Science & Technology

Rockets: Fuels and Propulsion

Chris Hadfield

Lesson time 20:59 min

Chris explains the pros and cons of different types of rocket fuels including liquid fuel, solid fuel, and ionized gas.

Chris Hadfield
Teaches Space Exploration
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Like all spaceships, rockets are a compromise design. You're trying to take something to space, and you have a finite amount of fuel inside your fuel tanks, you only have so much ability to steer through the atmosphere, and so you really want this thing we're taking up to be as light and as small as possible, because then you don't need so much fuel. The problem gets harder and harder if you're going somewhere, if, say, you're going all the way to Mars, because when you get to Mars, somehow you have to be able to slow down and land. So you're not just bringing the stuff that you need, but you have to bring another rocket ship up here in the end that will be able to take you down to land on the surface of Mars. And you need fuel for that rocket. And every ounce that is carried on the top is going to take pounds and pounds of fuel to get it away from the world and to slow down when you get to Mars. And it gets even worse, because you got to come back from Mars probably. And where does that fuel come from? Unless you can manufacture fuel on the surface of Mars using the raw materials that are there, that means not only are you bringing enough fuel to leave Earth, but you're bringing enough fuel to leave Earth and slow down and stop at Mars, land on Mars, blast off of Mars, accelerate, come all the way back to Earth again, and then land back on Earth. And it just magnifies on the amount of fuel that you need. So what does it really take, say, to put one thing on the surface of Mars? For every pound that we put on the surface of Mars, it takes about 200 pounds of rocket here on the surface of the world. Most of that is fuel. But for every pound that gets to the surface of Mars, it took 200 pounds to get it off the surface of the world, accelerate it out to the speed, and safely there. So every little fraction of a pound, every ounce that you can save on what it is you're putting on Mars will decrease the size of the rocket that you need to leave the Earth. So let's think. I want my T-shirt to be on Mars. Your T-shirt weighs some fraction of a pound. If your T-shirt weighs, I don't know, a third of a pound, then you need a third of 200. You're going to need, like, 70 pounds of rocket just to get your T-shirt onto Mars. So you really want to be efficient in packing, and thinking about what's the minimum amount of stuff that we can bring to Mars so that we can keep the size and the scale and the complexity and, therefore, the cost of the rocket to be as small as possible. What type of fuel do rockets use? It's varied over time. But essentially, it's fairly similar. We have some sort of fuel in a tank or a solid fuel inside a rocket like this, and then we have the oxidizer or oxygen that's stored in a separate tank. On the Saturn V, the rocket that took us to the moon, these first stages couldn't have been simpler. It was just kerosene. That was the fuel. Kerosene and oxygen. It was a pretty good first fuel, just using kerosene, oxygen....

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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.


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

Chris's clear passion for what he does is incredible. While I have an education in physics, it was still a joy to hear him explain it.

Now I know a bit more about space exploration. This class is just brilliant! Bravo, Chris!

The mix of enthusiastic story telling, real world examples of his astronaut experiences, PLUS the leadership and teamwork advice made this an amazing class that I will rewatch again and again.

Being a dreamer. Make things that impossible happens. Keep improving yourself to pursue your dreams and make them come true.



The sound of the chalk is so sandy and grinding that gives me goosebumps and sore teeth.

Yusuf N.

What effect does the gravitational pull of the moon have on the rocket? Will it cause the orbit to deform?

Ronald A.

That rocket equation was discovered by Constantin Tsiolkovski (1857- 1935). He builded that equation with the scenario of a fisherman getting to the opposite shore while trowing big rocks, pilled in the middle of the boat, in the opposite direction of the heading. I tough this should have being mentioned. Newton was not the only one interested in space.

Richard G.

I feel like liquid would be the most efficient way to get to Mars, considering the tech that is abtainable, because Ion rockets can't be used efficiently to get to even the moon, let alone Mars. Solid rockets would get to the place quicker, but would burn up more of our fuel supply, it's like the idea of getting the job done quickly gives you 85% hope, added to the fact that the storage spaces gives you about 10% hope. Giving you 95/100. If we used liquid rockets, we would be able to transport things to Mars at an acceptable rate, with 23% storage which gives roughly 50% hope, and the speed is only half of the incredibly powerful solid rocket, which is still monster force, which again gives approximately 50% hope, and 50 + 50 is 100/100, rather than 95/100. (:

Denny C.

Professor Hadfield; On the friction of Mars to slow you down, isn't that aerobraking?

Denny C.

Orbital Mechanics is essential because as we all know automation breaks down then it is up to MC and the astronaut to fly her

Abbott T.

amazing want to be astronaut really badly when i grow i liked the way he explained it basic but you still learn it

Rodger R.

I began my college career in Aerospace Engineering, which was interrupted by military service. After return I switched to chemistry. Space travel has always inspired and excited me--sometimes makes me regret switching majors. This course is very well presented, but could be pitched at a slightly more mathematical level. Otherwise--excellent conceptual presentation.

Ugo A. D.

Good break down of propulsion systems for rockets. I appreciate the chemical engineering required to find a fuel source to provide thrust for these rockets to get their destination and back.

Sergio N A.

Excellent. It revives what I learned from my lessons with the ISA League of New Worlds way back in the 90's. Going to Mars needs a mixture of rocket propulsion systems and ionic propulsion aystem. From Earth to an orbital height, we can use liquid fueled rockets and shot to escape velocity towards Mars where we can use ionic propulsion rocket. Towards Mars we can have another slingshot from Venus to speed up travel time and conserve more fuel and eneegy going to Mars. The spacecraft for Mars should be a little more complicated to maintain an Earth like gravity to prevent health hazards of prolonged exposure to microgravity otherwise we will have crippled or dying astronauts arriving in Mars. The vehicle in question shall be rotating to maintain an earth-like gravity to maintain good health among all of the astronauts. FROM Sergio N.Andres Jr.