What makes space travel so dangerous?

Open navigator

1. Space: An unnatural place to live

In July 1969 the world watched as two men set foot on the Moon. For the first time, humanity had ventured out of the planet we call home and touched the possibility of worlds beyond.

But our space travel ambitions seem to have stalled since the 1970s and 1980s. In over 30 years, we've ventured virtually no further than the original pioneers. And as more astronauts have spent more time aboard the various space stations, they have reported worrying health problems.

As recent tragic events have shown, the most dangerous part of any space journey is take off. Trying to reach the speeds needed to escape Earth's gravity is fraught with peril. But even once they reach space, astronauts are not out of danger. Instead they are exposed to a new set of risks which we are only just beginning to understand.

2. "What living in space did to me"

Astronaut Chris Hadfield spent months living in space aboard the International Space Station. Here, he describes how zero gravity changed his body and how he lived with the constant threat of high-speed micrometeorites.

Images courtesy of NASA and CSA.

We were made to live on Earth, not in the extreme conditions we find in space. So when astronauts like Chris Hadfield leave our planet they have to take their environment with them. That’s why they wear specially-designed spacesuits. But spacesuits do much more than just keep Earth's atmosphere around astronauts. Over the years, spacesuit design has evolved to protect humans from the harshness of space.

3. Protection from the harshness of space

This content uses functionality that is not supported by your current browser. Consider upgrading your browser.

In Earth's orbit, astronauts might experience temperatures as low as -129C (-200F) and as high as 121C (250F). Spacesuits have been cleverly designed to protect us from these extreme conditions. They also provide air pressure to prevent our bodily fluids from boiling in the hard vacuum of space. But astronauts can only travel so far in the spacesuits that exist today. Even our best suits are limited to a ‘low-Earth orbit’. To push farther into the Solar System we will need a new suit – one that will shield us from the lethal hazards of deep space. But even then, are we sturdy enough to survive a long mission? (Image courtesy of ILC Dover, LP.)

4. Life without gravity

A spacesuit may protect us externally, but space can have devastating effects on the internal workings of the human body.

On Earth, we have evolved to work in harness with gravity. Our muscles and bones have developed to expect this force and it’s needed to keep them strong and healthy. In space, astronauts float weightlessly. This looks like a lot of fun, but prolonged exposure to a microgravity environment can have insidious effects on the human body.

Space travel plays havoc with our blood circulation. Human cardiovascular systems are designed to pump blood steadily around the body against the force of gravity, which normally pulls blood towards our feet. But in the microgravity of space, blood moves up to the chest and head, giving astronauts puffy faces and raised blood pressure.

Muscles are also threatened by space travel. Without the need to work against gravity, muscles can start to waste, which increases the risk of tendonitis and fat accumulation.

The lack of gravity even makes astronauts stand up to two inches taller, as back vertebrae separate without the compression of gravity, leading to painful back-aches.

Over the long term, astronauts suffer the devastating consequences of bone loss. Microgravity causes the body to lose calcium and phosphorous, leading to a gradual weakening of bone and an increased risk of osteoporosis. Bone loss can be as high as 1.5% of its mass per month, that’s roughly 10% over a six-month stay in space, with the recovery after returning to Earth taking at least three to four years. In an attempt to combat this, astronauts living on the ISS must carry out 2.5 hours of exercise a day, six times a week.

5. Radiation: Annual doses on Earth and in space

Annual doses of radiation on Earth and in space

Radiation’s biological effect is measured in mSv, the millisievert. No matter where you live on Earth you receive a small dose of radiation each day, but an astronaut living on the International Space Station is exposed to over 80 times that amount. Head further into space and that figure rises to a deadly degree.

6. The invisible threat to humans in space

Cosmic rays are one form of space radiation. The damage they do to our bodies is different to any other form we know. Scientist Helen Czerski travelled to NASA’s Space Radiation Laboratory to see how this might limit humans’ time in space.

Images of cells courtesy of Brookhaven National Laboratory/NSRL.

On Earth we’re protected from cosmic rays because its magnetic field acts as a shield, but a lack of atmosphere in space means that astronauts are exposed to their destructive nature. Just one particle has the power to charge through human tissue and smash apart our DNA, potentially leading to cell mutation and cancers. Scientists are developing ways to reduce exposure, by shielding spacecraft with water for example. But given that the chances of developing terminal cancer on a mission to Mars could be as high as 30%, until we can fully protect ourselves we may not be going anywhere.

7. What have we learned from our mistakes?

Real life events have helped us overcome some of the difficulties of space travel. Select one of the three options to find out more. (Image: NASA)

Water-cooled space suits

Gemini astronaut Eugene Cernan walks in space © NASA

You selected

Water-cooled space suits

Eugene Cernan discovered that air makes a poor spacesuit coolant. He lost several pounds from dehydration during his 1966 spacewalk. Suits are now water-cooled.

Stopping space bacteria

Mir space station circles the Earth © NASA

You selected

Stopping space bacteria

Mir space station had 234 microbial species thriving on board, leading to infections. Astronauts now follow strict hygiene rules and sample the cabin for bugs.

Preventing space sickness

Astronaut Jake Garn sick aboard Space Shuttle Discovery © NASA

You selected

Preventing space sickness

In 1985 Jake Garn suffered the highest level of space sickness recorded. Now astronauts take motion sickness medicine as choking on their vomit could be fatal.