Author Topic: ITS Propulsion – The evolution of the SpaceX Raptor engine  (Read 40112 times)

Offline livingjw

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #20 on: 10/03/2016 05:15 PM »
One thing about 3-D printing the innards, I believe it limits what can be coated or left uncoated. Not sure what secret sauce is required, but previous engines of this type relied on some sort of covering to protect engine structures.

Matthew

I would think they would make use of a Mondaloy (or similar) oxidation resistant material instead of (or in conjunction with) coatings.

John

Offline ellindsey

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #21 on: 10/03/2016 05:16 PM »
The only question I have from that article concerns the use of heat exchangers. I always thought that you could tap the methane for pressurization right after it exits the regenerative channels and not need an additional heat exchanger for that.

Do we know that the methane channel will indeed use an exchanger?

From looking at the engine, it appears that the methane is tapped right after it comes out of the regenerative cooling circuit of the main combustion chamber and nozzle.  Only the oxygen feed has a separate heat exchanger for pressurization gas heating.

Offline baldusi

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #22 on: 10/03/2016 05:35 PM »
The only question I have from that article concerns the use of heat exchangers. I always thought that you could tap the methane for pressurization right after it exits the regenerative channels and not need an additional heat exchanger for that.

Do we know that the methane channel will indeed use an exchanger?

From looking at the engine, it appears that the methane is tapped right after it comes out of the regenerative cooling circuit of the main combustion chamber and nozzle.  Only the oxygen feed has a separate heat exchanger for pressurization gas heating.

I see more a tap for the LOX preburner. It is not quite clear now what's the exact schematic.

Offline DJPledger

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #23 on: 10/03/2016 05:55 PM »
The 1MN dev. model of Raptor should be mass produced to replace Merlin to do away with the He system on F9 and FH.

Offline John Alan

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #24 on: 10/03/2016 05:58 PM »
The only question I have from that article concerns the use of heat exchangers. I always thought that you could tap the methane for pressurization right after it exits the regenerative channels and not need an additional heat exchanger for that.

Do we know that the methane channel will indeed use an exchanger?

From looking at the engine, it appears that the methane is tapped right after it comes out of the regenerative cooling circuit of the main combustion chamber and nozzle.  Only the oxygen feed has a separate heat exchanger for pressurization gas heating.

I see more a tap for the LOX preburner. It is not quite clear now what's the exact schematic.

Speculation...
The heat exchanger is 3D printed into the pump housing between the pump output and the preburner inlet...
The hot gases going to tank pressurization would be cooled by the cold fluids chilling the housing...
Would have to see a print of the housing to know it's there...  ;)
It's amazing what 3D printing lets you do...  8)

Offline MAC74

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #25 on: 10/03/2016 06:01 PM »
One thing about 3-D printing the innards, I believe it limits what can be coated or left uncoated. Not sure what secret sauce is required, but previous engines of this type relied on some sort of covering to protect engine structures.

Matthew

My guess is that they are 3D printing or casting the parts that are exposed to oxygen rich hot gas from Mondaloy 200.  The parts that are on the fuel rich side will probably be Inconel.  Mondaloy is the new US equivalent to the exotic Russian metallurgy.  It is a zinc rich superalloy that can resist high temperature oxidation without a protective coating.

Offline RedLineTrain

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #26 on: 10/03/2016 06:08 PM »
It appears that Mondaloy is an Aerojet product, so I can imagine that SpaceX would not have access to it.

SpaceX and Tesla have hired Charles Kuehmann to lead materials development, so SpaceX probably has its own solution.

https://electrek.co/2016/02/24/apple-alloy-expert-tesla-spacex/
« Last Edit: 10/03/2016 06:13 PM by RedLineTrain »

Offline Dante80

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #27 on: 10/03/2016 06:23 PM »
I think that Musk will be doing and AMA this week or the next. It would be pretty cool to get some more answers about Raptor, especially after the added info we got from this great article.

1. Was the test firing using the full engines' powerpack, or was it only a chamber test?
2. Was TEA-TEB used, or a spark igniter (the video I think is inconclusive on that)?
3. Will this dev article reach during development the high pressures intended for the ITS Raptor?
4. Will the end of development for this 1MN variant involve an acceptance test at Stennis (as per the USAF contract)?


Offline matthewkantar

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #28 on: 10/03/2016 07:05 PM »
It appears that Mondaloy is an Aerojet product, so I can imagine that SpaceX would not have access to it.

SpaceX and Tesla have hired Charles Kuehmann to lead materials development, so SpaceX probably has its own solution.

https://electrek.co/2016/02/24/apple-alloy-expert-tesla-spacex/

I have been wondering about this. Since SpaceX keeps so much of the details of its tech secret, what other than honor stops them from copying all sorts of proprietary things.

Matthew

Offline DJPledger

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #29 on: 10/03/2016 07:23 PM »
It appears that Mondaloy is an Aerojet product, so I can imagine that SpaceX would not have access to it.

SpaceX and Tesla have hired Charles Kuehmann to lead materials development, so SpaceX probably has its own solution.

https://electrek.co/2016/02/24/apple-alloy-expert-tesla-spacex/

I have been wondering about this. Since SpaceX keeps so much of the details of its tech secret, what other than honor stops them from copying all sorts of proprietary things.

Matthew

The reason is ITAR why SpaceX have to keep details of it's tech. including Raptor secret.

Offline baldusi

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #30 on: 10/03/2016 07:49 PM »
I think that Musk will be doing and AMA this week or the next. It would be pretty cool to get some more answers about Raptor, especially after the added info we got from this great article.

