Cosmic ray atmospheric neutron measurements at high elevations over a sunspot cycle
Atmospheric neutron production by cosmic radiation over sunspot cycle, measuring energy spectrum with airplanes and balloon-borne instruments
Korff, S. A.↗
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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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EC/LSS thermal control system study for the space shuttle
The results of a parametric weight analysis of heat rejection systems for the space shuttle orbiter are presented. Integrating the suborbital heat rejection system with the overall heat rejection system design and the possible use of a common system for both on-orbit and suborbital operations require an overall system and parametric analyses applicable to all mission phases. The concept of equivalent weights, with weight penalties assigned for power, induced aircraft drag and radiator area is used to determine weight estimates for the following candidate systems: vapor cycle refrigeration, gas cycle refrigeration, radiators (space and atmospheric convectors), expendable heat sinks, and ram air. The orbiter power penalty, ram air penalty, and radiator weight penalty are analyzed. The vapor compression system and an expendable fluid system utilizing a multifluid spraying flash evaporator are selected as the two most promising systems. These are used for maximum on-orbit heat rejection in combination with or as a supplement to a space radiator.
Howell, H. R.↗
The MISSE 7 Flexural Stress Effects Experiment After 1.5 Years of Wake Space Exposure
Low Earth orbit space environment conditions, including ultraviolet radiation, thermal cycling, and atomic oxygen exposure, can cause degradation of exterior spacecraft materials over time. Radiation and thermal exposure often results in bond- breaking and embrittlement of polymers, reducing mechanical strength and structural integrity. An experiment called the Flexural Stress Effects Experiment (FSEE) was flown with the objective of determining the role of space environmental exposure on the degradation of polymers under flexural stress. The FSEE samples were flown in the wake orientation on the exterior of International Space Station for 1.5 years. Twenty-four samples were flown: 12 bent over a 0.375 in. mandrel and 12 were over a 0.25 in. mandrel. This was designed to simulate flight configurations of insulation blankets on spacecraft. The samples consisted of assorted polyimide and fluorinated polymers with various coatings. Half the samples were designated for bend testing and the other half will be tensile tested. A non-standard bend-test procedure was designed to determine the surface strain at which embrittled polymers crack. All ten samples designated for bend testing have been tested. None of the control samples' polymers cracked, even under surface strains up to 19.7%, although one coating cracked. Of the ten flight samples tested, seven show increased embrittlement through bend-test induced cracking at surface strains from 0.70%to 11.73%. These results show that most of the tested polymers are embrittled due to space exposure, when compared to their control samples. Determination of the extent of space induced embrittlement of polymers is important for designing durable spacecraft.
Snow, Kate E.↗
Impact of Total Ionizing Dose Radiation Testing and Long-Term Thermal Cycling on the Operation of CMF20120D Silicon Carbide Power MOSFET
Power systems designed for use in NASA space missions are required to work reliably under harsh conditions including radiation, thermal cycling, and extreme temperature exposures. Silicon carbide devices show great promise for use in future power electronics systems, but information pertaining to performance of the devices in the space environment is very scarce. A silicon carbide N-channel enhancement-mode power MOSFET called the CMF20120 is of interest for use in space environments. Samples of the device were exposed to radiation followed by long-term thermal cycling to address their reliability for use in space applications. The results of the experimental work are presentd and discussed.
thermal cycling tests↗
The Projection of Space Radiation Environments with a Solar Cycle Statistical Model
A solar cycle statistical model has been developed to project sunspot numbers which represent the variations in the space radiation environment. The resultant projection of sunspot numbers in near future were coupled to space-related quantities of interest in radiation protection, such as the galactic cosmic radiation (GCR) deceleration potential (f) and the mean occurrence frequency of solar particle event (SPE). Future GCR fluxes have been derived from a predictive model, in which GCR temporal dependence represented by f was derived from GCR flux and ground-based Climax neutron monitor rate measurements over the last four decades. Results showed that the point dose equivalent inside a typical spacecraft in interplanetary radiation fields was influenced by solar modulation up to a factor of three. One important characteristic of sporadic SPEs is their mean frequency of occurrence, which is dependent on solar activity. Projections of future mean frequency of SPE occurrence were estimated from a power law function of sunspot number. Furthermore, the cumulative probabilities of SPE during short-period missions were defined with the continuous database of proton fluences of SPE. The analytic representation of energy spectra of SPE was constructed by the Weibull distribution for different event sizes. The representative exposure level at each event size was estimated for the guideline of protection systems for astronauts during future space exploration missions.
