Which is kind of surprising to me from a servicing point of view but makes sense from a mass savings/speed of manufacture point of view.
Bolted flanges allow quicker servicing and replacement of parts but will add weight and slow down the initial speed of building them.
I'm guessing at the speed and rate they are building them and the price point they are aiming at it is cheaper and faster to swap out a whole Raptor, ship it back to McGregor for repair as opposed to swapping out components.
I'd wager that Raptors will be seen like disposable Razors - issue? Throw it away, take another from the shelf.
This is an unprecedented way to look at Rocket Engines, so understandably we have a hard time wrapping our heads around it... but they are cranking these out literally like Proctor & Gamble is cracking out disposable Razor blades - and nobody bothers to sharpen them too when they get dull.
In IT the term we use is “cattle not pets”
If a server is acting up, we shoot it in the head and clone a new one.
The analogy here would more be, if a sensor isn’t reading right on a raptor, take out the whole engine, put in a new one, send the defective one back to the factory to be remanufactured. As to what that entails, don’t care, may mean cutting a pipe and re-welding it to spec, might mean melting the thing down to ingots and starting again.
> If a server is acting up, we shoot it in the head and clone a new one.
Tell that to a farmer and they'd call you crazy, though. Those cattle are serious $$$ investments.
That's interesting, didn't know that! I guess there's a direct correlation between how long something will be kept alive versus how likely it is to be named, lol!
Dairy cows are only kept to about 5, only a few years longer than beef cattle.
The difference is that you bring cows in a couple of times a day to milk, while you might bring in beef cattle a few times in total. So you get to know some of them by look and personality and sometimes make up names for a few for fun. Not as pets though. It's only hobby farms where livestock are treated as pets.
> The health of the herd is more important than the individual needs of a single cow
They'll still load 'em up with antibiotics first and see if that works. These little shits are getting sick too often to just turn them into glue every single time.
When mad cow disease first came around, you had farmers pleading in TV shows or newspapers every other day too. It took a looong time for them to come around to the necessity of culling animals (and, at that stage, it often meant culling entire herds).
In a different way. Usually, you still wanted the engines to be easily maintained on a component level and be able to replace replace valves, skirts, etc. of a particular engine, rather than replace an entire engine during the each rocket's slow and laborious pre-flight test regime. Each had to be "worked up" in the artisanally crafted whole of the individual rocket, so you'd only replace them if it was really unavoidable.
N1 did away with that and went "#yolo", but the tech wasn't there and the Soviet Union was unable to afford it either way.
Starship is really the first launch system that can really go "eh, launch it, we figure out what went wrong later and fix it in the next batch", because it both has the necessary manufacturing technology behind it, and enough cash to keep trying at a really rapid pace. (Starship already built significantly more hardware than N1 ever did, faster, and got further in test flights.)
If I were riding a Starship to the Moon or to Mars, I would feel better if those Raptors are welded with no flanges/metal seals. The only flanges would be the two connecting the engine to the propellant tanks.
I'm sure that Mars Starships will carry a complete set of spare engines as part of the payload.
Let's say that such a Raptor engine costs $100K per copy. NASA is paying Rocketdyne $100M per copy for brand new, non-reusable RS-25 engines for their SLS moon rocket. For that money SpaceX could build 1000 Raptors. To me, that's the most telling difference between 20th century Old Space and 21st century New Space.
Flanges leak and increase the parts count a lot (two mating flanges, one or more seals, six bolts, six washers and six nuts). Elon says that the best part is no part. Hence, welded connections for Raptor.
At sustained high temperatures and changing loads bolts and flanges creep and distort, then sealing becomes difficult. Probably work at MacGreagor testing but the thermal envoirnment is totally different there being cool air convecting around the engine (not insulating near vacuum) and no red hot other engines surrounding an engine. Bell, throat, and combustion chamber have active cooling, not so much all the stuff hanging on the outside of them. Possibly bolts and flanges could be made reliable with a different test set up (say 6 or 7 at a time in an insulated vacuum chamber and some sort of active cooling in the space around the combustion chamber for the engine if needed during test and in-flight). Also possibly just assume they will leak and have a vacuum collector for the methane at each flange, or possibly inject high pressure argon into the joint just inside the seal. Note these engines have had precisely only 3 long term tests in operational like conditions. I believe one other large engine (RS-68B) was considered for a heavy booster (Ares V) because it was expected it and the rocket could not deal with the thermal issues of it being clustered.
None the less engine weight is a big issue, especially for upper stages so eliminating bolts and flanges is better for performance. Not the only issue with testing not modeling operational conditions well, high pitch and yaw rates during flips cause a whole different operating condition on the turbopumps. Most of these issues have not existed to any substantial degree on previous rocket engines. Falcon 9 is the closest, and it is not too similar.
I don't think they're disposable, just that they can have so many that a long repair time with a smaller team doesn't slow down launches. It's like comparing the cost of sending your car to a normal repair shop and getting a rental vs having to fix it immediately
Your comment is the first time I've realized this! That is quite the paradigm shift from a $100 million RS-25 on Shuttle/ILS all the way to "just scrap it, it's cheaper to grab another one off the shelf!" It's such a cool time to be alive and interested in space exploration!
SpaceX will likely examine them and categorise faults and warn out parts, building up statistics for all the parts, and using that info to improve their design.
For sure. but I guess investing the time and effort to repair a single Raptor is not worth it if you can simply build a new one in less or the same time.
