SpaceX Raptor LRE Proposed Successor: Project LEET-1337 LRE

[Sarigolepas]

We can all agree that the LEET engine is a methalox engine, so why does it need a new name?

My guess is that since the goal for raptor 3 and 4 is to reduce the number of parts and integrate as much as possible, meaning that the fuel-rich turbopump and injector will be one piece with no manifold then the LEET engine could add regenerative and film cooling to the preburner since the combustion chamber and preburner could be a single part.

So the new name would be because of a change in philosophy, they are making raptor easier to produce and for LEET they will take advantage of that to try new things that would make the current design too complicated?

https://www.nextbigfuture.com/2023/09/beyond-the-spacex-raptor-engine-is-the-breakthrough-spacex-leet-1337-engine.html

Also, do you trust this article?

Moderator edit of thread title to provide clarity.

[RedLineTrain]

The source for that article is Isaacson's biography of Musk.  The 1337 engine section is great in that it illuminates a portion that we are very interested in, but don't normally hear about publicly.  That said, there are a few details in the biography that are clearly wrong, so you have to be a bit careful to not read it literally.

Here is my summary of this in the Raptor thread...

https://www.nextbigfuture.com/2023/09/beyond-the-spacex-raptor-engine-is-the-breakthrough-spacex-leet-1337-engine.html

Forgive my posting if this has been posted (I’m working on a phone). 

This all sounds fantastical and maybe reaching beyond the possible.

It looks like his source is the Musk biography. Has anyone got a copy of that yet?

I just listened to that part yesterday.  Raptor wasn't hitting its cost and manufacturability targets.  It was hard to manufacture and cost $2 million per.  They were only building one every three days or so.  Musk ordered a surge on Raptor to get it to $200k per, but Musk felt the effort was stale.  So he began a clean sheet design called 1337, or LEET. No material, requirement, or method was sacred on 1337.  Eventually, they paused 1337 development to go back to Raptor.  As of late last year, they were able to produce more than one Raptor a day, so obviously they made some good progress.

It was left to the reader's imagination whether the 1337 effort was Musk's way to kickstart the development team's creativity on Raptor or whether eventually the team's attention will be turned back to 1337 after the successful ramp of Raptor.

My guess is that 1337 development was only paused (not canceled) and it will be or already has been restarted.  It's also possible that the reinvigorated Raptor development is showing better than hoped progress, making 1337 development moot.

[Sarigolepas]

Here is the thrust density versus efficiency chart I made a while ago, updated with the numbers from Brian Wang's article:

[Barley]

We can all agree that the LEET engine is a methalox engine, so why does it need a new name?

V1.0, V1.1, Full Thrust, Block 5

What is the next term in this sequence?

[whitelancer64]

We can all agree that the LEET engine is a methalox engine, so why does it need a new name?

V1.0, V1.1, Full Thrust, Block 5

What is the next term in this sequence?

You forgot V1.14159, More Fullerer Thrust and Full Thrust: the Return of the Thrustening.

Block 5 has also had significant improvements for reliability and reusability but SpaceX is still calling it Block 5.

The Merlin 1D really should be like Merlin 1H.

[steveleach]

There's no evidence that I've seen suggesting that 133T is still under development or will be picked up again. As far as I can tell it was an idea from back in the Raptor v1 times when Musk was getting very frustrated with the Raptor team's management (before he got rid of them).

Once the newly-unshackled Raptor team got back into their stride, I'm guessing they picked the best (most workable) ideas from it and incorporated them into Raptor v2 and then v3.

Giving it a different name was likely just part of the internal politics of the time; a way for Musk to clearly distinguish between the initiative he felt was failing, and the one he felt was the way forwards. Once he sorted out the underlying problem there was no need for 2 different engine design tracks, so no need for 2 different names.

[InterestedEngineer]

This is my first encounter with Brian Wang.  If this is the type of extrapolation he does then I am extremely not impressed.   If it's a troll (it's that silly) I'm slightly less not impressed.

f SpaceX Raptor engines currently cost $1 million each. There are nine engines for a Starship and having Starship at double the cost of the engines means a complete Starship costs $18 million.
If future SpaceX Raptor engines cost $500k each. Nine engines for a Starship. Starship at double the cost of the engines means a complete Starship costs $9 million.
If the SpaceX 1337 engine costs $200,000 each then nine engines on a Starship could reduce the price of a complete Starship to $3.6 million.
If the SpaceX 1337 engine costs $100,000 each then nine engines on a Starship could reduce the price of a complete Starship to $1.8 million.

The assumption that if you halve the cost of an engine you halve the cost of a rest of the Starship is so silly I wonder if Mr. Wang has ever run a spreadsheet before.

Based on that, I wouldn't take his assertions about 1337 with a grain of salt.  I'd need a salt mine.

[steveleach]

This is my first encounter with Brian Wang.  If this is the type of extrapolation he does then I am extremely not impressed.   If it's a troll (it's that silly) I'm slightly less not impressed.

f SpaceX Raptor engines currently cost $1 million each. There are nine engines for a Starship and having Starship at double the cost of the engines means a complete Starship costs $18 million.
If future SpaceX Raptor engines cost $500k each. Nine engines for a Starship. Starship at double the cost of the engines means a complete Starship costs $9 million.
If the SpaceX 1337 engine costs $200,000 each then nine engines on a Starship could reduce the price of a complete Starship to $3.6 million.
If the SpaceX 1337 engine costs $100,000 each then nine engines on a Starship could reduce the price of a complete Starship to $1.8 million.

The assumption that if you halve the cost of an engine you halve the cost of a rest of the Starship is so silly I wonder if Mr. Wang has every run a spreadsheet before.

Based on that, I wouldn't take his assertions about 1337 with a grain of salt.  I'd need a salt mine.

Though to give him his due, he has demonstrated his ability to do really simple maths.

[InterestedEngineer]

Though to give him his due, he has demonstrated his ability to do really simple maths.

He can divide a number by two, but he can't figure out what happens when you divide one element of a sum of elements by two.

That requires abstract thinking.  Or pattern recognition combined with playing with spreadsheets.

[ChrisC]

FYI here's the regular Raptor thread where this was already being discussed a little.  https://forum.nasaspaceflight.com/index.php?topic=53555.2540

[Slothman]

We can all agree that the LEET engine is a methalox engine, so why does it need a new name?

Because ol' musky is still a boy and names his children in unspeakable ways and in general has a weird way of naming things the way that a teenager in 1998 would name their AOL online account while playing Counterstrike v1.6.. but I don%t think that the "name" of the engine should be in focus, rather than its statistics.

[InterestedEngineer]

but I don%t think that the "name" of the engine should be in focus, rather than its statistics.

It weighs 100kg, gets 390 ISP, and 500t of thrust.  It'll single stage to the moon, and solve world hunger when it brings back some cheese.

What, not believable?  I didn't show any work?

Neither did Brian Wang, and only slightly crazier.

[Robotbeat]

BTW, like many things in the biography, we've already heard about this for a while.

[matthewkantar]

Is LEET an acronym?

[AnalogMan]

Is LEET an acronym?

Probably not (its derived from the word "elite"):
https://en.wikipedia.org/wiki/Leet

[sferrin]

There's no evidence that I've seen suggesting that 133T is still under development or will be picked up again. As far as I can tell it was an idea from back in the Raptor v1 times when Musk was getting very frustrated with the Raptor team's management (before he got rid of them).

Once the newly-unshackled Raptor team got back into their stride, I'm guessing they picked the best (most workable) ideas from it and incorporated them into Raptor v2 and then v3.

Giving it a different name was likely just part of the internal politics of the time; a way for Musk to clearly distinguish between the initiative he felt was failing, and the one he felt was the way forwards. Once he sorted out the underlying problem there was no need for 2 different engine design tracks, so no need for 2 different names.

