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Protection of astronauts and electronic components in satellites and spacecraft against space rays is one of the most important primary requirements in space missions. In this work, the effect of three materials, aluminum, as the most common material, polyethylene and a graded-z structure, in the protection of space radiations has been evaluated. The calculations of the dose caused by these radiations on the human body and a silicon piece have been carried out by MCNPX Monte Carlo code,. The dose caused by cosmic rays has been calculated after applying shields of aluminum, graded-z structure and polyethylene. The results showed that by using polyethylene and about 4.4% increase in weight compared to the aluminum shield, it is possible to reduce the dose caused by photons by more than 50% in the human body and 30% in silicon parts, and the dose caused by protons by about 30%. It cut both for astronauts and electronic components. Graded-z shielding performed very well in the dose attenuation caused by photons, but appeared ineffective in the dose attenuation caused by protons.

The presence of ionizing radiation in the space environment, due to trapped particles, solar particles and cosmic rays can be a serious threat to the proper functioning of electronic components used in satellites and spacecraft. In this work, the leakage current variation of a silicon diode, as the basic element of many electronic components, has been investigated in the exposure of space protons. For this purpose, the GEANT4 Monte Carlo code has been used to calculate the non-ionizing energy loss in the device. The simulation of electrical parameters for irradiation of space protons were also done by SILVACO software. The results show that the leakage current increases by about 1.85 times the amount of it before irradiation, up to about 96.2 nA/μm by the increase in the proton flux up to 2.1×1012 p/cm2. Irradiation of BPW34 photodiodes under 30 MeV protons was performed to validate the results of simulation.