The Engines That Came In From The Cold - And how The NK-33/RD-180 Came To The USA

[@robjones1328]

the re-burning system and syncing up 30 separate rocket engines is so impressive, especially for the times and tech they had to work with

[@jamallabarge2665]

The tough part would be managing failures. If a motor on one side fails then they need to rebalance the stack so that it flies correctly. One could shut off a motor or gimbal the motors so that the resulting thrust vector drives the stack where it needs to go. There were analog controls in those days which were very good and very effective. The tough part would be polishing them, getting them to prevent problems and to respond to problems. The problem with analog controls is parts tolerance. You have to adjust to overcome it. It's tough. Today we use digital controls. Digital controls bring the feedbacks into software, where it is more easily managed and modeled.

[@jamallabarge2665]

The part that confuses me is why the Soviet engineers wasted time and money on a super heavy lift vehicle. A more sensible solution would be to send up multiple payloads, rendevous them in orbit, then send the resulting married ship to the Moon. Energia could put 100,000 pounds into orbit. It was composed of multiple strap on stages of something like a Proton rocket. The Saturn Five third stage weighed 271,000 pounds. I am not sure about the total mass of the mission, assume that they're the same. That's 540,000 pounds. About five of these vehicles. Make seven in case of failure. Both sides had orbital rendezvous figured out by the mid 1960s. Duplicating the US Command Module with the Soyuz manned capsule and the Lunar module, plus a "tug" to get them out of orbit and back to Earth was not an insurmountable problem. This idea of huge heavy lift vehicles to get the whole mission up in one big mass simplifies planning but makes the engineering a lot tougher. I do not understand why the Soviets wasted time and money on the N1. They got the Energia to work just fine.

[@thesquirrel914]

20 years later, I have the pleasure of working with the man @ 39.33 Scott Conelly. He still works with energomash and Pratt & Whitney today. He told me "I had no idea what I was getting myself into, but it's been a hell a ride."

[@ronjon7942]

The technology changes and advancements during the Cold War make my head spin. It’s hard for me to comprehend this was all manageable; it must’ve been a heady time to be an engineer of ANY field. Thousands and thousands of years of slow, steady progress, then BLAM! To the moon, Alice.

[@adrianniemiec8669]

I remember watching a documentary about these engines about 15 years ago. The US bought several of them basically for pennies for that kind of technology which was still being perfected at that time. The unique feature was exhaust re circulation that made the engine about 30% more fuel efficient , a ginormous difference.

[@jamallabarge2665]

The turbine output was recycled back into the motor chamber to help with thrust. The key was Soviet metallurgy. They worked on a problem to make the metal durable enough to hande an oxidizing atmosphere.

[@geenerheimer9266]

🤔 yeah totally didn't pick all that up from the documentary we just watched. Thanks Capt obvious

[@warp65]

When the Kremlin says, "scrap everything" and you hide 60 engines, that must have taken guts.

[@billrandell4641]

Anything for a piss fight..right??

[@olegbauer3139]

@@djbeezy Perfectly. Suppose the Americans created engines that could send a rocket to the moon. Then, in this case, one small question arises: why the States still can not resume production of their own "superior to Russia" engines and how a beggar in pissed pants begs Russia to sell them their "backward shit" ? You're a bunch of fucking clowns and magicians. And all would be nothing , but your bearded jokes about the fact that "Russian you have stolen everything" and how much space technology USA surpass Russian technology so tired of everyone that everyone wants to puke . You are so predictable in your stupidity and bragging that you can no longer be funny and now only bring a sad smile to people.

[@petej8556]

People who don't know why I'm still waiting for my money back in my life and I don't have to understand what you want? I have to go to the gym with the same thing over and over again and I don't think it's a little too late for the rest of my friends and I love it when people say that you have no idea what I want a new phone and I have to go to bed and watch the game with the new version and now I'm just going through a series of events and it is not a good time to get my money. I need my money. I need my money.

[@vsvnrg3263]

@@djbeezy ,i think what this person might be getting at is that he thinks the us government blew up the world trade centre. nutcase.

[@glenturney4750]

@albert bahoogadin: We BOTH have superior technologies. BUT, we could quit with the arguing and act like adults and work together to further space explorations. As far as dropping buildings on ourselves, THAT was Arabs who are buddies with the BUSH'S who used that to further THEIR causes. WE didn't support that B.S, but they'll have to answer to God for that. I STILL think America and Russia can work together in peace and quit the squabbling.

[@anthonyellsmore4532]

Honest documentaries...how refreshing

[@zapszapper9105]

You have to admire the Russians, they never had the economic resources anything like that of the Americans.

[@alexv3357]

Their space program was run more like a collection of private companies too, since instead of being a single program, each individual project had to fight for patronage and resources. Tight budgets and competition helped with the need for rapid iteration.

[@tekmekster]

@@alexv3357 also Military was functioning this way. I wonder why they "believed" that Consumer sector had no place for competition?

[@alexv3357]

Because a strong civilian industry doesn't build warplanes and missiles to defeat the capitalists

[@chrisclarke3965]

Excuses dont win races or wars.

[@VG_164]

@@chrisclarke3965 They won the space race though. The American just moved the goalpost until they could win something.

[@billroy565]

A few years ago when I first learned that the US was using Russian rocket engines, I wondered why, and why we're we not using our own. Now I know. I bet there are other things that they could show us. We who are all too often inflated with too much pride.

[@PacoOtis]

Roger that! Agree completely. In science and technology there is no room for pride but only for good ideas and procedures.

[@jordan71323]

very well put.

[@WheelsRCool]

The "American way," to a good degree IMO, is to adopt the ideas and techniques of other cultures and integrate them into our own. That is what makes us so strong, i.e. our multicultural society and immigration over the years. If the Russians created an ultimately superior design, we should adopt it and learn from it and work to improve upon it.However, I would prefer we copy and build our own versions of it, not use Russian versions.

[@CommonCentsRob]

Let's not forget that US rocket technology came from Germany and for the most part so did the Russian's.

[@TheWilferch]

The running joke of the time between US and Russia was..... "our German engineers are better than your German engineers" ( or the other implication of simply being better funded).

[@theoracle6005]

These engines were engineered in the ground floor and were hand built and the net result is the testament to their reliability and power. Finest engineering that we must applaud.

[@NegativeRoot]

How relevant this old documentary has just become...

