Why A 1950's Rocket Engine Design Flies On NASA's 21st Century Moon Rocket.

The AJ-10 Series of Engines dates to the 1950's and an example flew last year on Artemis 1, propelling Orion into a distant retrograde orbit around the moon. It's not a single engine design, but the common factor is pressure fed, hypergolic bipropellent engines designed and built by Aerojet.
The earliest examples I can find were the AJ-10-24 on Aerobee sounding rockets, generating just over 1 ton of thrust. The AJ-10-37 propelled the Vanguard rocket second stage, which was a 3.5 ton thrust engine. That was adapted to fly on Thor/Delta, Atlas and Titan. Then the Apollo Service Propulsion system used a much larger design, which was largely a complete redesign.
The shuttle Orbital maneuvering system thrusters were a smaller 2.5 ton engine running on MMH/NTO and those same engines were refurbished for flight on Orion.
This is a fine table listing the known AJ-10 variants used in orbital spaceflight.
www.b14643.de/Spacerockets/Spe...
Follow me on Twitter for more updates:
/ djsnm
I have a discord server where I regularly turn up:
/ discord
If you really like what I do you can support me directly through Patreon
/ scottmanley

[@sirjohniv]

If it ain't broke, yeet it at the moon

[@Hungary_0987]

I yeeted the rest of my sanity at ksp2

[@rwboa22]

While the "same" model, the Orion's engine are repurposed engines. Plus the Orion engine uses Monomethylhydrazine for the fuel, while the SPS on Apollo, designed when Direct Ascent was still the principle option, used more powerful Aerozine 50. All they share is just the common AJ10 ancestry.

[@RLD_Media]

Literally came to the comments to post that exact same thing word for word lol. Tree’d my ass

[@forrestmorrisey]

I want this on a t-shirt

[@davidajayi1207]

@@Hungary_0987I can’t be bothered with that game for now

[@saundby]

One comment I'd like to add since I formerly tested AJ-10 engines is that the rated thrust was set to match the contract requirements and was not the maximum thrust that the AJ-10 was capable of. Versions after SPS could produce as much thrust, but the rated thrust was set to what the contract called for. In testing of the OMS engines, we ran them up to SPS thrust levels in test. The Delta K was typically not run up as high, but was run significantly higher than the rated thrust for the application. I didn't even know that the rated thrust was a lot lower than the tested thrust levels for the first few engines I worked on.

[@fensoxx]

As a Mainer I’d really like to know about this guy better known for building boats moving over to nozzles. What an epic career move.

[@nicholaskrell9610]

I second this!

[@ohmschool]

I was wondering about this too, but sadly after some research, I discovered this 'Guy from Maine' who worked on early development on the titanium nozzles was actually living and working in Massachusetts and ☹. He was a Norwegian toolmaker who apparently was quite a talented machinist and had been trying to start up a company to manufacture metal parts for boats. You can read more about him in the NASA publication - 'Remembering the Giants', starting on page 66 last paragraph, where Clay Boyce recounts how he found this small-town machinist and the role he played in the nozzle development. 'Remembering the Giants' is a NASA publication which was a transcript from a series of lectures given on April 25, 2006, at NASA’s John C. Stennis Space Center to celebrate 40 year anniversary of Apollo. Clay Boyce recently published a biography in 2022 that might have more information about this topic (Bringing Apollo Home: Clay Boyce Biography, The Journey From Mountaineer to Rocketeer, 2022)

[@fensoxx]

@@ohmschool well that’s cool if not slightly disappointing from a Maine perspective. Thank you.

[@leshill4577]

Thank you Scott! It seems no one remembers the crucial function of the AJ10 engines! My Dad worked on Apollo service module engine at Aerojet and I assembled and tested five OMS engines for the Shuttle. Even the Kennedy Space museum doesn't pay homage to the AJ10! Thank you again!

[@saundby]

Hey, Les! How are you doing? It's been a decade or three. I'm with you on this, the AJ-10 was a sweet piece of technology, and has been largely overlooked despite its critical role in so many missions both crewed and otherwise.

[@tateranus4365]

​@@saundbyI know ge manufactured some aerozine 50, by any chance did it come from near Cincinnati Ohio?

[@SimonAmazingClarke]

Its only like the Rolls Royce RB211 engine that first ran in 1969. It moved on in iterations and is now known as the Trent today and is flown on many aircraft. Actually my Mum, now in her 80s, worked in the test bay when they were developing it in the early 60s.

[@festerallday]

I think Nissan has used the same 2.4l 4cyl since around the same time.

[@BPJJohn]

Ironically Rolls Royce did actually make licensed versions of Rocketdyne's S-3D, the RZ.2 for the Blue Streak Missile.

[@tateranus4365]

​@@festeralldaysome campers (including my old one) have been using the same engines since the 80s at least... I doubt they even exist in the uk. If you are curious I'm referring to the 454 cubic inch v8.

[@festerallday]

@@tateranus4365 i think the LS6 454 was from the early 70s to 2006-2007ish.

[@seanpeacock4290]

I was just reminded of a time in my youth when we were launching model rockets, the small ones made from cardboard with solid fuel engines that had letter ratings for how powerful they were. Someone with a fancy rocket that required 3 strong rocket motors, put some of the weakest motors of the same diameter that we had in it. It just hovered a few inches off the launch pad before burning out and attempting to eject the parachute. Good times.

[@leehill9922]

Those old Estes rocket motors and kits were the best. I helped my nephew build and launch one not too long ago. He loved it.

