Liquid Rocket Engine Cycles

An overview of the various liquid rocket engine propulsion cycles.

[@YourTransmissionRepair]

That was the best explanation of the 5 types of liquid fueled rocket engines I've ever seen/heard. Thanks and keep up the good work! I was born and raised in Houston only about miles from NASA and I learned more from this video than from all the NASA tours I've been taking for the last 50 years! :-)

[@SpaceflightScience]

Hey, Wow thanks! That means a lot to me :)

[@ben1techie]

You should try playing Kerbal Space Program.

[@mysticalKaleidoscope]

One of the most immense , clear and brief lecture addressing all the explainations required to understand the 5 Liquid engine cycles. Thanks from the bottom of my heart..

[@oquevix]

This man is a very good teacher. I really like his style.

[@MegaStupidMonkeys]

This video deserves a lot more views.

[@sathish6601]

A very good teacher . Thanks

[@ComfortablyCasual]

It makes me happy that you used famous and infamous properly.

[@MadSparks164]

Fantastic, fascinating video. Thanks!

[@barthchris1]

You did a great job with this. Thanks!

[@AirForceBrat71]

Very well done demonstration.

[@Doofer911]

Awesome video and explained in such an easy to understand way. Will definitely be looking at more of your videos!

[@SvPVids]

great video, I was looking for this explanation for a long time

[@tonyb8660]

thanks a lot for your time! That was very good.

[@aliplayer1]

Great job! Well done

[@TommyJMaylee3141]

Thank you for this excellent summary. One very minor comment, Saturn program J-2 engines had preburners. The version of J-2 which was tap-off cycle is the J-2S, which has not actually flown

[@getrail3d994]

Very informative video! Thanks for sharing your knowledge!

[@comradekerman4189]

Really good explanation. I have been looking for the reasoning for the exhaust ducting on the F-1 engine for a long time now. Great video!

[@fiftystate1388]

+Jason Rivera I agree this is a good introduction to the subject. I thought the F-1 example was not a good choice. Find a Saturn-1 or early Atlas launch to see examples of turbopump exhaust. The F-1 pump exhaust was channeled into the bell/lower thrust chamber to provide a curtain of cooler fuel-rich gasses to protect the bell. You've probably noticed several feet of dark exhaust under the engines; that's the curtain. It blazes where it ignites.

[@joachim2464]

Great video. Very well explained!

[@StereoSpace]

Awesome video. Thank you.

[@simonrobertson1966]

Excellent video. Thank you very much for the explanation.

[@JonnyRambone]

Hi, at 14:00 you correctly mention the J-2 Engine, saying it was on the 2nd Stage of the Saturn V. That is correct, but you showed a picture of the 3rd stage which mounts the same engine. The second stage has five J-2 Engines, not one. The speed you use in talking is perfect for a good understanding of all the principles. Great job !

[@dederredy]

For the expander cycle, would it be possible to use the hot vapored fuel for a second stage turbopump (with subsequent gas generator)?

[@robertartac1853]

very well done! thank you.

[@thehelifreak]

Been really helpful. Thanks

[@baritonejp1]

Cool, thanks for that explanation

[@Vlaaadify]

Amazing video.

[@monsterhogan]

Really great video! Not surprised to see so many other positive comments! Thanks, and keep up the good work :)

[@vinayakchari9484]

nice video and explanation.. thank you so much for the video

[@Shawntawnproductions]

When you show the photo of the j-1 why is the nasa logo on the VAB from the movie “contact”?

[@vishalk4647]

Buddy can you suggest books on hypergolic propulsion system?

[@newrind]

Wow worth my like & subscribe! Please make more videos about rocketry.. Thanks for this!!

[@scitechscitech]

The V-2 engine used a peroxide based fuel for powering the turbines, separate from the rocket fuel.

[@ZoeTheCat]

Nice intro to these cycles. What are the selection criteria for these cycle designs? I would think that some cycles are more efficient (analogous to the ideal Carnot thermodynamic cycle). This would render the less efficient as inferior novelties. Does sizing preclude certain designs? Perhaps efficiency is a function of sizing or range of atmospheric operation? For example, I believe the Saturn-V F1 & J2 designs are different.

