The Most Efficient Rocket Engine - The RL10 Expander Cycle Engine

The new(ish) camera on the Delta IV showed the deployment of the RL-10B Nozzle extension so I thought I'd talk about this workhorse upper stage engine.
Lots more info on the evolution can be found on this page:
www.b14643.de/S...

[@SRFriso94]

That ice is freaky, being mere centimeters away from thousands of degrees.

[@NGC1433]

But it is the main product of that reaction, which heats it all up to thousands of degrees is water! And it cools down by expansion! Thermodynamics!

[@Lhunath]

Can anyone explain more in depth what causes the exhaust to get so cold there?

[@dubsy1026]

@@Lhunath the nozzle is cooled by liquid hydrogen

[@SRFriso94]

@@Lhunath Just like Scott explains: that version of the RL-10 has an actively cooled nozzle, and they do that by pumping the fuel an oxidizer, which are at something like -250 degrees Celcius, so the outer wall is really cold, while the inner wall is nice and warm. Space Shuttle used the same system.

[@mathboy_]

If obviously there is no heat being put out from the engine does that mean that standing right next to the nozzle would be possible? Or going even further, would there actually be a chilling effect outside of the nozzle?

[@Vaasref]

Those are not icicles, they are part of an ice based nozzle extension 3D printed of the fly.

[@charadremur333]

:D

[@stupidgenius42]

*on the fly

[@RobertCraft-re5sf]

Bravo

[@anarchyantz1564]

No matter how many times I see it, watching the thin blue line fading into the deep black is always fascinating.

[@theimperfectgod7140]

Oh hoo Agreed :)

[@ahaveland]

Icicles on a rocket nozzle? Mind boggled!

[@theimperfectgod7140]

nICE (*_,* )

[@duraikarthikeyan]

Loved that "omegA" pronunciation.

[@kristenburnout1]

"Oh Meg AAAAAAAH."

[@DobromirManchev]

Yeah, what was that about? I chucked out loud at work at that point in the video :D

[@kristenburnout1]

Someone should make a compilation of scott saying "Ohmeeeg-Aaaah".

[@kaptendavid5427]

Love from Tanzania, I just love how on the outside is freezing cold and on the inside its blazing hot..... Amazing... Thumbs up great video.

[@pseudotasuki]

It's a good thing Aerojet Rocketdyne started work on bringing down the cost of RL-10, as that's probably the only thing preventing them from being obliterated by Blue Origin.

[@afterburner119]

Well my money would still go behind the 60 some odd years AR/P&W has on the RL-10. Approximately 475+ missions with a success rate in which you can count the failures on one hand.

[@pseudotasuki]

@@afterburner119 Which is useless if nobody wants to buy them.

[@kazumiohta8727]

There’s no way that ULA is letting go of the RL-10

[@kazumiohta8727]

They like it too much

[@kazumiohta8727]

Also SpaceX is better.

[@QuietElite]

For me the RL-10 is probably the most iconic hydrolox rocket engine :)

[@RealityIsTheNow]

Naw...the RL-25. Bigger, dramatically displayed on the Shuttle for decades, reusable, etc etc.

[@gordonrichardson2972]

The Shuttle engines were RS-25, not RL-25.

[@rjherche]

J-2 son

[@rlstnnl1740]

RD-0120 or bust

[@MushVPeets]

@@rlstnnl1740 Um, no, that's just the _best_ hydrolox engine. Not really the most iconic. :P

[@MarkZacharias]

@Scott I just wanted to say thanks for keeping your intro short. I love that you get to the meat of the video in ~6 seconds.

[@georgegrubbs2966]

I worked on this rocket engine in 1962-1963 at Pratt & Whitney Aircraft Company in West Palm Beach, Florida. Yes, an excellent engine that is still in use today.