[@bobblum5973]

A8-3s replacing C6-3s, by any chance? 🤔🙂 In the rocket club I was in, we had a large diameter (2 inches) two-stage rocket we flew at demonstration launches. It used a B14-0 booster engine to kick it maybe 10 feet off the pad, then an Estes D12 in the upper stage for a "ka-whoomp" of audible power and decent altitude. The spectators loved it, they could see the staging. Then one day I flew mine with a Centuri B14-0. The thrust curve lied; lower peak thrust, longer burn time. More like a B8-0. It boosted up, slowed, fell back tail first, then pivoted to almost horizontal. Second stage fired; into the spectators. It grazed a guy's arm and proceeded to bound around the field a bit, unspiraling the body tube, etc. No one hurt, the guy even was happily saying that he could honestly claim he was hit by a rocket! We only flew that design with Estes B14-0 engines after that.

[@nocelebrity6042]

I remember one of the projects in my 8th Grade Industrial Arts class was to build a model rocket from scratch (except the Estes model rocket engine). We had photocopies of the teacher's handwritten instructions. The teacher did not allow us to ask any questions. We had to copy each page of diagrams and instructions by hand before we made any attempt at actually building that part of the rocket. It took a couple weeks for the students to complete their model rockets, and get them painted and decorated. I don't know what was the matter with those engines, though. Of all the model rockets that were constructed, only a handful had successful engine ignitions. Of the handful of model rockets whose engines successfully ignited, only a couple actually left the launch pad. One student's model rocket took off, turned sideways, and ejected its chute at waist level. The model rocket was smoldering, and the student stepped on it to stop it from burning, and broke one of the tail fins off. Mine launched straight upward into the partly cloudy sky, ejected its nose cone at the right moment, had the chute unfurl completely, had the nose cone remain tethered, the chute slowed the descent, and the rocket landed on its side in the grass. The one thing my model rocket didn't do completely right was that it landed just outside the school's fence, which was in the adjacent schoolyard. One of my classmates jumped the fence to grab it for me. Good times.

[@bobblum5973]

@@nocelebrity6042 I'm not sure what your engine troubles were caused by, but I do remember learning the best technique for the nichrome igniter wires with the plastic coating. We'd bend it into a V shape, put the point into the nozzle, then roll a bit of cotton into a tiny ball, placing it between the ignitor leads and poking it down inside with a wooden toothpick. Between that and using a car battery for the launch controller power, we had almost no misfires, even three engine clusters.

[@NotProFishing]

As a kid my uncle got me a Estes kit we built it and launched it a couple times then he came over one weekend and had made a very large kit himself in his basement it ran his home built motors I don't know what the equivalent was but I remember it disappearing into the sky and even with binoculars we couldn't see it awesome times then we took a road trip to large dangerous rockets meet and my love of space was solidified

[@marvintpandroid2213]

I'm not old, I'm just a well proven design.

[@otpyrcralphpierre1742]

This is the Oldest that I've EVER been!

[@Yutani_Crayven]

Up to date materials science and manufacturing methods might reduce parts point, improve reliability, and save on costs. Then there's also the other approach to redundancy. Instead of having multiples of the same things within the same, single engine, you can also reach redundancy by having multiple smaller engines that still allow you to fly even with engine failure. That, again, can save you a ton on cost. Which is a long way of saying: things don't need to broken in order for better alternatives to exist or be within reach.

[@MarsJenkar]

As I recall, the most common hydrocarbon-based rocket fuel in use is still RP-1, which was also developed in the '50s. While some research has been done into finding other propellant candidates since then, RP-1 has stood the test of time and is still in use. If it ain't broke, don't fix it.

[@jeromethiel4323]

Ed Zachary. Physics hasn't changed. Which means for a given set of performance criteria, only certain designs will work. While we have improved a LOT in materials and manufacturing science and techniques, at the end of the day, it has to work. And if it's my butt in the seat, i want a proven, robust design pushing said butt into orbit or whatever. For example, i would not have wanted to fly a rocket on the first generation Raptor engine. Not because it's a bad engine, it just wasn't proven yet. Which is another reason to respect the Apollo astronauts. They cut a few corners to beat the Russians to the moon. So those men had to have testicles of Ti to get into that rocket. And the gamble worked, most of the time.

[@ryder6070]

@@jeromethiel4323 Exactly. I live and sail on my boat in Alaska. The hull is nearly identical to a Classic North Sea Lifeboat. This is design from the 30's. Still is unmatched for it's intended purpose, "Do not die in gale"

[@scottmyers6441]

Another awesome video Scott. I love seeing the lineage of our modern rockets. If possible could you share where you found those awesome diagrams of the Thor rocket. I would appreciate it greatly, thank you.

[@declanfarber]

For anyone interested in the history of vintage rocket fuels, there’s a hugely entertaining book (now called?) Ignition!, by Clark, recently reprinted after being OOP for decades. Well worth reading, in the style of Louis Fieser (father of napalm, and prednisone for those who care about such things; he wasn’t such a bad person.) Those guys were nuts.

[@Jimorian]

I think the video where Scott talks about dangerous propellants was largely drawn from this book for data.

[@simongeard4824]

Yes, I think anyone who's followed Scott for a while is familiar with that one... it is indeed an entertaining and educational text.

[@extrastuff9463]

@@Jimorian I think Scott also cited it for a few anecdotes with a reference to the book either in that video or description. Also later when it was properly republished it got a video of its own suggesting people to go buy it if they're interested. Most people probably already know the book but I'm sure Scott will have picked up a few new viewers that didn't go through the backlog, repeating the praise for Ignition! in the comments occasionally where it's appropriate is probably a good thing.

[@DerickRethansXdebug]

I can recommend it too. I think I got it when Scott mentioned this when it just got reprinted a few years ago.

[@dancingdog2790]

FOOF FTW!