Elon did make a statement a week or so ago about the Starship/Super heavy having the thrust of "three Saturn Vs".  Maybe he meant with this engine?  Even the proposed Raptor 3 thrust doesn't get you to three Saturn Vs.  Granted, maybe he didn't mean literally/exactly but it's still interesting he went from two at one point to three.

[russianhalo117]

There's no evidence that I've seen suggesting that 133T is still under development or will be picked up again. As far as I can tell it was an idea from back in the Raptor v1 times when Musk was getting very frustrated with the Raptor team's management (before he got rid of them).

Once the newly-unshackled Raptor team got back into their stride, I'm guessing they picked the best (most workable) ideas from it and incorporated them into Raptor v2 and then v3.

Giving it a different name was likely just part of the internal politics of the time; a way for Musk to clearly distinguish between the initiative he felt was failing, and the one he felt was the way forwards. Once he sorted out the underlying problem there was no need for 2 different engine design tracks, so no need for 2 different names.

Elon did make a statement a week or so ago about the Starship/Super heavy having the thrust of "three Saturn Vs".  Maybe he meant with this engine?  Even the proposed Raptor 3 thrust doesn't get you to three Saturn Vs.  Granted, maybe he didn't mean literally/exactly but it's still interesting he went from two at one point to three.

There are Raptor developments beyond v3.0 but are not publicly assigned a version number yet. The LEET LRE is a long term research and development proposed to on ramp in time for the Mars and other applications programmes. LEET is supposed to combine multiple cycles currently being researched and developed i.e. rotating detonating detonation  cycle, Etal with FFSC and hybrid heat exchanger closed expander into a combined adaptive engine cycle to leverage their combined efficiency. Lessons learned from Raptor will be fed into Project LEET.

[RedLineTrain]

BTW, like many things in the biography, we've already heard about this for a while.

Where did we already hear about this?  Is my reading of L2 deficient?

[Alberto-Girardi]

There's no evidence that I've seen suggesting that 133T is still under development or will be picked up again. As far as I can tell it was an idea from back in the Raptor v1 times when Musk was getting very frustrated with the Raptor team's management (before he got rid of them).

Once the newly-unshackled Raptor team got back into their stride, I'm guessing they picked the best (most workable) ideas from it and incorporated them into Raptor v2 and then v3.

Giving it a different name was likely just part of the internal politics of the time; a way for Musk to clearly distinguish between the initiative he felt was failing, and the one he felt was the way forwards. Once he sorted out the underlying problem there was no need for 2 different engine design tracks, so no need for 2 different names.

Elon did make a statement a week or so ago about the Starship/Super heavy having the thrust of "three Saturn Vs".  Maybe he meant with this engine?  Even the proposed Raptor 3 thrust doesn't get you to three Saturn Vs.  Granted, maybe he didn't mean literally/exactly but it's still interesting he went from two at one point to three.

There are Raptor developments beyond v3.0 but are not publicly assigned a version number yet. The LEET LRE is a long term research and development proposed to on ramp in time for the Mars and other applications programmes. LEET is supposed to combine multiple cycles currently being researched and developed i.e. rotating detonating detonation  cycle, Etal with FFSC and hybrid heat exchanger closed expander into a combined adaptive engine cycle to leverage their combined efficiency. Lessons learned from Raptor will be fed into Project LEET.

Extremely interesting, but is there any public statement about this research effort on rotating detonation cycle by SpaceX?

[Robotbeat]

BTW, like many things in the biography, we've already heard about this for a while.

Where did we already hear about this?  Is my reading of L2 deficient?

He tweeted about it.

[RedLineTrain]

BTW, like many things in the biography, we've already heard about this for a while.

Where did we already hear about this?  Is my reading of L2 deficient?

He tweeted about it.

But I thought that was regarding Raptor rather than 1337?  What has he tweeted regarding 1337, besides some vague references?

I felt like this was indeed a lot of new detail in the biography.

[Robotbeat]

Yes, there are new details. But it was mentioned:

November 16th 2021 Updates: NEW ENGINE

Elon Musk @elonmusk
True, although it will look clean with close out panels installed.

Raptor 2 has significant improvements in every way, but a complete design overhaul is necessary for the engine that can actually make life multiplanetary. It won’t be called Raptor

[Robotbeat]

In fact, we have a whole 22 page thread on the topic from the end of 2021:
https://forum.nasaspaceflight.com/index.php?topic=55225.0

[RedLineTrain]

Yes, there are new details. But it was mentioned:

November 16th 2021 Updates: NEW ENGINE

Elon Musk @elonmusk
True, although it will look clean with close out panels installed.

Raptor 2 has significant improvements in every way, but a complete design overhaul is necessary for the engine that can actually make life multiplanetary. It won’t be called Raptor

Got it.  Yes, I was aware of this tweet.  But no details that I know of really came out until the biography.

[Alberto-Girardi]

A note about price.

If the price of Raptor is 1 million $, and we have no indication saying Musk was faking this number, it is already in a good spot (compared to other engines). But I know, he won't stop until they reach the limit.
In general I was surprised by the price of modern rocket engines compared to other complex machinery, like jet engines. The engines of the 737 MAX are 14.5 millions each. Sure the plane doesn't have 39 of them. But the price is comparable. Ofcourse  there are very big differences, but it isn't a totally out of the blue apples to oranges comparsion. I was initially surprised the prices were so close or maybe I was underestimating jet engine prices.

The BE4 engine costs about 8 milion, the RD180 25. The Merlin less than 1. The numbers are from EDA.

[Nomadd]

 You left out the craziest comparison. The RS-25.

[hplan]

A note about price.

If the price of Raptor is 1 million $, and we have no indication saying Musk was faking this number, it is already in a good spot (compared to other engines). But I know, he won't stop until they reach the limit.
In general I was surprised by the price of modern rocket engines compared to other complex machinery, like jet engines. The engines of the 737 MAX are 14.5 millions each. Sure the plane doesn't have 39 of them. But the price is comparable. Ofcourse  there are very big differences, but it isn't a totally out of the blue apples to oranges comparsion. I was initially surprised the prices were so close or maybe I was underestimating jet engine prices.

The BE4 engine costs about 8 milion, the RD180 25. The Merlin less than 1. The numbers are from EDA.

Those numbers are indeed crazy. But they aren't really comparable.

Elon always likes to talk about 'marginal cost' -- how much more it costs to make one additional engine. So the $1M figure doesn't include research and development, cost of the factory and equipment to build engines, profit, etc. No doubt if they were selling engines separately, the cost would be much higher.

[Robotbeat]

A big thing with Musk, though, is that although he talks about marginal cost, he’s also nearly always pushing for very high production rates where development and factory costs are amortized pretty quickly and the fully burdened cost can approach the marginal cost (or at least like a factor of 2).

SpaceX is producing hundreds of Raptors per year, about 2 orders of magnitude higher than, say, the manufacturer of RS-25.

[Alberto-Girardi]

You left out the craziest comparison. The RS-25.

I did that because, as you say, it is crazy. But being it made only for the government I give them the benefit of the doubt.

They are indeed around a little bit less than 100 millions each going to the latest contracts, but in the old days were like 60.
But incredibly when I read it I was reassured, because I don't  know where I had read they were 170 milions each, which isn't true (for now!).

[Robotbeat]

You left out the craziest comparison. The RS-25.

I did that because, as you say, it is crazy. But being it made only for the government I give them the benefit of the doubt.

They are indeed around a little bit less than 100 millions each going to the latest contracts, but in the old days were like 60.
But incredibly when I read it I was reassured, because I don't  know where I had read they were 170 milions each, which isn't true (for now!).

The higher figure includes the cost NASA paid to restart the production line. And it’s $146 million. $100 million or so is for the add-on contract by itself.

Note that expanding the production line would probably require additional cost as well. https://arstechnica.com/science/2020/05/nasa-will-pay-a-staggering-146-million-for-each-sls-rocket-engine/amp/

[DanClemmensen]

A big thing with Musk, though, is that although he talks about marginal cost, he’s also nearly always pushing for very high production rates where development and factory costs are amortized pretty quickly and the fully burdened cost can approach the marginal cost (or at least like a factor of 2).