[@ahmed634899]

very helpful thank you

[@nounours2627]

I have a question. In your version of the "tap-off cycle", it use exhaust gas to pressurise the turbopump and are then dumped overboard. But in wikipedia it says that "tap-off cycle" is the same that the "expander cycle" except that it takes a lesser part of the fuel but it directly dumps it overboard after the turbopump without burning it. The advantage is that the backpressure is lower (the turbopump have a bigger delta P) but it dump overboard directly unused fuel (less efficiency). Are there two kind of "tap-off cycle"? Or does wikipedia make a mistake and "expander bleed cycle" and "tap-off cycle" are two different cycle? en.wikipedia.org/wiki/Expander_cycle

[@roku_nine]

Good stuff

[@Chris-ub1ed]

But if the combustor tap-off cycle uses exhaust gases to pump the fuel, where does it get the exhaust gases if the fuel is not being pumped yet?

[@taraswertelecki7874]

They come from the thrust chamber itself.

[@koralgollful]

You showed me everything I wanted to know about rocket engines, thank you! But you haven't sum up your video: which of this engine is most efficient?

[@ImmelMasterTV]

It could be RD-170, also it is the most powerful. Not for having 4 nozzles it means that it is a combination of four engines, it is a single combustion chamber with 4 nozzles because Russians couldn't fix the combustion instability

[@kirchdubl1652]

In pressure-fed cycle is gas e.g. helium in liquid (cryogenic) state or as a high compressed gas?

[@marmaladekamikaze]

Think about what you're asking, do you really think they can keep Helium liquid inside a metal tube? The supporting equipment necessary to do that would be far too heavy. It is therefore obviously in a gaseous state.

[@StefanoBruna]

Nice. Thanks.

Very nice explanation! What software and hardware have you used for your drawing in this video?

[@digitalera4721]

Power point. www.ellenfinkelstein.com/pptblog/using-the-ink-pens%E2%80%94and-i-learn-something-new-about-powerpoint/

[@cylosgarage]

very good and informative video

[@s3zni381]

thanks

[@gatlandc]

The best explanation on rocket engines cycles I have seen. Thanks. Apparently there is now a 6th rocket engine "cycle" being developed by Rocket Labs in New Zealand which uses an electric motor to drive the turbopump. The Electron launch vehicle is a miniature carbon fibre two stage rocket. Question do you still call it a turbopump if it is driven by an electric motor or is it just a pump?

[@AntonelNeculai]

just a pump. "turbo" comes from turbine. Electric pumps use no turbines. Turbines use blades and moving gas to turn the blades, elecric motors use the electromagnetic field to generste the rotation.

[@DrZond]

Very nice explanation. Your videos could be a little better paced if you did jut a little editing. For instance you could see up the writing. Also I would like to have heard about the full flow cycle used by the Raptor. But I like it very much. Thank you.

[@flyfaen1]

You forgot the Full Flow Staged Combustion cycle (FFSC) where there is both oxy-rich and fuel-rich preburners and where all the fuel/oxidizer flow goes through the preburner turbines before entering the main combustion chamber/thrust chamber :) (the fuel ofc passing through the cooling jacket before entering its preburner)...

[@dack42]

The J-2 is a gas generator, not tap off. There was a tap-off variant of it in development (the J-2S), but it was never flown.

[@alexchew1945]

awesomeness

[@blackkissi]

Awesome video! An observation @16:41 "You don't want to pass oxidizer through a turbine, because it will erode" . How about the Full-flow staged combustion engine that will be used on the SpaceX Raptor engine using LOX and cryogenic methane. From what I've understood the both fuel and oxidizer pass through separate turbines in the Full-flow staged combustion engine

[@timstoffel4799]

One of the common Russian engines uses a preburner on the oxygen side. They have to make the parts out of some alloy that can withstand a hot oxidizing substance. They have also had launch failures due to it.

[@DrZond]

They are both done as staged combustion turbines. There are 2 separate turbines. The fuel turbine/pump is fuel rich and the other is Oxygen rich. Then it all goes back into the combustion chamber. The trick to understanding this is it's FULL FLOW. That means that in fuel side it's almost all of the fuel and the other side is almost all of the oxygen. That means that the pumps are cooled by all that liquid and so they run at lower temperatures. That's what protects the turbine.

[@halamkajohn]

I made a rough approximation of the fuel used for the turbine. It was about 5%. The larger nozzles can give about 10% more thrust at higher altitudes ( from a pamphlet type book) The higher the temperature the higher the exhaust gas velocity (speed). The Throat velocity is limited to the sonic velocity. About 40 psi makes air go sonic. Hydrogen gives a gas speed of about 12,000 ft/s. Lox and kerosene will give a gas speed of about 6000 ft/s. I have only made black powder rockets. I have a compressor and will spend more time on it. Engine was removed. etc.

