7 ms·

How SpaceX Streamlined the Raptor Engine

55 points by JumpCrisscross 1mo ago

avmich 1mo ago
The thrust vector control (TVC) subsystem is usually considered a part of the engine. The major change the Soviet NK-33 underwent for a USA model was the addition of TVC, and the engine was named differently, so there are two engines, named differently, which mostly differ by the presence of TVC. Raptors can be used without TVC. Be that by using differential thrust, or just not needing that - because rocket is controlled using other means, or other engines - it's possible. Tory Bruno specifically explained that he meant - among other things - that absence. A picture of the engine working on the test stand can be that for the engine - or for the chamber, a significant component of the engine, with or without turbopumps involved.
- w8vY7ER 1mo ago
  Oh yeah, Tory Bruno made that gaffe of a comment publicly, and completely unprompted, before he abruptly quit. I had forgotten, but you’re right of course.
- deleted 1mo ago
  [deleted]
- brandonagr2 1mo ago
  https://www.spacex.com/content/starship/holy-grail-of-rocketry https://www.spacex.com/content/starship/holy-grail-of-rocket... at 13:35 has a good view of a raptor 3 with TVC, do you think that adds substantially to what is pictured at the top of the article?
  - numpad0 1mo ago
    TLDW but TVC for rocket engines is usually achieved by like one hydraulic suspension rod each for X and Y axes(Y and Z in rocketry? idk) serving as parts of the engine mounting frame. It shouldn't add a lot to the system.
    - avmich 29d ago
      I didn't have a particularly good view from 13:35 frames. TVC is a relatively simple subsystem, but it's there.
    - topspin 29d ago
      Yes, that's the usual way. With SpaceX, however, Raptor engines are gimbled with electric actuators. And yes, the TVC adds very little to the complexity of Raptor 3's appearance: it still looks like science fiction, even when operating in Starship. Had TVC been present in the original SP1 image that had Tory accusing SpaceX of misleading everyone, it would have made no difference. > TLDW That video has beautiful shots of Raptor 3 firing and gimbling. It's worth watching.
- benjaminl 29d ago
  Tony Bruno, when referring to the partially assembled engine, was complaining about the lack of engine controllers, fluid management, and TVCs [1]. In addition, SpaceX isn’t cheating by not including TVCs. They purposely designed their rocket to need a minimum of them and fully take advantage of the space savings the lack of TVCs affords them. [1] “So, there is no need to exaggerate this by showing a partially assembled engine without controllers, fluid management, or TVC systems, then comparing it to fully assembled engines that do.” https://x.com/SawyerMerritt/status/1821679540973765026?s=20 https://x.com/SawyerMerritt/status/1821679540973765026?s=20
  - panick21_ 27d ago
    Tory was just wrong. Yes TVC wasn't there but that's because that's not inherent to the design, some Raptors are attached with TVC some without. But everything else was there. And if you see Raptor integrated on Starship you can see this clearly.
aaron695 1mo ago
[dead]
fragmede 1mo ago
3d printing metal has come a long way!
ecshafer 1mo ago
I find it mind boggling that you can 3d print rocket engines. I thought that the standard line is that 3d printing metal wasn't developed enough for anything serious. Not a mechanical/materials engineer, but if you can 3d print rockets what's off the table? Jet Engines and that's about it I think? From the article links, I am amused that SpaceX uses cybertrucks to tow their rocket engines around the grounds and not a normal cheaper truck. They also do it in a totally uncovered trailer, which must be good for the guys taking pictures for forums. But isn't that also good for guys taking pictures for competitors / Russians/ China?
- jackmott42 1mo ago
  3d printing metal has some strength downsides, I'm not sure what it is for the raptor engines, but I've heard other space companies claim ~5% less strength that traditional methods for aluminum structures, but that can be worth it in cases where you are able to make shapes that wouldn't be possible with traditional methods, or if you save enough money by printing it. Rocket engines often can benefit from intricate internal channels and shapes that you can 3d print as once piece with no way to do it via subtractive manufacturing.
  - fbd_0100 1mo ago
    It has mild strength downsides, but very severe fatigue and damage tolerance downsides. Knowing this, it makes sense that 3d printing tech would make headway in space industry but not (yet) in aviation
    - naasking 1mo ago
      What's the current theory for why this is?
      - tredre3 1mo ago
        3D printed metal is now as strong as machined metal, assuming an identical alloy. The process has been pretty well perfected. The strength loss comes from the fact that not all alloys are 3d-printing friendly, so you often have to compromise and you end up with a less than ideal alloy for your application.
philipwhiuk 1mo ago