Kim, Myung-Hee↗
Radiation Dose-effects on Cell Cycle, Apoptosis, and Marker Expression of Ataxia Telangiectasia-Heterozygous Human Breast Epithelial Cells
Ataxia-telangiectasia (A-T) is a radiation-sensitive genetic condition. AT-heterozygous human mammary epithelial cells (HMEC) were irradiated using a Cs137 source in order to compare cell cycle, apoptosis, and marker expression responses across 3 radiation doses. No differences in cell cycle and apoptosis were found with any of the radiation doses used (30, 60, and 90 rads) compared with the unirradiated control (0 rad). At the same doses, however, differences were found in marker expression, such as keratin 18 (kl8), keratin 14 (k14), insulin-like growth factor I receptor (IGF-IR), and connexin 43 (cx43). This may indicate that radiation sensitivity in the heterozygous state may be initiated through signal transduction responses.
Cruz, A.↗
Pyroelectric conversion in space: A conceptual design study
Pyroelectric conversion is potentially a very lightweight means of providing electrical power generation in space. Two conceptualized systems approaches for the direct conversion of heat (from sunlight) into electrical energy using the pyroelectric effect of a new class of polar polymers were evaluated. Both of the approaches involved large area thin sheets of plastic which are thermally cycled by radiative input and output of thermal energy. The systems studied are expected to eventually achieve efficiencies of the order of 8% and may deliver as much as one half kilowatt per kilogram. In addition to potentially very high specific power, the pyroelectric conversion approaches outlined appear to offer low cost per watt in the form of an easily deployed, flexible, strong, electrically ""self-healing'', and high voltage sheet. This study assessed several potential problems such as plasma interactions and radiation degradation and suggests approaches to overcome them. The fundamental technological issues for space pyroelectric conversion are: (1) demonstration of the conversion cycle with the proposed class of polymers, (2) achievement of improved dielectric strength of the material, (3) demonstration of acceptable plasma power losses for low altitude, and (4) establishment of reasonable lifetime for the pyroelectric material in the space environment. Recommendations include an experimental demonstration of the pyroelectric conversion cycle followed by studies to improve the dielectric strength of the polymer and basic studies to discover additional pyroelectric materials.
Olsen, R. B.↗
The flux of heavy nuclei in the primary cosmic rays over Texas in March 1962, and the solar cycle modulation
Flux of heavy nuclein primary cosmic radiation and solar cycle modulation
SOLAR CYCLE↗
Estimated Environmental Exposures for MISSE-7B
This paper details the 18-month environmental exposure for Materials International Space Station Experiment 7B (MISSE-7B) ram and wake sides. This includes atomic oxygen, ultraviolet radiation, particulate radiation, thermal cycling, meteoroid/space debris impacts, and observed contamination. Atomic oxygen fluence was determined by measured mass and thickness loss of polymers of known reactivity. Diodes sensitive to ultraviolet light actively measured solar radiation incident on the experiment. Comparisons to earlier MISSE flights are discussed.
Finckenor, Miria M.↗
Estimated Environmental Exposures for MISSE-3 and MISSE-4
Describes the estimated environmental exposure for MISSE-2 and MISSE-4. These test beds, attached to the outside of the International Space Station, were planned for 3 years of exposure. This was changed to 1 year after MISSE-1 and -2 were in space for 4 years. MISSE-3 and -4 operate in a low Earth orbit space environment, which exposes them to a variety of assaults including atomic oxygen, ultraviolet radiation, particulate radiation, thermal cycling, and meteoroid/space debris impact, as well as contamination associated with proximity to an active space station. Measurements and determinations of atomic oxygen fluences, solar UV exposure levels, molecular contamination levels, and particulate radiation are included.
