Abstract
Passive radiation shielding alone cannot provide adequate protection for astronauts on long-term, deep-space missions. High atomic number and energy (HZE) ions, and/or their secondaries, can penetrate any realistic mass shielding for long-term deep-space missions and cause damage to cells via direct energy deposition and/or through the production of secondary particles and fragmented nuclei. Active shielding, or the use of electromagnetic fields to deflect or stop incoming ions before reaching the spacecraft, has gained substantial attention over the last decade as a way to augment passive shielding. Recently, a mathematical relationship between a dimensionless scaling parameter characterizing the active shield and the incoming ion and a protected area formed on a downstream detector due to the deflection of HZE ions by the applied field was validated in Earth-based laboratory conditions. In the present work, the mathematical formulation is extended to relate electrostatic shielding efficacy with the ability to deflect positively charged ions with parameters relevant to space applications. Additionally, a modified scaling parameter is formulated to characterize the shielding efficacy of a “family” of electrostatic active shielding configurations for reducing flux density for a space-relevant isotropic source of energetic protons. The results of this study demonstrate a strong correlation among dimensionless scaling parameters and shielding efficacy metrics for space radiation-relevant HZE ions in beam and isotropic angular distributions. Furthermore, it establishes a framework for optimizing design of three-dimensional electrostatic shielding configurations to improve space radiation protection for astronauts on exploration-class missions.
Highlights
Space radiation is distinct from any radiation environment encountered on Earth
The results of this study demonstrate a strong correlation among dimensionless scaling parameters and shielding efficacy metrics for space radiation-relevant HZE ions in beam and isotropic angular distributions
The objective of investigating the beam-like source geometry was to establish a direct relationship between the scaling parameter magnitude and shielding efficacy for accelerator-relevant and space-relevant parameters
Summary
Space radiation is distinct from any radiation environment encountered on Earth. Outside low-Earth orbit (LEO), beyond the protection of Earth’s geomagnetic field and atmosphere, the radiation environment poses the threat of radiation exposure-related morbidity and mortality for astronauts.[1] Two principal sources of concern for any deep-space radiation shielding designer are (1) solar energetic particles (SEPs) and (2) galactic cosmic rays (GCRs). SEPs are comprised of mostly protons[2] and typically have a monotonically decreasing fluence spectrum. The maximum kinetic energy of a SEP event-integrated spectrum can exceed 3 GeV in extreme cases.[3,4] SEPs are capable of inducing deterministic radiation effects such as nausea, vomiting, and skin burns.[5,6]
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