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Science & Technology

Spacewalking: Spacesuits

Chris Hadfield

Lesson time 17:57 min

Chris gives a head-to-toe tour of an EMU (Extravehicular Mobility Unit), explaining how it keeps astronauts alive while spacewalking and conducting work outside the ship.

Chris Hadfield
Teaches Space Exploration
The former commander of the International Space Station teaches you the science of space exploration and what the future holds.
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Most of the time that I've been in space, I've been on the inside of a spaceship. And we can do most of the stuff outside with the robots, the big, robotic extensions of ourselves. But sometimes we need the dexterity of a human hand. We need the sensitivity of a set of arms to maybe turn a bolt or do something that requires judgment and the tactile nature of our interaction ourselves. And that's when we need to put on a suit like this and go outside. This is a spacewalking suit. EVA, Extravehicular Activity, going outside. Not intra-vehicular, extra. This is a suit that lets us do it. The environment outside is extremely unfriendly. Of course, the number one big difference is there's absolutely no air. So the suit has to be pressurized with a breathable environment inside. It's also wickedly hot and wickedly cold at the same time outside. In the sun, it's 120 degrees Fahrenheit on the outside of this suit. But in the shade on the other side, it's minus 100 degrees. The suit has to protect you from those big temperature extremes. You're also subject to getting hit by all the little tiny particles of the universe, like you're being sandblasted the whole time you're outside. This suit has to protect you from that. So it's not really a suit. It's more like a one-person spaceship, completely self-contained and different from the ship that you crawl out of. Here's how it works. On your back is a life support system. We call it the Personal Life Support System, the PLSS. And it has your oxygen purification system, it has your battery power, it has a radio, it has a cooling system. This is sort of the nuts and bolts, the guts of your suit that keeps you alive. We keep the suit as low a pressure as we possibly can, because if you pressurize this suit to the full same pressure as you get here at sea level, you'd be in a balloon where you could never even bend your elbow or close your fist. So we only run the suit down about one-third of the pressure that's around me right now. Instead of 14.7 PSI, we run the suit at about 4.3 PSI, because that's the trade off between what I need to keep my body healthy and how bendable we can make the elbows and the fingers on board this suit. What gas do you put inside the suit? We could have air. We could have a mixture of other gases. But if you're going to run down at just 4.3 PSI, then you really need all the oxygen you can get. And so we decided a long time ago the gas that's inside the suit is 100% oxygen, just down at a low pressure. Let me go over the suit top to bottom. Here at the top is a camera for the ground to watch what's happening. You reach up blind, you push this button right here, the little green light comes on, and these cameras are activated. If you push the button multiple times, it changes lenses, and that way everybody down in mission control can look over your shoulder and make sure you're doing all the things that you need to do, but also as you finish working in one part of t...

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.

This class help me realize that life is long! You need to know what you want to do and where you want to go. Then it's easier to find your path and decide what to do next. "Your life is not the grandiose statements, it’s just the sum total of all the things you chose to do." Chris is a true inspiration!!!

I also gifted this course to my son. I was mightily inspired. Great altitude.

Chris Hadfield is very well spoken and is very knowledgable. He is also excellent at explaining complex subjects at a beginners level.

i loved the 1-pager lessons and the anecdotes about lessons learned at different times during his experiences :)


Bernardo F.

I had too many misconceptions about spacesuits. First, I learned to scuba dive some years ago and one of the first lessons was about the composition of the gases we breath and what would happen if everything was oxygen; I had never imagined that spacesuits have pure oxygen. The last part is equally interesting, when I was a guide in the Natural History Museum we had a temporary exhibition about MARS and one of the pieces was the spacecuit from the TV series, I used to present it as the Iron-Man suit, specially for children, as the technology planned to be used resembles that that they already know and admire.

Shelly F.

wow, real scary stuff. I think the farthest in space I will ever go is on top of a mountain.

Grace S.

Loving Master-Class series. So informative, solved almost all my childhood's curiosity.

A fellow student

I love the walk through orientation on the space suit. I like how the controls are all different types of knobs, levers, etc. This way you are sure that you are grabbing the right thing, by feel. And large, fat, bulky controls too. So that you might be able to operate all things, even if you only had one digit left functioning.

William D.

In all my reading I've never come across a reference that says we keep spacesuit pressure low to improve mobility. Space suit pressure was low because early spacecraft pressures were low. This was done since weight was critical. Low space craft pressures, using pure oxygen, have lighter structures with lower weight. Another factor of low pressure suits is whether or not the Astronaut has to "pre-breath" prior to making the EVA. Shuttle was at a higher pressure. To go to low pressure and pure oxygen the astronauts making EVA had to pre-breath pure oxygen to purge their systems of nitrogen. Space suit construction is glossed over or ignored. I would have appreciated more information on the PLSS and SAFER. What about sanitary facilities? Is there any way for the astronaut to eat or drink during 7+ hour EVA's? Comment on contamination interesting but that leads to unanswered questions about hazardous gases and liquids floating around outside the ISS? Moon dust is a hazard that was brought to light with the Apollo moon landings. The Apollo suits took a beating in just 3 days of EVA's. Longer term stays would seriously tax current suit technology.


Fascinating! Question, how is the spacesuit cleaned from all the dust and ammonia back into the station?

A fellow student

Not that I've been watching Space documentaries every day during quarantine, but did he just say its 100F in the sunlight in space? I believe it's 100C :). Awesome class, well informative, and finally, a great teacher!

Maddie W.

I love how Chris Hadfield goes from describing the spacesuits as a "one-person spaceship" to an expensive "inflated bag" to an "amazing invention." Really cool to learn about all the systems that are in place and all the ways that astronauts can control their surroundings while out in space. Conducting a spacewalk is obviously something that only a select few people ever get to do so I really enjoy being able to understand it a bit more from the astronaut's perspective. "Nothing between me and everything else but the plastic of this visor." What an amazing description for a truly unique and wonderful experience.

Nakul M.

Wow, a jetpack is built into the suit a joystick to navigate. That is surreal! Even the fact that anything written on the suit is upside down so you can see it correctly in the mirror. Amazing!

A fellow student

that is awesome I already got a huge head start on learning about being an astronaut thanks to hadfield