Performance Study of Galactic Cosmic Ray Shield Materials

Performance Study of Galactic Cosmic Ray Shield Materials PDF

Author: National Aeronautics and Space Administration (NASA)

Publisher: Createspace Independent Publishing Platform

Published: 2018-07-09

Total Pages: 42

ISBN-13: 9781722482985

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The space program is faced with two difficult radiation protection issues for future long-term operations. First, retrofit of shield material or conservatism in shield design is prohibitively expensive and often impossible. Second, shielding from the cosmic heavy ions is faced with limited knowledge on the physical properties and biological responses of these radiations. The current status of space shielding technology and its impact on radiation health is discussed herein in terms of conventional protection practice and a test biological response model. The impact of biological response on the selection of optimum materials for cosmic ray shielding is presented in terms of the transmission characteristics of the shield material. Although the systematics of nuclear cross sections are able to demonstrate the relation of exposure risk to shield-material composition, the current uncertainty in-nuclear cross sections will not allow an accurate evaluation of risk reduction. This paper presents a theoretical study of risk-related factors and a pilot experiment to study the effectiveness of choice of shield materials to reduce the risk in space operations. Kim, Myung-Hee Y. and Wilson, John W. and Thibeault, Sheila A. and Nealy, John E. and Badavi, Francis F. and Kiefer, Richard L. Langley Research Center RTOP 199-45-16-11...

A Proposed Performance Index for Galactic Cosmic Ray Shielding Materials

A Proposed Performance Index for Galactic Cosmic Ray Shielding Materials PDF

Author: National Aeronautics and Space Administration (NASA)

Publisher: Createspace Independent Publishing Platform

Published: 2018-08-09

Total Pages: 28

ISBN-13: 9781725017238

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In past studies, the reductions in absorbed dose and dose equivalent due to choice of material composition have been used to indicate shield effectiveness against exposure to galactic cosmic rays. However, these quantities are highly inaccurate in assessing shield effectiveness for protection against the biological effects of long-term exposure to the galactic heavy ions. A new quantity for shield performance is defined that correlates well with cell killing and cell transformation behind various shield thicknesses and materials. In addition, a relative performance index is identified that is inversely related to biological injury for different materials at a fixed shield mass and is directly related to the ratio of the fourth- and the second-order linear energy transfer (LET) moments. Wilson, John W. and Wood, J. S. and Shinn, Judy L. and Cucinotta, Francis A. and Nealy, John E. Langley Research Center NASA-TM-4444, L-17199, NAS 1.15:4444 RTOP 592-43-21-01...

Shielding Strategies for Human Space Exploration

Shielding Strategies for Human Space Exploration PDF

Author: John William Wilson

Publisher:

Published: 1997

Total Pages: 496

ISBN-13:

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The purpose of the workshop was to define requirements for the development and evaluation of high performance shield materials and designs and to develop ideas regarding approaches to radiation shielding.

Estimates of Galactic Cosmic Ray Shielding Requirements During Solar Minimum

Estimates of Galactic Cosmic Ray Shielding Requirements During Solar Minimum PDF

Author: National Aeronautics and Space Adm Nasa

Publisher: Independently Published

Published: 2018-12-31

Total Pages: 34

ISBN-13: 9781792697661

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Estimates of radiation risk from galactic cosmic rays are presented for manned interplanetary missions. The calculations use the Naval Research Laboratory cosmic ray spectrum model as input into the Langley Research Center galactic cosmic ray transport code. This transport code, which transports both heavy ions and nucleons, can be used with any number of layers of target material, consisting of up to five different arbitrary constituents per layer. Calculated galactic cosmic ray fluxes, dose and dose equivalents behind various thicknesses of aluminum, water and liquid hydrogen shielding are presented for the solar minimum period. Estimates of risk to the skin and the blood-forming organs (BFO) are made using 0-cm and 5-cm depth dose/dose equivalent values, respectively, for water. These results indicate that at least 3.5 g/sq cm (3.5 cm) of water, or 6.5 g/sq cm (2.4 cm) of aluminum, or 1.0 g/sq cm (14 cm) of liquid hydrogen shielding is required to reduce the annual exposure below the currently recommended BFO limit of 0.5 Sv. Because of large uncertainties in fragmentation parameters and the input cosmic ray spectrum, these exposure estimates may be uncertain by as much as a factor of 2 or more. The effects of these potential exposure uncertainties or shield thickness requirements are analyzed. Townsend, Lawrence W. and Nealy, John E. and Wilson, John W. and Simonsen, Lisa C. Langley Research Center NASA-TM-4167, L-16715, NAS 1.15:4167 RTOP 199-04-16-11...

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