In weightless conditions water will not drip on the “floor”, but float around freely in droplets. There is a force called surface tension that works between the molecules in the water – it has an inward pull on the molecules at the surface. This makes the water behave as if it had a skin, and it explains why insects can walk on water and why water forms spheres in weightless conditions. All liquids are therefore kept in sealed containers – even the orange juice for breakfast.
Today, there is no shower on board the ISS. Even though there are suction tubes that collect the water in bags, it is always a hard job to ensure that no water droplets escape. Water also has a tendency to stick to surfaces, and since it floats around, it goes everywhere – even into the astronauts’ ears and noses!
Water would not run over you in the same way as in a shower on Earth. Most astronauts therefore find having a shower in weightless conditions not as relaxing as on Earth. On board the ISS, a very good alternative is to use washing cloths soaked with no-rinse soap or tissues treated with special disinfectant lotions. This also reduces the use of water.
Washing your hair
Astronauts use a special type of shampoo to wash their hair. It is applied like normal shampoo, but wiped off with a towel. There is no need for water to rinse it off. These shampoos can also be bought in some drugstores on Earth because they are useful on trips when access to water is limited.
Brushing your teeth
When brushing their teeth, the astronauts use regular toothpaste. They take water from a water dispenser, but there is no sink to spit into. Instead they spit into a tissue and throw it away. Alternatively, the astronauts can use edible toothpaste. This is toothpaste specially developed to save water.
Electric shaving is possible on board the ISS, but is has to be done next to a suction tube to avoid hairs floating around. To do wet shaving on board the ISS can be quite a challenge as there is no sink, and the water and shaving cream have a tendency to stick to the face. The cream and stubbles have to be wiped off from the razor blade with a tissue and carefully thrown away – the tiny and sticky stuff must not escape.
When astronauts go to the toilet, the first thing they have to do is to strap themselves to it – otherwise they would float around.
Instead of using water, the toilet has a suction tube that carries the waste away with an air stream down into a suction hole. The solid waste then gets compressed and stored for later disposal, while urine is collected in a separate container to be recycled. The purified urine is processed and breathing air for the crew is one of the products generated.