[@alexpennanen913]

Negative Root More relevant than anyone around here willing to admit ....Koshey/Кощей

[@z33r0now3]

@@alexpennanen913 can you tell me why?

[@patrickmclaughlin61]

Also interested.

[@mirasolovklose3888]

@@z33r0now3 I was curious too so I searched and the closest relation I can find in 2014 (when the comment was made) was the US sanction on import of Russian tech and SpaceX's lawsuit challenging that ban. As the US DOD concluded that it would take 5 years and $1 Billion to get RD-180 manufacturing in US.

[@BladerDark1]

Если бы люди перестали бы тратить силы на войны - мы бы уже летали к звёздам. If people would stop wasting energy on wars - we would already fly to the stars.

[@catalintimofti1117]

I mean not to be the one who likes wars But the space race was basicaly a direct result of WW2 german rocket program While devastating wars bring us eras of great technological progress

[@EburdeyGordei4]

Нихера бы мы не летали. Развитие человечества идет через страх уничтожения с древнейших времен. Гонка вооружений развивает прогресс. Без нее ты будешь сидеть и чесать жопу. Летать к звездам ты будешь только тогда, когда начнется гонка за захват планет солнечной системы и будут созданы двигатели на новый физических принципах после того, когда будут созданы новые виды вооружений.

[@BobSmith-dk8nw]

@@EburdeyGordei4 Yeah. That's about it. Without the Cold War - we still wouldn't have gone to the Moon. .

[@aur485]

Что-бы не было войн США не должно существовать.

[@Inception1338]

​@@catalintimofti1117War is a business and nothing else. They happen because everybody wants it. Profit, profit and profit.

[@wetdownunder]

Have to say they are 40+ year old rockets. Cutting edge technology back in the 70's.

[@dylanmccallister6739]

Actually they are cutting edge to this day, only a few rockets have a higher specific impulse and efficiency. This rocket was the first engine of any kind to have a near 100% efficient combustion cycle, it creates chemically pure water with very little C0.

[@Giganfan2k1]

@@dylanmccallister6739 was going to say this. It is pretty damn cutting edge today. Probem now is they are not reliable enough.

[@robjones1328]

@@dylanmccallister6739 the only thing that can produce only water as a byproduct of combustion is hydrogen burning in the presence of oxygen, H+O2=H20, H20 is water

[@timecomments]

@@Giganfan2k1 What is unreliable is human error.

[@stephenpage-murray7226]

U.S has purchased 122 RD-180 engines, most used in successful launches. 86 Atlas III and V launch’s used the RD-180.

[@kennethschultz6465]

THE RAPTOR IS A NK33 / RD180 BUILD IN 2023 MATERIALS NOTHING NEW AT ALL

[@thesnowspeaksfinnish]

​@@kennethschultz6465hey, could you please give some sources on that? That's very interesting to me

[@kennethschultz6465]

@@thesnowspeaksfinnish you need to look at the blueprints.. on both enigens.. both cloased loop systems non of them use preburners.. same same and only the russians culd make the cloased loop to work .. no american enigen used cloased loop too powerfull ... so by comparesion 1:1 they are identic.. and bending a tube anoter way ain´t making any difrence if it still performe same task .. are you finish... no i am danish

[@jessemilstead810]

A great documentary and I believe it also proves that if the soviets weren’t in such a rush then they would have gotten to the moon as well with their N1

[@shawnmelancon5483]

47:56 I love the way the chief gestures " save your clapping, we're not out of the woods yet"

[@timecomments]

It caught someone else's attention. The success of the metal children of the people.

[@vincentrusso4332]

That's an awesome documentary, definitely worth the watch. Together everyone accomplishes more!

[@scottcarlon6318]

Unless it’s NASA.

[@billyhack9673]

These engines produced 400 to 450 seconds of specific impulse, about two or three times better than ours. They used closed loop cycle, something US engineers thought was impossible. These engines were a triumph for the proletariat.

[@peterselie1779]

Nah, they got 311s @ sl to 338 @ vac. Afaik still the highest specific impusle for a hydrocarbon fueled engine that has ever been used. RS-25 got up to 452 s, but that's an LH2/LOX engine.

[@BobSmith-dk8nw]

If it had been up to the "Proletariat" under the Guidance of The Party - they would have all been destroyed. .

[@xXxTeenSplayer]

This video is super old... The raptor is far superior currently, and the raptor 2 is even better!.

[@lordlol3787]

​@@xXxTeenSplayerAnd what do you mean by this? How are the new Raptors any better than these 50+ year old rocket engines? So-so pride when it is known that the Raptors were created with these engines in mind.

[@ninjasiren]

btw both the US and the Russians did closed cycle Just that the US went Fuel-rich Closed-cycle with the RS-25 Space Shuttle Main Engines, LH2/LOX While the Russians went Oxygen-rich Closed-cycle, using RP1/Kerosene and LOX Russians do have Fuel-rich Closed-cycle, but its only a vaccum-optimized 3rd stage engine and also use LH2/LOX Tbh most of these engines are old already, and the current tech for rocket engines uses Full-flow staged combustion (where both the fuel and the oxidizer is Closed-cycle) Just like the the SpaceX Raptor (Methane/LOX)

[@kiwidiesel]

These Russian legends have managed to set the bar so high it comes with a 20 year lead. That's an achievement there. Bravo!

[@kennethschultz6465]

yes and this is WHAT SPACE X JUST COPY nobody do CREDIT THE RUSSIAN CIENTIST but well THIS IS A RAPOTOR BUILD WITH 2023 MATERIALS NOTHING NEW BUT MATERIALS.. ..

[@foobarmaximus3506]

lol

[@TheNobbynoonar]

Back in the days when TV was worth watching.

[@keithpenny1119]

yeah! Equinox and Horizon were great... now it's all shite gameshows and girly stuff, they're taking over I tell ya!

[@TheNobbynoonar]

@@keithpenny1119 Even though there were only 4 TV channels in the UK, the output was of much higher quality. Along with the science and technology programmes, there was light entertainment, historical drama's, comedies, ivestigive documentaries as well as high quality news and current affairs programmes. All seem to have gone now. Radio's gone the same way as well. A classic case of 'less is more'

[@NOOne-im5vg]

The Russians had and have some extremely clever people. Perseverance and hard work puts the US in the shade.