Finckenor, Miria M.↗
Europa Environmental Testing of Thermal Hardware for the Mapping Imaging Spectrometer for Europa (MISE) Instrument
The Europa Clipper spacecraft, scheduled for launch in June 2022, hosts a suite of instruments including the Mapping Imaging Spectrometer for Europa (MISE). MISE is a high-optical through-put pushbroom infrared imaging spectrometer that can collect measurements within Europa’s challenging radiation environment. It is externally mounted to the spacecraft and as a result is exposed to high radiation levels and cold temperatures. The instrument consists of a scan mirror assembly, an optical bench including a Dyson spectrometer and a telescope, and a structure that supports a cryocooler and a radiator. The cryocooler is used to actively cool the focal plane array and the spectrometer. The heat from the cryocooler is rejected through pyrolytic graphite sheet thermal straps to a honeycomb radiator. MISE will implement thermal hardware that will either not be used on other parts of the spacecraft or have a more extreme environment than the spacecraft. As a result, the MISE instrument performed numerous environmental tests on its thermal hardware. This paper discusses the results of the thermal cycling and radiation tests performed on the MISE thermal hardware including a Lockheed Martin Micro1-2 cryocooler, Pyrolytic graphite sheet thermal straps, Annealed pyrolytic graphite K-Core, Rosemount Platinum Resistance Thermometers, Tayco Kapton Thermofoil heaters, Dale Ohm resistors, and aluminum honeycomb and facesheets.
Strong, Patrick↗
Response of the Water Cycle of West Africa and Atlantic to Radiative Forcing by Saharan Dust
The responses of the atmospheric water cycle and climate of West Africa and the Atlantic to radiative forcing of Saharan dust are studied using the NASA finite volume general circulation model (fvGCM), coupled to a mixed layer ocean. We find evidence in support of the "elevated heat pump" (EHP) mechanism that underlines the responses of the atmospheric water cycle to dust forcing as follow. During the boreal summer, as a result of large-scale atmospheric feed back triggered by absorbing dust aerosols, rainfall and cloudiness are enhanced over the West Africa/Easter Atlantic ITCZ, and suppressed over the West Atlantic and Caribbean. region. Shortwave radiation absorption by dust warms the atmosphere and cools the surface, while long wave has the opposite response. The elevated dust layer warms the air over Nest Africa and the eastern Atlantic. The condensation heating associated with the induced deep convection drives and maintains an anomalous large-scale east-west overturning circulation with rising motion over West Africa/eastern Atlantic, and sinking motion over the Caribbean region. The response also includes a strengthening of the West African monsoon, manifested in northward shift of the West Africa precipitation over land, increased low-level westerlies flow over West Africa at the southern edge of the dust layer, and a near surface energy fluxes, resulting in cooling of the Nest African land and the eastern Atlantic, and a warming in the West Atlantic and Caribbean. The EHP effect is most effective for moderate to highly absorbing dusts, and becomes minimized for reflecting dust with single scattering albedo at 0.95 or higher.
Lau, K. M.↗
Geostationary earth climate sensor: Scientific utility and feasibility, phase A
The possibility of accurate broad band radiation budget measurements from a GEO platform will provide a unique opportunity for viewing radiation processes in the atmosphere-ocean system. The CSU/TRW team has prepared a Phase 1 instrument design study demonstrating that measurements of radiation budget are practical from geosynchronous orbit with proven technology. This instrument concept is the Geostationary Earth Climate Sensor (GECS). A range of resolutions down to 20 km at the top of the atmosphere are possible, depending upon the scientific goals of the experiment. These tradeoffs of resolution and measurement repeat cycles are examined for scientific utility. The design of a flexible instrument is shown to be possible to meet the two goals: long-term, systematic monitoring of the diurnal cycles of radiation budget; and high time and space resolution studies of regional radiation features.