1. Was the test firing using the full engines' powerpack, or was it only a chamber test?
2. Was TEA-TEB used, or a spark igniter (the video I think is inconclusive on that)?
3. Will this dev article reach during development the high pressures intended for the ITS Raptor?
4. Will the end of development for this 1MN variant involve an acceptance test at Stennis (as per the USAF contract)?

1) It was a complete rocket, it included a 27MW turbo machinery. It's in the article.
2) I don't know if it included the spark ignition. Somebody should include that question in the AMA.
3) I would guess that it has the capability of reaching full Pc, because 27MW is more MW/kN of any non hydrogen rocket.
4) I think it is a possibility. I don't have information but I would be surprised if two things were not true:
a) this won't be the only demonstrator.
b) this prototype or the next one isn't used to complete the USAF contract.

Offline AncientU

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #31 on: 10/03/2016 07:51 PM »
Nice article, Baldusi (by the way)
"If we shared everything [we are working on] people would think we are insane!"
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Offline mheney

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #32 on: 10/03/2016 08:37 PM »
It appears that Mondaloy is an Aerojet product, so I can imagine that SpaceX would not have access to it.

SpaceX and Tesla have hired Charles Kuehmann to lead materials development, so SpaceX probably has its own solution.

https://electrek.co/2016/02/24/apple-alloy-expert-tesla-spacex/

I have been wondering about this. Since SpaceX keeps so much of the details of its tech secret, what other than honor stops them from copying all sorts of proprietary things.

Matthew



Lawsuits.  People move around, and you couldn't keep stealing other people's work secret for long.

Offline dglow

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #33 on: 10/03/2016 08:42 PM »
Mr. Belluscio, a very nice article – thank you.

One note of correction: the 361s ISP you cite for the first stage's Raptors in vacuum is actually the sea level value for the three inner Raptors of the second stage. See pp. 36 of SpaceX's published PDF

Offline MAC74

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #34 on: 10/03/2016 08:49 PM »
It appears that Mondaloy is an Aerojet product, so I can imagine that SpaceX would not have access to it.

SpaceX and Tesla have hired Charles Kuehmann to lead materials development, so SpaceX probably has its own solution.

https://electrek.co/2016/02/24/apple-alloy-expert-tesla-spacex/

Mondaloy is an Air Force Research Laboratory program.  It says right on the program that the information is to be shared with the entire US Rocket Community.  Here are the exact words.

"The improved knowledge base, test results, and lessons learned in the HCB program and other BPTM activities are shared with the entire U.S. rocket propulsion community."

Offline Rocket Science

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #35 on: 10/03/2016 08:50 PM »
Great work on the article Alejandro, thank you! :)
“The laws of physics are unforgiving”...
Rob

Offline baldusi

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #36 on: 10/03/2016 09:09 PM »
Mr. Belluscio, a very nice article – thank you.

One note of correction: the 361s ISP you cite for the first stage's Raptors in vacuum is actually the sea level value for the three inner Raptors of the second stage. See pp. 36 of SpaceX's published PDF.
I believe that you are misreading the information. Vacuum optimized nozzle can't be used at sea level since they would get into flow separation issues. When they say Sea Level and Vacuum they refer to the two different Raptor versions.
There is no way you can get 361 seconds of isp with methane/LOX at sea level. Best I could get was 355 theoretical, without losses, and that was with a Pc of 70MPa. At 30MPa you can't get past 337s.

Offline dglow

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #37 on: 10/03/2016 09:24 PM »
Mr. Belluscio, a very nice article – thank you.

One note of correction: the 361s ISP you cite for the first stage's Raptors in vacuum is actually the sea level value for the three inner Raptors of the second stage. See pp. 36 of SpaceX's published PDF.
I believe that you are misreading the information. Vacuum optimized nozzle can't be used at sea level since they would get into flow separation issues. When they say Sea Level and Vacuum they refer to the two different Raptor versions.
There is no way you can get 361 seconds of isp with methane/LOX at sea level. Best I could get was 355 theoretical, without losses, and that was with a Pc of 70MPa. At 30MPa you can't get past 337s.

Understood. I'm simply pointing out the information SpaceX has and has not provided us with.

For the first stage SX provides thrust value only, not ISP. On the second stage they provide vacuum thrust only, then separate sea-level and vacuum ISP values.

The 361s value is interesting. Perhaps the second stage's three inner Raptors are configured differently than those on the first stage given they are used for Earth landing but not Earth lift-off.

Offline MATTBLAK

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Re: ITS Propulsion – The evolution of the SpaceX Raptor engine
« Reply #38 on: 10/03/2016 09:27 PM »
Has a version of the Merlin ever seriously been considered that runs on LOX/CH4? Even without all the full flow, staged combustion features of the Raptor; with subcooled propellants, what kind of performance could be squeezed out of them?
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Online MikeAtkinson

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Mr. Belluscio, a very nice article – thank you.

One note of correction: the 361s ISP you cite for the first stage's Raptors in vacuum is actually the sea level value for the three inner Raptors of the second stage. See pp. 36 of SpaceX's published PDF.

It says

Raptor Engines
   3 Sea-Level - 361 Isp
   6 Vacuum - 382 Isp

Meaning 3 Sea-Level engines and 6 Vacuum engines, with Isp 361 and 382 seconds in vacuum respectively.

It is easy to see that they mean the vacuum Isp for the Sea-Level engines as page 31 gives the sea-level Isp as 334 and the main use of the Sea-Level engines in the Ship will be for Earth ascent, Mars landing and Mars descent all of which are in near vacuum.

Edit: the Ship total thrust of 31 MN allows us to estimate the Raptor (SL) thrust in vacuum. As

(31- 6 x 3.5) / 3 = 3.33 MN
« Last Edit: 10/03/2016 09:49 PM by MikeAtkinson »

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