Accelerator-based tests of radiation shielding properties of materials used in human space infrastructures

Bearing Extremes: Impacts from Simulated Outer Space Conditions and Effective Ultraviolet Radiation Shielding Materials on Tardigrade Life History

ABSTRACT

Questions about astrobiological resilience, whether entities with evolutionary histories on Earth would survive in outer space or on distant planets, for instance, no longer reside exclusively in the science fiction realm. In this study, we assess life history characteristics for individuals in the tardigrade species Grevenius annulatus post exposure to simulated outer space conditions with nonionizing radiation as a proxy for anticipated oxidative stress and damage incurred from exposure to full-spectrum environmental radiation. Using a planetary environment simulator, we exposed unshielded and shielded specimens to UVB and UVC radiation for 30 min and monitored and recorded subsequent life history characteristics. Survivorship was lower in an unshielded group relative to control as well as Kevlar and polyethylene shielded groups, demonstrating that Kevlar and polyethylene reduce impact from these types of nonionizing radiation, which are not expected to fully penetrate the shields. Cumulative egg production was lowest in the unshielded group, but egg viability and average egg production rate was highest. Due to insignificant differences, additional research to determine the relative effectiveness for Kevlar and polyethylene as shielding materials from survivorship and reproduction perspectives is warranted. This work provides a progressive step from which important conditions excluded in the current study, like vibrations, temperatures, debris-impacts, and ionizing radiation, can be included in future studies.

Protons Interaction with Nomex Target: Secondary Radiation from a Monte Carlo Simulation with Geant4

The study of suitable materials to shield astronauts from Galactic Cosmic Rays (GCR) is a topic of fundamental importance. The choice of the material must take into account both the secondary radiation produced by the interaction between primary radiation and material and its shielding ability. The physics case presented here deals with the interaction of a proton beam with a Nomex shield, namely, a target material with a mass thickness of 20 g cm−2. The study was conducted with the simulation code DOSE based on the well-known simulation package Geant4. This article shows the properties of secondary radiations produced in the target by the interaction of a proton beam in an energy range characterizing the GCR spectrum. We observed the production of ions of masses and charges lower than the chemical elements that make up Nomex, and also a significant production of neutrons, protons, and 𝛼 particles.

An extensive study of depth dose distribution and projectile fragmentation cross-section for shielding materials using Geant4

Geant4 Monte Carlo simulation was executed for ¹⁶O beam in various elemental and hydrogenous materials for assessment of ion characteristics and shielding efficacy. In the energy-dependent comparison, at energies 200-594 MeV/n, the peak to entrance ratio decrement up to 78.6% in water target validates the substantial increase in fragmentation factor. Further, hydrogenous materials and low Z elements (C, Al) demonstrate a low peak-to-entrance ratio (0.92-1.66) compared to heavy element (Cu, Sn, Pb) ratio (2.73-3.54), at 594 MeV/n, indicating the high fragmentation properties of hydrogenous and low Z elements. Accordingly, the depth dose reduction percentage was found to be significantly higher for hydrogenous materials (0.92-1.72%) having 4.20-14.37 H wt.% than non-hydrogenous targets (0.09-0.82%). LiH was found to exhibit the lowest peak-to-entrance ratio and highest depth dose reduction. The high shielding effectiveness of LiH (12.59%) irrespective of having a low H fraction compared to polyethylene (14.37%) which is widely used shielding material, suggests the contribution of low Z element Li (87.41 wt%) over the C (85.63 wt%) element in the material. Also, simulated results of fragmentation for high Z materials were compared with the experimental data for the reliability of Geant4. Finally, the comparison of these properties recommends the use of hydrogenous materials with low Z elements for effective space radiation shielding.

Shielding of Cosmic Radiation by Fibrous Materials

Cosmic radiation belongs to the challenges engineers have to deal with when further developing space travel. Besides the severe risks for humans due to high-energy particles or waves, the impact of cosmic radiation on electronics and diverse materials cannot be neglected, even in microsatellites or other unmanned spacecraft. Here, we explain the different particles or waves found in cosmic radiation and their potential impact on biological and inanimate matter. We give an overview of fiber-based shielding materials, mostly applied in the form of composites, and explain why these materials can help shielding spaceships or satellites from cosmic radiation.

Performances of Kevlar and Polyethylene as radiation shielding on-board the International Space Station in high latitude radiation environment

Passive radiation shielding is a mandatory element in the design of an integrated solution to mitigate the effects of radiation during long deep space voyages for human exploration. Understanding and exploiting the characteristics of materials suitable for radiation shielding in space flights is, therefore, of primary importance. We present here the results of the first space-test on Kevlar and Polyethylene radiation shielding capabilities including direct measurements of the background baseline (no shield). Measurements are performed on-board of the International Space Station (Columbus modulus) during the ALTEA-shield ESA sponsored program. For the first time the shielding capability of such materials has been tested in a radiation environment similar to the deep-space one, thanks to the feature of the ALTEA system, which allows to select only high latitude orbital tracts of the International Space Station. Polyethylene is widely used for radiation shielding in space and therefore it is an excellent benchmark material to be used in comparative investigations. In this work we show that Kevlar has radiation shielding performances comparable to the Polyethylene ones, reaching a dose rate reduction of 32 ± 2% and a dose equivalent rate reduction of 55 ± 4% (for a shield of 10 g/cm²).