[@homers5699]

Sergej Koroljov yes 1 man that was smarter than the whole staf of nasa ironic

[@anglosaxonbreed]

You did not think all Russians where thick. Russians are the same as us. The have there fair share off dummies but the also got lot smart people too. USA has the money but some times money just not enough...

[@meepk633]

They could have named this doc. "Several People Surprised by the Fallibility of American Exceptionalism."

[@brentwilliams7941]

Or cosmodrome, its on Netflix.

[@djbeezy]

We are exceptional. We make some mistakes but we are far superior to everyone else.

[@VerissimusAurelius]

well said.

[@thethirdman225]

wash beezy Only the truly naive or racist/dominionists are capable of believing that.

[@markolukic6376]

Americans are exceptional at going to the Moon

[@keithpenny1119]

thanks for uploading this... it's one of my favourites I remember from the 90's!

[@geenerheimer9266]

Beautiful display of human technological capabilities

[@boxlid214]

Russians built some badass engines, americans built some badass nozzles that solved the turbulence problem on very large engines. Just think what both could've done together. Hopefully people get past the politics at some point.

[@charlesburgoyne-probyn6044]

Yes it was obvious when you wrote things were going downhill with Russia but for us all with the cold war dynamic peacefully ending and the honeymoon then steady then poor and now war. Communism Vs capitalism was a smokescreen it's just a powerplay actually

[@richardpase2066]

The Space Shuttle uses a closed cycle developed by American engineers without Russian input! The RD-180 was first evaluated by Pratt & Whitney engineers in Moscow in1991. I was one of the on-site engineering team.

[@kennethschultz6465]

true or false.. the new RAPTOR is a NK33 / RD180 on steorides build in 2023 materials.. nothing less :: greetings from Denmark .. Electro Engineer + Marine Engineer

[@teicangigi559]

Da, dar acele motoare erau cu 20 ani mai vechi. Voi ați luat RD180 și l-ați pus pe rachetele voastre.

[@ninjasiren]

Yes, the SSME (Space Shuttle Main Engines) RS-25 are closed cycle, but Fuel-rich While the Soviets went on the other side, rather than Fuel-rich They went Oxygen/Oxidizer-rich, which does need proper metal alloys to withstand the crazy high temps and other considerations with dealing of hot oxygen laden gas In the end though, both did good on their own While US did the Closed-cycle, Fuel-rich by using Liquid Hydrogen as fuel (which is much safer and more efficient, and will not cause blockages and soot in the engine.) The Russians did the Oxygen-rich Closed cycle because they used a much cheaper and abit more common fuel source, RP1/Kerosene If we use Fuel-rich closed-cycle with RP1/Kerosene, the engine will get plugged and may cause the engine to fail (because of the soot blocking the piping inside the engine, after the fuel pre-burner) At least now we can do a full-flow staged combustion, where we can both close the cycle on both the Oxidizer and the fuel, SpaceX Raptor Engine That uses Methane and LO2

[@xJownage]

@@kennethschultz6465 The raptor has almost nothing in common with the NK-33 or RD-180. The raptor uses full-flow staged combustion, which shares very little similarity in terms of challenges with oxygen rich staged combustion.

[@xJownage]

@@ninjasiren An RP-1 or any engine using a hydrocarbon-based fuel is still considered impossible to turn into a full-flow engine because of the sooting problem you mentioned.

[@Mega6501]

I thought it was ironic at 37:05 it was stated that US intercontinental ballistic missile pointed at Russia is now geared with Russian NK 33 closed cycle engine.

[@mav01]

That's called self destruction

[@StreuB1]

They really are exceptional motors. It shows what collaboration between the superpowers can yield. The melding of Russian and American aerospace groups really was a great marriage. Hopefully we can continue that marriage and grow together.

[@paulie-g]

Cooperation on space has so far survived all of the tensions, but this can not be expected to continue. So far, someone in the US would've needed to take an affirmative decision to stop cooperating while they could simply continue without much negative PR. Once there is an inflection point, like making a decision on the joint development of the next space station, I simply can't see how any US president/congress can get that through after all the Russophobic hysteria they've whipped up over the last decade. This is sad and unfortunate.

[@BobSmith-dk8nw]

@@paulie-g You make it sound like it's all our fault - and it isn't. If you look at some of the things the Russians have done - there are good solid reasons for our attitude. Just because the Russians have their side of the story - does not mean our side is invalid. .

[@JesperJames]

This aged well

[@StreuB1]

@@JesperJames LOL Tell me about it. SLAVA UKRAINI!!!!

[@jamesmandahl444]

@Jesper James there are still two sides. What was Nuland and Kerry doing at the maidan protests? The leaked call? The Wolfowitz doctrine of containment and ultimately regime change of Russia and its balkanization. Has the left gone nuts? It's like all notions of nation building and "spreading democracy " were forgotten once neocons were clever enough to wave rainbow flags.

[@alexduke5402]

This comments section is VICIOUS holy shit why is it impossible to think that another country might have a something better than your country imagine if we didn't have to spend trillions on war and military. How much further would our society as a whole be? Competition is what drives people to strive to be better but what if we came together too compare notes after. I was promised flying cars and a base on Mars when I was younger by 2000 but we're so worried about blowing each other up it's 2019 and we were robbed of our glorious future....

[@MrTaxiRob]

Check out what India is accomplishing on a relatively small budget, they have spacecraft orbiting Mars right now

[@adamkerman475]

@@MrTaxiRob really? I thought the closest they got to that was that lunar lander that’s impressive!

[@PacoOtis]

Excellent! Have viewed this many times and am exhilarated by it.

[@jackskillet]

anyone here no what a clean burning tip of a cetylene touch looks like...the back of those 30 rockets all burning at once...it is a beautiful flame

[@wagonroller3019]

Soviet manufacturing engineers take over the design of the rocket engine, because they look at the initial drawing and say, this is just a picture of what they think they might want.

[@OrangeDurito]

True. Sometimes those at the production line may have the better idea on how to improve the product even more.

[@toasterhothead3312]

I went to the comment section to find someone help me understand why they do it that way, thanks for making it ez to understand it,

[@leightonmacmillan3396]

So how do you like the SLS now Joe?

