The radiation environment in space is reviewed in short as an impact factor affecting onboard spacecraft electronics. The mass and energy distributions of the heavy component of space radiation and the contribution of galactic cosmic rays to the general flux are analyzed during a quiet period in solar activity. The nature of the limitations in the concept of linear energy transfer, including the effects of electronic semicon ductor component crystallinity, is discussed. Protective measures against upsets in onboard electronics, caused by cosmic ray ions, are considered.