[@edcallahan9536]

Thanks for all your deep dive content Scott…always interesting and engaging!

[@WayOffTheTrail]

Speaking of rocket history, have you been to the Cosmosphere Space Museum in Hutchinson, KS? You could geek out for days in there. Look it up if you haven't been!

[@marcmcreynolds2827]

Earlier this year my hobby group got an hour-long guided Zoom video tour of the place + Q&A after. I've been to the NASMs many times (including twice during my honeymoon -- sorry dear), and I have to say the Cosmosphere is special.

[@WayOffTheTrail]

@@marcmcreynolds2827 It's about the only thing to see in Hutchinson but so worth the trip. You can also visit Stratica, where you take a shaky elevator down 600 feet to explore an abandoned salt mine and museum. At least it's cool down there!

[@TheMrCougarful]

It's worth remembering, all this got its start with bamboo tubes full of gunpowder made by 9th century Chinese hobbyists. I wonder if any of them ever looked at their creations, glance up at the stars and, you know, speculated.

[@Anmeteor9663]

People being people, they almost certainly did. I think there is a legend of a Chinese gunpowder rocketman who strapped a lot of them to a chair and tried to launch to the moon. No idea what the result was but I am guessing he didn't get there or we would definitely here about it from the CCP.

[@marcmcreynolds2827]

If memory serves there are woodcuttings of such dreamers headed towards the moon in their creations. Might have worked, too... if the ancient Chinese FAA hadn't said "no" ; )

[@Spicy6969]

I watch several videos sped up and your intro is so cool at like a 1.5 speed lol

[@greezyhammer764]

You had me at "Direct ascent lunar midget". Perfect name for the first Starship lunar lander :D

[@otpyrcralphpierre1742]

Yet ANOTHER Excellent video. Thank you for all of your research, editing, and presentations. You are ALWAYS informative, personable, entertaining, and you don't engage in Hyperbole. We can always expect the Best from you.

[@georgejenkins8063]

Can't believe that at 70yo, I remember watching Neil and Buzz when I was 15yo and now at 70 living human being will return to the moon only they will be on an engine built when I was merely 5yo... my mind is Time warped !!

[@rodmorgan7041]

Always such interesting stories Scott. Thank you

[@connecticutaggie]

Excellent informative video - as always. Note: I would recommend raising up your prompter so it is not as obvious that you are reading from a script. Fly safe.

[@frankgulla2335]

Scott, what a great tale of "old tech" in the new world!

[@edki669]

AJ10 is also one of my favourites in KSP RP-1

[@Allan_aka_RocKITEman]

Great video, Scott...👍

[@dereklee7124]

Yay, I work on OME for AR in redmond!! So glad you did a video on this!

[@brianhall8030]

Love the Talking Heads & David Byrne. Great t-shirt.

[@jameswatson2755]

Scott I often feel for you. You make some of the most interesting and well explained space/engineering videos on the internet. Yet you still have to deal with the same ridiculous comments that all the people who put no effort or intelligence in get. Thanks for keeping it up anyway.

[@jamesmathews9098]

Always a fascinating watch!

[@gordonstewart5774]

"They put though whole thing out of its misery" made me think of the Starliner.

[@RCAvhstape]

Starliner actually works though, albeit with expensive bugs. It's not a bad design, it's bad management and QC issues.

[@richb313]

Thanks Scott for showing the best designs are sometimes the older ones.

[@MCsCreations]

Pretty interesting history indeed! Thanks, Scott! 😊 Stay safe there with your family! 🖖😊

[@Pan_cak]

Scott man I love your content

[@minikawildflower]

Sometimes the best design is the simplest one! It's great to innovate new and more complex designs, but there will always be a place alongside that for designs that rely on simple, longtime favorite concepts.

[@setituptoblowitup]

Long live AJ10🚀

[@user-li7ec3fg6h]

Old technican wisdom: Never change a running system 😊 It is a bit reminiscent of Koroljovs drive (who had already successfully tested liquid fuel rockets at the beginning of the 30s, apparently also encouraged by Goddard and Johannes Winkler from Bresslau, whose space flight rocket club moved from there to Berlin, in which Wernher von Braun was admitted and in which other prominent people were like Max Valiers - there were also other successful rocket builders in Germany and Austria who even wanted to shoot the first man into space in 1933: please see the MAGDEBURG ROCKET, which can also be seen there in the Technical Museum!). The Soyuz is still flying today and is considered one of the most reliable systems! It also shows that there were other capable rocket builders besides Goddard (who i also admire) in the US 😊 (regarding boosters, it's just strange that the Kalte Walther drive was forgotten, which was used by the Luftwaffe at the end of World War II - note: a reusable booster without any thermal stress! Can still be seen today in the Air Force Museum in Berlin Gatow!). There is a very good book by a Soviet engineer who, under Koroljov, took part in the first tests in Baikonur, where first the A4/V2 and then the R5 and R7 were tested. Unfortunately, the book is only available in Russian so far and it is still almost unknown in the West. But the book is online and you can read it with Google translate, for example. That would be of great interest to Scott (and Tim!).

[@ronschlorff7089]

Yup, just "ask" the paper clip or older VW!! ;D

[@otpyrcralphpierre1742]

Someone should try that in the Automotive business. New design every year is expensive and unnecessary. It would also be more "Environmentally Friendly".

[@setituptoblowitup]

@@otpyrcralphpierre1742 good idea 💡

[@-jeff-]

The Aerobee was probably every model rocketers first two stage project in the late 60's.