SpaceX is producing hundreds of Raptors per year, about 2 orders of magnitude higher than, say, the manufacturer of RS-25.

He also talks of a eventual marginal cost of $250,000. I suspect that this is when they are building the Mars fleet, at some crazy engine production rate. At that marginal cost, an internal true cost of $1 million might be realistic.

[RedLineTrain]

Just listening again to the biography, Chapter 63.  It states that the 1337 engine effort was only a month long in 2022.  They turned back to Raptor 2.

With Raptor now hitting its manufacturing goals (at least rate, if not $250k cost) and overperforming on chamber pressure, I wonder whether the 1337 engine is moot or pushed off into the far future.  Raptor was at least hitting its stride enough to merit a Raptor 3 this year.

[Robotbeat]

A big thing with Musk, though, is that although he talks about marginal cost, he’s also nearly always pushing for very high production rates where development and factory costs are amortized pretty quickly and the fully burdened cost can approach the marginal cost (or at least like a factor of 2).

SpaceX is producing hundreds of Raptors per year, about 2 orders of magnitude higher than, say, the manufacturer of RS-25.

He also talks of a eventual marginal cost of $250,000. I suspect that this is when they are building the Mars fleet, at some crazy engine production rate. At that marginal cost, an internal true cost of $1 million might be realistic.

No, I think they’re probably at around $1 million true internal cost already, not counting dev costs.

They want to get costs to Mars very low.

If you assume the ship is sent one-way to Mars with 9 Raptors and 75 passengers, the engine costs on the ship alone are like $120,000 per person, already half of the whole mission cost. If you assume $250k per engine, that’s just $30k per person.

…that is the relevance to making humanity multiplanetary

Likewise, say you send 100 tonnes of cargo with 9 Raptors one-way. $1 million means $90/kg from the ship engines alone. $250k cost means just $22.50/kg from the engines, much more reasonable.

Maybe, including amortization of engines on the booster and tankers, you get a round 10 tonnes of payload to Mars per engine, maybe 10 Martian settlers per engine.

So if they want about 2 million tons of payload on Mars per synod, that’s 100,000 Raptors per year they’ll want to make.

It’s automotive manufacturing scale. Even if they manage to increase reuse to a factor of 10 roundtrip missions per year or so, still 10,000 engines per year. Higher than all jet engine production on Earth combined.

[Alberto-Girardi]

A note about price.

If the price of Raptor is 1 million $, and we have no indication saying Musk was faking this number, it is already in a good spot (compared to other engines). But I know, he won't stop until they reach the limit.
In general I was surprised by the price of modern rocket engines compared to other complex machinery, like jet engines. The engines of the 737 MAX are 14.5 millions each. Sure the plane doesn't have 39 of them. But the price is comparable. Ofcourse  there are very big differences, but it isn't a totally out of the blue apples to oranges comparsion. I was initially surprised the prices were so close or maybe I was underestimating jet engine prices.

The BE4 engine costs about 8 milion, the RD180 25. The Merlin less than 1. The numbers are from EDA.

Those numbers are indeed crazy. But they aren't really comparable.

Elon always likes to talk about 'marginal cost' -- how much more it costs to make one additional engine. So the $1M figure doesn't include research and development, cost of the factory and equipment to build engines, profit, etc. No doubt if they were selling engines separately, the cost would be much higher.

Thanks for the explanation. This is indeed something I didn't consider. Hopefully raptor gets to the state of scaling that the marginal cost and the total ammortized price are nearly the same. IIUC what Elon says is useful if you want to make the design cheaper, but isn't good if you want to know the actual cost. He presumes they will get to the stage were R&D cost won't be vety significant.

[Alberto-Girardi]

Just listening again to the biography, Chapter 63.  It states that the 1337 engine effort was only a month long in 2022.  They turned back to Raptor 2.

With Raptor now hitting its manufacturing goals (at least rate, if not $250k cost) and overperforming on chamber pressure, I wonder whether the 1337 engine is moot or pushed off into the far future.  Raptor was at least hitting its stride enough to merit a Raptor 3 this year.

I haven't read the biography (maybe I should, but I don't generally read biographies of living people) , but IIUC we can't rule out that this was one of the many things that were talked about by Musk, explored internally at the company and nothig (at least until now) came out. Generally I would never take an old tweet of him as a proof of anything current unless there is evidence that has actually been done or has stayed the same since. I think the issue of landing the ship on the chopsticks and the ships forward flaps and traspirational cooling are examples of this that come to mind, albeit the first is a little bit more grounded.


edit: Is the snippet posted above everything in the biography about this project?

[RedLineTrain]

edit: Is the snippet posted above everything in the biography about this project?

The biography mentioned some deletion/simplification ideas that were batted around, if but briefly, with a cost goal of less than $1,000 per ton of thrust.

1.  Deleting the hot fuel gas manifold
2.  Merging the fuel turbopump with the main chamber injector
3.  Getting rid of skirt for booster

It's a long biography and contains mostly things that we already know.  So it might be boring to you, as you are waiting for the gold nuggets of new information.

[Hog]

When comparing the SLSME (RS25 production restart) we must remember that the service life is now 4 starts/1700 seconds of runtime vs the older Heritage-STS/SSME/RS25D/Block-2 service life requirement of 55 starts/27,000 seconds. IOW Expendable RS25 vs Reusable RS25.

EDIT: The correct attachment is there now.

[Robotbeat]

That sounds like a shockingly low number even for an expendable engine. Let’s say you have an engine acceptance test, a core stage acceptance test (like the green run), and then launch. That’s 3 of the four uses.

If you have to aborted lift-offs or green runs, you’d have to get new engines!

You can see why they deleted the green run even for crewed launches. They just don’t have the cycle life in the engines to afford that level of acceptance testing.

Just so very short-sighted.

[wannamoonbase]

That sounds like a shockingly low number even for an expendable engine. Let’s say you have an engine acceptance test, a core stage acceptance test (like the green run), and then launch. That’s 3 of the four uses.

If you have to aborted lift-offs or green runs, you’d have to get new engines!

You can see why they deleted the green run even for crewed launches. They just don’t have the cycle life in the engines to afford that level of acceptance testing.

Just so very short-sighted.

Maybe an extra restart cost $100M more per engine.

The RS25 is 50+ year old technology at this point, its embarrassingly expensive.

Beyond all the performance numbers and cost, the key to Raptor is going to be longevity. 

Merlin is doing very well but Raptor needs to be even easier to reuse and allegedly handle many more flights.  It may take a long time to get there.

[Robotbeat]

They’re using the low cycle count of RS-25e to push the max thrust to far higher than SSME. You get a few percentage points greater thrust in exchange for an order of magnitude fewer cycles.

[Hog]

That sounds like a shockingly low number even for an expendable engine. Let’s say you have an engine acceptance test, a core stage acceptance test (like the green run), and then launch. That’s 3 of the four uses.

If you have to aborted lift-offs or green runs, you’d have to get new engines!

You can see why they deleted the green run even for crewed launches. They just don’t have the cycle life in the engines to afford that level of acceptance testing.

Just so very short-sighted.

My apologies, I attached the incorrect graphic, it's corrected now.  The Arty-1 through Arty-4 engines are the Adaptation engines with 6 starts.  The Restart engines come into usage for Artemis-5.
Your points still stand.

[Sarigolepas]

Giving it a different name was likely just part of the internal politics of the time; a way for Musk to clearly distinguish between the initiative he felt was failing, and the one he felt was the way forwards. Once he sorted out the underlying problem there was no need for 2 different engine design tracks, so no need for 2 different names.

I think he is being serious about a new engine.

[Sarigolepas]

Elon did make a statement a week or so ago about the Starship/Super heavy having the thrust of "three Saturn Vs".  Maybe he meant with this engine?  Even the proposed Raptor 3 thrust doesn't get you to three Saturn Vs.  Granted, maybe he didn't mean literally/exactly but it's still interesting he went from two at one point to three.

