Extension of the high charge and energy (HZE) transport computer program HZETRN for angular trans... more Extension of the high charge and energy (HZE) transport computer program HZETRN for angular transport of neutrons is considered. For this paper, only light ion transport, Heⴠand lighter, will be analyzed using a pure solar proton source. The angular transport calculator is the ANISN/PC program which is being controlled by the HZETRN program. The neutron flux values are compared for straight-ahead transport and angular transport in one dimension. The shield material is aluminum and the target material is water. The thickness of these materials is varied; however, only the largest model calculated is reported which is 50 gm/cm² of aluminum and 100 gm/cm² of water. The flux from the ANISN/PC calculation is about two orders of magnitude lower than the flux from HZETRN for very low energy neutrons. It is only a magnitude lower for the neutrons in the 10 to 20 MeV range in the aluminum and two orders lower in the water. The major reason for this difference is in the transport modes: ...
Past space missions beyond the confines of the Earth’s protective magnetic field have been of sho... more Past space missions beyond the confines of the Earth’s protective magnetic field have been of short duration and protection from the effects of solar particle events was of primary concern. The extension of operational infrastructure beyond low-Earth orbit to enable routine access to more interesting regions of space will require protection from the hazards of the accumulated exposures of Galactic Cosmic Rays (GCR). There are significant challenges in providing protection from the long-duration exposure to GCR: the human risks to the exposures are highly uncertain and safety requirements places unreasonable demands in supplying sufficient shielding materials in the design. A vigorous approach to future radiation health-risk mitigation requires a triage of techniques (using biological and technical factors) and reduction of the uncertainty in radiation risk models. The present paper discusses the triage of factors for risk mitigation with associated materials issues and engineering design methods.
The purpose of this work is an assessment of the lunar lava tubes physical characteristics and an... more The purpose of this work is an assessment of the lunar lava tubes physical characteristics and an evaluation of the their actual safety features from the point of view of the ionizing radiation environment as potential habitats for future lunar exploration crews.
One major obstacle to human space exploration is the possible limitations imposed by the adverse ... more One major obstacle to human space exploration is the possible limitations imposed by the adverse effects of long-term exposure to the space environment. Even before human spaceflight began, the potentially brief exposure of astronauts to the very intense random solar energetic particle (SEP) events was of great concern. A new challenge appears in deep space exploration from exposure to the low-intensity heavy-ion flux of the galactic cosmic rays (GCR) since the missions are of long duration and the accumulated exposures can be high. Because cancer induction rates increase behind low to rather large thickness of aluminum shielding according to available biological data on mammalian exposures to GCR like ions, the shield requirements for a Mars mission are prohibitively expensive in terms of mission launch costs. Preliminary studies indicate that materials with high hydrogen content and low atomic number constituents are most efficient in protecting the astronauts. This occurs for two...
An optical model description of momentum transfer in relativistic heavy ion collisions, based upo... more An optical model description of momentum transfer in relativistic heavy ion collisions, based upon composite particle multiple-scattering theory, is presented. The imaginary component of the complex momentum transfer, which comes from the absorptive part of the optical potential, is shown to be the main contributor to the momentum loss of the projectile. Within the context of the Goldhaber formalism, predictions of fragment momentum distribution observables are made and compared with experimental data. Use of the model as a tool for estimating collision impact parameters is also discussed.
A solar cycle statistical model has been developed to project sunspot numbers which represent the... more 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 the near future were coupled to space-related quantities of interest in radiation protection such as the galactic cosmic radiation GCR deceleration potential phi and the mean occurrence frequency of solar particle events SPEs Future GCR fluxes have been derived from a predictive model in which GCR temporal dependence represented by phis 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 depends on solar activity Projections of future mean frequency of SPE occurrence were estimated fr...
The understanding of the risk from exposure to cosmic rays to personnel and electronic equipment ... more The understanding of the risk from exposure to cosmic rays to personnel and electronic equipment in spaceflight and in the upper atmosphere is confounded by the high energy nuclear interactions and the track structure of fast ions. The Langley Research Center has developed several radiation transport codes and associated nuclear interaction data bases for describing the passage of high energy protons, neutrons, and light and heavy ions through materials and tissue. We present and overview these transport codes and databases including comparisons to laboratory and spaceflight experiments. Several risk assessment models are considered in order to study the attenuation properties of selected shielding candidates. These comparisons show that in contrast to conventional risk models based on linear energy transfer (LET), track structure models indicate that only hydrogen rich materials are effective in reducing risk. The contrasting conclusions of the conventional and track structure based approaches are shown to be due to differences in the assessment of the effectiveness of secondary ions such as neutrons, protons, alphas, and heavy ion target fragments. Microdosimetric measurements with proton and heavy ion beams are also discussed and as reported earlier in this session by Dicello, reach the same conclusions as the track models on the importance of target fragmentation.