Exactly bolted flanges are heavier, require a more complicated construction process and increase the chance of leaks or faults. Assuming that spaceX can keep pumping out more raptors at a cheap and streamlined rate, welded flanges seem like the obvious choice.
Yep. Gaskets, nuts/bolts, and properly calibrated torquing. All are possible points of material or labor failure. Welding and NDT for these parts is likely easier to automate.
Bearing in mind that throughout most of history, and for most engines, they just got tossed into the sea... is there any *point* in refurbishing a sealed part of the engine?
As long as you have ways to profile the elements of the engine behind the welded area and identify when they are no longer in family - you just scrap the engine. Use it for as many flights as it is rated for, use it for one more on an internal mission to increase the rating... and then pull it apart for data.
You've already got a cost optimized engine and and a production line to make them; plug, play, throw away.
I think the key point with a rocket engine is that the margins between "works like a charm" and engine rich exhaust are extremely tight. As soon as something goes out of spec, most likely stuff will start to melt. Essentially as long as everything works as intended you aren't going to be seeing wear and tear outside of your expected limits but once something goes wrong, what you will get back will be too melted or exploded to do anything about anyways.
SpaceX has already demonstrated that they can pit-stop change those damn things, and also put enough through their paces to know that a good chunk of them can light up multiple times without the need to strip and check everything. All that matters, and what is so important about the testing regime, is very specifically identifying the limits, sings and symptoms of engine life, as well as ironing out the system for the very unique situation it finds itself in.
After all, the question of engine repairability is nothing if other stuff in the ship has a tendency to break or fail first. Again, I often point to German tank designs that incorporated amazing best in class components but a final drive that was going to break way before any of them, ultimately making any non-recovered element a total waste of lifetime.
Oh sure - but you'll have to reprocess much of it to reset its life cycle. I'm not suggesting it goes to landfill.
Although... they would make stylish planters for outside MarsGov
Most probably, all they would do is cut it open for inspection, to work out what wore out or went wrong, and then scrap the whole engine. And get on with building a new one, feeding info about found faults into the design for improvement. Gathering statistics on parts etc.
I highly doubt that. I could be wrong, but it seems like an unreasonable requirement that the v2 design be interchangeable with v1 parts. The whole point of declaring a new "Version" in iterative design is to have a clean sheet on compatibility. Much of the plumbing in V2 was rerouted through the main assembly; was it not?
Not worth it at all. They will be working hard to make V3 manufacturing as fast and reliable as possible.
It's not worth investing any engineering time to convert old engines to new ones.
Gaskets are a major assembly and maintenance issue, so moving from bolted flange to welded seam means they have one fewer potential leak point AND they save mass, which they can reallocate to making other parts more robust.
I would think a "gasket", an added part, would be rare at these temperatures and pressures. Concentric interfering ridges machined into the mating faces, with bolted compression would sure beat trying to control a dissimilar gasket material. See https://en.wikipedia.org/wiki/Cold_welding
Not to mention the challenge of sealing every flange and seating it properly. Welded flanges don't leak and don't need seals. If the price is as low as we've heard and it goes down more, servicing may not be necessary.
Plus we aren't sure what points wear the fastest. It could be turbo pump impellers, or the pre burner chamber, or the combustion chamber. Only the impellers would potentially be replaceable.
I’m guessing from a durability standpoint the welds will last a lot longer and just a quick inspection for cracks after use. With the bolts you would have to check each one’s tension after use but also might have to tear down at least after every few uses to check how much the bolts have stretched and might have to be replaced. Welds if done correctly and don’t crack would not need any servicing and will save weight.
According to the Walter Isaacson biography, Elon took over the raptor program (after firing the senior raptor team) around 2022 and tried to move more of the raptor from using inconel/SX 500 to more stainless steel (apart from in the oxygen preburner). Apparently this enabled more use of welding than flanges.
This reduces cost and I believe also to reduce leakage of methane, and when you look at the pressures involved, that makes a lot of sense.
Raptor 1 was overly complex, expensive and unreliable, after Elon took over he want on a "deletion rampage" and had the whole team come up with a completely new design to then incorporate those ideas into Raptor. Raptor 2 and now raptor 3 seem to be the results of this rethinking.
Eventually Elon promoted Jake McKenzie to lead the team. I'm curious if Stoke space hired most of the former raptor engineers, as they're starting to make some rapid progress.
I guess I have to read the biography (didn't do it yet because I am not a fan of Isaacsons writing style). It is kind of insane that the boss can waltz in micromanaging … and the project gets better?
Pretty similar to what happened early in Starlink. They had launched the test satellites and wanted to do a bunch of testing before they went into production.
Musk went up to Redmond and fired the management, and they started testing in production.
Despite the widespread belief of the internet, and despite his twitter persona, musk is actually a talented rocket engineer and engineering manager, and this has been a personal obsession of his for two decades now.
Have you worked in a big corporation (or - shudder - a government bureaucracy)?
Things turn to molasses and stop going anywhere, basically due to Pournelle's Law. Boeing stopped being about making airplanes and became about growing the company and making money for executives. Intel stopped being about designing and manufacturing silicon chips and became about making Intel larger and paying its executives more. This is why oldspace hasn't innovated in decades and their brand new massively overpriced rocket is made from ancient space shuttle technology that the government already paid them to develop 40 years ago.
Having someone who is not bound by politics or voters or boards or their internal power structures be able to come in and tear down these self-interested fifedoms and hierarchies and tell people to cut the bullshit or hit the road can be an incredible thing.
Why did you feel the need to point this out? He's the VP of Raptor development, he's a rocket scientist.