Do you have any source for that?
Also, 3 saturn V would be 320 tons of thrust per engine and more importantly a TWR of 1.8 at takeoff for an extended starship with a 6'000 tons gross weight. Such an high TWR makes sense if they make the second stage heavier relative to the first stage which would lead to lower velocity at MECO.

[Sarigolepas]

If the price of Raptor is 1 million $, and we have no indication saying Musk was faking this number, it is already in a good spot (compared to other engines). But I know, he won't stop until they reach the limit.
In general I was surprised by the price of modern rocket engines compared to other complex machinery, like jet engines. The engines of the 737 MAX are 14.5 millions each. Sure the plane doesn't have 39 of them. But the price is comparable. Ofcourse  there are very big differences, but it isn't a totally out of the blue apples to oranges comparsion. I was initially surprised the prices were so close or maybe I was underestimating jet engine prices.

Jet engines are very complicated. Gas turbines can operate at over 1'600°C, each blade has regenerative and film cooling unlike raptor turbopumps which operate at 600°C
That's why I expect the LEET engine to have film cooling in the turbopumps. They are merging the fuel-rich turbopump with the injector so unless I'm mistaken they could extend the cooling channels from the combustion chamber all the way to the turbopumps.
They probably won't be able to reach 1'600°C thought because the pressure is higher than a gas turbine.

[steveleach]

Giving it a different name was likely just part of the internal politics of the time; a way for Musk to clearly distinguish between the initiative he felt was failing, and the one he felt was the way forwards. Once he sorted out the underlying problem there was no need for 2 different engine design tracks, so no need for 2 different names.

I think he is being serious about a new engine.

A lot of things have changed since then, including new management for that division. He was probably serious about a new engine at the time, but he then found a different solution.

[Nomadd]

 Didn't the old, long life RS-25 need some pretty heavy refurbishment between launches?
 Maybe the low restart numbers for the single flight model is mostly from deleting the ability to overhaul it after every launch. Weld things that use to be bolted and such.

[Sohl]

Didn't the old, long life RS-25 need some pretty heavy refurbishment between launches?
 Maybe the low restart numbers for the single flight model is mostly from deleting the ability to overhaul it after every launch. Weld things that use to be bolted and such.

Seems reasonable and makes sense.  I don't have any particular knowledge of this, though.

[wannamoonbase]

Didn't the old, long life RS-25 need some pretty heavy refurbishment between launches?
 Maybe the low restart numbers for the single flight model is mostly from deleting the ability to overhaul it after every launch. Weld things that use to be bolted and such.

I recall that the SSME was intended to go some number of flights between work, 4 or 8 flights, something like that.

But that after Challenger more is always better so they took them out and serviced them on each flight.

I don't know if it was warranted and if they found anything, or if it was a reflexive overreaction that stuck.

Seems that after 50+ years that we can do a lot better than the SSME, just on materials and manufacturing alone the RS-25 should be easy to improve on.  And not be $100M per engine.

[Vahe231991]

Giving it a different name was likely just part of the internal politics of the time; a way for Musk to clearly distinguish between the initiative he felt was failing, and the one he felt was the way forwards. Once he sorted out the underlying problem there was no need for 2 different engine design tracks, so no need for 2 different names.

I think he is being serious about a new engine.

Since the notional new engine is mentioned by Elon Musk as intended to help mankind become a multiplanetary species, I'm guessing that the Starship/Super Heavy would need to have the first stage modified to use as many as 12 engines with a total of 20 million pounds of thrust and the Starship portion fitted with five engines totaling 6 million pounds of thrust in order to burn enough fuel to reach portions of the solar system beyond Mars.

[ETurner]

If the price of Raptor is 1 million $, and we have no indication saying Musk was faking this number, it is already in a good spot (compared to other engines). But I know, he won't stop until they reach the limit.
In general I was surprised by the price of modern rocket engines compared to other complex machinery, like jet engines. The engines of the 737 MAX are 14.5 millions each. Sure the plane doesn't have 39 of them. But the price is comparable. Ofcourse  there are very big differences, but it isn't a totally out of the blue apples to oranges comparsion. I was initially surprised the prices were so close or maybe I was underestimating jet engine prices.

Jet engines are very complicated. Gas turbines can operate at over 1'600°C, each blade has regenerative and film cooling unlike raptor turbopumps which operate at 600°C
That's why I expect the LEET engine to have film cooling in the turbopumps. They are merging the fuel-rich turbopump with the injector so unless I'm mistaken they could extend the cooling channels from the combustion chamber all the way to the turbopumps.
They probably won't be able to reach 1'600°C thought because the pressure is higher than a gas turbine.

Why would they want a turbine that operates at a much higher temperature? The combustion chamber is downstream.

[DJPledger]

Giving it a different name was likely just part of the internal politics of the time; a way for Musk to clearly distinguish between the initiative he felt was failing, and the one he felt was the way forwards. Once he sorted out the underlying problem there was no need for 2 different engine design tracks, so no need for 2 different names.

I think he is being serious about a new engine.

Since the notional new engine is mentioned by Elon Musk as intended to help mankind become a multiplanetary species, I'm guessing that the Starship/Super Heavy would need to have the first stage modified to use as many as 12 engines with a total of 20 million pounds of thrust and the Starship portion fitted with five engines totaling 6 million pounds of thrust in order to burn enough fuel to reach portions of the solar system beyond Mars.

An F-1B thrust class next gen. engine would be perfect for a much larger next gen Starship system in the far future having the same engine counts for booster (33 engines) and ship (6 engines) as the current Starship system has.

[Robotbeat]

Didn't the old, long life RS-25 need some pretty heavy refurbishment between launches?
 Maybe the low restart numbers for the single flight model is mostly from deleting the ability to overhaul it after every launch. Weld things that use to be bolted and such.

I recall that the SSME was intended to go some number of flights between work, 4 or 8 flights, something like that.

But that after Challenger more is always better so they took them out and serviced them on each flight.

I don't know if it was warranted and if they found anything, or if it was a reflexive overreaction that stuck.

Seems that after 50+ years that we can do a lot better than the SSME, just on materials and manufacturing alone the RS-25 should be easy to improve on.  And not be $100M per engine.

Why would the company making them want to charge less than $100 million per engine?

[OTV Booster]

A note about price.

If the price of Raptor is 1 million $, and we have no indication saying Musk was faking this number, it is already in a good spot (compared to other engines). But I know, he won't stop until they reach the limit.
In general I was surprised by the price of modern rocket engines compared to other complex machinery, like jet engines. The engines of the 737 MAX are 14.5 millions each. Sure the plane doesn't have 39 of them. But the price is comparable. Ofcourse  there are very big differences, but it isn't a totally out of the blue apples to oranges comparsion. I was initially surprised the prices were so close or maybe I was underestimating jet engine prices.

The BE4 engine costs about 8 milion, the RD180 25. The Merlin less than 1. The numbers are from EDA.

Those numbers are indeed crazy. But they aren't really comparable.

Elon always likes to talk about 'marginal cost' -- how much more it costs to make one additional engine. So the $1M figure doesn't include research and development, cost of the factory and equipment to build engines, profit, etc. No doubt if they were selling engines separately, the cost would be much higher.

Thanks for the explanation. This is indeed something I didn't consider. Hopefully raptor gets to the state of scaling that the marginal cost and the total ammortized price are nearly the same. IIUC what Elon says is useful if you want to make the design cheaper, but isn't good if you want to know the actual cost. He presumes they will get to the stage were R&D cost won't be vety significant.

Alberto, I'm just catching up on this thread.


Manufacturing and development costs are tricky and mushy so don't accept any of the numbers as you would an engineering number. For example, every hot fire of an installed engine and all launches to date can be considered engine development in some sense. To attribute the total cost of each hot fire or launch to engine development makes no sense but what proportion of costs should be apportioned to engine development?