We calculate the probability that large size ejecta from a major collision on a planet in an extr... more We calculate the probability that large size ejecta from a major collision on a planet in an extrasolar planetary system find their way to our solar system and collide with the Earth. The production rate of ejecta is estimated from the conditions in Our Solar System, and the evolution of the environment of the Sun is derived on the assumption
The Langley cosmic ray transport code and the Langley nucleon transport code (BRYNTRN) are used t... more The Langley cosmic ray transport code and the Langley nucleon transport code (BRYNTRN) are used to quantify the transport and attenuation of galactic cosmic rays (GCR) and solar proton flares through the Martian atmosphere. Surface doses are estimated using both a low density and a high density carbon dioxide model of the atmosphere which, in the vertical direction, provides a
Extension of the high charge and energy (HZE) transport computer program HZETRN for angular trans... more Extension of the high charge and energy (HZE) transport computer program HZETRN for angular transport of neutrons is considered. For this paper, only light ion transport, Heⴠand lighter, will be analyzed using a pure solar proton source. The angular transport calculator is the ANISN/PC program which is being controlled by the HZETRN program. The neutron flux values are compared for straight-ahead transport and angular transport in one dimension. The shield material is aluminum and the target material is water. The thickness of these materials is varied; however, only the largest model calculated is reported which is 50 gm/cm² of aluminum and 100 gm/cm² of water. The flux from the ANISN/PC calculation is about two orders of magnitude lower than the flux from HZETRN for very low energy neutrons. It is only a magnitude lower for the neutrons in the 10 to 20 MeV range in the aluminum and two orders lower in the water. The major reason for this difference is in the transport modes: ...
Past space missions beyond the confines of the Earth’s protective magnetic field have been of sho... more Past space missions beyond the confines of the Earth’s protective magnetic field have been of short duration and protection from the effects of solar particle events was of primary concern. The extension of operational infrastructure beyond low-Earth orbit to enable routine access to more interesting regions of space will require protection from the hazards of the accumulated exposures of Galactic Cosmic Rays (GCR). There are significant challenges in providing protection from the long-duration exposure to GCR: the human risks to the exposures are highly uncertain and safety requirements places unreasonable demands in supplying sufficient shielding materials in the design. A vigorous approach to future radiation health-risk mitigation requires a triage of techniques (using biological and technical factors) and reduction of the uncertainty in radiation risk models. The present paper discusses the triage of factors for risk mitigation with associated materials issues and engineering design methods.
The purpose of this work is an assessment of the lunar lava tubes physical characteristics and an... more The purpose of this work is an assessment of the lunar lava tubes physical characteristics and an evaluation of the their actual safety features from the point of view of the ionizing radiation environment as potential habitats for future lunar exploration crews.
One major obstacle to human space exploration is the possible limitations imposed by the adverse ... more One major obstacle to human space exploration is the possible limitations imposed by the adverse effects of long-term exposure to the space environment. Even before human spaceflight began, the potentially brief exposure of astronauts to the very intense random solar energetic particle (SEP) events was of great concern. A new challenge appears in deep space exploration from exposure to the low-intensity heavy-ion flux of the galactic cosmic rays (GCR) since the missions are of long duration and the accumulated exposures can be high. Because cancer induction rates increase behind low to rather large thickness of aluminum shielding according to available biological data on mammalian exposures to GCR like ions, the shield requirements for a Mars mission are prohibitively expensive in terms of mission launch costs. Preliminary studies indicate that materials with high hydrogen content and low atomic number constituents are most efficient in protecting the astronauts. This occurs for two...
An optical model description of momentum transfer in relativistic heavy ion collisions, based upo... more An optical model description of momentum transfer in relativistic heavy ion collisions, based upon composite particle multiple-scattering theory, is presented. The imaginary component of the complex momentum transfer, which comes from the absorptive part of the optical potential, is shown to be the main contributor to the momentum loss of the projectile. Within the context of the Goldhaber formalism, predictions of fragment momentum distribution observables are made and compared with experimental data. Use of the model as a tool for estimating collision impact parameters is also discussed.
A solar cycle statistical model has been developed to project sunspot numbers which represent the... more 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 the near future were coupled to space-related quantities of interest in radiation protection such as the galactic cosmic radiation GCR deceleration potential phi and the mean occurrence frequency of solar particle events SPEs Future GCR fluxes have been derived from a predictive model in which GCR temporal dependence represented by phis 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 depends on solar activity Projections of future mean frequency of SPE occurrence were estimated fr...
The understanding of the risk from exposure to cosmic rays to personnel and electronic equipment ... more The understanding of the risk from exposure to cosmic rays to personnel and electronic equipment in spaceflight and in the upper atmosphere is confounded by the high energy nuclear interactions and the track structure of fast ions. The Langley Research Center has developed several radiation transport codes and associated nuclear interaction data bases for describing the passage of high energy protons, neutrons, and light and heavy ions through materials and tissue. We present and overview these transport codes and databases including comparisons to laboratory and spaceflight experiments. Several risk assessment models are considered in order to study the attenuation properties of selected shielding candidates. These comparisons show that in contrast to conventional risk models based on linear energy transfer (LET), track structure models indicate that only hydrogen rich materials are effective in reducing risk. The contrasting conclusions of the conventional and track structure based approaches are shown to be due to differences in the assessment of the effectiveness of secondary ions such as neutrons, protons, alphas, and heavy ion target fragments. Microdosimetric measurements with proton and heavy ion beams are also discussed and as reported earlier in this session by Dicello, reach the same conclusions as the track models on the importance of target fragmentation.
We calculate the probability that large size ejecta from a major collision on a planet in an extr... more We calculate the probability that large size ejecta from a major collision on a planet in an extrasolar planetary system find their way to our solar system and collide with the Earth. The production rate of ejecta is estimated from the conditions in Our Solar System, and the evolution of the environment of the Sun is derived on the assumption
The Langley cosmic ray transport code and the Langley nucleon transport code (BRYNTRN) are used t... more The Langley cosmic ray transport code and the Langley nucleon transport code (BRYNTRN) are used to quantify the transport and attenuation of galactic cosmic rays (GCR) and solar proton flares through the Martian atmosphere. Surface doses are estimated using both a low density and a high density carbon dioxide model of the atmosphere which, in the vertical direction, provides a
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