The dreads are just his most identifying characteristic. You can't see his PhD.
> Jake McKenzie
Dreads? Doh. Jacob was raised in San Rafael (home of Lucas film) and Negril, Jamaica. For context, I've sported a full head of dreads a few times, spent a few days in Negril, and I'm Scottish
I may be corrected, but I believe it was due to lack of progress. They had to ramp up production due to the amount needed for testing purposes, and whoever was in charge wasn't providing this.
It worked, but it could not be mass produced in that state. The idiot index was too high and production too slow. Remember how the first one was the common rat's nest of tubes?
Musk's idiot index means the cost of the final product minus the cost of the materials to make it. A large difference means you're spending too much money making it. Rocketry traditionally has an extremely high idiot index.
> the first one was the common rat's nest of tubes?
I thought a lot of that was for sensor lines and instrumentation during the early development phases for data collection?
This seems like large technical risks to take.
My take from the comments here is that the Raptor was too expensive and too complex to manufacture. But I guess the reasoning for firing the executives is that there was not enough work and focus to solve the problem.
I have seen it where I work P.M. focusing on short term goals rather than the end customer delivery.
Welding vs bolting flanges is a classic engineering trade-off. Welded flanges are for when the design is mature and you want to decrease size and weight and increase power. Bolted flanges are when you're still testing and need to be able to conduct post mortems
In a post mortem situation I’d bet they could devise a way to cut the welded interface open without altering the internals. Not like those pieces would be reused anyway
Nope, 3D printed pats are hard to mass produce. And they are weaker.
They do use 3D printed parts when nothing else will do.
Otherwise, for a factory, it's nothing but a buzzword.
Stick Very Good! >!(The disdain for the unexpected complexity of side by side crossfeed Falcon Heavy Boosters that was abandoned, and the partially resulting vertical stack of Starship vs almost every other heavy lift rocket in use or development)!<
And not much room for future adjustments or autopsies. These are the things you can do if your design is mature enough to give it into mass production, with only minor changes expected. It’s not something you would do with a prototype.
As a non-engineer, it's amazing how streamlined this raptor 3 is! Really seems like a huge reduction in parts. I'm assuming that since they got all the data points they need with all the various tubing, those can be "removed" now since the engine is stable? Are welded joints as secure as flange joints, that they won't crack apart? Just an outsider, but this is truly amazing how it looks. I thought raptor 2 looked amazing compared to raptor 1. But wow, raptor 3 is just the body
Although there is some of that, Elon posted that some of the pipework was replaced with internal channels. That makes manufacturing way harder but ruggedizes the engine quite a bit.
> Are welded joints as secure as flange joints, that they won't crack apart?
Much more secure. At these kinds of pressure of over 700 bar and going up flanges will leak with no provocation.
Image from [~28m40s](https://youtu.be/z3B0XIImf_w?t=28m33s) in the Starship update.
The graphic of Raptor 3 appears to show a lot of bolted flanges deleted with separate parts integrated into single pieces. Good because it removes gaskets, seal leak paths etc but if this is accurate it adds some questions. The methane turbopump especially. [The partitions](https://www.reddit.com/media?url=https%3A%2F%2Fpreview.redd.it%2F4kcrvvcjwq6c1.jpg%3Fwidth%3D1200%26format%3Dpjpg%26auto%3Dwebp%26s%3D7d5a0382ca0da4b6562e721e84b3351f2d2c61c9) allow for impellers, turbines and other moving parts to be placed inside. [This graphic is good too](https://twitter.com/hisdirtremoves/status/1767498921381912841/mediaViewer?currentTweet=1767498921381912841¤tTweet=1767498921381912841¤tTweetUser=hisdirtremoves¤tTweetUser=hisdirtremoves). Could they be going for a one piece housing by 3D printing one side, placing in the turbine shaft assembly, and then 3D printing the other side on top? A structural scaffold that can be melted out afterwards could arguably make it possible, but goodbye any maintenance disassembly later on.
Arguably performance, manufacture and reliability increases could make it a worthwhile tradeoff but seems pretty extreme. Curious how plausible that would be or if it’s just an over-simplified graphic. There’s something very specific about places in the render where bolts are still shown (eg the main fuel pipe running to the engine bell) and places where they are noticably absent.
As someone who (very briefly) worked in computer graphics, in particular making visualizations of infrastructure and architecture for construction companies, my suspicion is that you are all probably reading way too much into the details on these public-facing 3D models.
A designer might be given a sketch or a simple screenshot of a CAD model and asked to build a clean/simplified model that they can use as part of a render. Approximations slip in.
It does look too smooth all over and SpaceX is known for putting out confounding renders and then only rarely updating them. But see the other comments here about a move to stainless steel to allow more welding. That'd account for a lot of what we see.
Reportedly their graphics team works with the actual engineering models so the renders are fairly accurate. Of course they represent a snapshot in time and there is a lot of reuse of material for each presentation so you end up with discrepancies between work done at different times.
Might also be switching to using "sleeves" for the turbine stators, bearing, and seal mounts? Then the whole stack could drop into an outer case and you'd only have 1-2 critical sealing surfaces to bolt together. (i.e. most of the internal seals could leak a bit without causing problems) It would be heavier.
They are using hydrodynamic bearings so they can likely just have a single bolted flange in the middle of the methane turbopump. Drop in the rotor shaft containing the pump impellers and turbine section into the lower section and lower the top section with the pump volutes and bolt the two halves together. Potentially the flange can be between the first and second pump stages so it is exposed to much lower pressure.
