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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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At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Systems analysis of Mars solar electric propulsion vehicles

Mission performance, mass, initial power, and cost are determined for solar electric propulsion vehicles across a range of payload masses, reference powers, and mission trajectories. Thick radiation shielding is added to arrays using indium phosphide or III-V multijunction solar cells to reduce the damage incurred through the radiation belts. Special assessments of power management and distribution systems, atmospheric drag, and energy storage are made. It is determined that atmospheric drag is of no great concern and that the energy storage used in countering drag is unnecessary. A scheme to package the arrays, masts, and ion thrusters into a single fairing is presented.

Hickman, J. M.↗
NASA NTRS1993

The initial flight anomalies of Skylab 1

At approximately 63 seconds into the flight of Skylab 1 on May 14, 1973, an anomaly occurred which resulted in the complete loss of the meteoroid shield around the orbital workshop. This was followed by the loss of one of the two solar array systems on the workshop and a failure of the inter stage adapter to separate from the S-II stage of the Saturn V launch vehicle. The investigation reported herein identified the most probable cause of this flight anomaly to be the breakup and loss of the meteoroid shield due to aerodynamic loads that were not accounted for in its design. The breakup of the meteoroid shield, in turn, broke the tie downs that secured one of the solar array systems to the workshop. Complete loss of this solar array system occurred at 593 seconds when the exhaust plume of the S-II stage retro-rockets impacted the partially deployed solar array system. Falling debris from the meteoroid shield also damaged the S-II inter stage adapter ordnance system in such a manner as to preclude separation. Of several possible failure modes of the meteoroid shield that were identified, the most probable in this particular flight was internal pressurization of its auxiliary tunnel which acted to force the forward end of the meteoroid shield away from the shell of the workshop and into the supersonic air stream. The pressurization of the auxiliary tunnel was due to the existence of several openings in the aft region of the tunnel. Another possible failure mode was the separation of the leading edge of the meteoroid shield from the shell of the workshop (particularly in the region of the folded ordnance panel) of sufficient extent to admit ram air pressures under the shield.

Source record↗
NASA NTRS1989

A parametric study of space radiation exposures to critical body organs for low earth orbit missions

It is shown that it is possible to calculate the extent of the exposure to space radiation of a specific body organ. Using a computerized anatomical man model and models of radiation environments and spacecraft shielding, a parametric study was carried out for several Space-Shuttle scenarios. The dose equivalent data for several blood-forming organ locations are presented (for a solar-minimum epoch) as a function of altitude and the shielding material, and the results are compared with the NASA crew exposure limits for these body organs.

Atwell, W.↗
NASA NTRS2019

Advances in Space Radiation Physics and Transport

The space radiation environment is a complex mixture of particle types and energies originating from sources inside and outside of the galaxy. These environments may be modified by the heliospheric and geomagnetic conditions as well as planetary bodies and vehicle or habitat mass shielding. In low Earth orbit (LEO), the geomagnetic field deflects a portion of the galactic cosmic rays (GCR) and all but the most intense solar particle events (SPE). There are also dynamic belts of trapped electrons and protons with low to medium energy and intense particle count rates. In deep space, the GCR exposure is more severe than in LEO and varies inversely with solar activity. Unpredictable solar storms also present an acute risk to astronauts if adequate shielding is not provided. Near planetary surfaces such as the Earth, moon or Mars, secondary particles are produced when the ambient deep space radiation environment interacts with these surfaces and/or atmospheres. These secondary particles further complicate the local radiation environment and modify the associated health risks. Characterizing the radiation fields in this vast array of scenarios and environments is a challenging task and is currently accomplished with a combination of computational models and dosimetry. The computational tools include models for the ambient space radiation environment, mass shielding geometry, and atomic and nuclear interaction parameters. These models are then coupled to a radiation transport code to describe the radiation field at the location of interest within a vehicle or habitat. Many new advances in these models have been made in the last decade, and the present review article focuses on the progress and contributions made by workers and collaborators at NASA in the same time frame. Although great progress has been made, and models continue to improve, significant gaps remain and are discussed in the context of planned future missions. Of particular interest is the juxtaposition of various review committee findings regarding the accuracy and gaps of combined space radiation environment, physics, and transport models with the progress achieved over the past decade. While current models are now fully capable of characterizing radiation environments in the broad range of forecasted mission scenarios, it should be remembered that uncertainties still remain and need to be addressed.