Development costs could be ended when an engine leaves MacGregor but that doesn't make sense either. Until the engines are successfully integrated into a working system it can not be considered a finished product no longer in development. Long story short, it's messy.


There is a set of rules called Generally Accepted Accounting Procedures (GAAP) that address issues like this but I suspect there's a lot of latitude. I am not an accountant but do have some small business background. A long as I kept the IRS happy, I was happy.

[OTV Booster]

Giving it a different name was likely just part of the internal politics of the time; a way for Musk to clearly distinguish between the initiative he felt was failing, and the one he felt was the way forwards. Once he sorted out the underlying problem there was no need for 2 different engine design tracks, so no need for 2 different names.

I think he is being serious about a new engine.

Since the notional new engine is mentioned by Elon Musk as intended to help mankind become a multiplanetary species, I'm guessing that the Starship/Super Heavy would need to have the first stage modified to use as many as 12 engines with a total of 20 million pounds of thrust and the Starship portion fitted with five engines totaling 6 million pounds of thrust in order to burn enough fuel to reach portions of the solar system beyond Mars.

An F-1B thrust class next gen. engine would be perfect for a much larger next gen Starship system in the far future having the same engine counts for booster (33 engines) and ship (6 engines) as the current Starship system has.

Opinion:

I'd think they'd want to design a new engine to fit the current package, otherwise the thrust structures and plumbing would have to radically change. That's maybe 20-25% towards a new design. OTOH, maybe a new design is a development branch they're looking at.

[steveleach]

Giving it a different name was likely just part of the internal politics of the time; a way for Musk to clearly distinguish between the initiative he felt was failing, and the one he felt was the way forwards. Once he sorted out the underlying problem there was no need for 2 different engine design tracks, so no need for 2 different names.

I think he is being serious about a new engine.

Since the notional new engine is mentioned by Elon Musk as intended to help mankind become a multiplanetary species, I'm guessing that the Starship/Super Heavy would need to have the first stage modified to use as many as 12 engines with a total of 20 million pounds of thrust and the Starship portion fitted with five engines totaling 6 million pounds of thrust in order to burn enough fuel to reach portions of the solar system beyond Mars.

An F-1B thrust class next gen. engine would be perfect for a much larger next gen Starship system in the far future having the same engine counts for booster (33 engines) and ship (6 engines) as the current Starship system has.

Opinion:

I'd think they'd want to design a new engine to fit the current package, otherwise the thrust structures and plumbing would have to radically change. That's maybe 20-25% towards a new design. OTOH, maybe a new design is a development branch they're looking at.

I think people are reading way too much into something that happened a couple of years ago, and that everyone involved has probably moved on from now.

[DJPledger]

Giving it a different name was likely just part of the internal politics of the time; a way for Musk to clearly distinguish between the initiative he felt was failing, and the one he felt was the way forwards. Once he sorted out the underlying problem there was no need for 2 different engine design tracks, so no need for 2 different names.

I think he is being serious about a new engine.

Since the notional new engine is mentioned by Elon Musk as intended to help mankind become a multiplanetary species, I'm guessing that the Starship/Super Heavy would need to have the first stage modified to use as many as 12 engines with a total of 20 million pounds of thrust and the Starship portion fitted with five engines totaling 6 million pounds of thrust in order to burn enough fuel to reach portions of the solar system beyond Mars.

An F-1B thrust class next gen. engine would be perfect for a much larger next gen Starship system in the far future having the same engine counts for booster (33 engines) and ship (6 engines) as the current Starship system has.

Opinion:

I'd think they'd want to design a new engine to fit the current package, otherwise the thrust structures and plumbing would have to radically change. That's maybe 20-25% towards a new design. OTOH, maybe a new design is a development branch they're looking at.

I think people are reading way too much into something that happened a couple of years ago, and that everyone involved has probably moved on from now.

So SpaceX will keep iterating Raptor and that LEET-1337 may have been cancelled or pushed back into the very far future. Perhaps SpaceX could go really radical and possibly dev. a RDRE after Raptor.

[OTV Booster]

Um, uh. What does RDRE mean?

[chopsticks]

Probably rotating detonation something or other.

[KilroySmith]

I was going to be a snarky little whatever and point out the acronyms thread: https://forum.nasaspaceflight.com/index.php?topic=34802.0
But then I noticed that it doesn’t include that particular one.  And, unfortunately, I’m as in the dark as you are.

[Perchlorate]

Rotating Detonation Rocket Engine

[Zed_Noir]

Wonder if the LEET-1337 will be developed as vacuum optimized engines for upgrading the Starship variants that goes beyond cisLunarspace later on?

Of course at least 16% better performance than the version that is written in the Issacson bio of Elon. 

[OTV Booster]

I was going to be a snarky little whatever and point out the acronyms thread: https://forum.nasaspaceflight.com/index.php?topic=34802.0
But then I noticed that it doesn’t include that particular one.  And, unfortunately, I’m as in the dark as you are.

I gave up on that a long time ago.

[Sarigolepas]

Why not something like this with film-cooled turbine blades?
I made this for laugh, but I'm serious xD

[meekGee]

Why not something like this with film-cooled turbine blades?
I made this for laugh, but I'm serious xD

The turbine in the main exhaust?

Rn it's at the exit of the pre burners, which is like a percent (well, some small fraction) of the total output.  I am not sure you can keep a turbine alive in the MCC.

[Sarigolepas]

Why not something like this with film-cooled turbine blades?
I made this for laugh, but I'm serious xD

The turbine in the main exhaust?

Rn it's at the exit of the pre burners, which is like a percent (well, some small fraction) of the total output.  I am not sure you can keep a turbine alive in the MCC.

I know, but this is the only cycle I can think of that could beat full flow.
Musk said that the engine that would make life multiplanetary would not be called raptor, implying it would have a different combustion cycle. And this is the only cycle left before we reach the physical limit in chamber pressure.

[meekGee]

Why not something like this with film-cooled turbine blades?
I made this for laugh, but I'm serious xD

The turbine in the main exhaust?

Rn it's at the exit of the pre burners, which is like a percent (well, some small fraction) of the total output.  I am not sure you can keep a turbine alive in the MCC.

I know, but this is the only cycle I can think of that could beat full flow.
Musk said that the engine that would make life multiplanetary would not be called raptor, implying it would have a different combustion cycle. And this is the only cycle left before we reach the physical limit in chamber pressure.

Playing along, the turbine will have lower pressure but higher temperature working fluid. (Two bada)  Not O2 rich. (Good).  A number of seals (bad).  Way too much power (bad) amf not really throttleable.

I think it's a bad trade, and is also something the first rocket builders looked at before going with power packs.

But you're right that this is Musk amd they will look at anything that doesn't violate the laws of physics, even if it's been looked at before.

[DJPledger]

Perhaps Raptor successor will be a RDRE which should give better performance than FFSC.

[Crispy]

Perhaps Raptor successor will be a RDRE which should give better performance than FFSC.

I've been having trouble pinning this down with google. Are we talking better thrust? ISP? T:W? And by how much?

[Robotbeat]

Rotating detonation engines are over-rated. None of them have demonstrated even mediocre performance, yet.

The detonation is just another way of trying to get a higher effective combustion pressure. A good pump system is at least as viable.

[Sarigolepas]

Playing along, the turbine will have lower pressure but higher temperature working fluid. (Two bada)  Not O2 rich. (Good).  A number of seals (bad).  Way too much power (bad) amf not really throttleable.

I think it's a bad trade, and is also something the first rocket builders looked at before going with power packs.

But you're right that this is Musk amd they will look at anything that doesn't violate the laws of physics, even if it's been looked at before.

The pressure is indeed lower in the main combustion chamber than the preburner, but if you put the turbine between the combustion chamber and the nozzle you have more power available to drive the turbine, which increases chamber pressure, in this case it could be as high as 2000 bar since the temperature is 4 times higher.

It's actually counterintuitive, more heat means more power which means more pressure, so the density of the gases is the only thing that is constant.
Which makes sense because there must be an ideal expansion ratio of the gases inside the combustion chamber.

