Rocket engine cycles: How do you power a rocket engine?

Rocket engines are incredibly complex machines, pushing the boundaries of material science and human ingenuity. And there’s a wide range of ways you can actually power a rocket engine and make it work.

They can be super simple, like just opening the valves of a tank under high pressure to having complex pumps arranged in a fashion so confusing it’s a miracle anyone ever figured out how to build them in the first place.

So today we’re going to talk about cold gas, pressure fed, electric pump fed, open cycle, closed cycle, full flow staged combustion, tap off and expander cycles. We’ll go over their pros and cons and lots of fun examples of each one!

00:00 - Intro
02:55 - Basics Of Rocket Engines
05:35 - Cold Gas Thrusters
10:25 - Monopropellant Pressure Fed
14:15 - Bipropellant Pressure Fed
17:45 - Electric Pump Fed
21:05 - Open Cycle
25:40 - Closed Cycle [Ox Rich]
31:15 - Closed Cycle [Fuel Rich]
35:25 - Full Flow Staged Combustion
44:25 - Tap-Off Cycle
46:45 - Expander Cycle
52:20 - Summary


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[PracticalEngineeringChannel]

Masterclass in breaking down a complicated topic. Great job to you and your team!

[sockpuppety]

honestly your content is beginning to feel more and more like curriculum as it gets fleshed out and cross referenced. very few people would have the stones to go into as much detail as you have done. thank you for caring about getting it right. you are a researcher and presenter of quality sir.

[ardag]

I think we forgot about the cycle where you rupture the propellant tanks and use the whole vehicle and its surroundings as the combustion chamber.

[koomaj]

I'm still amazed this level of content is totally free for everyone to watch. Thank you Professor Tim!

[DonDegow]

This video helped me a lot, gradually increasing the complexity is what made me understand, thank you!

[KevinTheCaravanner]

We use “rocket science” as a term to indicate something is extremely complex. And it is, but you present it so well that I understand it. You’re a legend Tim.

[jamesengland]

A "like" is a given; a comment is grossly inadequate to convey my gratitude for the stellar work you do!

[martinstedtler]

Can you make a video about the structural engineering of rockets? I am always amazed how they transmit hundreds or even thousands of tons of thrust into the chassis, without everything just getting crushed^^

[MethaloxBanditCamp]

I can't believe I didn't have to pay for this.

[robertgraham]

This is a masterpiece. Structure, flow, pacing, diagrams, animations, clips all spot on. Thank you very much.

[acanuck]

This, Tim Dodd, was a tour-du-force. Your attention to detail and the effort you put into ensuring that we (your loyal audience) actually understand what you are trying to explain to us was obvious. This video was a really good primer about rocket engines and the diverse choices that engineers and designers can make when trying to "build a better mouse trap". Thank you.

[fv]

Tim, the nerdier you get on mathematics and physics, the more enjoyable your videos are!

[Tech_Planet]

Excellent video about different types of rocket engines!

[TechNextLetsGo]

I learned more about rocket science in the last 30 minutes than I have in 5 years, wow dude. You are good at teaching this.

[yagwaw]

Absolutely magnificent! I thought I already had a pretty good idea of cycle types, but still learned a lot. Each time a question arose in my head, you did immediately address it in the next sentence or so.

[jasoncy]

I'm overwhelmed at how good this was, Tim. At first I thought "well, this is obviously a setup for a paid curriculum/class". Can't believe that you offer this for free to the world. You're doing an important service to space and science education and should be proud of what you've accomplished. Well done, sir.

[kellyfarrell]

The production quality on this channel is amazing! I think one day we will have variable expansion ratio combustion chambers and this will solve many issues like throttle ability, although of course, it’s anyone’s guess how material science and technology will evolve. Nevertheless this channel always sparks my creative mind and I appreciate the content.

[jukkiivi]

@EverydayAstronaut you didn't specify which orbit. Lunar Module Ascent Engine was pressure fed and it got Ascent Module on lunar orbit. It even managed it as a single stage to orbit.

[sergeyanikin]

Amazing, definitely your best video to date! Can't believe it was almost an hour. Thanks to all people involved in producing and reviewing the content for the hard work that made it so easy to watch, understand and enoy!

[zuthalsoraniz]

16:00 There were some other (never flown) rocket designs that planned to reach orbit with just pressure-fed engines, like the German company OTRAG's design of a cluster of a huge number of mass-produced cheap rocket modules, and the Sea Dragon that planned to get past the mass ratio issues of being pressure fed with simple brute force of being absolutely huge.