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  • 1
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    Interplanetary crew exposure estimates for galactic cosmic rays (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Using the Langley Research Center galactic cosmic-ray transport computer code and the Computerized Anatomical Man model, initial estimates of interplanetary exposure of astronauts to galactic cosmic rays, during periods of solar minimum activity, are made for a realistic human geometry shielded by various thicknesses of spacecraft aluminum shielding. Conventional dose assessment in terms of total absorbed dose and dose equivalent is made for the skin, ocular lens, and bone marrow. Included in the analyses are separate evaluations of the contributions from the incident primary ions, from subsequent-generation fragmentation products, and from target fragments. In all cases considered, the equivalent sphere approximation yielded conservative overestimates for the actual organ exposures.
    Keywords: AEROSPACE MEDICINE
    Type: Radiation Research (ISSN 0033-7587); p. 48-52.
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  • 2
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    Nuclear reaction effects in conventional risk assessment for energetic ion exposure (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A volume of tissue through which a monoenergetic ion fluence has passed is considered, and the energy absorbed by the media in the passage is evaluated. Various contributions to biological risk are quantified using quality factors presently in force. The effects of newly proposed quality factors are evaluated.
    Keywords: AEROSPACE MEDICINE
    Type: Health Physics (ISSN 0017-9078); 58; 749-752
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  • 3
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    Energy deposition at the bone-tissue interface from nuclear fragments produced by high-energy nucleons (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The transport of nuclear fragmentation recoils produced by high-energy nucleons in the region of the bone-tissue interface is considered. Results for the different flux and absorbed dose for recoils produced by 1 GeV protons are presented in a bidirectional transport model. The energy deposition in marrow cavities is seen to be enhanced by recoils produced in bone. Approximate analytic formulae for absorbed dose near the interface region are also presented for a simplified range-energy model.
    Keywords: AEROSPACE MEDICINE
    Type: Health Physics (ISSN 0017-9078); 59; 819-825
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  • 4
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    Interplanetary crew exposure estimates for the August 1972 and October 1989 solar particle events (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Detailed exposure estimates for the bone marrow, ocular lens, and skin of astronauts on manned missions beyond the earth's magnetosphere have been made for the large solar particle events (SPE) of August 1972 and October 1989. The estimates were made using the coupled neutron-proton space radiation transport computer code BRYNTRN and the CAM model for the human body. It is found that at least 10 g/sq cm aluminum shielding is needed to keep estimated dose equivalent values below current space radiation exposure guidelines recommended for LEO missions. Space suits currently being designed will not provide adequate crew protection and may not even ensure crew survival in the event of exposure to a large SPE during extravehicular activity.
    Keywords: AEROSPACE MEDICINE
    Type: Radiation Research (ISSN 0033-7587); 126; 108-110
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  • 5
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    Radiation safety in commercial air traffic - A need for further study (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The problem of radiation exposure of crewmembers in high altitude supersonic commercial aircraft is addressed. As a result of recent changes in the quality factors for radiological protection, it is found that worst case estimates of radiation exposure are now well above the exposure limits of the general population, and a reassessment of radiation impact on commercial aviation is needed, if the proposed quality factors are adopted. Calculations are presented from a study on neutron dosage equivalent rates. It is shown that a crew flying at altitudes near 13 km (43,000 ft) for 40 hr/mo would receive exposure levels of 47-75 Sv/yr, and it is suggested that such crewmembers be considered as radiation workers, rather than general population members. However, since present exposure estimates need to be improved, and the maximum permissible dose limits are currently under revision, the final exposure limits are, as yet, unclear, suggesting the need for further study to clarify the work status of commercial aircrews.
    Keywords: AEROSPACE MEDICINE
    Type: Health Physics (ISSN 0017-9078); 55; 1001-100
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  • 6
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    HZE reactions and data-base development (1993)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: The primary cosmic rays are dispersed over a large range of linear energy transfer (LET) values and their distribution over LET is a determinant of biological response. This LET distribution is modified by radiation shielding thickness and shield material composition. The current uncertainties in nuclear cross sections will not allow the composition of the shield material to be distinguished in order to minimize biological risk. An overview of the development of quantum mechanical models of heavy ion reactions will be given and computational results compared with experiments. A second approach is the development of phenomenological models from semi-classical considerations. These models provide the current data base in high charge and energy (HZE) shielding studies. They will be compared with available experimental data. The background material for this lecture will be available as a review document of over 30 years of research at Langley but will include new results obtained over the last year.
    Keywords: AEROSPACE MEDICINE
    Type: ; : Spaceflight mechan
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  • 7
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    Estimates of cellular mutagenesis from cosmic rays (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A parametric track structure model is used to estimate the cross section as a function of particle velocity and charge for mutations at the hypoxanthine guanine phosphoribosyl transferase (HGPRT) locus in human fibroblast cell cultures. Experiments that report the fraction of mutations per surviving cell for human lung and skin fibroblast cells indicate small differences in the mutation cross section for these two cell lines when differences in inactivation rates between these cell lines are considered. Using models of cosmic ray transport, the mutation rate at the HGPRT locus is estimated for cell cultures in space flight and rates of about 2 to 10 x 10(exp -6) per year are found for typical spacecraft shielding. A discussion of how model assumptions may alter the predictions is also presented.
    Keywords: AEROSPACE MEDICINE
    Type: NASA-TP-3453 , L-17377 , NAS 1.60:3453
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  • 8
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    Deep-space radiation exposure analysis for solar cycle XXI (1975-1986) (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Ionizing radiation exposures and associated dosimetric quantities are evaluated for the 11-year solar cycle ending in 1986. Solar flare fluences for the 55 largest flares occurring during the cycle are superimposed on the Galactic cosmic ray flux. Published summaries of flare data from the Interplanetary Monitoring Platform (IMP)-7 and IMP-8 satellites are used that include flares whose integrated fluences are greater than 10 to the 7th protons/sq cm for energies in excess of 10 MeV. A standard cosmic ray environment model for ion flux values at solar minimum and maximum is invoked with an assumed sinusoidal variation between the lower and upper limits. The radiation shielding analysis is carried out for equivalent water-shield thicknesses between 2 and 15 g/sq cm. Results are expressed in terms of cumulative incurred dose equivalents for deep-space missions lasting between 3 months and 3 years. It was found that medium-to-large flare contributions are of greatest importance for the shorter term missions, while the Galactic component dominates for the longer duration missions.
    Keywords: AEROSPACE MEDICINE
    Type: SAE PAPER 901347
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  • 9
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    Multiple lesion track structure model (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A multilesion cell kinetic model is derived, and radiation kinetic coefficients are related to the Katz track structure model. The repair-related coefficients are determined from the delayed plating experiments of Yang et al. for the C3H10T1/2 cell system. The model agrees well with the x ray and heavy ion experiments of Yang et al. for the immediate plating, delaying plating, and fractionated exposure protocols employed by Yang. A study is made of the effects of target fragments in energetic proton exposures and of the repair-deficient target-fragment-induced lesions.
    Keywords: AEROSPACE MEDICINE
    Type: NASA-TP-3185 , L-16988 , NAS 1.60:3185
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  • 10
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    Katz model prediction of Caenorhabditis elegans mutagenesis on STS-42 (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Response parameters that describe the production of recessive lethal mutations in C. elegans from ionizing radiation are obtained with the Katz track structure model. The authors used models of the space radiation environment and radiation transport to predict and discuss mutation rates for C. elegans on the IML-1 experiment aboard STS-42.
    Keywords: AEROSPACE MEDICINE
    Type: NASA-TM-4383 , L-17090 , NAS 1.15:4383
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