Study on Shielding Effectiveness of a Combined Radiation Shield for Manned Long Termed Interplanetary Expeditions

In the course of long-duration space missions, astronauts will be exposed to galactic cosmic rays (GCR) and solar particle events (SPE). The interaction with space radiation will lead to both severe and late effects on the crew members. Two countermeasures namely active and passive shields are available but both constitute some limitations. After briefly discussing active and passive methods for radiation shielding, this paper presents a novel combined radiation shield comprising an active shield attached with a polyethylene (PE) layer of 10 cm. The effectiveness of this PE layer as combined shield has been studied theoretically by Monte Carlo calculations code, Particle and Heavy Ion Transport code System (PHITS). While the cosmic rays will travel to the spaceships, in the active part, a superconducting toroid will deflect a specific portion of the incoming particles, after that a 10cm PE layer will provide the safeguard from the secondary particles that will be produced from the interaction with the active segment. The proposed superconducting toroid under certain conditions can theoretically deflect the lighter particles (Z< 3) up to 800 MeV/n, and for higher Z particles (Z<48) this cut-off energy is around 200 MeV/n. The particles that travel through the toroid coils will pose the additional dose to the crews. The proposed PE layer can reduce the absorbed dose rate of 1.9%, 7.3%, and 27.9% for proton, alpha, and carbon ion of 1GeV/n, respectively as calculated by the PHITS. Limitations of this type of shield are also briefly discussed.