Critical analysis of active shielding methods for space radiation protection

From time to time over the past several decades, designs utilizing active methods involving electromagnetic field configurations have been proposed for the purpose of protecting spacecraft crews from harmful space radiations. Designs affording protection from either solar energetic particle event protons or galactic cosmic rays or both have been proposed. Often these analyses are predicated upon simplified or even incorrect assumptions regarding the incident radiation spectra or their associated radiation risks and limits. At times the proponents of these designs make very optimistic assumptions about the abilities of the scientific and engineering communities to overcome existing technology gaps needed to move their designs from paper to practice. In this paper, various active shield methods proposed over the past several decades are reviewed and critiqued. Advantages and disadvantages of the proposed methods are presented. Shortcomings in the analyses of their shielding efficacies, where they exist, are described.