[@kevins260]

My grandfather Wesley Kuhrt was responsible for the overall design of the RL10 and was gifted the patent for the the RL-10 rocket at P&W. He came up with the original idea for changing the expander cycle and was a genius with regard to liquid hydrogen. My family used to tell a story about when he was 13 he accidenelt exploded a test tube with hydrogen in his basement and had glass imbedded in his chest. I have the original pump expander design patent plaques gifted in his name. He lead the research department for many years and ended as Executive Vice President of United Technologies in the 1980’s.

[@marksinclair701]

Impressive guy!

[@chrishunter7065]

I got to see this from 7 miles away. I loved the sound of this massive rocket.

[@Hopeless_and_Forlorn]

The RL-10 was designed by Pratt & Whitney, the same engine company responsible for the R-1830 engine used on the DC-3/C47 and many other iconic airplanes, the R-2800 that in effect became the war-winning radial engine equivalent of the British Merlin V-12, and the reliable R-4360 workhorse of post-war heavy hauling. Quite a legacy for a machine shop.

[@Sk1erDev]

Could an extending nozzle be used for an any altitude engine? As the pressure decreases, the nozzle extends more.

[@gordonrichardson2972]

The nozzle has to lock into place, otherwise there will be severe blow-back.

[@Sillydogification]

Far better would be to use an Aerospike Engine. The reason for the nozzle extension is to reduce the overall size of the engine, so the interstage structure can be shorter.

[@robertmiller9735]

Too bad nobody's willing to try aerospikes.

[@km5405]

its always a payoff between optimizing for a altitude and performance/weigth. a any altitude engine might not be ideal.

[@ryanrising2237]

Robert Miller loads of people are willing to try aerospikes, but it turns out they’re just very hard - beyond what normal rockets are.

[@phaseed]

The "Screws" are worm gears that are used on the extensions. Worm gear rods are stationary and worm gear drives are the square blocks you see in the video.

[@robrod7120]

I was there!!! Saw the NROL launch, my first launch ever. It was incredible and just left me in awe at the power of our machines

[@shadowraith1]

Historically I think a lot of rocketry was hidden from cameras for the general public. Everyone had their secrets. A lot of them still do. Blue Origins comes to mind as one. I have to credit SpaceX for raising the public's interest in space again. Their broadcast coverage of their success and failures. Has been enlightening for all of us space junkies. Every launch and recovery has been a sales pitch for the company giving them worldwide recognition. Using that business model has been pretty successful. I do wish they would get better at their drone ship landing videos. A couple of drones with transmitters chaining the transmission signal might help for better video. By the way do you have any idea what those fairing half's weigh? Was wondering if a helicopter might be useful. Put the copter on whatever drone ship is waiting for the Falcon 9. When the fairing's eject copter takes off catch the fairing drop it on net on the west coast. That was longer than expected.

[@TheEvilmooseofdoom]

The droneships lose the uplink to the satellite (and I doubt they'll spend the money to try and correct that) but spacex still gets the footage. It's only the stream that doesn't.

[@Anvilshock]

@@TheEvilmooseofdoom lose*

[@TheEvilmooseofdoom]

@@Anvilshock Got it. Thanks.

[@traviswinch4536]

Thanks for this video last week. You answered my exact question I had for Tim Dodd just before the launch. I could not recall ever seeing the deployment of the nozzle before but knew it existed...awesome video. Thanks.

[@wanjockey]

this was probably the coolest(no pun) videos I have seen of close up H-O engines firing. Thanks.

[@timandshannon03]

I also live in Norcal and took the wife and son to SoCal to watch the launch outside of Vandenburg! It was a beautiful launch!

[@willys4882]

RL-10 was originally built and tested with the H-1, Redstone, F-1 turbopumps etc. at the now closed North American Aviation Propulsion Division/ Rocketdyne/ Air Force Plant 65 in my home town of Neosho, MO. I remember exploring around the bases of the test stands as a Boy Scout when I was about 10-12 (1992-94). That is some fairly obscure space history!