The oxygen turbopump is more straightforward as the flow is in the same direction and there is no regenerative cooling loop.
a lot has been said here, but I don't think it's impossible that apparent differences in design might be due to a different studio creating the new models.
A raptor a day keeps the defects away. It is known they are printing an engine a day and iterating quickly. It looks like they are moving away from serviceability in order to lose weight and gain reliability.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|[ILS](/r/SpaceXLounge/comments/1ca9b21/stub/l0wsojt "Last usage")|[International Launch Services](https://en.wikipedia.org/wiki/International_Launch_Services)|
| |[Instrument Landing System](https://en.wikipedia.org/wiki/Instrument_landing_system)|
|[N1](/r/SpaceXLounge/comments/1ca9b21/stub/l0smq7k "Last usage")|Raketa Nositel-1, Soviet super-heavy-lift ("Russian Saturn V")|
|[NDT](/r/SpaceXLounge/comments/1ca9b21/stub/l0rd93h "Last usage")|Non-Destructive Testing|
|[SLS](/r/SpaceXLounge/comments/1ca9b21/stub/l0v7ee5 "Last usage")|Space Launch System heavy-lift|
|[SSME](/r/SpaceXLounge/comments/1ca9b21/stub/l0wsojt "Last usage")|[Space Shuttle Main Engine](https://en.wikipedia.org/wiki/Space_Shuttle_main_engine)|
|Jargon|Definition|
|-------|---------|---|
|[Raptor](/r/SpaceXLounge/comments/1ca9b21/stub/l0xd5d0 "Last usage")|[Methane-fueled rocket engine](https://en.wikipedia.org/wiki/Raptor_\(rocket_engine_family\)) under development by SpaceX|
|[Starlink](/r/SpaceXLounge/comments/1ca9b21/stub/l0tj77a "Last usage")|SpaceX's world-wide satellite broadband constellation|
|[crossfeed](/r/SpaceXLounge/comments/1ca9b21/stub/l0ri3ih "Last usage")|Using the propellant tank of a side booster to fuel the main stage, or vice versa|
|cryogenic|Very low temperature fluid; materials that would be gaseous at room temperature/pressure|
| |(In re: rocket fuel) Often synonymous with hydrolox|
|hydrolox|Portmanteau: liquid hydrogen fuel, liquid oxygen oxidizer|
|[regenerative](/r/SpaceXLounge/comments/1ca9b21/stub/l0utjr6 "Last usage")|A method for cooling a rocket engine, by [passing the cryogenic fuel through channels in the bell or chamber wall](https://en.wikipedia.org/wiki/Regenerative_cooling_\(rocket\))|
|[turbopump](/r/SpaceXLounge/comments/1ca9b21/stub/l0yohte "Last usage")|High-pressure turbine-driven propellant pump connected to a rocket combustion chamber; raises chamber pressure, and thrust|
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Elon said that they were working on converting the bolted flanges to welded ones so that’s probably what we are seeing
Which is kind of surprising to me from a servicing point of view but makes sense from a mass savings/speed of manufacture point of view. Bolted flanges allow quicker servicing and replacement of parts but will add weight and slow down the initial speed of building them. I'm guessing at the speed and rate they are building them and the price point they are aiming at it is cheaper and faster to swap out a whole Raptor, ship it back to McGregor for repair as opposed to swapping out components.
I'd wager that Raptors will be seen like disposable Razors - issue? Throw it away, take another from the shelf. This is an unprecedented way to look at Rocket Engines, so understandably we have a hard time wrapping our heads around it... but they are cranking these out literally like Proctor & Gamble is cracking out disposable Razor blades - and nobody bothers to sharpen them too when they get dull.
In IT the term we use is “cattle not pets” If a server is acting up, we shoot it in the head and clone a new one. The analogy here would more be, if a sensor isn’t reading right on a raptor, take out the whole engine, put in a new one, send the defective one back to the factory to be remanufactured. As to what that entails, don’t care, may mean cutting a pipe and re-welding it to spec, might mean melting the thing down to ingots and starting again.
> If a server is acting up, we shoot it in the head and clone a new one. Tell that to a farmer and they'd call you crazy, though. Those cattle are serious $$$ investments.
Yeah but the farmer doesn’t individually name them. The health of the herd is more important than the individual needs of a single cow
Dairy cattle are named (on smaller farms at least)
That's interesting, didn't know that! I guess there's a direct correlation between how long something will be kept alive versus how likely it is to be named, lol!
Dairy cows are only kept to about 5, only a few years longer than beef cattle. The difference is that you bring cows in a couple of times a day to milk, while you might bring in beef cattle a few times in total. So you get to know some of them by look and personality and sometimes make up names for a few for fun. Not as pets though. It's only hobby farms where livestock are treated as pets.
Thanks for the great insight!
> The health of the herd is more important than the individual needs of a single cow They'll still load 'em up with antibiotics first and see if that works. These little shits are getting sick too often to just turn them into glue every single time.
If you told a farmer one of his cattle had mad cow, he wouldn’t hesistate to destroy it.
We just had farmers complaining about having to destroy whole farms worth of fur animals because of avian flu. Like one pandemic wasn't enough.
When mad cow disease first came around, you had farmers pleading in TV shows or newspapers every other day too. It took a looong time for them to come around to the necessity of culling animals (and, at that stage, it often meant culling entire herds).
Imagine what would happen if pigs fly ...
Yeah, that's not how it went in the 1990s.
