Astronauts describe what life is like in space
David Bowie sang about Major Tom "sitting in a tin can" - and that is a fair description of life aboard the International Space Station (ISS).
The ISS consists of about a dozen pressurised modules - essentially "tin cans" - within which the crew work, sleep, and exercise according to a strictly regimented routine.
Together, they have roughly the same volume as two Boeing 747s.
Conditions are as far from the futuristic spacecraft of sci-fi as it is possible to imagine. The nearest earthly equivalent would be a submarine, but one that never surfaces.
The space station is designed with function, not comfort, in mind. Equipment, control panels, storage boxes, wires and pipes are crammed into every corner.
There are no beds - when they want to sleep, the astronauts wrap themselves inside sleeping bags hooked onto the walls of their cabins.
Windows are not a common feature either, apart from those in the "cupola", a dome-like observation deck offering magnificent views of the Earth.
Washing is done with a sponge - there's no shower or bath - and when every discarded particle is liable to float away great care must be taken when cutting hair, clipping nails or shaving.
Food is freeze-dried and vacuum packed and includes nothing liable to produce crumbs. Peanut butter has been described as the perfect space food.
One of the first challenges Tim Peake will have to face is overcoming space sickness. The effects of microgravity cause symptoms of nausea and dizziness that commonly affect crew members during their first few days. For this reason a special "barf bag" is standard issue.
Over time as astronauts get their "space legs" the feelings of sickness subside. Some experience vision problems - flashes and streaks of light - and it is also common to grow an inch taller in space due to the spine elongating. The face can also turn puffy as body fluids move upwards.
A more serious effect of microgravity is gradual loss of muscle and bone mass, so exercise is a vital part of life on the space station. For two hours each day, crew members use special exercise equipment including cycling and weight-lifting machines and a treadmill. Major Peake plans to use the treadmill to take part in the London Marathon in April.
Mental health is largely taken care of before crew members even get to the ISS. All the astronauts and cosmonauts are carefully chosen stable individuals who are likely to get on well with one another. Regular contact with families on Earth is permitted to help them feel at home.
An organised routine is essential when "day" and "night" interchange every 45 minutes as the Earth is lit up by the sun and then plunged into darkness. Sleep takes some getting used to - just as you nod off it can feel as if you have fallen off a high building.
The typical day begins at 7am UTC (co-ordinated universal time). Work consists of conducting a wide variety of experiments and non-stop maintenance of the space station's life support, power, and communication systems, some of which are 15 years old.
Tasks can range from fixing the suction toilets to stepping outside to clear debris from the solar panels. Like his crew-mates, Major Peake is qualified to carry out EVA (extra-vehicular activity) space walks.
The ISS, which weighs 450 tonnes, flies at an average altitude of 220 miles at a speed of 17,500 mph. It is essentially forever falling, and would crash to Earth if it slowed down. To keep it aloft, the space station gets an occasional boost from a rocket thruster.
A maximum of 10 crew members can live aboard the station. Major Peake and his two companions launching from Baikonur will join Nasa astronaut Scott Kelly and Russian cosmonauts Mikhail Kornienko and Sergey Volkov aboard the space station, bringing the crew complement to six.
Kelly and Kornienko are approaching the ninth month of their one-year ISS mission.