbit lifetimes ranging from 6 months to 30 years. The results show that radiation interacts with the epoxy matrix to embrittle the composite, beginning at relatively low total doses (10 to the 7th power rads). The embrittlement results in thermal expansion changes and significant laminate microcracking during thermal cycling. These property changes could limit the service life of this material in some spacecraft applications.
In modeling cometary ice, the properties of clathrate hydrates were used to explain anomalous gas release at large radial distances from the Sun, and the retention of particular gas inventories at elevated temperatures. Clathrates may also have been important early in solar system history. However, there has never been a reasonable mechanism proposed for clathrate formation under the low pressures typical of these environments. For the first time, it was shown that clathrate hydrates can be formed by warming and annealing amorphous mixed molecular ices at low pressures. The complex microstructures which occur as a result of clathrate formation from the solid state may provide an explanation for a variety of unexplained phenomena. The vacuum and imaging systems of an Hitachi H-500H Analytical Electron Microscope was modified to study mixed molecular ices at temperatures between 12 and 373 K. The resulting ices are characterized by low-electron dose Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction (SAED). The implications of these results for the mechanical and gas release properties of comets are discussed. Laboratory IR data from similar ices are presented which suggest the possibility of remotely observing and identifying clathrates in astrophysical objects.
Radiation encountered on an extended duration space mission (estimates of 3 Sieverts for a mission to Mars) poses a threat not only to human health, but also to the quality, nutritional value, and palatability of the food system. Free radicals generated by radiation interaction with foods may initiate many unwanted reactions including: 1) autoxidation in lipids that alters flavor, odor, and concentrations of essential fatty acids, and 2) depletion of antioxidants food products and dietary supplements. Studies have shown that antioxidants may provide long term health protection from oxidative stress caused by radiation exposure; therefore, consumption of antioxidants will be important. Stability of essential fatty acids is also important for astronauts long-term health status. The objectives of this study were to characterize the effects of low dose gamma-radiation on lipids and antioxidants by monitoring oxidation and reducing power, respectively, in model systems. Select oils and antioxidants were exposed to levels of gamma-radiation ranging from 0 to 1000 Gy (1 Gy = 1 Sv) using a Gammacell 220 and stored at ambient or elevated temperatures (65 C) for up to 3 months prior to analysis. A Fricke dosimeter was used to verify differences between the radiation doses administered. Primary and secondary products of lipid oxidation in soybean and peanut oils were monitored using conjugated diene and 2-thiobarbituric acid (TBARs) assays. Changes in fatty acid composition and formation and vitamin E levels were also measured. The reducing power of antioxidant compounds, including vitamins C and E and beta-carotene, was determined using the ferric reducing antioxidant power (FRAP) assay. Significant differences (alpha =0.05) were present between all radiation doses tested using the Fricke dosimeter. Increasing radiation doses above 3 Sv resulted in significantly (alpha =0.05) elevated levels of oxidation and free fatty acids in soybean and peanut oils. Decreases in concentrations of essential fatty acids upon increasing radiation doses were also observed. Increasing radiation doses caused significant (alpha =0.05) decreases in reducing power and hence the effectiveness of vitamins C and E as well as beta-carotene. This work establishes a need for quantifying the effects of space relevant radiation doses in the development of a food system for an extended duration mission and for identifying threshold radiation levels that will impact the useful shelf-life of the variety of foods that will be sent. Eventual rancidity of lipids and the loss of antioxidant bioprotective effects are major concerns for the acceptability and nutritional profile of a food system.
Single Event Transients (SETs) originating in linear bipolar integrated circuits are known to undermine the reliability of electronic systems operating in the radiation environment of space. Ionizing particle radiation produces a variety of SETs in linear bipolar circuits. The extent to which these SETs threaten system reliability depends on both their shapes (amplitude and width) and their threshold energies. In general, SETs with large amplitudes and widths are the most likely to propagate from a bipolar circuit's output through a subsystem. The danger these SET pose is that, if they become latched in a follow-on circuit, they could cause an erroneous system response. Long-term exposure of linear bipolar circuits to particle radiation produces total ionizing dose (TID) and/or displacement damage dose (DDD) effects that are characterized by a gradual degradation in some of the circuit's electrical parameters. For example, an operational amplifier's gain-bandwidth product is reduced by exposure to ionizing radiation, and it is this reduction that contributes to the distortion of the SET shapes. In this paper, we compare SETs produced in a pristine LM124 operational amplifier with those produced in one exposed to ionizing radiation for three different operating configurations - voltage follower (VF), inverter with gain (IWG), and non-inverter with gain (NIWG). Each configuration produces a unique set of transient shapes that change following exposure to ionizing radiation. An important finding is that the changes depend on operating configuration; some SETs decrease in amplitude, some remain relatively unchanged, some become narrower and some become broader.