[@larthallor]

The RL-10 was also used in the DC-X SSTO demonstrator project, in part due to its ability to throttle/restart.

[@donjones4719]

Wonder of that's when they developed the extendable nozzle. SSTO engines operating from sea level to space would really need that benefit, in spades.

[@richwaight]

That last bit about the icicles was mind bending!! Thanks for posting

[@bisowned13]

ALMOST 500 LIKES AND NO DISLIKES! No one produces content of this depth can quality! Thanks for all you do Scott!

[@nickdehart5702]

I just wanted to say Scott....I had ZERO interest in space about three years ago. However, I did like KZbin. I stumbled across one of your videos (I do not remember which one) and it started. Between you and Tim Dodd, it has lit a fire underneath me. I read and watch anything I can to learn. I often wonder what would have become of me as a high school student had I known I had such an passion for all things space? At thirty one years old, I feel my only option is to pass it to my son. Who, as of now, has no interest in anything but Fortnite. But that might change as he gets older. I just wanted to say thank you for all you do. You really do affect people in a positive way!

[@eannamcnamara9338]

Same thing but the big question do you play KSP

[@eannamcnamara9338]

And your son would love playing it to

[@cheesegrease8247]

@@eannamcnamara9338 kerbal space program: *_BATTLE ROYALE_*

[@eannamcnamara9338]

@@cheesegrease8247nasa begins default dancing on the constellation program it just killed (I don't play fortnite but I know the memes)

[@martinultimatevw3779]

Same here dude 🤟👌

[@robertbilling6266]

Really neat engineering, thanks.

[@Veptis]

hey Scott, thanks for keeping it up. I just went through 3 booksotres and look for Ignition by John D Clark, no chance as it seems to be not that common, but I ordered it and will pick it up soon. For the next few months I made two of my school project about rockets. You and your videos have been a great motivation to do so. The first one is a chemistry talk and experiment I want to present on rocket fuels. I chose to do a liquid hypergolic reaction on the basis of the book and the video by NileRed - if I somehow can get my teacher to allow it. The other is a really scaled up version of the history of rockets for history class. It is supposed to talk about the cold war and how nuclear bombs(thanks for your video series on this as well), missles(not rockets sadly) and information technologies(spy satellites) have dictated this period. My version tells this story by showing 3D models in 1:82 scale I print of soviet and american rockets and telling all the funny tales and twists to show my class a picture of how interesting space exploration can be. I use your videos and those of others like Curios Droid as references alongside wikipedia lists and some official archive material for the Kennedy speech etc. thank you!

[@BlackWolf42-]

I got it a few days ago from Amazon. It took almost 2 weeks to get here. Edit: Do get the physical version. The pages aren't as intoxicatingly odoriferous as other books but nothing beats a copy you can hold.

[@Sir_Uncle_Ned]

It really is remarkable how we can have fire and ice co-existing.

[@kenhelmers2603]

Amazing, ice on a rocket engine exhaust bell. Thanks Scott!

[@SermedAlWasiti]

Thank you for this vid, Scott...it expands on what you mentioned on Twitter.

[@Quirk91]

That nozzle extension is pure genius!

[@TheClintonio]

Scott - your outro music always gave a sense of satisfaction that the new music lacks.

[@neuterdude5932]

It is amazing to see those icicles on the nozzle!

[@Raptorman0909]

The expander cycle is the right choice for lunar landers -- well within the square-cube limit, low stress on the turbine, very high ISP -- and with 3D printing simplifying the construction and likely improving the reliability it just makes more sense than any other engine cycle for reusable landers on the Moon.

[@Marc83Aus]

I wondered why they were going for a new, heavier, slightly lower performance version of the old workhorse, I figured the new engine must be significantly cheaper to build. Then Scott pointed out the RL 10 is already the most efficient chemical rocket engine, so I suppose it can afford to lose a couple of ISP here or therel

[@BlackWolf42-]

Scott, I've been reading the book "Ignition!" that you recommended. It's a VERY good read for those that have a modest 'chem-thumb'. Those propulsion chemists have a neat job.