[@glenturney4750]

See, THIS is Cool! Two countries who CAN work together as one to create something GOOD for the benefit of mankind for space exploration. We need MORE of these kinds of projects to work together, instead of fighting each other, we should work together and get along. I hope that we can shoot for further space exploration together. ☺

[@adamkerman475]

Yeah I would keep expectations lower seeing how politics are so efficient at killing good projects

[@charlesburgoyne-probyn6044]

Ah wishful thinking, the optimism when you wrote was fading then there is too much hatred now just like the 1940s so it will have to burn itself out and the anger will exhaust and a new peace will follow

[@johnashton4086]

I met one of Korolev's proteges in Moscow in 1996. He was typical of very many Russian engineers and theoreticians in being tremendously talented. It was hard for them to be encased in a system that suppressed and distorted the economic c benefit that should have resulted from their great work. Russians are not be underestimated.

[@charlesburgoyne-probyn6044]

Indeed, with the war in Ukraine have been inept in many ways although wily in others

[@rodjarrow6575]

@@charlesburgoyne-probyn6044 Despite the fact that the US and the UK started the war in Ukraine in February 2014. Russia joined only as early as February 2022

[@charlesburgoyne-probyn6044]

@@rodjarrow6575 the hidden hand which drives these things both the USA and UK have issues with their own cohesiveness

[@rodjarrow6575]

@@charlesburgoyne-probyn6044 And, nevertheless, US Senator Lindsey Graham, who recently visited Kiev, called this war in Ukraine the best investment for the United States! Nothing new! Because War I and War II were the best investment for Business of the USA and the UK! Nothing new! The ancient Roman rule of finding the main culprit of the murder says: "Look who benefits from it!

[@charlesburgoyne-probyn6044]

@@rodjarrow6575 yes the candour is remarkable it proves the whole communist thing was a distraction ultimately more of a power play as the relationship is worse than the cold war. Perhaps be careful for what you wish for and when the god's wish to destroy you first they answer your prayers, pride before disaster arrogance before a fall Israel currently is a case in point although certainly not in particular jeopardy a case of how the strong may not be as strong as they may appear. Russia too in 2021 seemed to be in a stronger position but has subsequently lost its mantle 🫡

[@rubblejohnstone4460]

If only our leaders could learn from this, what could mankind achieve if we worked together.

[@VerissimusAurelius]

exactly what I was thinking. We could feed the world...eliminate poverty....everyone having a good life...I sound like a commie?? :O LOL

[@SquillyMon]

We could achieve much... albeit with smaller bank accounts. Cooperation isnt good for some persons bottom line...somebody has to be a dickhead capitalist at all times..over and over again.

[@mjlivie]

great doc i can still remember equinox from when i was young

[@ILOVEGERMANTECHNO]

When TV was worth watching. Now all we get is Celebrity Jungle FFS.

[@bad71hd]

Damn. 60 engines! All gold & Platinum and silver! Each engine probably worth over 10 million or more

[@Arctific]

My sense is that winning is not made less significant just because significant competition really exists. The achievement of the Russian engineers should be noted. There is a lot of sweat, ingenuity, determination and persistence there. Would the USA accept both risk and age of a design with the same nerve? Would Aerojet normally plan for 14 test runs? Would we let JPL have that kind of acceptable risk for its learning curve? Would the US Congress really let the US Air Force dare at that level?

[@jwenting]

yup, the Soviets had the advantage of near unlimited funds, no risk of being sued for billions by armies of lawyers if someone stubbed his toes, and armies of workers motivated by the very real threat of being sent to the Siberian logging camps and lead mines as slave labour if they failed to do as told. I doubt the USA would want that kind of system to drive innovation.

[@putinslittlehacker4793]

@@jwenting didnt the documetary say there work was underfunded?

[@rodjarrow6575]

​@@jwenting You have a distorted idea of the Soviet space production of rockets and rocket engines during the space race! Alas, US anti-Soviet propaganda has turned you into patients of a madhouse, judging by your references to Siberian logging camps and lead mines as slave labour if they failed to do as told...

[@budiman-kr5ug]

​@@jwentingi dont think so the reason is because there is a thread. No one can think genius under a pressure. It purely because it become their passion

[@charlesbritzman501]

Physics is physics. Metallurgy is metallurgy. We’re all working out of the same bucket of Physical Law. Politics adds drama that only underscores the camaraderie of scientists. We’ve got a Solar system and a Milky Way to explore. It’s us vs Out There, together.

[@khadijagwen]

I wish that the West and Russia would cooperate. Hopefully that will come.

[@vikruss]

+Khadijah Brown o yes,... man it maybe will happen but only, if ALL american, british and some european politicians will somehow, "disappear" or change their mind about "changing" others into that ugly image of "westernise democratic-moron" of their own, with their greedy ideas about how to control the world and let other nations also to develop and maybe help them to do so without politicizing and demanding "crap" that they themselves never care to follow... and start treat others the way they want to be treated, then other nations like Russia maybe will start to trust Americans again.

[@khadijagwen]

vikruss Do not be surprised that I do not argue with you. As a student of History, I see that the West has done some selfish things. It makes me feel shame.

[@usfootman]

+Khadijah Brown They are cooperating. Its all politicians. Thats who stoping us. Science, business, art all those cooperating. Crooked politicians thats what the problem is.

[@khadijagwen]

usfootman WE agree on this.

[@bassmith448bassist5]

Khadijah Brown yes!!!!!!!

[@rubblejohnstone4460]

When the running engine is already shaking the ground you stand on and the guy says Throttle Up!

[@bad71hd]

What could tell by my 75 million comments here is it this video is absolutely stellar! Seriously! They invented entirely new stainless steel and production to withstand the high pressure and temperature the engine produces! Pneumatic? Check! Electronics? Check! Hydraulics? Check! Low bandwidth VHF? Check! High bandwidth UHF? Check! Elite fuel line pressure check valve? Check! ... lol

[@KirkHermary]

Piss poor video quality... Check!

[@ddieder]

After all these years, I'm fairly amazed at how many similarities there are between the N1 with its 30 NK-15 engines and the SpaceX Super Heavy with its 31 Raptor engines.