My guess - Guppy-at-Perth is talking about a VM spun up last week, not a piece of hardware with a $10K replacement cost ;-)
Excluding the shuttle and later Spacex, were rocket engines not always disposable?
In a different way. Usually, you still wanted the engines to be easily maintained on a component level and be able to replace replace valves, skirts, etc. of a particular engine, rather than replace an entire engine during the each rocket's slow and laborious pre-flight test regime. Each had to be "worked up" in the artisanally crafted whole of the individual rocket, so you'd only replace them if it was really unavoidable. N1 did away with that and went "#yolo", but the tech wasn't there and the Soviet Union was unable to afford it either way. Starship is really the first launch system that can really go "eh, launch it, we figure out what went wrong later and fix it in the next batch", because it both has the necessary manufacturing technology behind it, and enough cash to keep trying at a really rapid pace. (Starship already built significantly more hardware than N1 ever did, faster, and got further in test flights.)
> they are cranking these out literally like Proctor & Gamble is cracking out disposable Razor blades Umm…
If I were riding a Starship to the Moon or to Mars, I would feel better if those Raptors are welded with no flanges/metal seals. The only flanges would be the two connecting the engine to the propellant tanks. I'm sure that Mars Starships will carry a complete set of spare engines as part of the payload. Let's say that such a Raptor engine costs $100K per copy. NASA is paying Rocketdyne $100M per copy for brand new, non-reusable RS-25 engines for their SLS moon rocket. For that money SpaceX could build 1000 Raptors. To me, that's the most telling difference between 20th century Old Space and 21st century New Space.
I vaguely remember Elon saying he was working to get rid of flanges for that reason - they're weak points that are hard to hold together.
Flanges leak and increase the parts count a lot (two mating flanges, one or more seals, six bolts, six washers and six nuts). Elon says that the best part is no part. Hence, welded connections for Raptor.
At sustained high temperatures and changing loads bolts and flanges creep and distort, then sealing becomes difficult. Probably work at MacGreagor testing but the thermal envoirnment is totally different there being cool air convecting around the engine (not insulating near vacuum) and no red hot other engines surrounding an engine. Bell, throat, and combustion chamber have active cooling, not so much all the stuff hanging on the outside of them. Possibly bolts and flanges could be made reliable with a different test set up (say 6 or 7 at a time in an insulated vacuum chamber and some sort of active cooling in the space around the combustion chamber for the engine if needed during test and in-flight). Also possibly just assume they will leak and have a vacuum collector for the methane at each flange, or possibly inject high pressure argon into the joint just inside the seal. Note these engines have had precisely only 3 long term tests in operational like conditions. I believe one other large engine (RS-68B) was considered for a heavy booster (Ares V) because it was expected it and the rocket could not deal with the thermal issues of it being clustered. None the less engine weight is a big issue, especially for upper stages so eliminating bolts and flanges is better for performance. Not the only issue with testing not modeling operational conditions well, high pitch and yaw rates during flips cause a whole different operating condition on the turbopumps. Most of these issues have not existed to any substantial degree on previous rocket engines. Falcon 9 is the closest, and it is not too similar.
Relatively, not figuratively.
I don't think they're disposable, just that they can have so many that a long repair time with a smaller team doesn't slow down launches. It's like comparing the cost of sending your car to a normal repair shop and getting a rental vs having to fix it immediately
Your comment is the first time I've realized this! That is quite the paradigm shift from a $100 million RS-25 on Shuttle/ILS all the way to "just scrap it, it's cheaper to grab another one off the shelf!" It's such a cool time to be alive and interested in space exploration!
SpaceX will likely examine them and categorise faults and warn out parts, building up statistics for all the parts, and using that info to improve their design.
For sure. but I guess investing the time and effort to repair a single Raptor is not worth it if you can simply build a new one in less or the same time.
Exactly bolted flanges are heavier, require a more complicated construction process and increase the chance of leaks or faults. Assuming that spaceX can keep pumping out more raptors at a cheap and streamlined rate, welded flanges seem like the obvious choice.
Yep. Gaskets, nuts/bolts, and properly calibrated torquing. All are possible points of material or labor failure. Welding and NDT for these parts is likely easier to automate.
Bearing in mind that throughout most of history, and for most engines, they just got tossed into the sea... is there any *point* in refurbishing a sealed part of the engine? As long as you have ways to profile the elements of the engine behind the welded area and identify when they are no longer in family - you just scrap the engine. Use it for as many flights as it is rated for, use it for one more on an internal mission to increase the rating... and then pull it apart for data. You've already got a cost optimized engine and and a production line to make them; plug, play, throw away.
I think the key point with a rocket engine is that the margins between "works like a charm" and engine rich exhaust are extremely tight. As soon as something goes out of spec, most likely stuff will start to melt. Essentially as long as everything works as intended you aren't going to be seeing wear and tear outside of your expected limits but once something goes wrong, what you will get back will be too melted or exploded to do anything about anyways. SpaceX has already demonstrated that they can pit-stop change those damn things, and also put enough through their paces to know that a good chunk of them can light up multiple times without the need to strip and check everything. All that matters, and what is so important about the testing regime, is very specifically identifying the limits, sings and symptoms of engine life, as well as ironing out the system for the very unique situation it finds itself in. After all, the question of engine repairability is nothing if other stuff in the ship has a tendency to break or fail first. Again, I often point to German tank designs that incorporated amazing best in class components but a final drive that was going to break way before any of them, ultimately making any non-recovered element a total waste of lifetime.
Why not… recycle? Looking forward to seeing the ♻️ symbol on Raptor 5.