> There turned out to be less detail available here than I hoped. I'm surprised the author was surprised that a component of a multi-billion dollar company which is vital to it's future success in the industry and is covered by US regulations governing information export wasn't available as a cut-away diagram.
- inemesitaffia 29d ago
  Someone was reverse engineering the engine in public on a spacex owned website. It got taken down.
thinkcontext 1mo ago
> And the problems haven’t been completely ironed out: the first launch attempt of Starship’s flight test 13 was aborted automatically by the vehicle’s flight software at T-0 (right before liftoff) this past July when several Raptor 3 engines failed to start And several engines failed to relight on the booster for flight 13. I believe ice in feed lines is viewed as the most likely cause.
- Tuna-Fish 29d ago
  I'm pretty sure that the heat exchanger is going to end up being one part they have to put back in. Pushing CO2 and H2O (both ices at prop temp) into the tanks just seems so ill-advised to me. The amounts of contamination are small, but there are just so many different ways that can go wrong.
advisedwang 1mo ago
> A full-flow staged combustion engine is very complex, and prior to the Raptor only two had been built, neither of which successfully flew on a rocket. Isn't the Space shuttle main engine / SLS engine a full-flow staged combustion engine?
- nbadg 1mo ago
  No, it's a fuel rich staged combustion cycle: https://en.wikipedia.org/wiki/RS-25 https://en.wikipedia.org/wiki/RS-25
- pixl97 29d ago
  As it said raptor was the first and the SLS engines are way older. I think China has made a full flow engine too.
- Tuna-Fish 29d ago
  In SSME, most of the LOX never goes through a preburner. The SSME uses the same kind of fuel-rich combustion chambers for both preburners. This presents a problem for the oxidizer side because any leaking along the shaft between ox pump and turbine in either direction would be catastrophic. This is resolved by an extremely expensive and complex multi-stage helium-purged rotating seal. One of the cool parts about most FFSC designs, and the raptor in particular, is that they can afford slight leaking from high pressure to low pressure through any seal in the system and it's broadly safe, and only marginally reduces performance. This allows them to be made much more cheaply.
WalterBright 1mo ago
According to Isaacson's biography of Musk, Musk relentlessly challenges the existence of every part in Tesla and SpaceX machines. He's willing to go too far, having to sometimes put a part back in. Everything in the manufacturing process is also challenged to justify its existence. This is how he managed to reduce the costs by 90%.
- nortlov 29d ago
  Slight aside, he also has driven capability that was challenging to justify existence for, and was later removed re: Dragon 2 propulsive landing via SuperDracos, landing legs, and the ballast sled. I'm sure the Dragonfly programs matured their abort programs, but surely, that was a ton of time and effort wasted. You win some, you lose some.
  - WalterBright 29d ago
    If you aren't failing now and then, you aren't really trying.
- nickff 29d ago
  >"According to Isaacson's biography of Musk, Musk relentlessly challenges the existence of every part in Tesla and SpaceX machines." This removal of surplus-age is common in the automotive industry, and one of the reasons that cars are such an amazing value. It seems like Musk's remarkable ability to achieve cost reductions (at least in the aerospace context) is attributable to his pursuit of vertical integration. Airframers (aeronautical vehicle designers & manufacturer) are bound by the costs dictated by their component suppliers, especially after a configuration has achieved regulatory approval. SpaceX has managed to avoid being 'held hostage' by pseudo-monopoly suppliers.
  - s1artibartfast 29d ago
    yes and no. Like you said, automotive and aviation industries are bound by a lot regulatory and path dependent constraints. Elon's strength is his willingness to pull the plug and transition away from suboptimal solutions. This is bolstered by his willingness to double down. Imagine if Boeing said "screw all this recertification technical debt for the 737 MAX airframe, we will start fresh. Customers can take it or leave it"
7e 29d ago
It’s extremely premature to celebrate something which hasn’t been shown to work in its intended application, nor at the original specs.
- xondono 29d ago
  Given the original specs are the kinds of numbers Musk pulls out of his behind, I wouldn’t expect it to anytime soon. It’s certainly an achievement of SpaceX engineering what they can do despite his constant meddling.
- panick21_ 27d ago
  The engines have proven repeatability and some have re-flown on a orbital rocket. By the standard of any company outside SpaceX, the Raptor has achieved remarkable things. Its at minimum the second most reusable engine in the world. It has not yet proven to be as reliable reusable as Merlin, but the test programs they have put Raptor threw are considerable. Raptor has successfully landed a rocket, and has successfully landed even an upper stage. Making it the only engine ever to achieve both. If at this point you call that 'premature' then you must be an Asian parent in terms of your exception.