[@serkorz3823]

U.S. copies old Soviet Technology, and is impressed by it; Interesting. Here is another old Soviet Technology from the 1960's, the stealth jet. "Stealth - A Russian Invention (English subtitles) part 3" kzbin.info/www/bejne/p3PLqGqaps5rfdU "Petr Ufimtsev and Russian Stealth Technology Aircraft's" kzbin.info/www/bejne/mpqVdmd8ad2sZ6M "Petr Yakovlevich Ufimtsev, Пётр Я́ковлевич Уфи́мцев is a Soviet/Russian physicist and mathematician, is the creator of modern stealth aircraft technology. Also called the father of stealth technology. In the 1960s he began developing stealth technology predicting the reflection of electromagnetic waves from simple two dimensional shapes in Russia. Ufimtsev's work was translated into English, and in the 1970s American Lockheed and Northrop engineers copy this 1960 Russian technology and start a concept of aircraft with reduced radar signatures based in Petr Ufimtsev work. Northrop use Ufimtsev's work in developing the B-2 bomber. American Lockheed and Northrop engineers concluded Petr Ufimtsev work and this Russian technology would be the future of the United States Air Force. The first Stealth aircraft in history was made in 1935 Russia. The Kozlov PS (Prozrachnyy Samolyot) an single AIR-4 was modified by Sergei G. Kozlov to demonstrate his technology of stealth or invisible aircraft for Russian air superiority. Covered with a transparent plastic sheeting and with interior structure and opaque parts painted silver, born the first stealth aircraft in the world. Ufimtsev was inspired in Kozlov concept of complete stealth or invisible technology but Ufimtsev not try an complete stealth or invisible concept as Kozlov, Ufimtsev focus in make a stealth or invisible technology only to radar. Sergei G. Kozlov believed the Russian Stealth technology must be stealth or invisible to everything including to the five sense organs of the human body. Aircraft and projects based in Petr Ufimtsev work and Russian stealth technology: Lockheed F-117 Nighthawk (Stealth attack aircraft) Northrop Grumman B-2 Spirit (Stealth bomber) Lockheed Martin F-22 Raptor (Stealth air superiority fighter) Lockheed Martin F-35 Lightning II (Stealth multirole fighter) Sukhoi OKB Sukhoi PAK FA T-50 (Stealth / Anti-Stealth / air superiority / multirole fighter) Sukhoi OKB and Hindustan Aeronautics Limited Sukhoi/HAL FGFA (Stealth Air superiority fighter) Tupolev OKB, Sukhoi (UAC) Tupolev PAK DA (Stealth supersonic strategic bomber) Russian Aircraft Corporation MiG MiG Skat (Stealth UCAV and A.I bomber) Chengdu Aircraft Industry Group Chengdu J-20 (Russian-Chinese Hybrid Stealth air superiority fighter / multirole combat aircraft)"

[@vandarkholme4745]

The engines actually used pyrotechnic valves, which can only be used once, making them impossible to test beforehand

[@skywayminicabs6292]

an explosive valve ? or a "plug" to keep fluid's separated untill needed

[@boathemian7694]

I knew George. Really interesting guy to have drinks with.

[@peterseinfeld]

A perfect example of being able to substitute a bit of crazy for a bit of intelligence and it actually being ideal .

[@andgate2000]

It’s not technology you want....it’s reliability.

[@timecomments]

What is unreliable is human error.

[@McIlwainMobilitySolutions]

It's funny, I found myself as a kid back in 1992 looking at this Forrest of engines in real life and there is no mention of Mel McIlwain, the person who really was responsible for bringing these engines into the US.

[@dustinandtarynwolfe5540]

Well, you clearly have a story to tell, let's hear it. I'll assume your a relative of this man

[@jerga2002]

So those engines took James Webb telescope to L2 orbit

[@Taketimeout3]

Back in those hopeful days when Russia was friendly. And when documentaries were not dumbed down. British , of course. EQUINOX! Early 90s.

[@DrTWG]

Yep, 'Equinox' was great , as was 'Horizon' on BBC2 - I loved watching them as a kid - even then I could tell they were serious docu's . I think it's the fantastic Barbara Flynn narrating this one .

[@zahrans]

It wasn't Russia who became 'unfriendly', it was the collective west who decided that Russia should be treated as the enemy once more once a certain V. Putin came into office. Reason being he didn't bend over to western DEMANDS like his predecessor.

[@rodjarrow6575]

Russia has always been and remains a friendly country for everyone who loves and respects Russia! Unfortunately, most of the Western politicians are greedy liars who are interested in Russia exclusively as a cheap source of income, which is not acceptable for Russia!

[@patricknintemann924]

33:01 Rocket Engine Face

[@TarlanT]

Space Shuttle was powered by closed cycle engines RS-25. The only difference - RS-25 uses hydrogen. NK-33 uses kerosene.

[@ShadowFalcon]

That's a quite significant difference though. With RP-1 you can't do a fuel rich preburner staged combustion cycle because of all the soot, which necessitates an Oxygen rich preburner, which comes with other difficulties. The Soviets managed to make an alloy that could withstand high temperature, high pressure oxygen for their preburner and turbopump, while the Americans figure that was impossible and went with a fuel rich preburner.

[@adamkerman475]

@@ShadowFalcon you put that very well and didn’t throw around insults so hats off to you.

[@ShadowFalcon]

@@adamkerman475 Oop, sorry. Mixed up replies ;)

[@ShadowFalcon]

@@adamkerman475 Honestly sorry. I was replying to someone else, who were sharing a link to someone who claimed Pi wasn't approx 3.14, and was trying to "debunk" the metric system. Got your comments mixed around :P

[@adamkerman475]

@@ShadowFalcon no need to be sorry everyone makes mistakes and your reply still fits the comment

[@andrewlambert7246]

Aircraft engine designer makes the worlds best semi-cryogenic engine. Incredible! The Russians are terrific designers. They dont rely on super-computers. They use paper and pen.and come up with some super-designs. Its mind-boggling.

[@Leon-Hardt]

The first cosmonaut/astronaut out of earth, the first woman cosmonaut, the first space walk, the fisrt ICBM, the first space station, the first ship orbit around the moon, the first fully oprational probe in venus (95 athmospher pression), the first artificial satelite, the first VTOL plane (Yak-130), the first close-cycle rocket engine, the firts...WTF! Russia Rules!

[@gobodrodiont]

+the first spacecraft on the Moon, the first spacecraft on the Venus, the first spacecraft on the Mars

[@EburdeyGordei4]

+David Rojas The first space station on the orbit

[@polygamous1]

+TheBrodsterboy yes dead right both countries have top technologies and i see no problem with this at all, no one has a monopoly on top technologies both excel at something n this is a fact also both the usa n Russia in their first jet fighters used a RR engine or a variation of it as thr RR jet engine was the best in the world then

[@spearhead787]

+David Rojas They orbited it yes,but they couldn't manage to get a manned space craft off the ground to do the same. That honour goes to Apollo 8 in 1968. Followed as we all know with the first manned moon landing with Apollo 11 in 1969. Followed by 5 more.

