Manned space travel: from a race between nations to a race against the environmental stressors beyond earth.

The International Space Station (ISS), the largest man-made object in space, is a collaboration between space agencies of the United States, Canada, Russia, Europe and Japan. This research laboratory circles around the Earth at about 400 km above the Earth’s surface and houses international crews around the clock to perform experiments ranging from the effects of microgravity on the physiology of humans and other organisms, the cultivation of plants and food crops in space, to astronomy and physics observations. Since its inception, more than 200 men and women have inhabited the ISS for different lengths of time. Individual crew members stay in the ISS for missions of a total of about 3months to a year, while some people have completed multiple missions. Nearing the end of its life, the ISS is expected to fulfill its duties until about the year 2030. With the ending of the ISS approaching quickly, plans are made for manned missions deeper into our solar system, such as to the moon, other near-Earth objects such as asteroids, and even the planet Mars. Currently, the National Aeronautics and Space Administration (NASA) aims to begin operating in the cis lunar space in the 2020s and to build the Space or Lunar Gateway, a space station orbiting the Moon and allowing missions deeper into space. Then, NASA is tasked to complete manned missions orbiting Mars in the 2030s, with the final goal of crew expeditions to the surface of Mars. During missions into deep space, men and women will be exposed to a combination of stressors related to the nature of the space environment. Moreover, missions may be much longer than the current stays of astonauts at the ISS. In order to make future manned missions into deep space possible, these stressors need to be well understood and controlled or minimized by physical and/or medical means. Complicating the matter, during deep space missions, crew members cannot return to Earth for emergency medical attention. Therefore, health risks need to be well understood and appropriate medical facilities should be incorporated into mission planning.