How to be an astronaut 4: Roughing it in orbit

You've won a place at astronaut school, you've survived the training programme, you've faced up to the possibility of sudden, unpleasant death - and you've made it to space. A universe of wonders awaits, but so do some gritty realities.

Bad taste

Space missions can last for months, and the nearest supermarket is a long way off. That means food has to last for the duration. Most fresh food, such as fruit and vegetables, is in any case frowned upon for other reasons: it can decompose and produce persistent, unwelcome odours. Bananas are out of the question. But dry food can be problematic, too: crumbs can get into delicate instruments, or even into the lungs of our intrepid space explorers.

As a result, space food often takes the form of freeze-dried, dehydrated or irradiated versions of the kind of food we might normally eat on Earth. Food preserved this way tends not to look, smell or taste like it does on Earth. More seriously, it also loses some of its nutritional value, which means that till now astronauts have had to take cocktails of supplements to maintain their health.

Future astronauts may fare better. Synthetically grown meat could liven up their diets without the challenges of animal husbandry, although you might balk at other attempts to create tastier space food, drawing on algae and radiation-loving fungi.

But that might seem positively delectable compared to what you'll wash it down with. Water is heavy and is used up quickly, so the inhabitants of the International Space Station drink their own urine, although not before it has been cleaned using a combination of filters and ion-exchanges. And in future, what is euphemistically termed astronauts' "solid waste" is likely to be recycled into food, oxygen and water, or at the very least used to fertilise plants grown for food.

Poor health

Being in space is bad for your health. Astronauts in micro-gravity experience a drop in their red blood cell count - making the body less efficient at taking oxygen on board - and a gradual wasting of their bones and muscles. To combat these problems, astronauts are encouraged to work out in space, using devices like NASA's vertical treadmill.

Astronauts also have to be careful: wounds don't heal properly in the absence of gravity, so even a cut can be bad news. NASA is ploughing money into ways to speed up the healing process in space; the current front runner is a wound-healing material derived from shrimp shells, of all things.

But the most common health problem for astronauts is space sickness . Perhaps that's not surprising, given that many of us feel travel sick when we're on a bus, let alone in disorienting micro-gravity of space. It can put astronauts out of action for a days, but anti-sickness goggles that flash strobe lighting into the unfortunate astronaut's eyes may provide some relief.

Oh so lonely

You might think that you'd never tire of the glamour of being in space. But in fact, weeks spent in cramped conditions, cut off from friends and family, can prove extremely stressful. Astronauts have previously refused to do their assigned tasks, had bloody brawls, given each other the silent treatment for months and made unwanted sexual advances. Space agencies hope that simulating the experience of lengthy space missions here on Earth will help them understand how to prevent such occurrences.

If you are still not convinced it's a tough gig, consider that many of life's basic pleasures are denied to astronauts. To pick the most obvious, NASA doesn't allow sex in space, and there's no evidence - despite persistent rumours - that it has ever happened. This is seen as a practical issue as much as a moral one: sexual tensions could be profoundly disruptive during a long mission.

The notorious case of former Shuttle robotics specialist Lisa Nowak, who drove across several states to mount an attack on an alleged rival for a fellow astronaut's affections, highlighted how the pressured nature of an astronauts' life can combine unhappily with sexual liaisons - and the need for thorough psychological screening.

Despite some pioneering early work in orbital beer studies, booze is out too. NASA clamped down on astronauts' intake after an investigation revealed several incidents of intoxication while on duty. Shuttle astronaut Mike Mullane wrote in his biography that some of his colleagues drank beer in order to reduce the need to urinate at a later, more critical, juncture .

If you're confident that you can survive the food, the company and the tedium, there's only one thing left to decide. Where should you go? We'll check out the options tomorrow, in the fifth and final part of this series.