The thrust vector control (TVC) subsystem is usually considered a part of the engine. The major change the Soviet NK-33 underwent for a USA model was the addition of TVC, and the engine was named differently, so there are two engines, named differently, which mostly differ by the presence of TVC. Raptors can be used without TVC. Be that by using differential thrust, or just not needing that - because rocket is controlled using other means, or other engines - it's possible. Tory Bruno specifically explained that he meant - among other things - that absence. A picture of the engine working on the test stand can be that for the engine - or for the chamber, a significant component of the engine, with or without turbopumps involved.

w8vY7ER 1mo ago
Oh yeah, Tory Bruno made that gaffe of a comment publicly, and completely unprompted, before he abruptly quit. I had forgotten, but you’re right of course.
deleted 1mo ago
[deleted]
brandonagr2 1mo ago
https://www.spacex.com/content/starship/holy-grail-of-rocketry https://www.spacex.com/content/starship/holy-grail-of-rocket... at 13:35 has a good view of a raptor 3 with TVC, do you think that adds substantially to what is pictured at the top of the article?
- numpad0 1mo ago
  TLDW but TVC for rocket engines is usually achieved by like one hydraulic suspension rod each for X and Y axes(Y and Z in rocketry? idk) serving as parts of the engine mounting frame. It shouldn't add a lot to the system.
  - avmich 29d ago
    I didn't have a particularly good view from 13:35 frames. TVC is a relatively simple subsystem, but it's there.
  - topspin 29d ago
    Yes, that's the usual way. With SpaceX, however, Raptor engines are gimbled with electric actuators. And yes, the TVC adds very little to the complexity of Raptor 3's appearance: it still looks like science fiction, even when operating in Starship. Had TVC been present in the original SP1 image that had Tory accusing SpaceX of misleading everyone, it would have made no difference. > TLDW That video has beautiful shots of Raptor 3 firing and gimbling. It's worth watching.
benjaminl 29d ago
Tony Bruno, when referring to the partially assembled engine, was complaining about the lack of engine controllers, fluid management, and TVCs [1]. In addition, SpaceX isn’t cheating by not including TVCs. They purposely designed their rocket to need a minimum of them and fully take advantage of the space savings the lack of TVCs affords them. [1] “So, there is no need to exaggerate this by showing a partially assembled engine without controllers, fluid management, or TVC systems, then comparing it to fully assembled engines that do.” https://x.com/SawyerMerritt/status/1821679540973765026?s=20 https://x.com/SawyerMerritt/status/1821679540973765026?s=20
- panick21_ 27d ago
  Tory was just wrong. Yes TVC wasn't there but that's because that's not inherent to the design, some Raptors are attached with TVC some without. But everything else was there. And if you see Raptor integrated on Starship you can see this clearly.

aaron695 1mo ago

[dead]

fragmede 1mo ago

3d printing metal has come a long way!

ecshafer 1mo ago

I find it mind boggling that you can 3d print rocket engines. I thought that the standard line is that 3d printing metal wasn't developed enough for anything serious. Not a mechanical/materials engineer, but if you can 3d print rockets what's off the table? Jet Engines and that's about it I think? From the article links, I am amused that SpaceX uses cybertrucks to tow their rocket engines around the grounds and not a normal cheaper truck. They also do it in a totally uncovered trailer, which must be good for the guys taking pictures for forums. But isn't that also good for guys taking pictures for competitors / Russians/ China?

jackmott42 1mo ago
3d printing metal has some strength downsides, I'm not sure what it is for the raptor engines, but I've heard other space companies claim ~5% less strength that traditional methods for aluminum structures, but that can be worth it in cases where you are able to make shapes that wouldn't be possible with traditional methods, or if you save enough money by printing it. Rocket engines often can benefit from intricate internal channels and shapes that you can 3d print as once piece with no way to do it via subtractive manufacturing.
- fbd_0100 1mo ago
  It has mild strength downsides, but very severe fatigue and damage tolerance downsides. Knowing this, it makes sense that 3d printing tech would make headway in space industry but not (yet) in aviation
  - naasking 1mo ago
    What's the current theory for why this is?
    - tredre3 1mo ago
      3D printed metal is now as strong as machined metal, assuming an identical alloy. The process has been pretty well perfected. The strength loss comes from the fact that not all alloys are 3d-printing friendly, so you often have to compromise and you end up with a less than ideal alloy for your application.

philipwhiuk 1mo ago

> There turned out to be less detail available here than I hoped. I'm surprised the author was surprised that a component of a multi-billion dollar company which is vital to it's future success in the industry and is covered by US regulations governing information export wasn't available as a cut-away diagram.

inemesitaffia 29d ago
Someone was reverse engineering the engine in public on a spacex owned website. It got taken down.

thinkcontext 1mo ago

> And the problems haven’t been completely ironed out: the first launch attempt of Starship’s flight test 13 was aborted automatically by the vehicle’s flight software at T-0 (right before liftoff) this past July when several Raptor 3 engines failed to start And several engines failed to relight on the booster for flight 13. I believe ice in feed lines is viewed as the most likely cause.