[@marcmcreynolds2827]

It was a very popular subject going back to even early 1960s model rocket building. Ironically, those were almost always just the upper stage being modeled. I recall true-scale ones including a booster showing up at scale modeling contests by the 1980s, but likely there were at least a few much earlier.

[@teebob21]

It was my first 2-stage project in the mid 90's, too. I experienced the most fabulous Rapid Unplanned Disassembly of my life right at the moment of upper stage ignition, and the second stage flew off to the southeast at full thrust like an air-to-surface missile. We never did find it.

[@grimmity9240]

Thanks Scott. As an avid history buff I really enjoy these vids. Not to mention the KSP advice. 👍✌️💨

[@zandvoort8616]

I love space and this channel.

[@d.jensen5153]

Huh. I've known since 1967 that the Titan II was fueled with Aerozine 50. But only today did I learn that Aerozine 50 was homogenized!

[@TechNed]

That was very interesting. Thank you.

[@rohesilmnelohe]

Haven't seen it but probably for the same reason why the Rd170/RD180 series rockets are the most flown engines of all time... they are just really, really good.

[@LEDewey_MD]

Awesome explanation of rocket science! ❤

[@ronschlorff7089]

Yes, sometimes it's pretty easy: "If it isn't broke, don't try to fix it"!! LOL

[@alanpareis734]

A. Great one, Scott, thank you.

[@TheJoefussGarage]

Scott, what a history lesson!!! This one distant cousin/variant topic journey, gave me such a better technical perspective on our own USA rocket 🚀 history and pedigree!!! Thank you so much 👍

[@craigw.scribner6490]

Thanks, Scott!

[@RCAvhstape]

Over the years, Rocketdyne got all the glamour jobs with engines like the F1 Saturn V main engine and the RS-25 Space Shuttle Main Engine, and it always seemed Aerojet lost out on the big contracts. But Aerojet had done well for themselves building engines like the AJ-10 and most of the thrusters used for attitude control and as propulsion on satellites. I'm a bit old school, so it's a bit disappointing that they merged into one company. As far as them being owned by L3 Harris, unless I am mistaken, I think Rocketdyne has spent most of its history owned by other bigger companies, and if so this is just more of the same.

[@saundby]

Aerojet lost a lot of contracts because of USAF interference. They largely considered Aerojet "their" rocket company, and didn't want other work going there that they felt might interfere with Titan. When we did get large liquid development contracts, for example for NASA, they'd start a fight with NASA that would go to Congress and get our funding frozen. For their part, though, I have to say that Aerojet had a terrible marketing department and no lobbyist pull with which to fight the situation. Many among upper management just resigned themselves to it.

[@RCAvhstape]

@@saundby Did you work for them before they merged with Rocketdyne?

[@onedeadsaint]

loved this storied history! makes me think of previous generations of humans using the same stones for building for generations, or re-using chainmail armor from previous wars, or passing down a set of tools! and now this one engine that was part of the space shuttle is being reused on a completely different spacecraft. so cool!

[@thecountbassy_]

In a similar vein, many modern satellites use the RAD750 single board computer to run their flight software, originally released in 2001, with absolutely no plans of updating any time soon. Flight proven is much better than latest/most powerful tech.

[@vicroc4]

And before that it was the RAD 6000. My father used to write software for them, and always was impressed at just how much he could actually make them do considering how little processing power they had.

[@ronschlorff7089]

..since 2001, eh? Guess they got scared off by the HAL 9000! LOL ;D

[@Ergzay]

Which explains why they're getting their socks beat off them by Starlink.

[@44R0Ndin]

Latest/most powerful tech is actually an actively bad thing in satellite flight computers, for a reason. That reason is that the smaller you make the feature size of the processor's silicon die (basically, the smaller you make the individual transistors) the more prone the whole system gets to being upset by radiation. And there's a lot of radiation in space. Basically, a 100nm transistor will be unintentionally bit-flipped less often than a 10nm transistor, and this works both when scaling up and down (bigger transistors are always harder to upset, smaller ones are always easier to upset). This also explains why modern solid state data storage hasn't reached the radiation exposed parts of spacecraft yet. Space radiation will reliably either render an SSD inoperable or scramble the data on it to the point that it can't be recovered to 100% integrity.

[@drofwarcnwahs2108]

@@Ergzay Different use case. Starlink satellites are designed to be disposable and have short lifespans by design. They plan on replacing these in only a few years as they itterate to newer versions. Version 1 is already obsolete but only been in service for a few years. Also, if one fails it's no big deal since you are putting tens of thousands of them in orbit. Most other satellites are designed to last upwards of a decade or more so reliablility and redundancy is far more important.

[@Dan-56]

I want to hear more about the boat ⛴️ builder from Maine who was making rocket 🚀 nozzles 🤪👍!

[@MerrickSternEditz]

Love the channel

[@ronschlorff7089]

Nice one Scott. As a former daily worker in Sacramento, my commuter bus passed AeroJet General in Rancho Cordova/Folsom, CA. twice a day, for decades; they we very proud of their long history in U.S. Areo space. And as a bonus they have preserved many acres of open land around them, free from the runaway housing development of the entire Sacto area. I did not work for them but have been interested in space since I was a kid. Nice to see all the rockets you showed, I built many of them as flying models using Estes products for their propulsion. They have not "updated" their solid rocket motor products much since 1958 too, and they fly as reliably well today as they did when I was in the 8th grade, eons ago. LOL. Yes, it is interesting the oft "contorted evolution" of space vehicles, back in the day, like the Able, which was dubbed the "not so able" at the time, LOL. Some things change a lot, and still don't work well, like Star ship, for example, and others went to the moon and back many many times, many many years ago, LOL. And don't' even get me started on the Soviet, Russian R-7 the venerable rocket that has flown since days of Sputnik, Vostok, and Soyuz, no doubt updated many times but still was used as a Russian "Uber ride" for astronauts to the ISS until the recent Falcon 9 took over!! I've made flying rocket models of them too, the R-7, as Vostok, Voskhod, and Soyuz; and they fly well without any big fins (only slightly larger than stock scale fins are needed) since the four external strapped on fuel tanks act as "stabilizers" well enough for straight up flights, a really cool design that, and real crowd pleaser when I fly my rocket models!! LOL ;D

[@marcmcreynolds2827]

> they fly as reliably well today as they did when I was in the 8th grade < I occasionally fly Estes (and other's) motors which were actually manufactured around then (early 70s anyway), and they also work reliably now.