[@KB4QAA]

+David Rojas Yes, it's amazing what a totalitarian government can accomplish when it does not have to follow democratic procedures and principles. The Yak-130 is not a VTOL plane, it is a recent trainer/attack model. I don't know what aircraft you had in mind. I think the West pretty well laid the ground work on VTOL/VSTOL in the 50's/60's for any Soviets in that area.

[@mickdunn8423]

GREAT STUFF! A lot of sheer genius on show...by EVERYONE!!1

[@sthompson4049]

this would be like finding a warehouse of Duesenberg modal J chassis'

[@robc3056]

typical equinox doc always very very good the turbo f1 is a seriously good watch .Documentaries for people with an attention span !!

[@fantasticania]

an awesome documentary and what a captivating story... - what happened during this short window of opportunity when Russian and Americans scientists were able to work together... before the old Cold War came back :( what might have been if it didn't ...

[@jamesmandahl444]

What is the Wolfowitz doctrine of containment? The color revolutions? The regime changes of "undemocratic nations"?

[@charlesburgoyne-probyn6044]

What's known as a honeymoon period, a lesson for us all i remember the optimism in the late 80s and 90s . Also as schoolboy in how people were niave to the growing dangers of war in the 1930s and blinded by wishful thinking and for our generation to take note of this so we could spot the signs and beware and yet how many people now are swept up in the hysteria

[@asdfasdf825]

There's something about this story I dont quite get. It says the Americans were unfamiliar with closed cycle engines and that they picked up these RD-180 engines and tested for the first time in 1995, and yet, the SSMEs ARE closed cycle engines and were developed in the late 70s! Am I missing something here??

[@kosmosyche]

They are different types of staged combustion. SSME uses fuel-rich staged combustion cycle, while NK-33 uses oxidizer-rich staged combustion cycle. One is easier to implement, the other is more efficient, but they are two very different technologies.

[@asdfasdf825]

That's right! Forgot about that! Great answer, and thanks!

[@murfleblurg]

Funny emphasis on this, the whole "They were ahead of us in technology" theme. A Russian company had a visionary military/high-tech system that was promised to be a generation ahead, but which failed and failed, and got canceled. In retrospect it turns out that it really was visionary. This isn't a unique story. "Someone came up with a better way of doing it but before the bugs could be ironed out, conditions changed and it was terminated." The unusual thing with this story is that someone came along 20 years later and finished bringing it to market, and they all lived happily ever after. It's the story of the little rocket engine that could, not a lesson of some sort about national virtue and hubris.

[@brokilon800901]

" but which failed and failed, and got canceled" - Umm, what do you mean?

[@psilvakimo]

"They were ahead of us in technology" This is the same crap I have been hearing since the 50's.

[@Megaghost_]

Very interesting. Thanks for sharing!

[@petemoore5104]

Yuri, don't worry, this is very safe.

[@OleDiaBole]

You are breathtakingly original.

[@petej8556]

Well I guess I'll just go back to sleep and wake up at the same time as the most beautiful thing in my room. I have to do that for a while and then you can get the chance of getting my hopes up and I don't have to go back and get my money, I have to get my money, I miss my money, I need my money, I need my money. The fact I can see it in the morning and I'm not sure how much I miss my money. I have to go get my money. You know how much I miss my money? Did you see my money? The best way of saying that it would mean so so much for me is John the coyote saying that he had been in my underwear on the other day and I don't think it's time for that matter, but it would mean the world to me to get my money back.

[@kanishka.b8550]

Superb documentary! Thank you.

[@d2966-m8t]

Amazing human engineering, to think outside of the box, in this case the Russians.

[@quadnine7814]

Cosmodrome, is an amazing documentary on this.

[@j.k.v2050]

Watching this just shows that we and other countries can get along and do things together . It was nice of Russia to share there rocket ideas to the USA .. I think if Russia shared light into the rocket idea I can imagine what more is kept secret .. old technology just proves agin ,well build technology with a bit of hiccups .. from watching this I give credit too the person who took all those rockets and stash them away without being killed .💀💀🚀🚀

[@andyharman3022]

They didn't "share" the engine technology. They were well-paid for it. After the Soviet Union collapsed, the Russians needed hard currency, and their space technology was one of the few things of value that they could do as well or better than the west.

[@jhyland87]

12:15 hmm.. I always thought of the turbines as the "heart" (its what pumps the lox/fuel around)

[@obsoleteprofessor2034]

Ever look at close ups of the injector? Tons of holes at all angles. I met a guy in Yuba City Ca who bought surplus from Aerojet. He had several suitcases (indexes) of drill bits from hair diameter all the way up to your wrist and the Bridgeports to drive them.

[@revolution475]

It's 2019 and I'm watching this documentary. I last watched it in 2016. It never gets old. NPO Energomash has made vast improvements to the RD engine family. It's interesting how the US engineers accept that their technology is inferior. We are just humans and no one can be great at everything. In the scientific environment there is always room to improve. Of course you would definitely worry about your job and retirement, when you need go to Congress and tell them that there's better technology with the competition and it's 20 years old 😬, but more efficient and reliable than what you have invested in for more than a decade. Anyway...😃

[@thepoultrypeople]

so im also guessing they used these rockets in their icbms as well? must be hundreds of them out there....

[@NameNotAlreadyTaken2]

thepoultrypeople No, not at all. RD-180 is a kerosene fueled engine, not suitable for weapons at all.

[@thepoultrypeople]

damn thats a shame, i was sort of hoping that there would be a lot of them out there capable of being reused for satellite launching or whatnot rather than being what they are, just useless wastes of good steel and engineering

[@NameNotAlreadyTaken2]

thepoultrypeople Well the Russians have developed the RD-191, which is basically one-fourth of a RD-170 (one nozzle) that they're using with the Angara rocket family. And they've created a lower-thrust version, the RD-193, which is intended to be a drop-in replacement for the NK-33. It doesn't have the crazy thrust to weight of the NK-33, but it's a lot safer.

[@oliverepsom1566]

+thepoultrypeople No, the vast majority (Possibly all) ICBMs in service today are solid-fuel devices. It is not safe to store Liquid fuel rockets fully fuelled for any length of time, and for an ICBM you need a quick response time. So the first generation of ICBMs used liquid fuel but needed to be fuelled before launch, which was a difficult procedure. Liquid fuel motors are generally used for Civilian launches due to their higher efficiency, but such rockets are fuelled on the pad immediately before launch.

