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Radiation considerations for interplanetary missionsGalactic cosmic radiation (GCR) poses a serious radiation hazard for long-duration missions. In designing a lunar habitat or Mars transfer vehicle, the worst-case radiation exposure determines shielding thickness and, hence, the weight of spacecraft. Using the spherically symmetric diffusion theory of the solar modulation of GCR, it was possible to use data on the differential energy spectra of hydrogen, helium, oxygen, and iron from 1954 to 1989 to show that the flux at 1 A.U. is determined by the diffusion parameter, K, which is a function of the time in the solar cycle. This analysis also showed that the solar minimum of 1976 to 1977 was the deepest minimum in the last 37 years. Using this theory, we have obtained the GCR spectra for all the nuclei and calculated the depth-dose as a function of aluminum shield thickness. Using the ICRP-26 definition of the quality factor, it is shown that the shielding required to stay below the LEO recommended annual limit of 50 cSv is 17.5 (+8, -3), g/sq cm of aluminum; if the limit is raised to 60 cSv, the required shielding is 9 (5, -1.5) g/sq cm. We also discuss the issues and shielding needs for protection against solar particle events.
Document ID
19940007087
Document Type
Conference Paper
Authors
Badwar, Gautam D. (NASA Lyndon B. Johnson Space Center Houston, TX, United States)
Oneill, Patrick M. (NASA Langley Research Center Hampton, VA., United States)
Cucinotta, Francis A. (NASA Langley Research Center Hampton, VA., United States)
Date Acquired
September 6, 2013
Publication Date
February 1, 1993
Publication Information
Publication: Sixth Annual Workshop on Space Operations Applications and Research (SOAR 1992), Volume 2
Subject Category
SPACECRAFT DESIGN, TESTING AND PERFORMANCE
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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IDRelationTitle19940007055Analytic PrimarySixth Annual Workshop on Space Operations Applications and Research (SOAR 1992), volume 2