[meekGee]

Playing along, the turbine will have lower pressure but higher temperature working fluid. (Two bada)  Not O2 rich. (Good).  A number of seals (bad).  Way too much power (bad) amf not really throttleable.

I think it's a bad trade, and is also something the first rocket builders looked at before going with power packs.

But you're right that this is Musk amd they will look at anything that doesn't violate the laws of physics, even if it's been looked at before.

The pressure is indeed lower in the main combustion chamber than the preburner, but if you put the turbine between the combustion chamber and the nozzle you have more power available to drive the turbine, which increases chamber pressure, in this case it could be as high as 2000 bar since the temperature is 4 times higher.

It's actually counterintuitive, more heat means more power which means more pressure, so the density of the gases is the only thing that is constant.
Which makes sense because there must be an ideal expansion ratio of the gases inside the combustion chamber.

I think pressure out of the pre burners should be higher than the MC chamber...   Only a fraction of the flow, but higher pressure.

And it's a lot easier to extract work from high pressure and low temperature fluid than from low pressure high temperature fluid.

[RobLynn]

Rotating detonation engines are over-rated. None of them have demonstrated even mediocre performance, yet.

The detonation is just another way of trying to get a higher effective combustion pressure. A good pump system is at least as viable.

Detonation destroys metals - the combination of extreme pressure fluctuations and ultra high temperatures penetrates normal boundary layers exposing surface of metals to destructive thermal spikes and pressure forces that are normally buffered by protective boundary layers.  This breaks down metal surfaces, stripping oxide protections and wrecks cavitating water pumps, water turbines, items left too long in sound nodes of ultrasonic baths, engine pistons + rings and other combustion chamber elements etc.  I strongly doubt that RDE's will ever be more than lab curiosities - much as they have been (in the form of variant pressure gain combustors) for 60 years.

[InterestedEngineer]

Rotating detonation engines are over-rated. None of them have demonstrated even mediocre performance, yet.

The detonation is just another way of trying to get a higher effective combustion pressure. A good pump system is at least as viable.

The detonation velocity of methalox is about half the exhaust velocity of a Raptor.

[redneck]

Why not something like this with film-cooled turbine blades?
I made this for laugh, but I'm serious xD

Or taking it to the next level, regenerative cooled turbine blades in which the liquid flow through the blades is the last pump stage.

[warp99]

Rotating detonation engines are over-rated. None of them have demonstrated even mediocre performance, yet.

The detonation is just another way of trying to get a higher effective combustion pressure. A good pump system is at least as viable.

The detonation velocity of methalox is about half the exhaust velocity of a Raptor.

An RDE engine has the detonation wave front circling at right angles to the exhaust flow so the detonation speed is not a limit on the exhaust velocity.  What is an issue is that a nozzle does not provide a significant gain in Isp as the collimation of the exhaust is set by the slot geometry.

[edzieba]

Rotating detonation engines are over-rated. None of them have demonstrated even mediocre performance, yet.

The detonation is just another way of trying to get a higher effective combustion pressure. A good pump system is at least as viable.

The point of RDREs is not increased efficiency or performance: turbomachinery-pumped engines can already get pretty close to the theoretical limits there. The point of an  RDRE is to achieve the same combustion pressures and temperatures without the turbomachinery, giving you an engine with the mechanical complexity and (similar) mass of a pressure-fed engine but the performance of a turbopump engine. Improved TWR with fewer moving parts.

[rsdavis9]

I was going to be a snarky little whatever and point out the acronyms thread: https://forum.nasaspaceflight.com/index.php?topic=34802.0
But then I noticed that it doesn’t include that particular one.  And, unfortunately, I’m as in the dark as you are.

I gave up on that a long time ago.

As long as we are on the subject: What does LRE stand for? Long Range Engine?

[niwax]

I was going to be a snarky little whatever and point out the acronyms thread: https://forum.nasaspaceflight.com/index.php?topic=34802.0
But then I noticed that it doesn’t include that particular one.  And, unfortunately, I’m as in the dark as you are.

I gave up on that a long time ago.

As long as we are on the subject: What does LRE stand for? Long Range Engine?

Liquid rocket engine. As opposed to SRB.

[rsdavis9]

So cross post from impulse thread.

ORSC targeting ~375s. Gotta love it when a propulsion engineer like Mueller talks about the trades with a degree of depth. Duration is also brought up; they already have to have a reasonable amount of insulation given that they're launching inside a fairing, but was only thinking a couple days maybe.

Engine cycle discussion at this timestamp
https://www.youtube.com/live/pojbt_bsafo?si=-ChW40dcx0dEs9c5&t=3482

So the deneb engine that impulse and mueller built is ORSC(oxygen rich staged combustion) and he talks why the raptor is FFSC(from sea level) and his engine is ORSC(in space).

[rsdavis9]

Also I really like impulse space's RCS system. Using the Saiph thruster.
The low toxicity of their N2O and Ethane is no laughing matter.
I think they are storing gas for these engines but I am not sure.

[Sarigolepas]

I think pressure out of the pre burners should be higher than the MC chamber...   Only a fraction of the flow, but higher pressure.

And it's a lot easier to extract work from high pressure and low temperature fluid than from low pressure high temperature fluid.

Yes, the pressure is higher in the preburner than the main combustion chamber, but in this case the main combustion chamber is the preburner, and it's a preburner 4 times hotter so you have 4 times more energy to spin the turbine.

So you actually have even more pressure than you might expect from the increase in temperature, because you removed the loss of pressure and other inefficiencies caused by having two combustion chambers in a row. You still lose some pressure between the combustion chamber and the throat though, because you added a turbine there.

[meekGee]

I think pressure out of the pre burners should be higher than the MC chamber...   Only a fraction of the flow, but higher pressure.

And it's a lot easier to extract work from high pressure and low temperature fluid than from low pressure high temperature fluid.

Yes, the pressure is higher in the preburner than the main combustion chamber, but in this case the main combustion chamber is the preburner, and it's a preburner 4 times hotter so you have 4 times more energy to spin the turbine.

So you actually have even more pressure than you might expect from the increase in temperature, because you removed the loss of pressure and other inefficiencies caused by having two combustion chambers in a row. You still lose some pressure between the combustion chamber and the throat though, because you added a turbine there.

I'm kinda imagining that if anyone tries this  the turbine will be on a parallel path, tapping to only a small fraction of the flow.  Still between MCC and nozzle, or MCC and throat.  Probably the former.  Shrug.  Not a rocket scientist obviously.

[InterestedEngineer]

chamber pressures temperatures are 3700K.

No turbine material can survive that.  Turbojet turbines achieve maybe half that temperature

A big advantage of FFSC is cooler turbines.  A turbine in the chamber or early in the exhaust would negate that advantage

[deltaV]

chamber pressures are 3700K.

You mean chamber temperatures.

[Sarigolepas]

I'm kinda imagining that if anyone tries this  the turbine will be on a parallel path, tapping to only a small fraction of the flow.  Still between MCC and nozzle, or MCC and throat.  Probably the former.  Shrug.  Not a rocket scientist obviously.

That's called a combustion tap-off cycle. That way you can allow the gases to cool down or expand before spinning the turbine so it doesn't melt.
But there is no advantage in chamber pressure, you lose some pressure by putting the turbine between the combustion chamber and the nozzle but you gain way more pressure because of all the additional energy you get back. We just don't know yet if it's possible to build a turbine that doesn't melt.

[Sarigolepas]

chamber pressures temperatures are 3700K.

No turbine material can survive that.  Turbojet turbines achieve maybe half that temperature

A big advantage of FFSC is cooler turbines.  A turbine in the chamber or early in the exhaust would negate that advantage

Gas turbines used in powerplants operate at 1700K so twice the temperature of Raptor turbopumps, just by adding cooling.
And those turbines are using air, not oxygen, so it's likely that they are limited by the flame temperature, not by what the turbine can handle.