Campbell, G. Garrett↗
Effects of Radiation and Long-Term Thermal Cycling on EPC 1001 Gallium Nitride Transistors
Electronics designed for use in NASA space missions are required to work efficiently and reliably under harsh environment conditions. These include radiation, extreme temperatures, and thermal cycling, to name a few. Data obtained on long-term thermal cycling of new un-irradiated and irradiated samples of EPC1001 gallium nitride enhancement-mode transistors are presented. This work was done by a collaborative effort including GRC, GSFC, and support the NASA www.nasa.gov 1 JPL in of Electronic Parts and Packaging (NEPP) Program
Patterson, Richard L.↗
Use of TRMM Data to Test an Improved Parameterization of Stratiform Precipitation
By incorporating the TRMM satellite orbital information into the most recent geodesic version of the Colorado State University General Circulation Model (CSU GCM), we are able to fly a satellite in the GCM, and sample the simulated atmosphere in the same way as the TRMM sensors sample the real atmosphere. The TRMM sampling statistics of precipitation and radiative fluxes at annual, intra-seasonal, monthly-mean and composited diurnal time scales are evaluated by comparing the satellite-sampled against fully-sampled simulated atmospheres. This information provides a valuable guidance for efficient usage of TRMM data and future satellite mission planning. We have also evaluated the effects of TRMM sampling errors on the inferred tropical-mean hydrologic cycle and radiative fluxes. We have found that there are strong spurious oscillations associated with the TRMM orbital geometry, with periods of 23 days and 3-4 months, in tropical-mean daily and monthly precipitation. Caution must therefore be used when applying TRMM observations of tropical-mean precipitation to interpret climate variations at intraseasonal and interannual scales.
Randall, David A.↗
Comparison of Gas-Turbine Cycles for Space Applications
On the basis of the radiator area required for rejecting cycle waste heat, Rankine vapor cycles are far superior to the basic Brayton gas cycle for space turbogenerating powerplants. The present analysis considers modifications of the basic Brayton cycle and compares the modified cycles to the basic cycle with radiator area as the criterion of merit. The results indicate that reductions in radiator area attainable by modifying the basic Brayton cycle are small, and thus the competitive position of gasturbine cycles relative to Rankine vapor cycles is unchanged.
English, Robert E.↗
Earth radiation budget measurements from satellites and their interpretation for climate modeling and studies
The annual and seasonal averaged Earth atmosphere radiation budgets derived from the most complete set of satellite observations available are presented. The budgets were derived from a composite of 48 monthly mean radiation budget maps. Annually and seasonally averaged radiation budgets are presented as global averages and zonal averages. The geographic distribution of the various radiation budget quantities is described. The annual cycle of the radiation budget was analyzed and the annual variability of net flux was shown to be largely dominated by the regular semi and annual cycles forced by external Earth-Sun geometry variations. Radiative transfer calculations were compared to the observed budget quantities and surface budgets were additionally computed with particular emphasis on discrepancies that exist between the present computations and previous surface budget estimates.
Vonderhaar, T. H.↗
Identification and Evaluation of Integration and Cross Cutting Issues Across HRP Risks
The HRP Integrated Research Plan contains the research plans for the 32 risks requiring research to characterize and mitigate. These risks to human health and performance in spaceflight are identified by evidence and each one focuses on a single aspect of human physiology or performance. They are further categorized by aspects of the spaceflight environment, such as altered gravity or space radiation, that that play a major role in their likelihood and consequence. From its inception the "integrate" in the Research Plan has denoted the integrated nature of risks to human health and performance, the connectedness of physiological systems within the human body regardless of the spaceflight environment, and the integrated response of the human body to the spaceflight environment. Common characteristics of the spaceflight environment include altered gravity, atmospheres and light/dark cycles, space radiation, isolation, noise, and periods of high or low workload. Long term exposure to this unique environment produces a suite of physiological effects such as stress; vision, neurocognitive and anthropometric changes; circadian misalignment; fluid shifts, deconditioning; immune dysregulation; and altered nutritional requirements. Matrix diagraming was used to systematically identify, analyze and rate the many-to-many relationships between environmental characteristics and the suite of physiological effects. It was also to identify patterns in the relationships of common physiological effects to each other. Analyses of patterns or relationships in these diagrams help to identify issues that cut across multiple risks. Cross cutting issues benefit from a multidisciplinary approach that synthesizes concepts or data from two or more disciplines to identify and characterize risk factors or develop countermeasures relevant to multiple risks. They also help to illuminate possible problem areas that may arise when a countermeasure impacts risks other than those which it was developed to mitigate, or identify groupings of physiological changes that are likely to occur that may impact the overall risk posture.
Steinberg, S. L.↗