Space radiation↗
NASA NTRS1992

Plasma effects on the passive external thermal control coating of Space Station Freedom

The current baseline chromic acid anodized thermal control coating on 6061-T6 aluminum meteoroid debris (M/D) shields for SSF has been evaluated. The degradation of the solar absorptance, alpha, and the thermal emittance, epsilon, of chromic acid anodized aluminum due to dielectric breakdown in plasma was measured to predict the on-orbit lifetime of the SSF M/D shields. The lifetime of the thermal control coating was based on the surface temperatures achieved with degradation of the thermal control properties, alpha and epsilon. The temperatures of each M/D shield from first element launch (FEL) through FEL+15 years were analyzed. It is shown that the baseline thermal control coating cannot withstand the -140 V potential between the conductive structure of the SSF and the current plasma environment.

Carruth, Ralph, Jr.↗
NASA NTRS2018

Juno at Jupiter: The Mission and Its Path to Unveiling Secrets of the History of the Solar System

The Juno mission is described, focusing on its orbits at Jupiter, how the plan evolved, and science return so far. Juno is a NASA New Frontiers spacecraft in a near-polar highly elliptical 53-day orbit at Jupiter. Since arrival in July 2016, it has used 9 science investigations to study the planet’s atmospheric composition and structure, magnetic and gravity fields, and polar and extended magnetosphere. A radiation monitoring investigation contributes to our understanding of Jupiter’s environment. Juno’s primary science goal is to understand the origin and evolution of Jupiter, to shed light on how the Earth and other planets formed. Baseline objectives will be satisfied with 32 science orbits, a spin-stabilized solar powered spacecraft, an electronics vault for radiation shielding, and a robust payload with microwave receivers, X- and Ka-band radio science hardware, vector magnetometers, high- and low-energy charged particle detectors, radio and plasma wave antennas, UV and IR spectroscopic imagers, and a visible light camera for public outreach. Observations are made in a limited number of orientations, including Gravity Science (spin axis and main antenna pointing to Earth), and microwave atmospheric sounding (spin plane passing through Jupiter’s center). Prime science data are collected near closest approach (perijove), plus calibrations, occasional remote sensing, and continued magnetospheric observations in the outer parts of the orbit. Juno’s mission plan has evolved since the 2005 proposal due to design and ops choices, e.g., mission design (cruise or early orbital trajectory), orbit period (11, 14, then 53 days), perijove attitudes (2 or more), and DSN coverage (34- and 70-m stations). Choices were partly motivated by the effect on science return. Selected preliminary science results are summarized, including the benefits of decisions as the plan evolved. Juno has begun to unveil Jupiter – peeling apart its interior by measuring gravity and magnetic fields, using microwaves to probe its atmosphere down to 100s of km, exploring its polar and extended magnetosphere, and imaging the poles for the first time. In doing so, it is revealing secrets of the history of the Earth and solar system.

Stephens, Stuart K.↗
NASA NTRS2000

Considerations Concerning the Development and Testing of In-situ Materials for Martian Exploration

Natural Martian surface materials are evaluated for their potential use as radiation shields for manned Mars missions. The modified radiation fluences behind various kinds of Martian rocks and regolith are determined by solving the Boltzmann equation using NASA Langley s HZETRN code along with the 1977 Solar Minimum galactic cosmic ray environmental model. To make structural shielding composite materials from constituents of the Mars atmosphere and from Martian regolith for Martian surface habitats, schemes for synthesizing polyimide from the Mars atmosphere and for processing Martian regolith/polyimide composites are proposed. Theoretical predictions of the shielding properties of these composites are computed to assess their shielding effectiveness. Adding high-performance polymer binders to Martian regolith to enhance structural properties enhances the shielding properties of these composites because of the added hydrogenous constituents. Laboratory testing of regolith simulant/polyimide composites is planned to validate this prediction.