[@liamailiam]

which is the most efficient? and which has the most thrust potential?

[@fiftystate1388]

+blueskyday Staged combustion. The Soviets perfected the metallurgy for an oxidizer rich staged cycle. When US engineers tested the example engines they were startled by the 10% performance gain. While the USSR was concentrating on staged-oxygen rich design, the US was focused on cyrogenic, liquid hydrogen(LH,) fuel. LH was a 25% improvement. There are several differences between the USSR and US approaches and both had successes. While reading about them keep a critical eye open for people who dismiss out-of-hand one or the other.

[@fiftystate1388]

+blueskyday As for thrust potential, my opinion is the staged and open cycles are about the same. The US's F-1 and the USSR/Russian RD-170 use different cycles but they both have massive thrust with the RD-170 about 15% greater.

[@liamailiam]

Fifty State thats interesting. i heard the soviets fell behind with technology when they failed to master the design of a large engine like the F1. i dont remember why the soviet design was inferior. i think it had something to do with the soviets using several small thrusters instead of a few large ones

[@fiftystate1388]

Even though I might appear to place Russian accomplishment ahead of the US's, everyone knows which one landed on the Moon, explored the outer planets, maintained Hubble, weather, communications, GPS, commercialized LEO, etc. In my opinion the US is still the world leader even though we are not putting men into orbit at this time. In a few years US government and separately US commercial launches will put more people than ever into orbit. In the early '60s the USSR accomplished many "firsts," but at the expense of long-term development and risk of life. It is ironic that the secretive USSR program would make headlines after the fact but the wide open, real-time coverage US program constantly "failed." The US was working on a clear, rigorous program to put a man on the Moon and publishing its milestones beforehand. Basically all the Soviets needed to do was pick a US milestone they could meet first with careful planning and go for it. Putting three men in orbit was probably the best example of that tactic. That vehicle had no business doing that stunt. A developmental contrast was with orbital rendezvous. The US Gemini program was designed to maneuver great distances to rendezvous and dock. The USSR put up the first pair of capsules that could see each other in orbit but not even they credit themselves with anything more than a very precise second launch. The Soviet capsules could see each other; the US parked themselves within a foot of each other and literally flew circles around each other. Enough of that, I'm obviously rooting for the home team! I think Americans who complain about the lack of US manned launch capability are off base. The Russians, Putin basically, is taking advantage of lull in the development cycle to wave the Russian flag at the expense of the long term. The US is on track with a comprehensive program that resembles the program of the '60s on a smaller scale combined with the Space Shuttle development - but with lessons learned. To reply to your frame of reference, the large/small design is one of the divisions of the US and USSR programs. This reply is in context of the late '60s and how it affects today. To say the Soviet engine design was inferior or fell behind ignores the fact that the engine they built for their Moon landing program is still in use, man-rated and putting astronauts into orbit in 2016. The Soviet N-1 Moon rocket was too complex for their ability. By that I mean, the US had far more advanced computers and monitoring. The Saturn Instrument Ring is one of the program's greatest accomplishments. Saturn had system failures but was able to recover from them real-time. The best two examples that come to mind are the second stage failures of the Apollo 6 unmanned and the Apollo 13 manned missions. Apollo 6's second stage engines were literally was mis-wired (oops.) One of them failed and was appropriately shut down, but it caused a second engine to shut down. That caused a major objective of the mission to be aborted, but it didn't blow up. A similar thing happened to Apollo 13 on lift-off but the system responded and the mission was not affected. That had nothing to do with the historic accident 55 hours later. The Soviet N-1 vehicle, on the other hand, had 30 smaller engines and there were simply too many things that could go wrong and the system could not respond quickly enough. As a result, they had cascading system failures that ultimately caused the rockets to explode. What blows me away about this massive Soviet rocket, and it was every bit as big as the US Saturn, is the US knew nothing about it until 20 years after it had begun. Only after the fall of the Soviet Union did the scientists and engineers start to let the world know about it.

