How long can humans travel in space

How long can you survive in space?

(hp) On Wednesday, the American astronaut Scott Kelly and the Russian astronaut Mikhail Kornijenko returned to Earth from the International Space Station. For almost a whole year - 340 days to be precise - the two of them lived and worked on the station, which orbits the earth at an altitude of around 400 kilometers.

Astronauts normally only spend around six months on the station before they are relieved. These two astronauts were on the ISS for a special reason: They were used to research how a very long stay in space affects people and their health. What is particularly interesting for the researchers is that Scott Kelly has a twin brother who is even an astronaut himself and has also been to space before. Using these two, the researchers can now compare particularly well how Scott's health has changed compared to that of his twin brother Mark after a year in space.

The scientists want to research this, because astronauts are supposed to fly to Mars sometime in the 2030s. The return flight would take about 450 to 500 days together.
The astronauts should of course survive this journey in the best possible health. Unfortunately, there are many health risks for us humans in space, some of which are life-threatening: For example, the so-called "cosmic radiation" is up to 400 times stronger there than on the earth's surface, because the protective earth atmosphere is missing in space. Cosmic rays are very dangerous and can damage the astronauts' genetic makeup and cause cancer.

Another major risk for astronauts is muscle and bone loss. Because of the weightlessness in the space station, the muscles and bones of the astronauts are no longer stressed and therefore regress - the faster the longer you stay in space. A regression of the bones beyond a certain limit is life-threatening. And for some astronauts, this limit could possibly be reached during a trip to Mars.

The astronauts' heart and circulation also suffer from weightlessness and after a while they no longer function as well as they did on earth. In addition, many astronauts develop visual disturbances after a while, and they often have sleep problems because there is no natural day and night rhythm on a space station or in a spaceship as there is on earth. Even the astronauts' immune system suffers and does not function as well after a while. The longest uninterrupted time a person has been in space during a single mission has been 437 days; and the longest total time a person has been up there is 878 days in a total of five missions. Astronauts shouldn't spend much more time in space in their professional life, as otherwise the risk to their health and life will become greater and more threatening.

The researchers do not know exactly how long a person could survive in space in a spaceship.
Of course, nobody wants to and can simply try it out in an experiment, as this would endanger a person's life.