Kim, M.-H. Y.↗
NASA NTRS2001

Radiation protection using Martian surface materials in human exploration of Mars

To develop materials for shielding astronauts from the hazards of GCR, natural Martian surface materials are considered for their potential as radiation shielding for manned Mars missions. The modified radiation fluences behind various kinds of Martian rocks and regolith are determined by solving the Boltzmann equation using NASA Langley's HZETRN code along with the 1977 Solar Minimum galactic cosmic ray environmental model. To develop structural shielding composite materials for Martian surface habitats, theoretical predictions of the shielding properties of Martian regolith/polyimide composites has been computed to assess their shielding effectiveness. Adding high-performance polymer binders to Martian regolith to enhance structural properties also enhances the shielding properties of these composites because of the added hydrogenous constituents. Heavy ion beam testing of regolith simulant/polyimide composites is planned to validate this prediction. Characterization and proton beam tests are performed to measure structural properties and to compare the shielding effects on microelectronic devices, respectively.

NASA Center LaRC↗
NASA NTRSDate not supplied

Initial Results of the MISSE-Flight Facility Polymers and Composites Experiment 1-4 (PCE 1-4)

Spacecraft in low Earth orbit (LEO) are subjected to harsh environmental conditions, including radiation (cosmic rays, ultraviolet (UV), x-ray and charged particle radiation), micrometeoroids and orbital debris, temperature extremes, thermal cycling, and atomic oxygen (AO). These environmental exposures can result in erosion, embrittlement and optical property degradation of susceptible materials threatening spacecraft performance and durability. To increase our understanding of effects such as AO erosion and radiation induced embrittlement of spacecraft materials, NASA Glenn Research Center has developed a series of experiments that are flown as part of the Materials International Space Station Experiment (MISSE) missions on the exterior of the International Space Station (ISS). These experiments have provided critical space environmental durability data such as AO erosion data of polymers and composites, and radiation induced mechanical property degradation of spacecraft insulation materials, after long term space exposure. In continuing these studies, four Glenn experiments with 365 flight samples have been flown on ISS’s external MISSE-Flight Facility (MISSE-FF). These experiments are the Polymers and Composites Experiment-1 (PCE-1) flown as part of the inaugural MISSE-9 mission, the PCE-2 flown as part of the MISSE-10 mission, the PCE-3 flown as part of the MISSE-12 and MISSE-15 missions, and the PCE-4 flown as part of the MISSE-13 mission. The primary objective of the PCE 1-4 experiments is to determine the AO and radiation durability of spacecraft polymers and composites. In addition, each experiment has a wide variety of spacecraft materials and hence they each have numerous additional sample objectives. Each of the PCE 1-4 is designed to examine the consequences of AO interactions including AO erosion yield (Ey) and optical and thermal property characterization. Several polymers were flown in both ram and zenith flight orientations to determine the effect of varying solar to AO ratios on Ey. Common spacecraft materials including Teflon FEP, white Tedlar and Upilex-S were included on multiple MISSE missions so erosion dependence on environment exposure can be determined. The PCE-1 includes epoxy composite samples with varying ZnO levels to determine the effect of inorganic filler level on AO durability. And, a variety of samples were flown to characterize AO scattering and AO undercutting processes. All four PCE experiments include samples to provide better insight into radiation durability of polymers and composites. The MISSE-9 PCE-1 includes Teflon FEP tensile samples flown in the wake and zenith direction so variations in radiation exposure from the different flight directions can provide insight into radiation induced embrittlement of Teflon FEP. Teflon FEP tensile samples were also flown in the wake direction as part of the MISSE-13 PCE-4. In addition, shape memory alloys, shape memory composites, melanin based composites, stressed and unstressed gossamer sun shield materials, coated and uncoated docking seal samples, and new solar cell cover slides were flown for space radiation durability and/or shielding assessment. This paper provides an overview of Glenn’s PCE 1-4 MISSE-FF experiments and provides initial post-flight observations and results.

