Exploring the depths of space is an exciting and ambitious endeavor, but it comes with a unique set of risks. Prolonged exposure to the space environment can have serious and potentially life-threatening effects on the human body. Significant adverse effects include muscle atrophy and skeletal deterioration, slowing down of the cardiovascular system, decreased red blood cell production, balance disorders, vision disorders, changes in the immune system, fluid redistribution, loss of body mass, nasal congestion, sleep disorders, and excessive flatulence. Gravity always acts on us while we're on Earth, so even if we're not really aware of it, we're always using the muscles in our lower body.
When bodies don't have to work against the force of gravity to stay upright, muscles are used much less and therefore wear out over time. This is why astronauts on the International Space Station (ISS) spend so much time exercising. As you might expect, floating without gravity also causes dizziness in some people. Called spatial dizziness or spatial adaptation syndrome, this occurs when people find it difficult to adapt to microgravity and may experience nausea, vertigo or headaches. Immunodeficiency caused by lack of gravity can also lead to the rapid spread of infection among crew members, especially in the confined areas of spaceflight systems.
Most of the current data comes from short-term missions, so some of the long-term physiological effects of living in space are still unknown. Technology such as spaceships or spacesuits can protect people from the harshest conditions. When gravity is eliminated or reduced during space exploration, blood tends to pool in the upper body, causing facial edema and other unwanted side effects. Short-term exposure to microgravity causes space adaptation syndrome, self-limited nausea caused by a vestibular system disorder. The psychological effects of living in space have not been clearly analyzed yet. However, there are analogies on Earth such as research stations and submarines in the Arctic that can provide insight into how humans can survive and work in space for extended and possibly indefinite periods of time.
Sleep is regularly interrupted on the ISS due to mission demands such as programming incoming or outgoing space vehicles. The engineering problems associated with leaving Earth and the development of space propulsion systems have been examined for more than a century. The only human beings known to have died from exposure to a vacuum in space are the three crew members of the Soyuz 11 spacecraft: Vladislav Volkov, Georgi Dobrovolski and Viktor Patsayev. In recent years there has been an increase in research on how humans can survive long-term space flights including a mission to Mars. The results could influence long-term space flights and help us better understand how humans can survive in extreme environments.