[@rafts02]

when in a near future i have to leave this planet it will be with a russian rocket 🗼very impressed by this docu and what i already though about russian space program is only acknowledged

[@kentslocum]

Clearly Elon Musk hasn't watched this video, since he didn't build flame diversion trenches for his Starship. The Russians, on the other hand, knew the importance of keeping the flame and debris away from the engines. Edit: I am very much impressed that the pressurized-water sprinkler actually works!

[@vinecewanza8268]

He has watched it, he even refers to this exact documentary in one of his videos with the everyday astronaut

[@vinecewanza8268]

In fact Elin musk is the one who made me look for this video

[@evilforhire]

Those of you bemoaning the lack of cooperation by the US, Russia (USSR during the space race) and China etc are completely ignoring the fact that all 3 countries all have vastly different priorities and objectives in regards to nearly every policy topic. Any expectation for these countries to work together in any geopolitical arena of any real or lasting consequence requires both willful ignorance and oversimplification of culture, ideology, philosophy, and policy to the point of outright dishonesty. Is there room for SOME cooperation? Absolutely- but the amount of starry-eyed whining that is routinely present in all of these "space as the final frontier" type comments that are about the lack of international cooperation and resource pooling is not grounded in any sort of realistic geopolitical reality.

[@fiftystate1388]

I hate to agree with you, but I do.

[@AFlyingCookieLOL]

It is the lack of cooperation on the US side. You can see it on the UNCONSTITUTIONAL RESTRICTIONS ON ACTIVITIES OF THE OFFICE OF SCIENCE AND TECHNOLOGY POLICY IN SECTION 1340(A). In other words, all researchers from the U.S. National Aeronautics and Space Administration (NASA) are prohibited from working bilaterally with Chinese citizens affiliated with a Chinese state enterprise or entity.

[@456swagger]

That would be your little secret.

[@donkerouac3746]

You guys should familiarize with the International Space Station. It's true that the US built most of it but it is still an international cooperative effort. In my engineering company, I have electrical components from Russia, Bulgaria, China, Montenegro, Germany, Belgium and many other countries. Some of my lab grade test equipment has been sold to all these countries and more. You are all living 40 years in the past!

[@456swagger]

And your Head is in Rectal Defilade.

[@christopherscottgutierrez3323]

form of spectroscopes, fuels being speced out, computer module of build does not seem logical, how fast did the computer put together motors and fuels, thought would say it would advance right away without slow seeming form, seems to be midway what it could be with out radiation control and possible artifiical solar systems safe sier law???

[@aegystierone8505]

30 rocket engines in the first stage alone, holy crap.

[@erangamadubashana]

and starship going to have 31 engines in its first stage

[@aegystierone8505]

@@erangamadubashana 29 actually

[@erangamadubashana]

@@aegystierone8505 that was for the first orbital test flight elon mentioned that they gonna probably add more raptors in to the superheavy

[@erangamadubashana]

@J J Not exactly just wait few months and see.

[@erangamadubashana]

@J J they did indeed. But all 4 N2 launches are failures unfortunately. 😐 This time starship trying it with 33 raptor. 😎

[@jtveg]

Thanks for sharing. 😎👌🏼

[@bearbaler1456]

Got to love Russia. The most ingenious and resourceful scientists and engineers in the world.

[@1835dueber]

trump loves Russia, how about you trumptard.

[@Giganfan2k1]

Then it all gets buried because the soviets wanted to do something else. Everyone that hid the engines could have been killed or sent to a camp for subversion.

[@joem551]

Americans were playing it safe, but Soviet engineers didn't have that luxury of playing it safe, otherwise they will meet their graves sooner than later lol. Never underestimate what people can do when death or life imprisonment with hard labor is the only alternative available to them.

[@AnatoliyTerentevNODSPBNEViPOB]

Американцы обнаглели до полной бессознательности, от развала СССР, и в 2001 сняли фильм The Engine That Came In From The Cold в котором не стесняясь рассказывают как им сдавали наши ракетные секреты, а они просто в шоке от того, что им лет 50 до наших технологий ещё топать надо было бы. До сих пор нет космического аппарата и двигателя для него, который не только прилунится на повехность Луны, но и взлетит с нее и вернет космонавтов на Землю, кроме русской Н-1.

[@MyZhargal]

Это не американцы сняли, это британцы.

[@jasons44]

is this all the info in the world on these nk-33 engines?

[@Kaxlon]

The irony of Baikonur is the only space port for manned space flight today. I guess the lie of being enemies is just, a lie. I hope we all can work together in a near future.

[@justinzeh7706]

SPACEX

[@Kaxlon]

@@justinzeh7706 SpaceX has not made one single manned space flight yet. Atleast not public. =)

[@justinzeh7706]

@@Kaxlon I should have clarified. I was just putting their name out there as someone to watch. I think they may soon be a means other than the Soyuz.

[@Kaxlon]

@@justinzeh7706 Gotcha. Yeah we really need more manned launched sites. That should speed up development world wide.

[@shadesofgold24]

This is what happens when you have a government who doesn’t care about what it costs, so long as it makes you better than everyone else. Rocket design is always “Cheap/powerful/reliable, choose only two”. The us seems to not be able to do anything unless one of the choices is cheap

[@citizenblue]

7:19 Sounds familiar... I think Elon calls it the "iterative process".

[@jasondrummond9451]

If you think about it - it is the same as 'natural selection' - modify, test, modify, test ....

[@rattywoof5259]

42:15 Oxygen gas is NOT flammable itself - it is what supports the combustion of whatever fuel is used. It's the fuel that's flammable.

[@green4ao]

You don't understand what means "to burn". It is exothermic reaction of TWO chemical elements..

[@andyharman3022]

Iron burns. The product is rust. Burning is an oxidation reaction.

[@rleequ]

It wasn't mentioned in this video, but I wonder if, once these 60 engines were discovered, and access was granted, did anyone think to dismantle one of them and see why, what was thought to be so dangerous, worked so well.

[@Giganfan2k1]

One would almost assume you had to. Lots of the engens were converted to a different design. While doing that they probably had to at least figure out how to build them from scratch or make new diagrams for them.