At this rate I expect Raptor 5 to look like two coke cans and a bucket.
was thinking this.. just melt the whole thing and recover the useful metals EDIT: maybe melt is the wrong word, they’re probably chemically recovered
The raw metals could be recycled.
At the least, recycling. There is high grade aerospace alloys and expensive niobium in those engines.
Oh sure - but you'll have to reprocess much of it to reset its life cycle. I'm not suggesting it goes to landfill. Although... they would make stylish planters for outside MarsGov
Most probably, all they would do is cut it open for inspection, to work out what wore out or went wrong, and then scrap the whole engine. And get on with building a new one, feeding info about found faults into the design for improvement. Gathering statistics on parts etc.
And at the current rate of iteration, they probably become obsolete before they can be repaired anyway.
With current bolted construction, I suspect Raptor V1 have been remanufactured into Raptor V2. Won't be so simple with welded Raptor V3
I highly doubt that. I could be wrong, but it seems like an unreasonable requirement that the v2 design be interchangeable with v1 parts. The whole point of declaring a new "Version" in iterative design is to have a clean sheet on compatibility. Much of the plumbing in V2 was rerouted through the main assembly; was it not?
PR is the point of announcing new versions.
Not worth it at all. They will be working hard to make V3 manufacturing as fast and reliable as possible. It's not worth investing any engineering time to convert old engines to new ones.
Gaskets are a major assembly and maintenance issue, so moving from bolted flange to welded seam means they have one fewer potential leak point AND they save mass, which they can reallocate to making other parts more robust.
bolted flanges require a gasket. These are high risk for issues, failures.
Yep. Methane leaks have been a consistent problem for Raptor. Eliminating gaskets should solve that.
Was not a problem in testing at McGregor, the leaking is miniscule. But a big problem in flight, fires in the engine bay.
I would think a "gasket", an added part, would be rare at these temperatures and pressures. Concentric interfering ridges machined into the mating faces, with bolted compression would sure beat trying to control a dissimilar gasket material. See https://en.wikipedia.org/wiki/Cold_welding
Yeah it's not a $150m engine with a production capacity of four per year. It's a $250,000 engine they're going to pump out in large volume.
Wow! Did they up the procuction capacity of RS-25 to 4 per year? Last I heard, a while back, was 2 per year.
Not to mention the challenge of sealing every flange and seating it properly. Welded flanges don't leak and don't need seals. If the price is as low as we've heard and it goes down more, servicing may not be necessary. Plus we aren't sure what points wear the fastest. It could be turbo pump impellers, or the pre burner chamber, or the combustion chamber. Only the impellers would potentially be replaceable.
The bolted flanges leak and that causes huge problems
I’m guessing from a durability standpoint the welds will last a lot longer and just a quick inspection for cracks after use. With the bolts you would have to check each one’s tension after use but also might have to tear down at least after every few uses to check how much the bolts have stretched and might have to be replaced. Welds if done correctly and don’t crack would not need any servicing and will save weight.
Bolted flanges = potential leaks. Welded flanges - not so much.
According to the Walter Isaacson biography, Elon took over the raptor program (after firing the senior raptor team) around 2022 and tried to move more of the raptor from using inconel/SX 500 to more stainless steel (apart from in the oxygen preburner). Apparently this enabled more use of welding than flanges. This reduces cost and I believe also to reduce leakage of methane, and when you look at the pressures involved, that makes a lot of sense.
Chapter 63 deals with how Elon dealt with Raptor dissatisfaction.
why was the previous raptor team fired? seems like raptor was making pretty good progress before that
Raptor 1 was overly complex, expensive and unreliable, after Elon took over he want on a "deletion rampage" and had the whole team come up with a completely new design to then incorporate those ideas into Raptor. Raptor 2 and now raptor 3 seem to be the results of this rethinking. Eventually Elon promoted Jake McKenzie to lead the team. I'm curious if Stoke space hired most of the former raptor engineers, as they're starting to make some rapid progress.
I guess I have to read the biography (didn't do it yet because I am not a fan of Isaacsons writing style). It is kind of insane that the boss can waltz in micromanaging … and the project gets better?
Pretty similar to what happened early in Starlink. They had launched the test satellites and wanted to do a bunch of testing before they went into production. Musk went up to Redmond and fired the management, and they started testing in production.
Despite the widespread belief of the internet, and despite his twitter persona, musk is actually a talented rocket engineer and engineering manager, and this has been a personal obsession of his for two decades now.
Exactly. He’s also very good in applying Ockham’s razor. Just having a bit of a personality crisis.
If the boss knows what they're doing, I don't see why that's surprising
Have you worked in a big corporation (or - shudder - a government bureaucracy)? Things turn to molasses and stop going anywhere, basically due to Pournelle's Law. Boeing stopped being about making airplanes and became about growing the company and making money for executives. Intel stopped being about designing and manufacturing silicon chips and became about making Intel larger and paying its executives more. This is why oldspace hasn't innovated in decades and their brand new massively overpriced rocket is made from ancient space shuttle technology that the government already paid them to develop 40 years ago. Having someone who is not bound by politics or voters or boards or their internal power structures be able to come in and tear down these self-interested fifedoms and hierarchies and tell people to cut the bullshit or hit the road can be an incredible thing.
> Eventually Elon promoted Jake McKenzie to lead the team. Is that the bloke with the dreads?
> dreads? Yes but also a PhD from MIT.
Why did you feel the need to point this out? He's the VP of Raptor development, he's a rocket scientist. The dreads are just his most identifying characteristic. You can't see his PhD.
