What If...

An astronaut gets thirsty?

What if an astronaut gets thirsty?

Classroom view

Activity overview

15 mins
Ages 9 – 11

Science topics:

Materials , States of matter

Get your class thinking and talking with this fun question! Having a broad question means you'll get a wide range of ideas coming from your pupils.

Run the activity

1. In pairs, discuss what might be a Plus, Minus and Interesting way to think about the question. Stuck for ideas? They could think about:

  • Is there any water in space?
  • How could we get drinking water onto a space station? Why might this be difficult or expensive?
  • Is the human body a source of water?

2. Ask the children to share their partner's ideas then encourage a broader discussion as a class, remember there is no wrong or right answer!

Background science

Up to 80% of the water that astronauts drink on the International Space Station is recycled sweat, urine and other waste water. Even the water vapour that astronauts breathe into the air can be collected by cooling and condensing it.

Sweat and urine contain many different substances dissolved in water. Dissolving is a reversible change, so the waste water can be filtered to remove salts, bacteria and chemicals. Astronauts drink the clean water – and the cycle starts again. NASA has calculated that Astronaut Scott Kelly drank 730 litres of recycled sweat and urine during his year in space.

Recycling waste water into drinking water means that fewer rocket launches are needed to carry supplies up into orbit. This makes space travel less expensive. The technology may also one day make it possible to travel longer distances from Earth, and to colonise moons or planets that don’t have liquid water.

Take it further

You could ask your class to discuss other things humans need to survive, and how these can be provided in space. Watch Tim Peake explain how astronauts stay alive in space in this BBC Bitesize clip or watch former ISS Commander Chris Hadfield talk about recycling water onboard the space station.

Many technologies developed for space travel have become useful in everyday life, including digital cameras, training shoes, and wireless headsets. You could start a discussion about how the water purification systems onboard the ISS might be useful on Earth. For example, to recycle drinking water in extreme environments or to clean the water in swimming pools.

Carry out an experiment to purify ‘astronaut wee’: a solution of salt, water and yellow food colouring. Does sieving or filtering help the class to separate the solution? If you have distillation apparatus at school, you could demonstrate how to heat the solution to evaporate the water, and how to collect and cool the water vapour so it changes back into liquid water. You can also watch a clip of how urine is recycled in space on the BBC Bitesize website. Ask the class if distillation would be a good method to use in space. Why or why not?

Image credit: WikiImages via Pixabay CC0