atomic oxygen↗
NASA NTRS1990

Space radiation shielding for a Martian habitat

Radiation shielding analyses are performed for a candidate Mars base habitat. The Langley cosmic ray transport code and the Langley nucleon transport code are used to quantify the transport and attenuation of galactic cosmic rays and solar flare protons through both the Martian atmosphere and regolith shielding. Doses at the surface and at various altitudes were calculated in a previous study using both a high-density and a low-density Mars atmosphere model. This study extends the previous low-density results to include the further transport of the ionizing radiation that reaches the surface through additional shielding provided by Martian regolith. A four-compound regolith model, which includes SiO2, Fe2O3, MgO, and CaO, was selected based on the chemistry of the Viking 1 Lander site. The spectral fluxes of heavy charged particles and the corresponding dosimetric quantities are computed for a series of thicknesses in the shield media after traversing the atmosphere. These data are then used as input to algorithms for a specific shield geometry. The results are presented as the maximum dose received in the center of the habitat versus various shield thicknesses for a base at an altitude of 0 km and 8 km.

Simonsen, Lisa C.↗
NASA NTRS2005

Cross Section Sensitivity and Propagated Errors in HZE Exposures

It has long been recognized that galactic cosmic rays are of such high energy that they tend to pass through available shielding materials resulting in exposure of astronauts and equipment within space vehicles and habitats. Any protection provided by shielding materials result not so much from stopping such particles but by changing their physical character in interaction with shielding material nuclei forming, hopefully, less dangerous species. Clearly, the fidelity of the nuclear cross-sections is essential to correct specification of shield design and sensitivity to cross-section error is important in guiding experimental validation of cross-section models and database. We examine the Boltzmann transport equation which is used to calculate dose equivalent during solar minimum, with units (cSv/yr), associated with various depths of shielding materials. The dose equivalent is a weighted sum of contributions from neutrons, protons, light ions, medium ions and heavy ions. We investigate the sensitivity of dose equivalent calculations due to errors in nuclear fragmentation cross-sections. We do this error analysis for all possible projectile-fragment combinations (14,365 such combinations) to estimate the sensitivity of the shielding calculations to errors in the nuclear fragmentation cross-sections. Numerical differentiation with respect to the cross-sections will be evaluated in a broad class of materials including polyethylene, aluminum and copper. We will identify the most important cross-sections for further experimental study and evaluate their impact on propagated errors in shielding estimates.

Heinbockel, John H.↗
NASA NTRS2005

Managing Lunar and Mars Mission Radiation Risks: Cancer Risks, Uncertainties, and Shielding Effectiveness - Part 1

This document addresses calculations of probability distribution functions (PDFs) representing uncertainties in projecting fatal cancer risk from galactic cosmic rays (GCR) and solar particle events (SPEs). PDFs are used to test the effectiveness of potential radiation shielding approaches. Monte-Carlo techniques are used to propagate uncertainties in risk coefficients determined from epidemiology data, dose and dose-rate reduction factors, quality factors, and physics models of radiation environments. Competing mortality risks and functional correlations in radiation quality factor uncertainties are treated in the calculations. The cancer risk uncertainty is about four-fold for lunar and Mars mission risk projections. For short-stay lunar missins (<180 d), SPEs present the most significant risk, but one effectively mitigated by shielding. For long-duration (>180 d) lunar or Mars missions, GCR risks may exceed radiation risk limits. While shielding materials are marginally effective in reducing GCR cancer risks because of the penetrating nature of GCR and secondary radiation produced in tissue by relativisitc particles, polyethylene or carbon composite shielding cannot be shown to significantly reduce risk compared to aluminum shielding. Therefore, improving our knowledge of space radiobiology to narrow uncertainties that lead to wide PDFs is the best approach to ensure radiation protection goals are met for space exploration.