Tuna-Fish 29d ago
I'm pretty sure that the heat exchanger is going to end up being one part they have to put back in. Pushing CO2 and H2O (both ices at prop temp) into the tanks just seems so ill-advised to me. The amounts of contamination are small, but there are just so many different ways that can go wrong.

advisedwang 1mo ago

> A full-flow staged combustion engine is very complex, and prior to the Raptor only two had been built, neither of which successfully flew on a rocket. Isn't the Space shuttle main engine / SLS engine a full-flow staged combustion engine?

nbadg 1mo ago
No, it's a fuel rich staged combustion cycle: https://en.wikipedia.org/wiki/RS-25 https://en.wikipedia.org/wiki/RS-25
pixl97 29d ago
As it said raptor was the first and the SLS engines are way older. I think China has made a full flow engine too.
Tuna-Fish 29d ago
In SSME, most of the LOX never goes through a preburner. The SSME uses the same kind of fuel-rich combustion chambers for both preburners. This presents a problem for the oxidizer side because any leaking along the shaft between ox pump and turbine in either direction would be catastrophic. This is resolved by an extremely expensive and complex multi-stage helium-purged rotating seal. One of the cool parts about most FFSC designs, and the raptor in particular, is that they can afford slight leaking from high pressure to low pressure through any seal in the system and it's broadly safe, and only marginally reduces performance. This allows them to be made much more cheaply.

WalterBright 1mo ago

According to Isaacson's biography of Musk, Musk relentlessly challenges the existence of every part in Tesla and SpaceX machines. He's willing to go too far, having to sometimes put a part back in. Everything in the manufacturing process is also challenged to justify its existence. This is how he managed to reduce the costs by 90%.

nortlov 29d ago
Slight aside, he also has driven capability that was challenging to justify existence for, and was later removed re: Dragon 2 propulsive landing via SuperDracos, landing legs, and the ballast sled. I'm sure the Dragonfly programs matured their abort programs, but surely, that was a ton of time and effort wasted. You win some, you lose some.
- WalterBright 29d ago
  If you aren't failing now and then, you aren't really trying.
nickff 29d ago
>"According to Isaacson's biography of Musk, Musk relentlessly challenges the existence of every part in Tesla and SpaceX machines." This removal of surplus-age is common in the automotive industry, and one of the reasons that cars are such an amazing value. It seems like Musk's remarkable ability to achieve cost reductions (at least in the aerospace context) is attributable to his pursuit of vertical integration. Airframers (aeronautical vehicle designers & manufacturer) are bound by the costs dictated by their component suppliers, especially after a configuration has achieved regulatory approval. SpaceX has managed to avoid being 'held hostage' by pseudo-monopoly suppliers.
- s1artibartfast 29d ago
  yes and no. Like you said, automotive and aviation industries are bound by a lot regulatory and path dependent constraints. Elon's strength is his willingness to pull the plug and transition away from suboptimal solutions. This is bolstered by his willingness to double down. Imagine if Boeing said "screw all this recertification technical debt for the 737 MAX airframe, we will start fresh. Customers can take it or leave it"

7e 29d ago

It’s extremely premature to celebrate something which hasn’t been shown to work in its intended application, nor at the original specs.

xondono 29d ago
Given the original specs are the kinds of numbers Musk pulls out of his behind, I wouldn’t expect it to anytime soon. It’s certainly an achievement of SpaceX engineering what they can do despite his constant meddling.
panick21_ 27d ago
The engines have proven repeatability and some have re-flown on a orbital rocket. By the standard of any company outside SpaceX, the Raptor has achieved remarkable things. Its at minimum the second most reusable engine in the world. It has not yet proven to be as reliable reusable as Merlin, but the test programs they have put Raptor threw are considerable. Raptor has successfully landed a rocket, and has successfully landed even an upper stage. Making it the only engine ever to achieve both. If at this point you call that 'premature' then you must be an Asian parent in terms of your exception.