Science & Technology

The ISS: Life Support Systems

Chris Hadfield

Lesson time 12:39 min

Learn about the many systems that work together to keeps astronauts alive aboard the ISS and how those systems are evolving so that we can travel even further in space.

Chris Hadfield
Teaches Space Exploration
In 28+ lessons, the former commander of the International Space Station teaches you the science of space exploration and what the future holds.
Get All-Access


Inside the space station right now, there are six people, living and working, running the experiments, exercising to keep their bodies strong. Breathing in, breathing out. Every time you breathe in, almost a magical thing happens in your lungs, where your body extracts the oxygen from the air and then extracts the carbon dioxide from your blood and does an exchange, so that when you breathe out, it's a different gas. You breathed in oxygen-rich, you breathe out some certain percentage of carbon dioxide. And here on earth, that's not such a big deal, because the entire planet is evolved to expect that. We have plants that take the carbon dioxide and process them using the energy from the sun and photosynthesis to release oxygen. It's a lovely big balance that's evolved on the planet. But what do we do on a spaceship? When you breathe out in space, how does that wasted or poisonous gas of carbon dioxide get reabsorbed? And where does the new oxygen come from? It's one of the problems we needed to solve. The best answer would be if we could just have a mini earth, and somehow completely recycle our oxygen. Maybe we could fill the whole space station with trees, and that way we could just use photosynthesis and the natural processes. But even if you-- say you planted beans. If you have a crop failure, everybody dies. And so, at least in this stage of space exploration, rather than counting on being able to grow plants to do that chemical transformation for us, we thought it would be better if we built machinery that we can count on and repair. And so on board the space station, we have carbon dioxide removal equipment. There are various ways to trap the gas, and through absorbent beds and different type of chemical processes to extract the carbon dioxide from the air. And if we do it properly, then we can separate the carbon from the oxygen, release the oxygen back into our atmosphere again, and then either trap the carbon or get rid of the carbon. And there are designs that trap that CO2 and then rotate the trapped gas to the vacuum of space, heat it so that it releases the gases you don't want and still keeps the oxygen, and then release the gas of oxygen back into the ship. But it's still not perfect. No machine is perfect. No recycling program is 100% perfect. And so in addition to doing the best we can to maintain the oxygen on board, we also have to bring up oxygen from Earth. Every resupply ship that comes up-- every one of these little ships that comes up and docks-- brings some quantity of fresh oxygen from Earth. Sometimes just the air that's inside it. Sometimes we've over pressurized that thing so that it's bringing just a free little bit of oxygen. Or sometimes, we actually bring up oxygen in pressurized tanks, even liquid oxygen, at times, in order to be able to resupply the ship to keep us healthy on board. To go to Mars, we aren't going to be able to resupply our oxygen on board. We're going to have to continue to invent ...

Explore the unknown

Impossible things happen. At age nine, Chris Hadfield knew he wanted to go to space. He eventually went there three times, becoming a commander of the International Space Station. In his MasterClass, Chris teaches you what it takes to explore space and what the future holds for humans in the final frontier. Learn about the science of space travel, life as an astronaut, and how flying in space will forever change the way you think about living on Earth.


Students give MasterClass an average rating of 4.7 out of 5 stars.

Amazingly inspirational. Complex but greatly simplified for the common understanding.

Chris Hatfield is so unbelievably accomplished. He is probably an alien transplant.

Discipline Vision Commitment Incrementalism Assiduousness Diligence

Spectacular class. So much more than astrophysics.


Alexis P.

Are we using the wasted gas as a propellant, because I didn't hear Chris mention anything? I mean you do have that in abundance up there, and the same goes for all space flights.

A fellow student

I think that it would be a good idea to use the experience with recycling in space (for example water) in countries on Earth which suffer from lack of it. That could save life of a large number of people.

laura J.

Is the food appetizing or even considered exceptional? what would be considered your best meal or is everything fitted into just calories needs.

laura J.

WE are going to space again, time to learn and understand what astronauts are learning to survive a great story!

Jerry R.

Interesting challenge for going to Mars. How do you produce glucose without using another carbon source except CO2 and not biologically. In other words, no photosynthesis?

Pedro C.

Listening about recycling CO2 and liberating the O2 made me think about global warming. Why it is still a practice to release CO2 at industries; instead of treating it to decompose CO2 into O2 and carbon?


That was exactly what I wanted to know about the ISS. How you consume food and the possibilities of creating your own. Hydroponics was my first thought. How many calories an the average does a person need to consume on any given day?

Rob G.

As I listen to this I can happily confirm the safe arrival of Anne McClain, David Saint-Jacques, and Oleg Kononenko to the ISS, safely docking at 11:33 p.m. (1733 GMT) on Monday, Dec 3, 2018. An astronomically happy day! It's also great to have a fellow Canadian back aboard the ISS :).


This is the most interesting lesson to me so far. How to keep and get what you need to stay alive while on board and in space is obviously the most important part to traveling further and further and to explore higher reaches. Very cool how they maintain water supply... Now we need a great idea to keep the oxygen levels stable. "Bring a mini Earth" I like that one.!!! :)

Terra C.

In San Francisco, the public works building is not only architecturally interesting to look at, beautiful in the way it integrates plants and living things with the form and function of the building, but also, "Key sustainability features include on-site clean energy generation through photo voltaic; 100 percent of waste water treated on site; use of lowflow toilets; 45 percent daylight harvesting; and the consumption of 55 percent less energy and a 32 percent less electricity demand from the main power grid ... One of the first buildings in the nation with onsite treatment of gray and black water to be recycled for toilet-flushing. It was the first in California and the first system to be permitted under the Non-potable Program in San Francisco." There are ways to support and promote exploration of these ideas, recycling water, harvesting daylight, maximizing the benefit and use of energy in day to day living (also known as survival), living sustainably on Earth seems to support the exploration of ideas which may help humans live sustainably wherever we may roam. learn a little more about SF Public Works living machine following this link - if you're in the area, 525 Golden Gate, inquire about the public tour ...