[@fiftystate1388]

blueskyday I'm writing this separately because it's something you might want to know about rocket engines. There are two raw measurements of engines and one of the measurements has two ways to be expressed. The two measurements are power and efficiency. An engine can be very powerful and inefficient, like solid rocket boosters, and vice-versa, like ion propulsion. You'll never get off the ground with ion propulsion and you'll never go very (very) fast with solid propellant. Power is simply the amount of force an engine makes. "A million pounds of thrust" for example. Thrust is a great word. Think of sitting in an office chair on a basketball court, holding a bowling ball like you want to make a basketball type chest pass. Thrust the ball away, the ball moves, you move, thrust. Efficiency is called "specific impulse (Isp)" and is measured two ways: in seconds (time) and speed. As seconds Isp is based on how much thrust the engine generates. Say an engine has a thrust of 1,000,000 lbs. If it takes exactly 5 minutes for the engine to burn 1,000,000 lbs of fuel, it has an Isp of "300 seconds." As velocity Isp is based on how fast the gasses or propellant is being thrust out of the engine; higher velocity equal higher Isp and more efficiency. Propellant type makes most of the difference here. Burning kerosene and LOX mostly makes CO2. Burning hydrogen, LH2 and LOX makes water, H2O. A molecule of CO2 weighs more than a molecule of H2O. Back to the basketball court. You thrust a bowling ball away every 10 seconds and move across the court. Now imagine constantly thrusting away one basketball after another so every 10 seconds the same weight of basketballs and bowling balls are thrust away. There's more to it than that and I invite you to ask more questions. If anyone has an objection with my model I welcome your input.

[@milosavage7327]

Body you are a professor. Did you graduate from MIT or Indian institute of Technology

[@michaelc.kushlan7956]

Milo Savage "".

[@halamkajohn]

flashing btu's might explain the russian american explosion (maybe it needed extra cold lox ) a few btu. Everybody has a different rocket engine version. NASA is of course a victorian house of architecture on some intervals. Make your first turbine light enough to fly. Someone mentioned reusable. Should you be rebranded?

[@SampleroftheMultiverse]

Which type of cycle do the Russians use to make their engine's camber pressures so efficient.

[@NikopolAU]

RD-170 and derivatives (RD-180, RD-190, etc.) use staged combustion cycle with oxygen-rich preburner.

[@SampleroftheMultiverse]

Thanks for the response.

[@Krasnoye158]

I saw a documentary film about this, USSR needed a small and high efficient rocket engines. So, their chief engineer decided to take a different approach for their engines, which the US didn't want to use because of its unreliability, the Staged combustion cycle. The first operational prototype was the NK 33. (Sorry for the loooong "opening ":/)

[@jamesconner8275]

Great explanations! Russia was able to get a closed system to work and provide more thrust from their first stage engine. Why was NASA unable to make the F-1 and closed system?

[@j.muckafignotti4226]

Major issues with combustion instability. The direction of the flame front in the combustion chamber was changing direction several thousand times a second destroying the injector head leading to the total loss of several pre-production engines. The solution, which was really just a stop gap, was to place copper beryllium baffles on the face of the injector plate. This disrupted the flow pattern of the instability and the engine was able to stay together for its complete burn length. Very fascinating fix if you read the tech on what they had to go through to get the F-1 to work as the combustion instability was a show stopper.

[@markholm7050]

James Conner The Russian RD-170, very large, staged combustion, kerosine-LOX engine did not fly until 1985. The F-1 first flew November 9, 1967. You fly to the Moon with the engines you have, not the engines you wish you had. More to the point, high specific impulse is more important in upper stages. In order to achieve that, the Saturn V used LH2/LOX engines for its second and third stages. LH2/LOX leapfrogs right over any Kerosine/LOX or N2O4/UDMH-Hydrazine engine in terms of specific impulse. Staged combustion produces the highest specific impulse for Kerosine/Lox, but don't touch the specific impulse of LH2/LOX, even in a gas generator cycle.

[@Ms3DiT]

The F1 used the expansion cycle.....

[@markholm7050]

Toypar Sanchez F-1 rocket engines use the gas generator cycle, not the expander cycle. For an expander cycle engine, see the Rocketdyne RL10. Also read the Wikipedia articles en.m.wikipedia.org/wiki/Expander_cycle en.m.wikipedia.org/wiki/Gas-generator_cycle en.m.wikipedia.org/wiki/Staged_combustion_cycle_(rocket) en.m.wikipedia.org/wiki/Rocketdyne_F-1

[@wawrow_-]

where liquid rocket engine eevee

[@karpcalmari4628]

No wonder they call this rocket science. This seems very advance.

[@Robert-mi6tn]

Well, this isn't rocket science. Oh, wait......

[@roku_nine]

Good stuff