The risk of infectious disease to select individuals has historically been difficult to predict in either spaceflight or on Earth with health care efforts relying on broad-based prevention and post-infection treatment. Over the past 10 years, quantitative microbial risk assessment evaluations have evolved to formalize the assessment process and quantify the risk. This process of hazard identification, exposure assessment, dose-response assessment, and risk characterization has been applied by the water and food safety industries to address the public health impacts associated with the occurrence of and human exposure to pathogens in water and food for the development of preventive strategies for microbial disease. NASA is currently investigating the feasibility of using these techniques to better understand the risks to astronauts and refine their microbiological requirements. To assess these techniques, NASA began an evaluation of the potable water system on the International Space Station to determine how the microbial risk from water consumption during flight differed from terrestrial sources, such as municipal water systems. The ultimate goal of this work is to optimize microbial requirements which would minimize unnecessary cargo and use of crew time, while still protecting the health of the crew. Successful demonstration of this risk assessment framework with the water system holds the potential to maximize the use of available resources during spaceflight missions and facilitate investigations into the evaluation of other routes of infection, such as through the spaceflight foods system.
For long duration missions of solar sails, the sail material needs to survive harsh space environments and the degradation of the sail material controls operational lifetime. Therefore, understanding the effects of the space environment on the sail membrane is essential for mission success. In this study, we investigated the effect of simulated space environment effects of ionizing radiation, thermal aging and simulated potential damage on mechanical, thermal and optical properties of a commercial off the shelf (COTS) polyester solar sail membrane to assess the degradation mechanisms on a feasible solar sail. The solar sail membrane was exposed to high energy electrons (about 70 keV and 10 nA/cm2), and the physical properties were characterized. After about 8.3 Grad dose, the tensile modulus, tensile strength and failure strain of the sail membrane decreased by about 20 ~ 95%. The aluminum reflective layer was damaged and partially delaminated but it did not show any significant change in solar absorbance or thermal emittance. The effect on mechanical properties of a pre-cracked sample, simulating potential impact damage of the sail membrane, as well as thermal aging effects on metallized PEN (polyethylene naphthalate) film will be discussed.
For long duration missions of solar sail vehicles, the sail material needs to survive the harsh space environment as the degradation of the sail material determines its operational lifetime. Therefore, understanding the effects of the space environment on the sail membrane is essential for mission success. In this study, the effect of simulated space environments of ionizing radiation and thermal aging were investigated. In order to assess some of the potential damage effects on the mechanical, thermal and optical properties of a commercial off the shelf (COTS) polyester solar sail membrane. The solar sail membrane was exposed to high energy electrons [about 70 keV and 10 nA/cm(exp. 2)], and the physical properties were characterized. After about 8.3 Grad dose, the tensile modulus, tensile strength and failure strain of the sail membrane decreased by 20 to 95%. The aluminum reflective layer was damaged and partially delaminated but it did not show any significant change in solar absorbance or thermal emittance. The mechanical properties of a precracked sample, simulating potential impact damage of the sail membrane, as well as thermal aging effects on metallized PEN (polyethylene naphthalate) film, will be discussed.
Total ionizing dose and displacement damage dose testing were performed to characterize and determine the suitability of candidate electronics for NASA spacecraft and program use.
Previously, samples of coarse grained (CG, grain diameter > 1 µm), ultra-fine grained (UFG, 1 µm> grain diameter> 100 nm), and nanocrystalline (NC, 100 nm> grain diameter) grade 91 steel were neutron irradiated in the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL). Grade 91 is a ferritic/martensitic steel alloy with a nominal composition of Fe-9%Cr-1%Mo by weight, and it is being studied for applications in advanced nuclear reactor designs including as a fuel cladding material in gas cooled reactors. To assess the viability of this alloy for nuclear applications, the role of grain boundary size has not been sufficiently explored as a mechanism for developing radiation-tolerant materials. To achieve an UFG microstructure the material was processed using equal channel angular pressing (ECAP), and the NC microstructure was achieved through high pressure torsion (HPT). Such samples of various geometries for different types of characterization were irradiated to a dose of 6 displacements per atom (DPA) at separate temperature conditions of 300 °C and 500 °C. Thus, there were a total of 6 experimental conditions, three grain sizes (CG, UFG, and NC), each irradiated at two different temperature conditions (300 °C and 500 °C).
The NASA Human Research Program’s (HRP) Space Radiation Element (SRE) funds research to characterize and mitigate adverse health outcomes from exposure to space radiation to enable deep space exploration and sustained human presence in space. Damage to the cardiovascular system has been observed after exposure to clinically relevant doses of ionizing radiation. However, an association between lower radiation doses and cardiovascular disease (CVD) remains controversial, and questions pertaining to dose thresholds, radiation quality and dose-rate effects, and gaps in characterizing the mechanisms and major pathways of CVD remain. To solicit new ideas for characterizing and mitigating this risk, the SRE is organizing a series of miniature technical interchange meeting (Tiny-TIM) that provide a venue for HRP-funded investigators and thought leaders to present ongoing work and engage in open discussion on relevant topics. The initial Tiny-TIM: Upping the Ante on Characterizing and Mitigating Cardiovascular Disease Risk from Space Radiation Exposure, held at the NASA HRP Investigators’ Workshop (IWS) earlier this year, consisted of two 90-minute sessions; the first focused on current knowledge of CVD risk from space radiation exposure, and the second focused on innovative ideas, and newer approaches and techniques to accelerate research. The second session was followed by an open, spirited discussion amongst peers on the current issues impeding the characterization of CVD risk. SRE leadership facilitated the discussion using a set of pressing questions and gaps in knowledge that need to be addressed by the scientific community. This poster presents the outcomes of the Tiny-TIM, along with proposed future workshops and the SRE’s other initiatives.