[@lucidonoccasion5012]

Love the videos on rocket engines, keep em coming!

[@davidmorgan8612]

Excellent video

[@Katia_Managan]

Hey, don’t mind me. Just dropping by to let you know that the thumbnail looks just like an album cover for an indie rock band and I totally dig it.

[@zakiranderson722]

I never knew a nozzle extension existed, I thought the vaccuum nozzle on the engine itself would be the final solution!!

[@F1fan4eva]

Awesome info Scott! Subbing to you is like literally signing up for a channel that reports rocket/space news. And the best part? It's free!! Someone did once say the best things in life are free :)

[@poisonouspython1410]

That's a pretty COOL rocket motor design...

[@tomjones1258]

Scott, rocket-cam on NASA EFT-1, December 5, 2014

[@jr5234]

I once read that during a ground test of an RL-10 engine the nozzle extension was inadvertently lowered after the engine had already begun firing. Apparently it chugged on through the transition as if nothing was wrong. There was some talk of in-flight nozzle extension deployment as a way to boost first stage performance on future rockets but I don't think it was developed far enough to be tested.

[@CyberiusT]

I had never seen that ice formation before. That is nuts. My brain understands why it happens, but that sure isn't something I would ever have thought of.

[@ipudisciple]

5:00 I was wondering how specific impulse could be measured in seconds. I mean, it's the time for what exactly? So I looked it up and decided to share. As far as I can tell, if you were to let the propellant free fall in a vacuum under earth gravity for that amount of time, then it reaches some speed, and that's the exhaust speed we're talking about. Of course, this is useful because the momentum of the propellant gets transferred (negatively) to the rocket.

[@scottmanley]

The other way to think about it is if you multiply the acceleration of earth’s gravity by the specific impulse in seconds you get velocity. And this works regardless of whether you use meters per second of feet per second.

[@Kieselmeister]

specific impulse = (impulse per unit weight-on-Earth of propellant) Calculated via -> Thrust (mass*distance/seconds^2)= gravity(distance/second^2) * ISP(seconds) * Fuel consumption rate (mass/second). Thus Isp in seconds = the number of seconds a rocket engine can generate thrust from a weight of fuel equal to the thrust of the engine.

[@RappinPicard]

There's an RL-10B-2 as part of a Delta III upper stage and fairing that's on display next to the 5 in Santa Ana that I drive past every day.

[@positronundervolt4799]

I like ULAs self immolation method of getting to space.

[@thomascharlton8545]

Thanks Scott, Great content!

[@_tyrannus]

I must say that without the RL-10 variants, KSP with Realism Overhaul would be much more complicated in terms of 2nd stage design.

[@gizmothewytchdoktor1049]

the con trail reminds me of an umbilical cord. thanks rocketcam...i will never look at one of these in quite the same way again! :-)

[@waedi73]

Wow ! Sooo crazy to see it ! Ice forming on a rocket booster bell ! This video is outstanding interesting ! Thank you very much ! and the mün is bloody exciting love

[@brocktechnology]

Those ball screws seem a slightly excessive solution for a single use actuator. Also, those icicles are mind blowing.

[@erictaylor5462]

That is wild to see ice on a rocket engine like that.

[@ryccoh]

Been waiting for this.

[@adamantium1983]

Love the ice... looks unreal

[@alexlandherr]

Maybe a detailed video on rocket engineering cameras perhaps? I would love to see those explained in great detail by you.

[@AlphaSquadZero]

I want to stick something into that exhaust stream.

[@tommyboy054]

Wow, just wow.

[@j_sum1]

Looks like something between a dalek and a steampunk petticoat.

[@bernardolozano7429]

Great vid

[@avejst]

Thanks for sharing this😀👍

[@ig2d]

That thumbnail looks like some kind of haute couture ball gown

[@quoniam426]

Now ask girls to coseplay as RL10 exhausts !