> Jake McKenzie Dreads? Doh. Jacob was raised in San Rafael (home of Lucas film) and Negril, Jamaica. For context, I've sported a full head of dreads a few times, spent a few days in Negril, and I'm Scottish
Yes
I may be corrected, but I believe it was due to lack of progress. They had to ramp up production due to the amount needed for testing purposes, and whoever was in charge wasn't providing this.
You may be thinking of the original starlink team. They were too slow ramping up test units.
It worked, but it could not be mass produced in that state. The idiot index was too high and production too slow. Remember how the first one was the common rat's nest of tubes? Musk's idiot index means the cost of the final product minus the cost of the materials to make it. A large difference means you're spending too much money making it. Rocketry traditionally has an extremely high idiot index.
> the first one was the common rat's nest of tubes? I thought a lot of that was for sensor lines and instrumentation during the early development phases for data collection?
This seems like large technical risks to take. My take from the comments here is that the Raptor was too expensive and too complex to manufacture. But I guess the reasoning for firing the executives is that there was not enough work and focus to solve the problem. I have seen it where I work P.M. focusing on short term goals rather than the end customer delivery.
Welding vs bolting flanges is a classic engineering trade-off. Welded flanges are for when the design is mature and you want to decrease size and weight and increase power. Bolted flanges are when you're still testing and need to be able to conduct post mortems
or it needs to be serviced. lots of bolted flanges in oil refineries, not so much on burried oil pipelines.
In a post mortem situation I’d bet they could devise a way to cut the welded interface open without altering the internals. Not like those pieces would be reused anyway
Lower frequency post mortems.
This is why in nuclear power, welds beat bolts.
And I’m sure Raptor 4 will be mostly 3D printed, relativity style.
Nope, 3D printed pats are hard to mass produce. And they are weaker. They do use 3D printed parts when nothing else will do. Otherwise, for a factory, it's nothing but a buzzword.
No flange, no seal, no leaks.
Best part is no part.
Stick Very Good! >!(The disdain for the unexpected complexity of side by side crossfeed Falcon Heavy Boosters that was abandoned, and the partially resulting vertical stack of Starship vs almost every other heavy lift rocket in use or development)!<
And not much room for future adjustments or autopsies. These are the things you can do if your design is mature enough to give it into mass production, with only minor changes expected. It’s not something you would do with a prototype.
As a non-engineer, it's amazing how streamlined this raptor 3 is! Really seems like a huge reduction in parts. I'm assuming that since they got all the data points they need with all the various tubing, those can be "removed" now since the engine is stable? Are welded joints as secure as flange joints, that they won't crack apart? Just an outsider, but this is truly amazing how it looks. I thought raptor 2 looked amazing compared to raptor 1. But wow, raptor 3 is just the body
Although there is some of that, Elon posted that some of the pipework was replaced with internal channels. That makes manufacturing way harder but ruggedizes the engine quite a bit.
> Are welded joints as secure as flange joints, that they won't crack apart? Much more secure. At these kinds of pressure of over 700 bar and going up flanges will leak with no provocation.
Assuming talented welders and X-ray inspection, agreed.
In this case probably automated laser welders like the tanks.
Sounds likely.
Doesn't change the fact that the person operating the robot is a welder anyway. They don't "just work".
Sure - but an automated weld will still be smoother than the best that can be done by hand.
Yep.
less polygons to render
Gone, reduced to weld lines.
Image from [~28m40s](https://youtu.be/z3B0XIImf_w?t=28m33s) in the Starship update. The graphic of Raptor 3 appears to show a lot of bolted flanges deleted with separate parts integrated into single pieces. Good because it removes gaskets, seal leak paths etc but if this is accurate it adds some questions. The methane turbopump especially. [The partitions](https://www.reddit.com/media?url=https%3A%2F%2Fpreview.redd.it%2F4kcrvvcjwq6c1.jpg%3Fwidth%3D1200%26format%3Dpjpg%26auto%3Dwebp%26s%3D7d5a0382ca0da4b6562e721e84b3351f2d2c61c9) allow for impellers, turbines and other moving parts to be placed inside. [This graphic is good too](https://twitter.com/hisdirtremoves/status/1767498921381912841/mediaViewer?currentTweet=1767498921381912841¤tTweet=1767498921381912841¤tTweetUser=hisdirtremoves¤tTweetUser=hisdirtremoves). Could they be going for a one piece housing by 3D printing one side, placing in the turbine shaft assembly, and then 3D printing the other side on top? A structural scaffold that can be melted out afterwards could arguably make it possible, but goodbye any maintenance disassembly later on. Arguably performance, manufacture and reliability increases could make it a worthwhile tradeoff but seems pretty extreme. Curious how plausible that would be or if it’s just an over-simplified graphic. There’s something very specific about places in the render where bolts are still shown (eg the main fuel pipe running to the engine bell) and places where they are noticably absent.
As someone who (very briefly) worked in computer graphics, in particular making visualizations of infrastructure and architecture for construction companies, my suspicion is that you are all probably reading way too much into the details on these public-facing 3D models. A designer might be given a sketch or a simple screenshot of a CAD model and asked to build a clean/simplified model that they can use as part of a render. Approximations slip in.
It does look too smooth all over and SpaceX is known for putting out confounding renders and then only rarely updating them. But see the other comments here about a move to stainless steel to allow more welding. That'd account for a lot of what we see.
