Why doesn't the International Space Station run out of air?

That's a very good question. Simply put, astronauts and cosmonauts (i.e., Russian astronauts) carry oxygen from Earth and also produce it by electrolyzing water. This electrolysis process uses electricity to break down water into hydrogen and oxygen.

Both the air and water on the space station initially come from Earth. Astronauts and cosmonauts transport these vital supplies to the space station aboard Soyuz spacecraft, a type of spacecraft. They also receive resupplies from unmanned spacecraft, such as the Russian Progress and the American Dragon. "Unmanned" means there are no people on board the spacecraft.

However, relying solely on fresh supplies from Earth is not enough to sustain operations on the space station. This means that if you were on the space station, you would have to be very mindful of recycling resources. The space station's water recycling system is capable of converting wastewater, sweat, and even urine into purified drinking water. As astronaut Douglas Wheelock put it, "Yesterday's coffee is tomorrow's coffee."

Water, which is made of oxygen and hydrogen atoms, is also used to maintain the oxygen supply on the International Space Station. Astronauts and cosmonauts use electricity to break down water into oxygen and hydrogen through an electrolysis process. It's important to emphasize, please do not try this at home; water and electricity generally don't mix, and attempting this would be very dangerous.

The space station's electricity does not come from Earth, but rather is generated by large solar panels that convert sunlight into electricity. So, what happens to the leftover hydrogen? Through some chemical reactions and clever engineering, they are actually able to convert the hydrogen back into water. The hydrogen combines with the carbon dioxide exhaled by the astronauts and cosmonauts, producing water and methane. This provides more drinking water, and the methane is released as waste gas into space through special vents.

So, if you have a chance to see the space station tonight, you can marvel at many things. Marvel at a spacecraft flying at over seven kilometers per second, marvel that you can see people living 400 kilometers above the Earth, and also marvel at how recycling sustains human life in the harsh environment of space.