Cosmic radiation hazard is cornerstone of space flights safety. Different properties of solar electromagnetic and corpuscular radiation with emphasis on its dangerous influence on astronauts and spacecraft equipment and systems are discussed. Solar and galactic cosmic rays (SCR and GCR) pose a serious obstacle in terms of safety and security of space flights, especially beyond the Earth's magnetosphere. Solar flares and GCR are of special concern. Solar flares are distinguished as extremely complex phenomena observing across the whole electromagnetic spectrum from radio wavelength to extreme ultraviolet, X-ray and gamma ray. Powerful fluxes of energetic particles in very wide energetic spectrum are generated which interact with the home planet and disturbing tremendously our space environment. Altogether, it is referred to as space weather. Geomagnetic storms induced by solar flares affect the ground facilities, social-economic infrastructure and global system operations involving electric power supply, aviation and ground transportation, oil-gas pipelines, geographic information system/data management (GIS), etc. As systems become more complex over time, the impacts of space weather on space flights and humanity in general are likely to increase. We analyze flares complexity and classification depending on their size, duration, morphology or magnetic topology and characteristic corpuscular radiation based on different classification systems as well protective measures to mitigate their consequences. Humans will encounter extremely serious problems of space flights safety at the beginning of new phase of the Moon exploration. Of the risks evaluation of habitation in the lunar hostile environment, specifically in the potential sites of Lunar Base deployment, monitoring of radiation doses absorbed by astronauts on the lunar surface is the first one. Underground shelters could be used to provide safe habitation and maintain the long-term humans' activity. Nowadays we face numerous problems involving many unknowns and dangers of the natural origin in the outer space, which runs in parallel with the needs of great technological advancements and breakthroughs. It is incremental in the course of growing complexity of space flights and progressive development of the human missions with an ultimate goal of undertaking manned flights to the Moon, Mars and beyond. © 2020 IAA