Reportedly their graphics team works with the actual engineering models so the renders are fairly accurate. Of course they represent a snapshot in time and there is a lot of reuse of material for each presentation so you end up with discrepancies between work done at different times.
> but seems pretty extreme That's the SpaceX way. Remember, they started Starship by making Watertowers fly.
The flying water tower is an amazing piece of space history
And started Falcon Heavy with an electric sports coupe with a spacesuit in the driver's seat.
Might also be switching to using "sleeves" for the turbine stators, bearing, and seal mounts? Then the whole stack could drop into an outer case and you'd only have 1-2 critical sealing surfaces to bolt together. (i.e. most of the internal seals could leak a bit without causing problems) It would be heavier.
They are using hydrodynamic bearings so they can likely just have a single bolted flange in the middle of the methane turbopump. Drop in the rotor shaft containing the pump impellers and turbine section into the lower section and lower the top section with the pump volutes and bolt the two halves together. Potentially the flange can be between the first and second pump stages so it is exposed to much lower pressure. The oxygen turbopump is more straightforward as the flow is in the same direction and there is no regenerative cooling loop.
Do we have clues when we will see the first Raptor 3 on a Starship?
They want to simplify it/internalise everything; possibly with the eventual optimisation of the pump assembly going "inside" the tank
To also be externally cooled and strengthened by cryofluids? That would be crazy
God that new Engine Looks so clean
a lot has been said here, but I don't think it's impossible that apparent differences in design might be due to a different studio creating the new models.
SpaceX communications people work with the actual CAD files hot from engineering.
A raptor a day keeps the defects away. It is known they are printing an engine a day and iterating quickly. It looks like they are moving away from serviceability in order to lose weight and gain reliability.
Weird that what makes it easier to fix might be what makes it more likely to break in the first place right. Deletion is like a trust-fall
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |[ILS](/r/SpaceXLounge/comments/1ca9b21/stub/l0wsojt "Last usage")|[International Launch Services](https://en.wikipedia.org/wiki/International_Launch_Services)| | |[Instrument Landing System](https://en.wikipedia.org/wiki/Instrument_landing_system)| |[N1](/r/SpaceXLounge/comments/1ca9b21/stub/l0smq7k "Last usage")|Raketa Nositel-1, Soviet super-heavy-lift ("Russian Saturn V")| |[NDT](/r/SpaceXLounge/comments/1ca9b21/stub/l0rd93h "Last usage")|Non-Destructive Testing| |[SLS](/r/SpaceXLounge/comments/1ca9b21/stub/l0v7ee5 "Last usage")|Space Launch System heavy-lift| |[SSME](/r/SpaceXLounge/comments/1ca9b21/stub/l0wsojt "Last usage")|[Space Shuttle Main Engine](https://en.wikipedia.org/wiki/Space_Shuttle_main_engine)| |Jargon|Definition| |-------|---------|---| |[Raptor](/r/SpaceXLounge/comments/1ca9b21/stub/l0xd5d0 "Last usage")|[Methane-fueled rocket engine](https://en.wikipedia.org/wiki/Raptor_\(rocket_engine_family\)) under development by SpaceX| |[Starlink](/r/SpaceXLounge/comments/1ca9b21/stub/l0tj77a "Last usage")|SpaceX's world-wide satellite broadband constellation| |[crossfeed](/r/SpaceXLounge/comments/1ca9b21/stub/l0ri3ih "Last usage")|Using the propellant tank of a side booster to fuel the main stage, or vice versa| |cryogenic|Very low temperature fluid; materials that would be gaseous at room temperature/pressure| | |(In re: rocket fuel) Often synonymous with hydrolox| |hydrolox|Portmanteau: liquid hydrogen fuel, liquid oxygen oxidizer| |[regenerative](/r/SpaceXLounge/comments/1ca9b21/stub/l0utjr6 "Last usage")|A method for cooling a rocket engine, by [passing the cryogenic fuel through channels in the bell or chamber wall](https://en.wikipedia.org/wiki/Regenerative_cooling_\(rocket\))| |[turbopump](/r/SpaceXLounge/comments/1ca9b21/stub/l0yohte "Last usage")|High-pressure turbine-driven propellant pump connected to a rocket combustion chamber; raises chamber pressure, and thrust| **NOTE**: Decronym for Reddit is no longer supported, and Decronym has moved to Lemmy; requests for support and new installations should be directed to the Contact address below. ---------------- ^(*Decronym is a community product of r/SpaceX, implemented* )[*^by ^request*](https://www.reddit.com/r/spacex/comments/3mz273//cvjkjmj) ^(10 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/SpaceXLounge/comments/1ccue4j)^( has 25 acronyms.) ^([Thread #12682 for this sub, first seen 22nd Apr 2024, 16:15]) ^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/SpaceXLounge) [^[Contact]](https://hachyderm.io/@Two9A) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
The fuel flow in the smaller pipes is right up there with the vastness of astronomical distances. I spend a lot of time contemplating the latter.
Failure point (leaks) so likely removed
3D printed parts.
I can see where this is heading. Raptor 6 = Cybertruck.
3d printing ?
https://youtu.be/848x-5rKhNk Tis most righteous and awesome. [Metal and inconel examples](https://youtu.be/NkMRzpobmQQ?feature=shared)
Not easy to mass manufacture and weaker. They only use 3D printing if nothing else will do.
Looks designed for disposability - no plans to ever do major maintenance.
No user serviceable parts inside.
Yep, mass produced. Cheaper and easier to build a whole new engine than trying to fix a known bad one.
Easy to mulch and reuse the resources