[@DUKE_of_RAMBLE]

I'm not sure that your comment about Starship is valid... heh It's breaking new ground, and teething problems are to be expected. Many previous super-heavy attempts didn't get anywhere near Starship's current level of 'success', and were promptly abandoned after their failure... whereas others didn't even get off the drawing board. 🥴 _[I'm not a diehard SpaceX fanboy, just someone that likes being fair and giving credit where due 😊]_

[@ronschlorff7089]

@@marcmcreynolds2827 yes, they have a long "shelf life" if stored properly, not too moist. ;D

[@ronschlorff7089]

@@DUKE_of_RAMBLE Yes, as in all things, "baby steps" first. That's where SpaceX is and will start walking and running soon, particularly for their "Deep Space crewed vehicles" that is, I predict. They've done well in LEO. Same with all others interested in going very far into the "great void", (starting, once again, with the moon), for some "ungodly reason", as some "groundlings" would put it!! LOL ;D

[@calessi]

On the Apollo Service Propulsion System and the Lunar Module Descent and Ascent engines, helium was injected directly into the tanks to pressurize them. In order to avoid helium ingestion into the engine combustion chambers, a "zero-G can" was mounted at the base of each tank over the outlet tube. The can's filter took advantage of the fuel or oxidizer's viscosity by trapping an adequate amount of each within the can, which prevented the problem of "chugging" when the engine was first ignited. For smaller tanks such as those used in the Reaction Control System, the fuel and oxidizer was stored in an elongated bladder within each respective tank. The helium would pressurize the area between the tank wall and bladder and squeeze the contents out, much like toothpaste from a tube. This arrangement worked fine in smaller tanks and obviated the need for a zero-G can.

[@ryanhardin3256]

The company I work for is making some valves for AR for the new engine. Super exciting to be a part of the future of this historic engine!

[@chrisheath5888]

Love your content Scott, keep it up! That being said, any chance on you doing a video on this new room temperature supercondive material (LK-99)?

[@YossiRafelson]

He said on Twitter that he only knows enough about it know that his take would probably be wrong. And that on the other hand that doesn't seem to have deterred other science commentators from firing off videos.

[@chrisheath5888]

@@YossiRafelson Totally logical, thanks for the info!

[@shazam6274]

As an EE, it's BS. No performance data or test condition info, no specifications; just hyperbole generalizations and most importantly: fake demo video showing on their web site shoeing Lorenz effect (i.e. creating eddy current in the copper sample suspended on strings by moving the magnet).

[@offspringfan89]

Complete bovine manure. Besides the ridiculously fake demonstration video, other scientists reproduced the experiment but failed to validate the findings from the researcher who supposedly discovered this material.

[@JoannaHammond]

I love using the AJ10 in KSP RP1 :D

[@Ergzay]

A lot of people in the comments are ignoring the fact that even though they're old, these engines are incredibly expensive. You usually use old things in the way of "if it's not broke, don't fix it" primarily because of cost, but that is completely reversed in this case.

[@jacksons1010]

Are you sure about that? Pressure-fed engines are about as simple as can be. What makes them expensive?

[@psoltan]

I tell people that rockets really get to space by burning money, not rocket fuel. SpaceX has brought the cost way down but it's still out of reach of the average Joe. I dream of a future like the movie Serenity, where a group of people can scrape together the money to buy something for interplanetary trade. 😉

[@jacksons1010]

@@psoltan Not so sure SpaceX has brought the cost “way down”. It’s a private company and their actual costs remain unknown. They sure don’t give NASA and the DoD much of a discount.

[@fensoxx]

@@jacksons1010they cost about $60 million. That’s a lot cheaper than historically has been available.

[@psoltan]

@@jacksons1010 I'm talking about the cost to the customer, which we do know. SpaceX, according to Google, is around $2,700/kg for LEO were it did cost over $18,000/kg between 1970 and 2000. The DOD and NASA usually have much more expensive requirements, like geostationary orbits or polar orbits.

[@stephenkramme7063]

Informative video as usual. Unless I missed the persons name you said: "some guy that was building boats in Maine". Do you remember this fellows name? I'm curious how two seemingly unrelated fields combined to achieve this engine's performance and reliability.

[@DUKE_of_RAMBLE]

Not too dissimilar from our current hodgepodge of expertise coming together to built Starship and Super Heavy... Where Grain Silo fabricators were hired to create the stainless steel skins! 😊

[@4077Disc]

I am also super interested in the answer to this. I wonder if it has anything to do with Bath Iron Works? I work for a company in Southern Maine that makes a high tech material that is used in high energy thermal protection, like missile tips and nozzles as well as re-entry heat shields for NASA, but i doubt that is related...

