Science & Technology

Rockets: Orbital Mechanics

Chris Hadfield

Lesson time 23:51 min

Chris uses familiar situations—like driving a car and jumping off a diving board—to illustrate how the laws of orbital mechanics govern spaceflight and navigation

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.
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The first human being to ever leave the earth was, of course, Yuri Gagarin. And then the next was Al Shepard, and then Gus Grissom, and onto eventually John Glenn orbiting the world as well. And they launched from two specific places. Yuri launched from Baikonur, Kazakhstan and the Americans launched from Florida from Cape Canaveral and what became the Kennedy Space Center. So why did they choose those places on board this globe? And it's actually sort of a question of physics. The world, of course, turns. It spins around on its axis once every 24 hours. And at the equator , the world, it's about 24,000 miles around or 25,000, and it goes around in 24 hours. So that's nice, easy math. If you're standing on the equator, you're 24,000 or 25,000 miles around, and you go around 24 hours. You're going about 1,000 miles an hour if you think about it. If you're standing on the equator, you are going 1,000 miles an hour to the east just by standing there. If you're on the North Pole, you're not going anywhere. You're just standing there, and the world sort of turns underneath you. So if you're a rocket designer, you want to get that 1,000 miles an hour for free if you can. So you want to launch as close to the equator as you possibly can. And that's why the Russians got as far south as they could down here into Baikonur right into Kazakhstan so that they could launch and take advantage of the rotation of the Earth. Politics didn't let them go any further south. The Americans did the same thing. They launched as far south down on the east coast as they could, because they're going east. And they launched down here on what became the Kennedy Space Center in Florida for the same reason. Since then, we've built launch sites closer-- even in Brazil has built one on the equator. And we actually have portable launch sites that sometimes get on a barge and get on a launch from the equator just to steal as much of that Earth's rotation as possible. Because every bit of spin you get from the Earth is one less kilogram of fuel that you need to put in your rocket. Sometimes, though, you want to launch into a different orbit for a scientific purpose. Let's say you want to map the whole world and have it turn underneath you. It would be kind of nice if your satellite was orbiting around the world from north pole to south pole, because then the whole world would turn underneath you. If you just launch east out of Florida, then you won't go any further north than Florida or no further south than that as you're orbiting around the equator of the world, and you'll never see the north or the south. And so sometimes, we launch rockets rather than taking advantage of the spin of the Earth, and we launch them straight south or straight north. And then they end up in an orbit. Even though it may not take advantage of the Earth's spin, it does put us in an orbit that serves the purposes of that rocket launch. I like holding a globe. It reminds me of act...

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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.


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I have been really impressed with the calibre of the lessons in this class. Chris has really helped to inform me about how astronauts get to space, while simultaneously forcing me to ask myself even more questions about the future of space exploration.

Chris has opened my mind to once again explore the second part of my talents or Arts meets Science. I am now exploring The Quantum Field. Thank You.


A outstanding class where Chris keeps the view engaged with is wealth of knowledge that is presented in such a way that I want to meet him!


A fellow student

Thank you for your explanations Chris - captivating to hear this from a real astronaut, spoken with clean space between concepts. Time to digest each point, word perfect with no errors. I am curious if Chris uses an autocue for this, because it seems so polished; I have a feeling he is talking "off the cuff" as he has had rather a lot of practise at doing this!

Chelsea B.

When would astronauts use Newton's equation? What kind of tasks would they be doing?

Justin T.

Please correct me if I'm wrong, but aren't you indeed going faster when you get to a higher orbit? I know your orbital period will increase (Taking longer to complete one orbit) but isn't the reason you "fall behind" things at a lower orbit just because your orbital path increases by double as the radius of your orbit increases? I'm guessing he's probably talking about ground speed, because then yes, as you increase your altitude, you would be travelling slower over the ground, but I'm pretty sure your velocity would still be higher from a stationary point of reference.

Ken C.

Excellent! I like the hint that it's a bit more complicated in real life. The flight controllers monitoring the ISS do these calculations as precisely as possible, and then measure the effects of each orbital adjustment. The atmosphere "boils" due to the energy from the sun, so it is not a smooth spherical surface and the drag on the ISS is not a constant.

A fellow student

I have a question. Is the Hohmann transfer done manually or does a program/AI do it? Also I am having a science fair on rockets and I was wondering if you have any suggestions or ideas that I can put on my board. Thank you.

Yuri K.

Perfect and very simple explanation. Will show that to my 14 y/o daughter - she has similar topics in a school program now

Philippe H.

Master is someone who can make complicated stuff - like space travel - sounds easy.

ahmad T.

Very very good teacher and can explain very easy and understand very quick

Captain B.

You're right about most of this stuff, Chris, but the Earth is flat. Do your research!

Denny C.

I love this class I want more sir. Any chance we could have examinations and graded quiz's?