[@davidmoore1253]

The thumbnail looks like an unmasked dalek.

[@williamhedegaardlangvad2630]

Did the delta IV from Orion EFT-1 not carry a rocket cam?

[@gordonrichardson2972]

There is a lot of information into the video, though no mention of the fact that the RL10 was designed to be man rated, but only used on Saturn 1 for Apollo boiler-plate test launches. The initial Saturn-IV proposal would have used 6 RL10 engines, but the revised S-IVB design used a single J-2 engine. The RL10 engine never made it into the final Apollo moon landing designs, though it did inspire the development of the J-2 and F-1 engines.

[@Strike_Raid]

There isn't much in common between the RL-10, J-2 and F-1 other than when they were developed.

[@alexsiemers7898]

I want to know how an extendable nozzle could work for the Raptor on the BFR. In particular, it could be used in a retracted state for an atmospheric (much smaller) nozzle. Plus, the LCH4 fuel means that the regenerative cooling wouldn’t be as necessary due to the lower temperatures.

[@stephenirwin2761]

Great video!

[@AndrewScott83815]

Hey Scott! I would really love to see a video about how rocket engines are vacuum tested on the ground. Can they test upper stage solid boosters in a vacuum at sea level? What type of equipment is used to sustain a vacuum for testing? Anyway! Great vid!

[@Clap_My_Dog]

That's a beast of a rocket

[@freesaxon6835]

Another winner video

[@hydrolox3953]

Im Scott Manley, expand safe!

[@erfquake1]

Hey Scott, idea for a show: the old Russian NK-33 (?) engine; revolutionary closed system, much better performance, had a bad run with the N-1, put in storage, rediscovered by the West as "sliced bread 2.0", cleaned up, renamed AJ-26, had a bad run with Antares, and now what? Was it finally tossed as a concept, or are there versions still kicking around? What's your take on that evolutionary line of engine design?

[@notmadeofpeople4935]

3:10 The RL10 looks like a dalek in this picture.

[@WonTonChickon]

this is cool

[@erictaylor5462]

I grew up in California, and I can tell, that is no California accent you sport there, Scott.

[@scottmanley]

It's not.

[@IvorMektin1701]

It's a very small motor too, the power head will fit on a desk.

[@joe_mckirdy]

Fun facts: RL-10C-1 -> Atlas RL-10C-2 -> Delta IV RL-10C-3 -> SLS RL-10C-5 -> Omega RL-10C-X -> 3d printed

[@technicalsupport6016]

evening from uk Scott

[@jidgeanimations6866]

Lovely fireball

[@memespeech]

4:55 the stats seem to be in favor of the A-4-2 and B-2, unless the C-1 is cheaper or more reliable, but that's not in the stats..

[@UpLateGeek]

From the thumbnail it looked like you were talking about Daleks!

[@DouglasJohann]

So, the second stage engine don't fire before the nozzle is fully extended, that has to cost a bit of performance (like not firing it right away after stage sep.). I'm sure the overall benefit must make it worth it but just thinking.

[@AcydDrop]

Thank you for the video. Scott, quick question for you, if you have a second. Do you still play Eve Online? I know you were active at one point just curious if you still are.

[@baarni]

Why does there appear to be a bunch of frames missing from the footage at the point of booster separation? It doesn't appear to be a signal issue as the cut is very clean when you look at it frame by frame

[@TheEvilmooseofdoom]

There are dropped frames in several spots not just there.

[@toddjohnson5692]

I thought they had added more pre-launch hydrogen burn off capability to reduce the size of the flame that turns the orange covering black on launch. But this one looked like the old style. Or was that planned for later? Just wondering if they had tried to add the flame reduction system and that had affected the previous launch attempt and so they removed it.