[@QueenSaffryn]

The old addage of "If it ain't broke, dont fix it" holds true in so many ways, like the internal combustion engine, it's been around for over 100 years, we have just gotten better at making them :)

[@mpetersen6]

Better materials. Better manufacturing technology. The only thing with IC engines is the push to extract as much efficiency (and power) from them. This has resulted in engines that can be problematical as total time increases. Interference engines that destroy the engine if the valve timing gets out of time. Low friction piston rings that have a higher chance of failure simply because they are so thin. Internal components such as connecting rods made as light as possible. Plus they are made from scintered materials in many cases. Another problem with IC engines is owners not ignoring the maintenance schedule. Or in some cases going by the factory recommended oil change schedule. Which in some cases is 10,000 km or more between changes.

[@ronschlorff7089]

yes, and the more you see of electrics' issues, the more I like them!!

[@mpetersen6]

@@ronschlorff7089 Around 15 years ago there was a lot of work being done on mechanical batteries. Also known as flywheels. Supported in magnetic bearings and spinning in a sealed vacuum casing. Made of carbon fiber they did have some problems with delamination. They could be spun up quickly. Only they needed to be installed in pairs spinning in opposite rotation. Otherwise the vehicle handling could be problamatical.

[@hedgehog3180]

Internal combustion engines do happen to have the terny tiny problem that using them leads to a mass extinction.

[@Yutani_Crayven]

Up to date materials science and manufacturing methods might reduce parts point, improve reliability, and save on costs. Then there's also the other approach to redundancy. Instead of having multiples of the same things within the same, single engine, you can also reach redundancy by having multiple smaller engines that still allow you to fly even with engine failure. That, again, can save you a ton on cost. Which is a long way of saying: things don't need to broken in order for better alternatives to exist or be within reach. That's on the theoretical level. As for this engine in particular - rightfully colour me a cynic, but I don't believe for a second that this engine continues to see use because it is the best option. Seems more likely that it stays in operation because there are specific jobs on the line.

[@Sharpthingy]

Love the American Utopia shirt Scott!

[@HYEOL]

Only 7 atmospheres?? Rocket science is clearly above my head

[@ronschlorff7089]

Yes, me too, except I know that "flaming end down and pointy end up" is the way to go,.. unlike the last launch of "orbital Star ship"!! LOL ;D

[@Yutani_Crayven]

7 atmospheres above the sea

[@TheEvilmooseofdoom]

@@ronschlorff7089 As a place to start, that's a good one!! :)

[@goldgeologist5320]

Back the rocket engine up Scott! I want to know the story about the boat builder and the Apollo engine!

[@hometheater8428]

good video thanks

[@jasonlast7091]

Low key was hoping for that video on room temperature superconductors but this is good! 😊

[@paulbow78]

I kinda wish we weren’t disposing of these engines like this. Considering we aren’t making any more of them, they should be going to museums.

[@ronschlorff7089]

some are, attached to space craft!!

[@adrianf.5847]

4:00 What is affected is the specific impulse. The thrust depends also on the amount of propellant that is blown out during a time interval.

Love your videos! I would to love to hear your perspective on the recent possible ambient temperature and pressure super conductor LK-99, maybe similar to your livestream on the titan submarine.

[@ddegn]

Have you watched the video by Sabine Hossenfelder on the topic? It really doesn't look very promising in my opinion.

[@Damien.D]

Dave of EEVblog busted that thing. It's not a zero resistance material and their demo is crap.

[@user-li7ec3fg6h]

​@@ddegnSabine Hossenfelder is very cool (I'm one of her Follower), but sometimes a little bit biased (by not only a few topics). She is realy very, very smarte, but sometimes also a little bit fast and strong in her opinions. Its allways super to learn from her, but it is better that we all think by our owen. Says also Sabine and therefore constantly recommends that we should all educate ourselves. 😊

[@General12th]

Hi Scott! Rockets are cool!

[@ceejay0137]

It's remarkable how tall and skinny the Vanguard rockets were. There must have been a disadvantage due to the weight per unit volume of a tank that shape. I wonder why the engineers built it that way: what the advantage was that made it worthwhile. Were they trying to minimise air resistance?

[@SeanBZA]

Probably constrained by either production plant size, or by the control system to be able to control it, with only a single engine or three at the base, long and narrow to get the stability easier to handle, without a complex computer system on board. Narrow as they had to weld the parts together, and thus were likely limited by the diameter the horizontal lathe they used to machine the parts could handle in the rotating section.

[@RCAvhstape]

They were trying to build a rocket without Von Braun's help, so they only half knew what they were doing.

[@hamzahkhan8952]

@@RCAvhstape lol

[@joshuaanderson4090]

I think some of this was also due to it being cobbled together from several other rockets and test platforms? I may not be remembering it correctly but I don't think each stage was designed with the others in mind and it was a hacked together solution to try and get to orbit. And as someone else pointed out they weren't getting help from the German engineers who had a lot more experience than them

[@owensmith7530]

Based on the title I was expecting a video on the RL-10, it's nearly as old.

[@Fleetwing1627]

Among the things that I thought I've never, ever see, an Ercoupe performing a JATO-assisted takeoff is definitely one of them. Holy cow.

[@alphasixty1316]

I wish I could have seen the "American Utopia" tour.

[@markiangooley]

Now I’m thinking back to the last time I read the book Ignition!

[@LuciFeric137]

+ 1000 for Jack Parsons reference..

[@samuraidriver4x4]

The comments about the nozzle might be an idea for another video. What materials have been used to make nozzles and what are their properties.

[@lsedge7280]

Have you considered emailing Aerojet (or NASA) about the numbering sequence? I feel like you have a decent chance of them responding and explaining.

[@morrisgraeme]

Thanks for the video! Can you make a video explaining why some tanks bulge (like the ones from Copenhagen Suborbitals) and others don't? Unless others do?

