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

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

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

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

Icicles on a rocket nozzle? Mind boggled!

Loved that "omegA" pronunciation.

I just wanted to say Scott....I had ZERO interest in space about three years ago. However, I did like KZfaq. 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!

At about the 1.00 mark, you can see the rocket exhaust trail back down to the lower atmosphere. I love this ; it gives perspective to the ascent! Smiles

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.

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.

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

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.

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.

@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.

I interned with Rocketdyne and my grandpa retired from there so it’s always great to see you talking about them and their engines :)

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.

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

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.

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

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

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

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.

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.

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

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!

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!

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

As always, great video. Just a tiny correction: the C-C composite nozzle extension of the RL-10 is not ablatively cooled, it's radiatively (and sometimes film) cooled. You are probably mistaking it with the carbon composite extension of the other delta engine, the RS-68

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.

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!

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

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

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

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.

I'd love to hear you talk about the venerable AJ-10 that seems to be on every rocket mankind has ever built (vanguard, thor, delta, apollo, space shuttle, titan, and atlas.)

Always good to see another video. Outro music?

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

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.

That nozzle extension is pure genius!

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.

Really neat engineering, thanks.

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

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

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 :)

It is amazing to see those icicles on the nozzle!

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.

Love the videos on rocket engines, keep em coming!

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

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! :-)

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.

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

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

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

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

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.

Excellent video

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

I like ULAs self immolation method of getting to space.

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

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

Thanks Scott, Great content!

Looks like something between a dalek and a steampunk petticoat.

I want to stick something into that exhaust stream.

Rocket engine icicles are awesome!

Been waiting for this.

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.

Love the ice... looks unreal

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

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

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

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

Wow, just wow.

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.

The thumbnail looks like an unmasked dalek.

Thanks for sharing this😀👍

That thumbnail looks like some kind of haute couture ball gown

Another winner video

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

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!

I have a question that is bothering me that I know you can answer. As an A&P mechanic I understand the theory of the fuel control, throttling, and the Brayton cycle of a jet engine. My question is this: 1.what is the stoichiometric of a rocket engine, 2. how do you throttle a liquid rocket engine, it has no carb or fuel injectors, 3. how do you start engines with no ignitor/spark device, 3. Is it a self sustaining cycle? (i.e. jet engine)? TX! I will be waiting for your answer!

Great video!

Im Scott Manley, expand safe!

Great vid

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..

That's a beast of a rocket

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?

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

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

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?

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.

Lovely fireball

We will know we are truly in the space age when Aldi and Lidl start selling tickets to the moon. Maybe not. lol

this is cool

Nice video

Inverse Baked Alaska? Ice on the outside, baked stuff on the inside.

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

Ice forming on the edge of an engine bell.. ya I remember that video, pretty crazy, and cool, (sorry). Also, wasn't it you that talked about the very severe thermal gradients in engine bell structures, and the engineering challenges involved? Having ice form on the edge of the bell , maybe not such a big deal. What are the chances of ice forming up inside under certain conditions? If it does, might pose a bit of a concern with smooth flow? I know the engineers included a way to control the cooling on the RS-25 bells for the shuttle, based on the throttle setting. Maybe something similar? Regards!

evening from uk Scott

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.

Glad the Delta Heavy launched without problems. I tried three times to watch it live from the beach, but scrubbed. Of course it launches when I can't watch it live, lol. I'm also becoming concerned with SpaceX. Perhaps I'm being paranoid for the company, but it seems the unfair competition it faces might be impacting its progress.