Kevlar® as a Potential Accident Radiation Dosimeter for First Responders, Law Enforcement and Military Personnel

Today the armed forces and law enforcement personnel wear body armor, helmets, and flak jackets composed substantially of Kevlar® fiber to prevent bodily injury or death resulting from physical, ballistic, stab, and slash attacks. Therefore, there is a high probability that during a radiation accident or its aftermath, the Kevlar®-composed body armor will be irradiated. Preliminary study with samples of Kevlar® foundation fabric obtained from body armor used by the U.S. Marine Corps has shown that all samples evaluated demonstrated an EPR signal, and this signal increased with radiation dose. Based on these results, the authors predict that, with individual calibration, exposure at dose above 1 Gy can be reliably detected in Kevlar® samples obtained from body armor. As a result of these measurements, a post-event reconstruction of exposure dose can be obtained by taking various samples throughout the armor body and helmet worn by the same irradiated individual. The doses can be used to create a whole-body dose map that would be of vital importance in a case of a partial body or heterogeneous exposure.

Space radiation protection: Destination Mars

National space agencies are planning a human mission to Mars in the XXI century. Space radiation is generally acknowledged as a potential showstopper for this mission for two reasons: a) high uncertainty on the risk of radiation-induced morbidity, and b) lack of simple countermeasures to reduce the exposure. The need for radiation exposure mitigation tools in a mission to Mars is supported by the recent measurements of the radiation field on the Mars Science Laboratory. Shielding is the simplest physical countermeasure, but the current materials provide poor reduction of the dose deposited by high-energy cosmic rays. Accelerator-based tests of new materials can be used to assess additional protection in the spacecraft. Active shielding is very promising, but as yet not applicable in practical cases. Several studies are developing technologies based on superconducting magnetic fields in space. Reducing the transit time to Mars is arguably the best solution but novel nuclear thermal-electric propulsion systems also seem to be far from practical realization. It is likely that the first mission to Mars will employ a combination of these options to reduce radiation exposure.

Effects of shielding on the induction of 53BP1 foci and micronuclei after Fe ion exposures

High atomic number and high-energy (HZE) particles in deep space are of low abundance but substantially contribute to the biological effects of space radiation. Shielding is so far the most effective way to partially protect astronauts from these highly penetrating particles. However, simulated calculations and measurements have predicted that secondary particles resulting from the shielding of cosmic rays produce a significant fraction of the total dose and dose equivalent. In this study, we investigated the biological effects of secondary radiation with two cell types, and with cells exposed in different phases of the cell cycle, by comparing the biological effects of a 200 MeV/u iron beam with a shielded beam in which the energy of the iron ion beam was decreased from 500 MeV/u to 200 MeV/u with PMMA, polyethylene (PE), or aluminum. We found that beam shielding resulted in increased induction of 53BP1 foci and micronuclei in a cell-type-dependent manner compared with the unshielded 200 MeV/u Fe ion beam. These findings provide experimental proof that the biological effects of secondary particles resulting from the interaction between HZE particles and shielding materials should be considered in shielding design.

Tests of shielding effectiveness of Kevlar and Nextel onboard the International Space Station and the Foton-M3 capsule

Radiation assessment and protection in space is the first step in planning future missions to the Moon and Mars, where mission and number of space travelers will increase and the protection of the geomagnetic shielding against the cosmic radiation will be absent. In this framework, the shielding effectiveness of two flexible materials, Kevlar and Nextel, were tested, which are largely used in the construction of spacecrafts. Accelerator-based tests clearly demonstrated that Kevlar is an excellent shield for heavy ions, close to polyethylene, whereas Nextel shows poor shielding characteristics. Measurements on flight performed onboard of the International Space Station and of the Foton-M3 capsule have been carried out with special attention to the neutron component; shielded and unshielded detectors (thermoluminescence dosemeters, bubble detectors) were exposed to a real radiation environment to test the shielding properties of the materials under study. The results indicate no significant effects of shielding, suggesting that thin shields in low-Earth Orbit have little effect on absorbed dose.

Heavy ion carcinogenesis and human space exploration

Before the human exploration of Mars or long-duration missions on the Earth's moon, the risk of cancer and other diseases from space radiation must be accurately estimated and mitigated. Space radiation, comprised of energetic protons and heavy nuclei, has been shown to produce distinct biological damage compared with radiation on Earth, leading to large uncertainties in the projection of cancer and other health risks, and obscuring evaluation of the effectiveness of possible countermeasures. Here, we describe how research in cancer radiobiology can support human missions to Mars and other planets.