Yes, full flow engines use all the flow to drive the turbopumps, which is why they get more power for the same temperature.
But that's the whole point, raptor already uses all the flow of the engine so the only way to get more power is to increase the temperature, hence why they need film-cooled turbines.

They will probably add film-cooled turbines to raptor and over time increase the turbopump temperature to something like 1700K. Once they made sure that it works they will start working on a new engine that won't be called raptor, meaning it will have a different combustion cycle. So a single combustion chamber must be it.

[redneck]

chamber pressures temperatures are 3700K.

No turbine material can survive that.  Turbojet turbines achieve maybe half that temperature

A big advantage of FFSC is cooler turbines.  A turbine in the chamber or early in the exhaust would negate that advantage

Gas turbines used in powerplants operate at 1700K so twice the temperature of Raptor turbopumps, just by adding cooling.
And those turbines are using air, not oxygen, so it's likely that they are limited by the flame temperature, not by what the turbine can handle.

Yes, full flow engines use all the flow to drive the turbopumps, which is why they get more power for the same temperature.
But that's the whole point, raptor already uses all the flow of the engine so the only way to get more power is to increase the temperature, hence why they need film-cooled turbines.

They will probably add film-cooled turbines to raptor and over time increase the turbopump temperature to something like 1700K. Once they made sure that it works they will start working on a new engine that won't be called raptor, meaning it will have a different combustion cycle. So a single combustion chamber must be it.

You might check out the single rotor turbine engine patented by LANL. Go to liquid cooling instead of air and you’d be on the same page.

added later when back on the computer.
https://patents.google.com/patent/US6430917B1/en
https://selenianboondocks.com/2008/11/affordable-triprop-pumped-engine/

[Sarigolepas]

Speaking of much larger surface area to protect against heat, here are two 3d printed aerospike combustion chambers:

I'm sure 3d printing is the key to make complex parts like this possible and there is nothing that could prevent them from adding cooling channels to the turbine. They have already integrated many cooling channels into raptor 3 much higher in the engine, probably even around the turbopumps.

[warp99]

Film cooled turbine blades are typically laser drilled with thousands of small holes that the cooling air bleeds out of.  On a rocket engine that cooling role role would be taken by liquid methane propellant which would burn immediately after it was released through the cooling holes. 

What if that was made a feature instead of a bug so that the methane turbine replaced the injectors as the primary mixer for fuel and oxidiser.  The LOX turbopump would be similar to the present arrangement.  The methane turbopump would be constructed as a spinning sleeve inside the main combustion chamber so running coaxially with the oxygen turbopump.  The pump impellers would exhaust to integrated cooling channels and circulate through the chamber walls, throat and then the bell.  On return the liquid methane would be used to support the sleeve on the walls of the combustion chamber as a hydrodynamic bearing and would travel through the vanes of the turbopump to cool them while being injected into the combustion chamber to mix with the pumped LOX and ignite. 

The rotation speed of the turbine means that there would be good mixing of the propellants similar to a swirl injector.  The turbine blades would remain well cooled even though they are physically placed at the upper end of the combustion chamber.  The combustion chamber temperature local to the turbine section would be intermediate between the LOX inlet temperature of say 800K and the final combustion chamber temperature and combination of evaporative and film cooling would keep the blade temperature under 1300K and with reducing conditions.

[InterestedEngineer]

I'm trying to figure out why the power head is getting optimized here with all sorts of fancy ways of dealing with fragile turbopumps that throws away what was learned with Raptor's power head.

Is the powerhead really the limiting factor on current state of the art methalox engines?

From what Elon says, it's temperature of the combustion chamber that's the problem. It gets very melty.  The other big problem is startup and shutdown sequences for FFSC, but they appear to be very far along on working that out.

Thrust and exhaust velocity is proportional to chamber pressure and temperature (de Laval equation).  If you aren't increasing those, then you aren't increasing Isp or thrust.

The combustion chamber is already 99.5% efficient an knitting the molecules together on Raptor.  What further energy do you think you can extract from methalox?

[redneck]

I'm trying to figure out why the power head is getting optimized here with all sorts of fancy ways of dealing with fragile turbopumps that throws away what was learned with Raptor's power head.

Is the powerhead really the limiting factor on current state of the art methalox engines?

From what Elon says, it's temperature of the combustion chamber that's the problem. It gets very melty.  The other big problem is startup and shutdown sequences for FFSC, but they appear to be very far along on working that out.

Thrust and exhaust velocity is proportional to chamber pressure and temperature (de Laval equation).  If you aren't increasing those, then you aren't increasing Isp or thrust.

The combustion chamber is already 99.5% efficient an knitting the molecules together on Raptor.  What further energy do you think you can extract from methalox?

There's always more crazy ideas to explore.  https://selenianboondocks.com/2008/10/rollerthroat-pump/       This one has rollers in the throat to reduce the heat load there with some minor pumping action for reverse film cooling of the main chamber.

The Raptor is state of the art at this time. The question being if it will be  like the piston engine we see in cars that would have been recognizable from over a century ago? Or is the rotary engine trying to edge the pistons out?  Or is it the 50s piston engine in Warbirds about to be eclipsed by turbojets?

[Sarigolepas]

Film cooled turbine blades are typically laser drilled with thousands of small holes that the cooling air bleeds out of.  On a rocket engine that cooling role role would be taken by liquid methane propellant which would burn immediately after it was released through the cooling holes. 

What if that was made a feature instead of a bug so that the methane turbine replaced the injectors as the primary mixer for fuel and oxidiser.  The LOX turbopump would be similar to the present arrangement.  The methane turbopump would be constructed as a spinning sleeve inside the main combustion chamber so running coaxially with the oxygen turbopump.  The pump impellers would exhaust to integrated cooling channels and circulate through the chamber walls, throat and then the bell.  On return the liquid methane would be used to support the sleeve on the walls of the combustion chamber as a hydrodynamic bearing and would travel through the vanes of the turbopump to cool them while being injected into the combustion chamber to mix with the pumped LOX and ignite. 

The rotation speed of the turbine means that there would be good mixing of the propellants similar to a swirl injector.  The turbine blades would remain well cooled even though they are physically placed at the upper end of the combustion chamber.  The combustion chamber temperature local to the turbine section would be intermediate between the LOX inlet temperature of say 800K and the final combustion chamber temperature and combination of evaporative and film cooling would keep the blade temperature under 1300K and with reducing conditions.

That's pretty much how monopropellant turbopumps work, there is a catalyst on the turbine blades so the reaction happends when the monopropellant touches the turbine.

Propellant moves from the highest pressure to the lowest pressure, what makes a turbopump work is that despite the pressure being higher in the fuel injector than on the turbine blades those gases expand as they burn so the flow rate is higher on the turbine than in the injector, which means the turbine gets back more power than it has to give to inject fuel.

That principle would also work if fuel injection was done on the turbine, the small holes only cover a tiny percentage of the area of the turbine so as the fuel burns and expands the overall force on the turbine is increased even if the pressure is reduced.

[Sarigolepas]

I'm trying to figure out why the power head is getting optimized here with all sorts of fancy ways of dealing with fragile turbopumps that throws away what was learned with Raptor's power head.

Is the powerhead really the limiting factor on current state of the art methalox engines?

From what Elon says, it's temperature of the combustion chamber that's the problem. It gets very melty.  The other big problem is startup and shutdown sequences for FFSC, but they appear to be very far along on working that out.

Thrust and exhaust velocity is proportional to chamber pressure and temperature (de Laval equation).  If you aren't increasing those, then you aren't increasing Isp or thrust.

The combustion chamber is already 99.5% efficient an knitting the molecules together on Raptor.  What further energy do you think you can extract from methalox?

It gets melty because they use as little film cooling as possible in order to have a good combustion efficiency.
You don't gain anyting by adding more cooling than necessary to the main combustion chamber because it's already burning at close to stoichiometric ratio.

But on a turbine you have so much to gain by going from 800K to 3500K that a little combustion inefficiency is worth it. More pressure also means an higher nozzle expansion ratio so it might ends up more efficient overall anyways.

