How Long Can Astronauts Stay In Space?

So, in short.

The exact duration for which astronauts can stay in space remains unknown due to ongoing technological advancements and the need to assess how the human body reacts to the conditions of outer space. While astronauts require a certain level of physical fitness, their ability to withstand long-duration spaceflight is yet to be fully understood.

Which astronaut has been in space the longest?

The crews that typically occupy the space station hail from countries such as the US, Europe, Canada, Japan, and Russia. Mike Lopez-Alegria, a NASA astronaut, currently holds the record for the longest expedition from the US space station, having spent 215 days there. However, this record was later broken by Scott Kelly, who spent 340 days in space. Valeri Polyakov, a Russian astronaut, surpassed Kelly's record and set the latest record for the longest stay in space at 437 days. Mark Vande Hei, another NASA astronaut, is the current record holder for the longest stay in space by a US astronaut, having spent 355 days in space.

Why is staying long durations in space dangerous?

Zero Gravity

When it comes to space travel, leaving Earth's orbit and escaping its gravitational pull is the first challenge. Once in space, astronauts experience a range of physical issues. For instance, they may experience fluid in their legs, facial swelling, congestion, and headaches. However, these symptoms are typically not serious and usually disappear within a few days. Astronauts may also feel dizzy at first, but this usually passes once they become accustomed to zero gravity.



The real challenge is maintaining muscle and bone health. Our bodies are designed to work against gravity, so in zero gravity, muscles and bones can deteriorate rapidly. The heart muscle can shrink, and bones may become neglected and stop maintaining themselves, leading to issues like kidney stones and fractures. Spending too much time in space can also harm the immune system, making astronauts more susceptible to pathogens and autoimmune problems.

Radiation and light

Astronauts face significant risks of radiation exposure when they venture into space. Without adequate protection, they may be exposed to solar radiation, solar cosmic particles, galactic cosmic radiation, and geomagnetically bound radiation, all of which can cause cell mutations leading to cancer and epigenetic changes that can harm the body. Some forms of radiation can even be lethal. Radiation can also negatively impact bodily functions, including weakening the immune system, damaging bone marrow, and causing cataracts in the eyes. Despite the use of advanced shields, astronauts remain vulnerable to exposure to secondary radiation from energetic neutrons or gamma rays. In addition to radiation, other light sources in space can significantly affect the human body. To mitigate these risks, astronauts undergo rigorous physical and psychological testing.

Recovery when they return to Earth

Upon returning to Earth, astronauts have to readjust to gravity, which can cause them to feel dizzy or nauseous. If an astronaut has been in space for two weeks, it may take them a couple of days to fully readjust to gravity. However, if they have spent six months in space, it can take several weeks for their body to return to its normal state.