Space radiation is one of the main factors that cause damage to living organisms and threaten the health of astronauts during long-term manned spaceflight. Therefore, space radiation risk assessment is an important issue in astronaut radiation risk warning and protection in manned spaceflight engineering.

This study aims to evaluate the biological effects of space radiation environment by simulating the radiation-induced DNA damage process using Monte Carlo method to digitize the damage yield at the cellular level.

Firstly, based on the main radiation sources in the space environment, five energy points with intervals of 10~10⁵ MeV for monoenergetic protons, helium ions, carbon ions, oxygen ions, silicon ions, and iron ions were set for the Monte Carlo damage simulation program (MCDS) applied to the calculation of DNA damage induced by high-energy protons and heavy ions in space. Simultaneously, typical solar proton event, as well as the main spectra in galactic cosmic rays during solar minimum and maximum, were selected as radiation sources to simulate the yields of DNA double strand breaks (DSBs), single strand breaks (SSBs), and other damages. Then, the effects of hypoxic and oxygen enriched cellular environments on damage yields and relative biological effectiveness were analyzed.

Simulation results of single energy radiation show that the number of SSBs gradually increases whilst the number of DSBs gradually decreases with the increase of energy. When the cell oxygen concentration is only 2%, the yields of DSBs caused by 10³ MeV protons, helium ions, carbon ions, and oxygen ions are reduced by 14.23%, 15.8%, 14.84%, and 12.08%, respectively, compared to the results under normoxic environment. The percentage reduction of silicon ions and iron ions can be ignored. Among the six types of monoenergetic space radiation particles, the relative biological effectiveness of silicon ions and iron ions with higher atomic numbers are more significantly affected by oxygen concentration. The results of DNA damage induced by proton spectrum during solar maximum and minimum show that the production of SSBs induced by proton spectrum during solar maximum is increased whilst the yield of DSBs is decreased when compared with that in solar minimum. For typical solar proton events, the yield of DNA damage is higher than that of galactic cosmic rays, with relative biological effect factors of 1.75 and 1.84 under 21% and 2% oxygen concentration, respectively.

This study uses a Monte Carlo damage model to evaluate the radiation effects of high-energy radiation particles in space at the cellular level. This model can be applied to quick prediction of the relative biological effects under different radiation, which is conducive to the development of radiation dosimetry and the establishment of a better space radiation dose monitoring model.