Cucinotta, Francis A.↗
NASA NTRS1976

Preliminary analysis of the implications of natural radiations on geostationary operations

The natural radiations present at geostationary orbit are discussed. Low-level galactic cosmic rays are important for careers spending a year or more at geostationary altitude. Trapped radiation will on occasion require interruption of extravehicular activity (EVA). The spacesuit shield requirements are strongly affected by the number of interruptions allowed. EVA cannot proceed during a large solar event and maximum allowable doses are exceeded in a few hours unless a heavily shielded area is provided. A shelter of 10 g/sq cm with personal shielding for the eyes and testes would contain exposure to within the presently accepted exposure constraints. Since radiation levels can increase unexpectedly to serious levels, an onboard radiation monitoring system with rate and integration capabilities is required for both surface-dose and depth-dose monitoring.

Wilson, J. W.↗
NASA NTRS1972

Flying automated laboratories to the planets.

Review of results obtained by instrumented spacecraft in investigation of the planets, mainly Mars. It appears that Mars is a world of varying topographical structure, some of which must have been created by the same processes that sculptured the moon and by others thus far unique in the solar system. The atmosphere is too thin to shield the surface, and there are no traces of liquid water. The very large recent dust storm is discussed. Mariner 9 has revealed definite indication of probable volcanic activity on Mars in recent geologic times.-

Pickering, W. H.↗
NASA NTRS1983

Cosmogenic neon from precompaction irradiation of Kapoeta and Murchison

Neon from hand-picked Murchison and Kapoeta grains, selected on the basis of the presence or absence of solar flare particle tracks, was analyzed in order to delineate the precompaction history of this material. The irradiated grains showed large enrichments of cosmogenic neon relative to the unirradiated grains. Galactic cosmic ray (GCR) exposure ages for the unirradiated grains yield the nominal values reported for the recent exposure history of these meteorites. Apparent minimum precompaction galactic exposure ages of 28 m.y. and 56 m.y. would have been obtained for Murchison and Kapoeta, respectively, if the cosmogenic effects in the irradiated grains were due to GCR irradiation. Since this seems unreasonably long, the cosmogenic neon in the irradiated grains may be due to spallation by solar cosmic rays. This, however, would require a more active early sun. The isotopic composition of the cosmogenic neon in these grains suggests a harder energy spectrum than is characteristic of present solar flares. Lack of apparent solar wind effects may require some kind of shielding, such as nebular gas.

Caffee, M. W.↗
NASA NTRS1993

Space radiation health research, 1991-1992

The present volume is a collection of 227 abstracts of radiation research sponsored by the NASA Space Radiation Health Program for the period 1991-1992. Each abstract has been categorized within one of three discipline areas: Physics, Biology and Risk Assessment. Topic areas within each discipline have been assigned as follows: Physics - Atomic Physics, Theory, Cosmic Ray and Astrophysics, Experimental, Environments and Environmental Models, Solar Activity and Prediction, Experiments, Radiation Transport and Shielding, Theory and Model Development, Experimental Studies, and Instrumentation. Biology - Biology, Molecular Biology, Cellular Radiation Biology, Transformation, Mutation, Lethality, Survival, DNA Damage and Repair, Tissue, Organs, and Organisms, In Vivo/In Vitro Systems, Carcinogenesis and Life Shortening, Cataractogenesis, Genetics/Developmental, Radioprotectants, Plants, and Other Effects. Risk Assessment - Risk Assessment, Radiation Health and Epidemiology, Space Flight Radiation Health Physics, Inter- and Intraspecies Extrapolation and Radiation Limits and Standards. Section I contains refereed journals; Section II contains reports/meetings. Keywords and author indices are provided. A collection of abstracts spanning the period 1986-1990 was previously issued as NASA Technical Memorandum 4270.

Jablin, M. H.↗