This module concerns itself with food on a Space Station.

In the early days of science fiction, it was assumed that space travellers would live on concentrated food tablets. These would contain all the nutrients necessary for survival, but would produce no waste, and would be easy to store. During the first manned flights, food was prepared in tubes, to squeeze like toothpaste. Unfortunately, it was a lovely idea that was doomed to failure. The human body has lagged behind the human brain's aspirations. We still have the same digestive needs as our primitive ancestors - that is, we need bulk and fibre for our digestive systems to work on, otherwise we run risks of serious illnesses, including cancer. We therefore face the fact that whatever food is taken into space, it has to be as far as possible normal food, thus producing waste, and creating storage problems.

Storage can be solved by dehydrating the food before it is sent to the space station, and only rehydrating it when it is needed. Students might like to try dehydrating things like fruit and vegetables, to see how much their bulk - mass and volume - reduces. This could lead into a discussion regarding how much water is present normally in what we eat, and as to why manufacturers add water, as in ham and bacon. Dehydration is also the principal method of food preservation currently in space, as there are no fridges or freezers in use at present, due to the weight, high power requirements, and potential gas hazards. But that may change.

Students might like to do research into how travellers on long sea voyages used to preserve foods, and any health hazards this caused, such as scurvy. Perhaps students would also like to look at the methods used to preserve food in different cultures. Other modern methods include freeze-drying, ultra-high temperature processing, and general drying of meat and fruit. Older methods include pickling, preservation in salt or brine, smoking and emmersion in solutions such as sugar and alcohol. What is the aim in each method, and how is it achieved? Can they make a list of such foods that they have at home?

All nutrition has to be balanced, especially in space. One particular problem is the loss of bone mass caused by weightlessness. Our bodies are designed to work against gravity, and to use it to promote healthy growth. Ask your students what foods they might choose to send to combat the effects of bone demineralistaion. Point out that patients undergoing long bed rest can suffer similar problems.

Eating can be a messy business. Ask the students to list foods that are messy to eat: spaghetti bolognese, soup, beans, ice cream, crumbly biscuits, salt, pepper and drinks. Get them to think what problems these foods would present in a Space station under microgravity, and how these might be solved. What about wanting milk and sugar in your coffee or tea? In Skylab, food also came in tins. This food was made to be stickier than normal so that it wouldn't float about. Can students think of how these "problem foods" might be made less problematic? People also prefer traditional hot foods to be "hot", so some method must be found to heat up the food. In the shuttle, they use a convection oven that circulates hot air, heating it to 74 C. Weightlessness also poses problems for keeping the food still while eating it, and for not losing your knife and fork. Ask the students to devise methods to keep food containers on trays. This has the added application for some disabled people, who might find it useful to have something like that on Earth.

Ownership of food is also important. Shuttle food is individually packaged in colour-coded packaging, and is stored in eating order.

To summarise, the following facts are useful to remember: The Shuttle has no refrigerator or freezer. Food is preserved by dehydration or other heat treatments, such as thermostabilisation. Food has to be compact and lightweight for storage and weight. Fresh foods must be eaten in the first few days of the mission. Calorie content is calculated at 2,800 per person per day. To prevent hazard, salt is available in water and pepper in vegetable oil. Shuttle astronauts are allowed about 1.6 kg (3.5 lbs) of food per day. Food items are separately packaged to allow for flexibility in menu planning. Food packages are designed to stick to the tray by either having velcro attachments, or by being made to fit tightly on the tray. Cutlery can be attached by magnets.

The mass/volume of food is a cost consideration too. Typical costs for launching a one kilogram mass into space at present (1999) are of the order of $1000. So you can see, lunch on a space station is dearer than at the world's most expensive restaurants!

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