24 hours lost in space

The crew are awoken by an alarm each "morning" - perhaps interrupting the dreams of weightlessness that many astronauts experience - and stir out of their beds to begin their day. Most astronauts would have hooked their sleeping bags to a wall the night before. Sleep spots need to be carefully chosen - somewhere in line with an ventilator fan is essential. The airflow may make for a draughty night's sleep but warm air does not rise in space so astronauts in badly-ventilated sections end up surrounded by a bubble of their own exhaled carbon dioxide. The result is oxygen starvation: at best, they will wake up with a splitting headache, gasping for air.

A few brave souls try floating free, but their sleep is likely to be interrupted by collision with an air filter that is trying to suck them into its grill. Along with other station equipment, all these fans and air filters make for a noisy night - some astronauts have compared duty on a space station to living inside a giant vacuum cleaner - so some of the crew prefer to sleep with earplugs. But most eventually acclimatise to the noise, just as people on Earth get used to living on a main road. The background sound of these systems dedicated to keeping them alive actually seems reassuring.

Once stirred, the astronauts tend to adopt a foetus-like posture as they move weightlessly about the station. Sometimes referred to unflatteringly as the "simian hunch", it seems to be the natural human attitude in microgravity; perhaps it really is an echo of the weightless months that every growing embryo spends floating in its mother's womb.

The crew dress as quickly as they can: no easy task when your limbs float out at odd angles. They wear disposable clothes, replacing them once every three days: there are no washing machines in space. But the ISS does have a shower. Water squirts out of the "top" to be sucked down by an air fan at the "bottom". The shower has to be used sparingly to conserve water, but it is a luxury item that earlier space pioneers would have envied. and today's astronauts cherish.

For the men on board, wet shaving remains a laborious task. Surface tension generally keeps water and shaving cream stuck to an astronaut's face, while cream and stubble stick to the razor blade until wiped on a towel which is then rolled up to prevent the deposits escaping. Electric shaving is also possible, although it has to be done next to a suction fan to ensure the hairs don't float away. Many male astronauts prefer to shave as little as possible, and all agree that it's one area in which their female colleagues have all the advantages.