The future of Moon spacewalks: Next-generation radiation protective spacesuit

Background: The desire of mankind to travel back to the Moon, and eventually Mars, entails that the need for specialised spacesuits has become more pressing than ever. Lunar missions will require astronauts to undertake an average of 50-70 spacewalks during their stay. Missionrelated assignments will ask for improved mobility without the loss of protection against factors related to the harsh environment of space. One factor is the omnipresent space radiation, which includes all kinds of ionising radiation types. The sources of this radiation are solar particle events, galactic cosmic rays and particles trapped in the Earth’s magnetic field. With future space exploration missions in mind, it is important to comprehend the risks that come with long-term radiation exposure and how shielding may prevent those from happening. Objective: The aim of this paper is to investigate the radiation protective properties of different polymer-based materials and the potential they might hold for future spacesuit manufacturing. Methods: Different polymer-based materials (high-density polyethylene (HDPE), polycarbonate (PC), neoprene and polytetrafluoroethylene (PTFE)) were used as shielding against x-rays. Their radiation protective properties were compared to those of both lead and aluminium. Shielding thicknesses from 1 cm up to 5 cm were used for each material. The fraction of x-ray dose that was able to penetrate was measured with dosimeters. Densities and attenuation coefficients of each material were also used to theoretically calculate their shielding capacity. Human primary fibroblasts, as a skin model, were placed behind each layer of shielding and, after irradiation, stained for phosphorylated histone H2AX (γH2AX) to identify double strand breaks as a biological endpoint. Results: While it has already been shown that lead provides great protection against different radiation types, it was confirmed here once more. The material with the lowest density, neoprene, provided the least protection. The fraction of the dose that was able to penetrate multiple centimetres of PTFE came close the measurements for aluminium. Less γH2AX foci were observed in the nuclei of the cells with PTFE as shielding. Polycarbonate and HDPE also showed a decrease in doses and γH2AX spots with more layers of protection added, albeit less than PTFE. Besides the radiation protection that polymer-based materials provide, their potential for future use in spacesuit manufacturing is amplified by the fact that these materials are easily available, lightweight, easy to shape and form fewer secondary particles due to their elemental structures. This is touched upon in the comprehensive discussion. Conclusion: It is clear that one polymer provides better protection against ionising radiation than another. The formation of composites could, on top of that, significantly improve the radiation protection characteristics compared to the pristine material. Further additions to future spacesuits, in the form of dust-repelling mechanics, 3D-printing, recycling, etc… need to be investigated and implemented to allow for sustainable long-term space missions, independent from Earth’s resources, to be undertaken. This paper serves as a proof of concept in order to encourage further research into the differences between many materials and for possible additions to future space suits.