[@TheEvilmooseofdoom]

What do you mean by bulge? I have to also admit it took a great deal of self control not to turn that into something a little off color. :P

[@boredgrass]

Please tell more about the shipbuilder! Please!

[@joshualux8309]

Finally someone who does not speak with an accent!

[@sadham2668]

Literally everyone has an accent, what are you talking about? Or is this a joke I’m to stupid to get.

[@joshualux8309]

@@sadham2668 I used to believe when I was younger that I did not have a distinct local accent. I was shocked when I traveled for the first time as an adult, that people knew immediately that I was from Texas. My grandfather was a highly educated man from the UK and listening to this man’s voice reminded me of him a little bit.

[@loveskngm31hstsdaily1]

@@joshualux8309 neat

[@LiamDennehy]

I'm doing a KSP RSS/RP-1 playthrough with Soviet engineering, and it is so difficult without access to the AJ10 series... It's so versatile, reliable, and performant.

[@dandare3627]

Perhaps Von Braun's ingenuity had the "imprint", just as from the same period, the Soviet NK-33 engines are equally famous... the answer: it was an era of ingenuity to create something new and durable

[@mytube001]

Sometimes you find a good design early on. Bicycles have remained essentially unchanged since the 1890s. More gears, better materials, better manufacturing techniques and some minor refinements, but a normal bike from 1895 looks very much like a bike from today.

[@user-li7ec3fg6h]

Hi there 😊 Because I am also very much interested in space history: As always very interesting! It is a bit reminiscent of Koroljovs drive (who had already successfully tested liquid fuel rockets at the beginning of the 30s, apparently also encouraged by Goddard and Johannes Winkler from Bresslau, whose space flight rocket club moved from there to Berlin, in which Wernher von Braun was admitted and in which other prominent people were like Max Valiers - there were also other successful rocket builders in Germany and Austria who even wanted to shoot the first man into space in 1933: please see the MAGDEBURG ROCKET, which can also be seen there in the Technical Museum!). The Soyuz is still flying today and is considered one of the most reliable systems! It also shows that there were other capable rocket builders besides Goddard (regarding boosters, it's just strange that the "Kalte Walther drive" was forgotten, which was used by the Luftwaffe at the end of World War II - note: a reusable booster without any thermal stress! Can still be seen today in the Air Force Museum in Berlin Gatow!). There is a very good book by a Soviet engineer who, under Koroljov, took part in the first tests in Baikonur, where first the A4/V2 and then the R5 and R7 were tested. Unfortunately, the book is only available in Russian so far and it is still almost unknown in the West. But the book is online and you can read it with Google translate, for example. That would be of great interest to Scott (and Tim!).

[@billlyell8322]

Question a rocket lifts off at 3g, and you said the pump did 7 atmospheres. Does that include the additional pressure from the 3g acceleration, or is it in addition to it?

[@scottmanley]

It doesn't include the head pressure, that's relevant for some rockets.

[@billlyell8322]

@scottmanley but wouldn't that make a difference??? Depending on which part of the system your talking about. You specifically pointed out 7 atmosphere tank pressure, I get that. But wouldn't the chamber pressure be 10? And does it matter if it is??

[@gavindavies793]

I've been meaning to ask for ages... What/who is the pencil portrait on the wall in the background? I can't quite read the writing.

[@Pystro]

Hearing about that "the pressure in the combustion chamber can't be larger than the pressure in the tanks" limitation made me wonder if dynamic pressure effects could lower the pressure that the injection nozzles perceive below the actual pressure in the chamber. For example, you could impart a spin onto the contents of the combustion chamber and inject the propellants from its center. That way both the flow speed and the centrifugal forces would help "suck the propellants out of the injectors". The combustion chamber would effectively function like a centrifugal pump that is driven by the increase in volume. Although with my limited intuition on fluid dynamics I might be overlooking where there would be a hidden pressure drop on the exhaust side of that vortex. But it should at least be possible to "turbopump" the reaction so that it happens at a higher pressure than what the injectors and the exhaust nozzle experience.

[@Eazpezey]

Keep it simple and efficient

[@niftybass]

Your "on mic" voice has changed since becoming a pilot. I get it; i just think it's cool that we can hear it. :)

[@CD3WD-Project]

Gives a new meaning to they just don't make it like they used to.

[@jimmyhemmer2893]

You should do a video on Jack Parsons!

[@marcmcreynolds2827]

... and title it "Probably best that you don't stand next to me".

[@AnonymousFreakYT]

The saddest thing about SLS to me is the fact that engines that were meant to be reusable are just being thrown away. Both the SSME and the OMS. These programs are so expensive, just manufacture new disposable engines (as they'll have to do once they run out of STS-used engines anyway) and send the old STS-used engines to museums…

[@TimbavatiLion]

So the brand new Orion capsules are flying literally the same engines that propelled the Space Shuttles in and around orbit. Cool 😁

[@codymoe4986]

And got to orbit, using the main shuttle engines as well, courtesy of SLS...

[@jshepard152]

10:12 The result of this redundancy was Jim Lovell's comment from the moon. "Please be advised there is a Santa Claus."

[@ronschlorff7089]

Yes, and he left some duct tape in their stockings!! ;D

[@kalon9999]

Scott, please adjust the "Dark Bramble" Outer Wilds poster you have framed behind you! It's starting to slip in the frame!

[@petergorian535]

Any comments on the starship launch pad redesign?? Seems overly complex.

[@sidv4615]

14:10 same can be said about the B-52. Does its job, isn't a garage queen. What else do you need?