[@JackieWelles]

I wonder does ULA has any plans to launch any reusable rocket like Falcon 9 or upcoming New Glenn rocket? Or is their plan to reduce the cost as much as possible and continue flying in the old way ? awesome video as always btw! 😁

[@kristenburnout1]

They have a method under development called "Smart Reuse" which means dropping off the engine section (which will also include avionics and other expensive stuff) and recover them by a parachute /ballute and grab them with a helicopter (Similar to the way they used to recover film canisters from spy satelites). Sounds crazy, but they think it will work. It will supposedly save 70% of the costs of the first stage without sacrificing much performance, as they don't need to reserve fuel for landing.

[@rdfox76]

@@kristenburnout1 Never sounded crazy to me. It's a logical extension of the stage-and-a-half technology used on the original Atlas to jettison the booster engines, and something that Boeing had proposed for a second order of Saturn Vs to reduce the cost, a stage-and-a-half first stage where the four outboard engines on the first stage would be jettisoned and recovered by parachute for reuse, with the center engine being a sustainer that would be expended along with the stage. It's simple, but that's what makes it so smart; rather than attempt to recover the entire stage like SpaceX, with the attendant payload hit, you recover the expensive bits and replace the cheap part (let's face it, the tanks cost next to nothing to build) instead. There's a place for both--SpaceX's theory of recovering the whole stage allows for rapid reuse, but this is akin to the use of drop tanks on aircraft; it gains *most* of the advantages, at a minor cost in replacing the expended tanks that you jettison. (After all, fuel tank sections are something well-suited to mass production, so they could easily have a stockpile of them ready for having recovered power sections mounted for use.)

[@geertwilders3161]

Nice video

[@Yaivenov]

What would be the specific impulse for an RL10 and its tidy expander cycle switched over to the unholy mixture of liquid fluorine and liquid hydrogen?

[@karstenschuhmann8334]

Dear Scott, i have one question regarding the Atlas HLV and Delta 4 Heavy. Wouldn't it be more useful to combine one delta central stage with two Atlas booster stage. This would combine the higher thrust of the Atlas at the start with the higher specific impulse of the Delta later in flight.

[@tanksandturtles1131]

Cool

[@bradallen1832]

"Landing on the Mun"

[@giglefreakz]

Question: On the animation shown by ULA, you can see the engine of the main booster stage is without it's white fairing when it shows stage seperation. Does this jettison somewhere in flight?

[@shanent5793]

Boiling the hydrogen seems like a really bad idea, the heat capacites are unpredictable, and the resulting gas/liquid mixture can't be good for the turbine. Boiling also limits the chamber pressure to no more than 200 psi so it's unlikely that it would reach the quoted performance. The pressures must have been much higher to allow the supercritical fuel to smoothly expand through the cooling jacket and turbine, as the cycle's name suggests

[@eannamcnamara9338]

Aorojet rocketdyne's KSP couldn't run so they made the engine out of copper to lower the part count by 90%. Now it kinda runs correctly.

[@RealityIsTheNow]

lol they've been making excellent rocket engines for over 50 years. The RL-10 is one of the greatest engines of all time...it doesn't "kinda run correctly". lol

[@eannamcnamara9338]

@@RealityIsTheNow sorry i accidentally removed KSP

[@mauroabidalcarrer4083]

nice new outro

[@Sciolist]

5:03 and OMEGA. Curious why it was said like that.

[@bartk07]

Hi! As this launch is discussed, did you see stage 1 engine flame instabilities in the first tens of seconds? Where are they come from?

[@Confuseddave]

With the nozzle extender, shown at the start of the video, does it link up the plumbing to the brazed pipes, or is it just a passive shell?

[@donjones4719]

I can't imagine how that would work, practically and reliably. The F9 upper stage Merlin has the same actively cooled plumbing (but 3D printed!) bell as the lower stage, but with the big bell extension bolted on. That has no plumbing/cooling. The gasses are expanded/diffuse enough. Don't recall what it's made of.

[@scottmanley]

It’s a passive shell.