A key goal in drug development is optimized dosing for patients. Interactions between drug developers and regulatory scientists throughout development are important for the optimization of dosing and serve as a forum to discuss approaches for optimal dosing, such as precision or individualized dosing. To date, there has not been a systematic assessment of the advice provided by the US Food and Drug Administration (FDA) to drug developers from an individualized dosing perspective. Here, we reviewed FDA recommendations on dose selection for efficacy trials at end‐of‐phase meetings between the FDA and drug developers for 76 new molecular entities approved between 2013 and 2017 that are considered amenable for an individualized dosing method, response‐guided titration. Forty FDA dosing recommendations were identified as specific to dose selection and design of the respective efficacy trials and subsequently: (i) characterized based on if they were supportive of individualized dosing and (ii) compared with dosing regimens used in efficacy trials and labeling at approval to evaluate if FDA recommendations were implemented. Of these 40 recommendations for efficacy trials, 35 (88%) were considered supportive of individualized dosing. Eighteen of these 40 recommendations (45%) were incorporated into efficacy trials and 11 (28%) were incorporated into labeling. This research suggests that early FDA‐sponsor interactions can support the study of doses in efficacy trials that may lead to individualized dosing strategies in labeling.
BACKGROUND: Outside the protection of the terrestrial environment, astronauts on any long-term missions will unavoidably be exposed to fields of charged particle radiation dominated by protons. These fields and their biological risks are modified in complex ways by the presence of protective shielding. METHODS: To examine the long-term effects of space-like proton exposures on immune status, we treated female C57BL/6 mice with 3 or 4 Gy of 250 MeV monoenergetic protons or the complex space-like radiation field produced after 250 MeV protons are transported through 15 g x cm(-2) aluminum shielding. The animals were euthanized 122 d post-irradiation and lymphocyte phenotypes, hematological parameters, and lymphocyte blastogenesis were characterized. RESULTS: There were significant dose-dependent decreases in macrophage, CD3+/CD8+ T, NK, platelet, and red blood cell populations, as well as low hematocrit and hemoglobin levels. In contrast, dose-dependent increases in spontaneous, but not mitogen-induced, blastogenesis were noted. The differences in dose composition between pristine and shielded proton fields did not lead to significant effects in most measures, but did result in significant changes in monocyte and macrophage populations and spontaneous blastogenesis in the spleen. CONCLUSIONS: The data indicate that whole body exposure to proton radiation at doses of the order of large solar particle events or clinical treatment fractions may have long-term effects on immune system status.
Electron beam microscopy and related characterization techniques play an important role in revealing the microstructural, morphological, physical, and chemical information of halide perovskites and their impact on associated optoelectronic devices. However, electron beam irradiation usually causes damage to these beam-sensitive materials, negatively impacting their device performance, and complicating this interpretation. Here, the electron microscopy and spectroscopy techniques are reviewed that are crucial for the understanding of the crystallization and microstructure of halide perovskites. In addition, special attention is paid to assessing and mitigating the electron beam-induced damage caused by these techniques. Since the halide perovskites are fragile, a protocol involving delicate control of both electron beam dose and dose rate, coupled with careful data analysis, is key to enable the acquisition of reliable structural and compositional information such as atomic-resolution images, chemical elemental mapping and electron diffraction patterns. Limiting the electron beam dose is critical parameter enabling the characterization of various halide perovskites. Novel methods to unveil the mechanisms of device operation, including charge carrier generation, diffusion, and extraction are presented in scanning electron microscopy studies combined with electron-beam-induced current and cathodoluminescence mapping. Future opportunities for electron-beam-related characterizations of halide perovskites are also discussed.
Characterization of the Radiation Calibration and Spectroscopy Laboratory (RCS) Co-60 source radiation pool was successfully completed. The characterization was done by performing several measurements of dose rate in the center of the Co-60 source radiation pool and at multiple heights from the bottom of the pool. The measurements were taken between November 2018 through January 2019. Opti-Chromic FWT-70-40M dosimeters were used for this measurement. A 7.3 cm inner diameter stainless steel cylinder (vessel) was used to lower the dosimeters to the bottom of the pool inside the 16 cm dimeter Co-60 source basket. The dose rate was measured at heights of 5.5, 12, 19, and 23 cm from the bottom of the pool. The report “Tour of the Standards and Calibration Laboratory” includes information about the Co-60 source radiation pool. The importance of performing the Co-60 source characterization is to confirm previously reported Co-60 source dose rate measurements and to provide a documented measuring procedure for researchers and others who want to use the Co-60 source to evaluate the effects of radiation on space-based equipment for other applications. The measured dose rate at the abovementioned heights was 0.65, 0.69, 0.53, 0.23 krad/min respectively with the highest coefficient of variation of less than 10%.