[@bigpjohnson]

I'm positive they were torn down and inspected and overhauled, with blueprints made in the meantime. Seals and other parts degrade over time, moisture and insects get in, etc. You cant just add fuel to a 20 year old rocket or motor engine and just turn the key.

[@concernedcitizen8665]

The critical advancement was in alloys. America's fear of nuclear proliferation by means of using the centrifuge method has America actively suppressing knowledge and experimentation with alloys.

[@denisiwaszczuk1176]

That was so good to watch .Thank you . The Foresight of those guys saving the engines .

[@sietzevandeburgt681]

Good inertia thrusters thanks mister chekhov now mister scotty can start his work with them !!! thanks Real life star trek !!!

[@phoenixrising4573]

The makers of this documentary understand the NK33 and the RD-180 are two very different engines right?

[@la_potat6065]

By the looks of things they do indeed understand it actually as 2 totally different engines. NK33 just recycles the preburner exhaust waste back into the combustion chamber at 15:00. Rather risky because potential soot formation from unburnt/incomplete combustion of preburner waste could clog up the fuel injector causing the engine to be destroyed. Perhaps that explains all the new filtration systems added on nk33 after the nk15 which uses the same cycle. No surprise that barely any rockets use this closed cycle due to how questionable the soot from the recycled preburner mixture is, being rather inferior to the oxidiser rich preburner staged combustion closed cycles from the RD-58 and onto the RD-180. RD-180 uses the more advanced staged combustion cycle where the entirety of the oxygen is sent to the preburner mixed with partial rp1 to vaporise the liquid oxygen in superheated gaseous form on an oxidier rich preburner 42:00. In effect having vaporised super heated oxygen (from the oxidiser rich preburner) in the combustion chamber to meet with the unvaporised RP-1 fuel results in the complete combustion of RP-1 fuel. Thus a clean burn is achieved with only CO2 and H20 for exhaust, and all the former soot formation problems are resolved. The requirement however was to produce a nickle super alloy metal that won't literally burst into flames in an oxidiser rich preburner environment.

[@andyharman3022]

The impression they make is the RD180 is just a scaled up NK33.

[@RUHappyATM]

Remember, you cannot be top-dog everytime.

[@terrydavis8451]

6:39 I always laugh at him holding 2 phones with that look on his face.

[@vader1a]

6:50 id say space x adopted the philosophy to a certain extent

[@jerga2002]

12:50 30 engines for the first stage is almost the same as the 33 engines planed for Spacex Starships... Russians were so ahead...

[@Jeffrey314159]

We Americans would have sent men to Mars long before now if Senator Proxmire hadn't gutted funding for manned space exploration in the early 1970's

[@daleeasternbrat816]

I remember Proxmire . He was an ass.

[@geoffheard5768]

Stop giving money to Israhell....You can go anywhere then...

[@phoobar9640]

@@geoffheard5768 We give 10X more to Muslim countries, and you still can't safely travel through most of them. I guess Allah doesn't like tourists. Just think how much money we could save!

[@hydrolox3953]

@@geoffheard5768 Israhell?

[@markos.5539]

Are there more russian rocket engine documentary?

[@tristanwegner]

Who else googled NK33 after the Every Day Astronaut Interview with Elon Musk?

[@ukashi694]

Which part was Tim specifically referring to?

[@DroneDocs]

What jet engine uses turbo pumps?

[@thethirdman225]

Turbo pumps are derived from turbines. The name should give you a clue.

[@andyharman3022]

No jet engine uses turbopumps. I don't believe the people that wrote this documentary were engineers.

[@DroneDocs]

Yes the lessons learned from high temp turbines on turbojets would indeed help.

[@muhammadazeem1262]

I always love russian engineering marvel's world has no match

[@robjones1328]

42:14 oxygen is not flammable! oxygen is required for fire, ignition, etc but without a fuel source, oxygen cannot burn. but an oxygen rich environment can make normally non flammable items flammable

[@ansar1809]

At that temperatures, metal that contains itself becomes a fuel source!.

[@burntorangeak]

Space Lada.

[@allandavis8201]

@ 6:28 the NASA controller was saying that no American had the same amount of authority,responsibility or autonomy as the Russian space program controller, and that it took a whole bunch of American scientists/engineers to equate to the Russian approach, which is probably why Russia was so far ahead, one person pulling everything together is always better than having disparate groups of people trying to achieve the same goal but not working together on their aims. A huge difference between the two systems was that the USA had, or should have had a massive advantage in terms of technology having got most of the Nazi rocket scientists out of Germany and into America to build up what became NASA, and in my opinion that actually backfired on the USA, they relied on the V2 technology and the ex-Nazi scientist team to take the USAs programme forward, and so they were trying to advance technologies that were already as far advanced as they could be taken and only when that was realised did they start rethinking their approach and technologies in the space race, in the meantime the USSR had overtaken them by starting from scratch, or at least with a lesser reliance upon the Nazi rocket engineering, allowing them to advance quicker by exploring more than one option/design at a time. @ 11:16 the narration mentioned that Kusnetsov did not have any experience with rocket engines and that it was a gamble bringing him into the space programme, but really apart from Von Braun and his team nobody really had any experience of rocket propulsion on a large scale, and sometimes that can be an advantage, no preconceived idea of what a rocket looked like or how it worked, or you could say that he was not just going to take what was already accepted as the “gold standard” of rocket propulsion systems and try and make it do something it was not capable of doing. Think 💭 about the amount of money that both the USA and USSR ploughed into the space race and into the Cold War in general, and then think 💭 about what that money could have been used to do, things like building more schools 🏫 and hospitals 🏥, highway 🛣️ maintenance and construction, a better welfare and housing system, medical research into things like cancer and heart ❤️ disease, all these things would have benefited the citizens of their countries but that would never have been even thought 💭 about, at the time of the Cold War was so much more important to the political leadership of the individual countries and the world, at a time where money to “fight” the Cold War was almost limitless, especially in the USA 🇺🇸 and USSR, driven by a rational fear of WWIII, and the M.A.D scenario, which in my opinion was not driven by the general population of the world but by the political leadership’s insecurity and paranoia. Some people would say that without the Cold War we would probably be earthbound and so many other advances attributable directly to the Cold War would probably still be only a dream of inventors everywhere, and they would probably be correct.

[@rodjarrow6575]

Dilettante type of reasoning! Because large-scale infrastructure projects of the state are not evaluated by the size of pensions or the number of homes for the elderly... etc.