Tim Peake has spoken of the wonder of weightlessness and soaking up glorious views of planet Earth, but he was sent to the International Space Station (ISS) to do science.
It was a busy job which saw him working up to 14 hours a day during his six months in orbit.
Together with his crew mates, Peake participated in more than 250 experiments devised by teams of scientists from the UK, Europe, and around the world.
And for some, the British astronaut was his own guinea pig as he tested his body’s responses to the space environment…
1. Airway Monitoring experiment: Floating dust particles in weightless conditions can irritate the lungs. A test developed for this research could benefit hundreds of thousands of people suffering from asthma on Earth. Peake and fellow astronaut Tim Kopra had to breathe into a specially-developed mask that measures the nitric oxide they exhaled to monitor any inflammation in their lungs.
2. Detection of Osteoporosis in Space and Muscle Biopsy experiments: Microgravity is known to lead to bone thinning and muscle weakening. Samples of Peake’s muscles were taken for analysis, and Magnetic Resonance Imaging (MRI) scans will compare the state of his bones before and after the mission.
3. Skin-B experiment: Astronauts’ skin ages faster in space, becoming fragile and taking longer to heal from injuries. To investigate these effects, Peake carried out tests on his own skin.
4. Energy experiment: Humans lose body mass in space, so how much food should astronauts eat? Peake measured changes in his energy expenditure to help mission planners devise the right diet for future space travellers.
5. Brain-DTI experiment: The brain is not immune to weightlessness. Scans will reveal any changes to Peake’s brain wiring during the mission. He has also kept a record of headaches or similar symptoms while in orbit.
6. Circadian rhythms experiment: With 16 sunrises and sunsets every day, the ISS is an ideal place to investigate the effects of space travel on the biological clock, the internal timer that helps us sleep and influences many body processes. The findings will not only help future missions, but also people working irregular hours on Earth such as doctors and firefighters.
7. Immuno-2 experiment: More than half of astronauts show signs of immune system dysfunction after long missions. A battery of tests, including examination of samples of Peake’s hair, will investigate how the stress of space travel affects the immune system.
8. Biological studies: Peake also conducted biological studies of muscle, bone and heart cells to see how microgravity affected their growth and genes.
9. Micro-organisms in vacuum study: Another experiment looked at the ability of tough micro-organisms to survive in the frigid vacuum of space. For the Expose-R2 experiment, bacteria and fungi were housed in a container outside the ISS for more than a year. Some experts believe hardy microbial spores may have helped to spread life between planets.
10. The effect of weightlessness on metal alloys study: The material science package investigated the effects of weightlessness on the structure of metal alloys. It featured a “levitating” furnace that heated metals to more than 2,000C and then cooled them rapidly, a technique familiar to blacksmiths.
11. The effect of microgravity on metal fire study: Peake said playing with fire to investigate combustion in microgravity was the “coolest” part of his scientific mission. During a briefing with journalists he said: “Certainly seeing open naked flames on a space station was something I wasn’t quite expecting.”
12. Gardening project: The astronaut enlisted the help of schoolchildren to conduct a gardening experiment involving “space rocket” seeds. During his stay on the space station, Peake took charge of two kilograms of rocket seeds which were returned to Earth in March and distributed to some 10,000 British schools. The children will grow the salad plants to see if they have been affected by space travel.
13. Remote driving experiment: Another experiment tested Peake’s driving skills as he remotely steered a prototype Mars rover on Earth.