Badhwar G D, Cucinotta F A, O'Neill P M
NASA Johnson Space Center, Houston, Texas 77058.
Radiat Res. 1993 Apr;134(1):9-15.
Galactic cosmic rays (GCR) pose a serious radiation hazard for long-duration missions. In designing a lunar habitat or a Mars transfer vehicle, the radiation exposure determines the shielding thickness, and hence the weight of spacecraft. In designing a habitat one has to focus on the worst-case radiation flux and its uncertainties. Using the spherically symmetric diffusion theory of the solar modulation of GCR, and data on the differential energy spectra of hydrogen, helium, oxygen, and iron from 1965 to 1989, it has been shown that the flux is determined by the diffusion parameter which is a function of the time in the solar cycle. This analysis also showed that the fluxes in the 1954 and 1976-1977 solar minima were similar and higher than those in 1965. In this paper, we have extended the spherical solar modulation theory back to 1954. These results show that the 1954-1955 GCR flux was nearly the same as that from 1976 to 1977 and that the 1965 flux values were nearly the same as those in 1986. Using this theory we have obtained the GCR spectra for all the nuclei and calculated the depth dose as a function of aluminum thickness. Using the ICRP 26 value for the quality factor, and the 1976-1977 spectra, it is shown that the shielding required to stay below 0.5 Sv is 17.5(-3)+8 g cm-2 of aluminum, and 9(-1.5)+5 g cm-2 to stay below 0.6 Sv. The calculated dose equivalent using the ICRP 60 values for quality factors is about 15% higher than that calculated using the ICRP 26 value. However, the errors on the quality factor itself may be substantial and are not taken into account.
银河宇宙射线（GCR）对长期任务构成严重的辐射危害。在设计月球栖息地或火星转运飞行器时，辐射暴露决定了屏蔽层厚度，进而决定了航天器的重量。在设计栖息地时，必须关注最坏情况下的辐射通量及其不确定性。利用GCR太阳调制的球对称扩散理论，以及1965年至1989年期间氢、氦、氧和铁的微分能谱数据，研究表明通量由扩散参数决定，而扩散参数是太阳周期中时间的函数。该分析还表明，1954年以及1976 - 1977年太阳活动极小期的通量相似且高于1965年的通量。在本文中，我们将球对称太阳调制理论扩展到了1954年。这些结果表明，1954 - 1955年的GCR通量与1976年至1977年的通量几乎相同，1965年的通量值与1986年的几乎相同。利用该理论，我们获得了所有原子核的GCR谱，并计算了作为铝厚度函数的深度剂量。使用国际辐射防护委员会（ICRP）26号出版物中关于品质因数的值以及1976 - 1977年的能谱，结果表明要使剂量低于0.5 Sv，所需的铝屏蔽层为17.5(-3)+8 g/cm²，要使剂量低于0.6 Sv，则需要9(-1.5)+5 g/cm²。使用ICRP 60号出版物中品质因数的值计算出的剂量当量比使用ICRP 26号出版物的值计算出的约高15%。然而，品质因数本身的误差可能很大，本文未予以考虑。