[@brentboswell1294]

Re: OMS shuttle engines, as I understand it, an OMS burn was conducted during shuttle launches headed to the ISS. It provided some extra delta-v while the main engines were burning, which helped loft the heavy ISS construction payloads into the highly inclined ISS orbit. The shuttle was kind of at the limits of what it could do launching from the Cape to the ISS...which was placed in the orbit it was so that Soyuz and Progress could service it on orbit 😉

[@marcmcreynolds2827]

AFAIK there was always an OMS burn. Otherwise the external tank would go into orbit. For a while that was actually studied, e.g. for outfitting into space lab modules, but you otherwise didn't want them up there, coming down in some random place as well as cutting into payload capability

[@brentboswell1294]

@@marcmcreynolds2827 yes, we're familiar with the OMS burn for orbit injection after the external tank is jettisoned. But I was talking about the OMS engines burning at the same time as the main engines.

[@marcmcreynolds2827]

@@brentboswell1294 I missed that. Sorry.

[@rdfox76]

OK, there was always at least *one* OMS burn during the launch and ascent phase, and sometimes as many as *three*. Here's the breakdown: The original shuttle mission profile worked on the assumption that the guidance and engine control systems wouldn't be *quite* precise enough to get to exactly the apogee that was desired for a given mission. (Why this is the case when every mission before the Shuttle had successfully done a direct single-burn-to-orbit insertion into the desired orbit, I'll never really understand.) Thus, the plan was to have MECO occur when the apogee was still slightly below the desired target orbital altitude, with the Shuttle then using a short burn (OMS-1) to both gain separation from the jettisoned external tank, and to fine-tune that apogee. 45 minutes later, at that apogee, a second, longer burn (OMS-2) would be performed to raise the perigee and circularize the orbit. However, after a while, it was recognized that the vehicle was entirely capable of hitting the target initial apogee bang-on, and a new procedure that used only the circularization burn was adopted. (Said burn was still designated OMS-2, because each mission was planned around using an OMS-1 burn if MECO didn't come exactly on schedule; if it did come on schedule, the crew would be informed that they were approved to skip the OMS-1 burn.) Meanwhile, fairly early on in the program, it was recognized that an OMS burn performed during the late phases of main engine powered flight could serve as an "afterburner" of sorts and get a little more total impulse out of the vehicle, allowing it to carry another couple of tons to any given orbit. This was not a completely standard procedure for most of the program (because the extra burn would reduce the delta-V available for orbital maneuvers), but it was used on certain missions that required a particularly heavy payload to a particularly high inclination. However, once construction of the ISS commenced, it became a de facto standard procedure because the small amount of extra upmass per launch would, over time, add up to multiple entire *flights* to the ISS, saving money in the long run. Note that this burn was in *addition* to the OMS orbital insertion burn or burns following MECO. Additionally, all of the (intact) Shuttle post-SRB ignition launch abort scenarios included at least one OMS burn. This was both to assist in getting the required total impulse to complete the abort trajectory with one or more main engines out, and, more importantly, to dump the OMS propellants that would have been consumed during the orbital insertion and deorbit burns, so that the vehicle's landing weight and center of gravity would be within limits. In the RTLS and TAL modes, the burn would be conducted before MECO, and in the ATO mode, you basically just did the normal OMS burns (because you're putting the spacecraft into a stable, if low, parking orbit). I'm not certain when the OMS burn(s?) occurred in the AOA mode, since that was a mode that would only be used in a very brief period, after you had too much energy for a TAL and not enough for an ATO.

[@RCAvhstape]

Read Mike Mullane's book, he was an astronaut at the time and was one of the people who did the math and recommended using the OMS during the main engine burn, long before the ISS. One reason was to give them an extra push for transatlantic abort scenarios.

[@robertoler3795]

one of (yes my family has three) Ercoupes was the one that did the test :)

[@Rumblestrip]

Something to be said about "if it aint broke, dont fix it."

[@Skorpychan]

So, 'because it's a proven design that works', and 'because reliability is important when in space'? Good to know they're using the space equivalent of the I4 petrol engine.

[@etelmo]

The way they get the rocket fuel to mix sounds an awful lot like the homogenization process for milk so the fat doesn't separate out lol

[@Rebar77_real]

Did you see the steam first stage rocket progress? Cheers!

[@YMandarin]

Me having played RP1: yeah I know most of the AJ10 versions

[@joyl7842]

9:40 I'm confused here. You said it was powering the service module, but then you're talking about the lander. I thought the lander's rocketmotor was a Grumman product?

[@andrewreynolds9371]

like with the Soyuz module, this engine follows the old engineering adage of "If it ain't broke, don't 'fix' it!"

[@felipe88alves]

Hey, hey. Eyes up here young man

[@coreys2686]

Yet another relic of the Shuttle program getting dumped into the drink. At least they're getting used I suppose. I'd be interested to find out about other pieces of Shuttle program, aside from the RS-25 and AJ-10.

[@Embassy_of_Jupiter]

Can you do a video on what fuel modern missiles are powered by. You alwaye see these amateur rocket engines run out of fuel after 5 seconds, but military missiles have insane enturance comparatively.

[@target844]

Some military rocket engines burn out in a fraction of a second, and some burn for a longer time. An example of a very quick burn is the bazooka rocket engine burns out in the launch tube. If you look at rocket artillery where you have rockets size with comparable size to amateur rockets the burn time is just a few seconds too, you can get smoke out of them for another few seconds but there is minimal thrust. Take a look at a GMLRS rocket launched from a HIMARS in Ukraine and you see around 7 seconds of smoke A large solid rocket engine can be made to burn longer, the Space Shuttle Solid Rocket Booster did burn for 127 minutes. If you need an engine that can be on for a very long time like in a cruise missile the solution is a turbojet engine used after the initial solid fuel boosters.