[CorvusCorax]

A big limiting factor on LRE is chemistry.

You can't make the combustion much hotter, because if you do the temperature exceeds the disassociation point of your combustion results ( its too hot for H2O and CO2 to remain molecules ) But since this recombination provides the energy for your engine, the only way to further increase exhaust velocity is to increase MCC pressure.

Anything that ups MCC pressure is fair game

[redneck]

A big limiting factor on LRE is chemistry.

You can't make the combustion much hotter, because if you do the temperature exceeds the disassociation point of your combustion results ( its too hot for H2O and CO2 to remain molecules ) But since this recombination provides the energy for your engine, the only way to further increase exhaust velocity is to increase MCC pressure.

Anything that ups MCC pressure is fair game

Part of the concept seems to be that will all the extra power available, pressure can be increased considerably. I can't remember the formulas anymore. I think it would be something like triple the temp would allow triple the power which could increase pump pressures by sqrt3 or about 1.7 times pressure. which would increase power to the turbine which would again increase......

Right at the moment quite annoyed that Hill and Peterson is still in storage years later.

[Sarigolepas]

Part of the concept seems to be that will all the extra power available, pressure can be increased considerably. I can't remember the formulas anymore. I think it would be something like triple the temp would allow triple the power which could increase pump pressures by sqrt3 or about 1.7 times pressure. which would increase power to the turbine which would again increase......

Right at the moment quite annoyed that Hill and Peterson is still in storage years later.

Using basic hydraulics (power = pressure*volumetric flow) for a given fuel injector size, 3 times the energy per kg of fuel, so 3 times the pressure and 1.7 times the flow, so 5 times the turbopump power for a rocket engine that is only 70% more powerful but has a much smaller combustion chamber.

That's interesting, the volumetric flow of the injectors increase with the quare root of the pressure while the volumetric flow of the combustion chamber increases proportionnally to the pressure. So rocket engines with higher chamber pressure need bigger injectors to keep up with the combustion chamber. That probably makes deep throttling very difficult.

Now for a given combustion chamber size, 3 times the energy per kg of fuel so 3 times the pressure for 3 times the flow. So 9 times more turbopump power for a rocket engine that is 3 times more powerful.

[Sarigolepas]

I asked Tim Dodd on discord and he doesn't seem to believe in film-cooling for the turbine. I still hope he asked Elon about this during his interview. Especially since we know that raptor 3 has cooling channels at least on the outside of the turbopump.

[Sarigolepas]

It worked:

Answer at 46:25
Seems like the video was cut, maybe an issue with ITAR?

[IKM]

RE: We can all agree that the LEET engine is a methalox engine, so why does it need a new name?

Not sure that is the long term plan ...... fuel production is the real issue further down the track, in this case methalox, generations of the Raptor Engine and Mars all fit together.
However Raptor was conceived to burn hydrogen and oxygen propellants.

In 2012, Raptor became a methane-fueled rocket engine, because of the presence of underground water and carbon dioxide in Mars atmosphere, methane, a simple hydrocarbon, that could be synthesized on Mars using the Sabatier reaction. NASA found in-situ resource production on Mars to be viable for oxygen, water, and methane production.

So anything that comes out of LEET-1337 that can be used/modified for Raptor "methalox" Engnes, is a bonus, but lets not lose sight on the bigger more ambigious plans, beyond Mars, and alternative propellants.

[r8ix]

RE: We can all agree that the LEET engine is a methalox engine, so why does it need a new name?

Not sure that is the long term plan ...... fuel production is the real issue further down the track, in this case methalox, generations of the Raptor Engine and Mars all fit together.
However Raptor was conceived to burn hydrogen and oxygen propellants.

In 2012, Raptor became a methane-fueled rocket engine, because of the presence of underground water and carbon dioxide in Mars atmosphere, methane, a simple hydrocarbon, that could be synthesized on Mars using the Sabatier reaction. NASA found in-situ resource production on Mars to be viable for oxygen, water, and methane production.

So anything that comes out of LEET-1337 that can be used/modified for Raptor "methalox" Engnes, is a bonus, but lets not lose sight on the bigger more ambigious plans, beyond Mars, and alternative propellants.

There are other reasons, such as rocket structure, propellant handling, and so forth, that make methane preferable to hydrogen, especially for a lo-cost, rapidly reusable rocket system.

[baldusi]

RE: We can all agree that the LEET engine is a methalox engine, so why does it need a new name?

Not sure that is the long term plan ...... fuel production is the real issue further down the track, in this case methalox, generations of the Raptor Engine and Mars all fit together.
However Raptor was conceived to burn hydrogen and oxygen propellants.

In 2012, Raptor became a methane-fueled rocket engine, because of the presence of underground water and carbon dioxide in Mars atmosphere, methane, a simple hydrocarbon, that could be synthesized on Mars using the Sabatier reaction. NASA found in-situ resource production on Mars to be viable for oxygen, water, and methane production.

So anything that comes out of LEET-1337 that can be used/modified for Raptor "methalox" Engnes, is a bonus, but lets not lose sight on the bigger more ambigious plans, beyond Mars, and alternative propellants.

There are many reasons why it will be methalox. Among those: liquid temperature of oxygen and methane are similar, and can be kept liquid in space with minimum insulation, the density (i.e. tank size) if good, and most important: is the only one where going full flow staged cycle gets a huge kick. There's a reason Raptor 3 is the rocket with best T/W and has the most chamber pressure and highest isp outside of hydrogen (which has a lot of problems of its own).

[Sarigolepas]

RE: We can all agree that the LEET engine is a methalox engine, so why does it need a new name?

Not sure that is the long term plan ...... fuel production is the real issue further down the track, in this case methalox, generations of the Raptor Engine and Mars all fit together.
However Raptor was conceived to burn hydrogen and oxygen propellants.

In 2012, Raptor became a methane-fueled rocket engine, because of the presence of underground water and carbon dioxide in Mars atmosphere, methane, a simple hydrocarbon, that could be synthesized on Mars using the Sabatier reaction. NASA found in-situ resource production on Mars to be viable for oxygen, water, and methane production.

So anything that comes out of LEET-1337 that can be used/modified for Raptor "methalox" Engnes, is a bonus, but lets not lose sight on the bigger more ambigious plans, beyond Mars, and alternative propellants.

There are many reasons why it will be methalox. Among those: liquid temperature of oxygen and methane are similar, and can be kept liquid in space with minimum insulation, the density (i.e. tank size) if good, and most important: is the only one where going full flow staged cycle gets a huge kick. There's a reason Raptor 3 is the rocket with best T/W and has the most chamber pressure and highest isp outside of hydrogen (which has a lot of problems of its own).

Interesting.
In a perfect gas temperature is proportionnal to the amount of energy per mole, so for a given turbopump temperature you get more power if you have a higher flow of moles per second.
Both hydrogen and methane have 2 moles of one propellant for 1 mole of the other. So at first glance they would get the same kick for going full flow.
But a fuel-rich hydrogen engine can run hotter because hydrogen is not corrosive while an oxygen-rich methane engine would still run at the same temperature as full flow. So methane is where you get the biggest kick.
As for heavier fuels, you have way more moles of oxygen than fuel so it's not worth it.

[Skye]

Why not something like this with film-cooled turbine blades?
I made this for laugh, but I'm serious xD

Can we call this direct injection (full flow) staged combustion (DISC - pronounced as a word, rather than an acronym like disc) the reason I exclude the FF from the pronunciation because disc is easier to say than diffsc. Or maybe we could just call it DIFFS for Direct Injection Full Flow Staged?

[Skye]

Wait I just realised there’s nothing that exchanges fuel and oxidiser into their preburners where is that? And, actually, where are the preburners and would adding them increase efficiency?

[Skye]

Also could I make a thread about it in advanced concepts? It seems like an idea worth discussing in its own thread as well. I will credit Sarigolepas for the concept and diagram.