Author Topic: multiple combustion chamber Merlin  (Read 19363 times)

Online Zed_Noir

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Re: multiple combustion chamber Merlin
« Reply #20 on: 10/29/2011 02:42 am »

And since SpaceX was confident enough to put 9 turbo pumps in a stage, I don't see why they would ever feel the urgent need to reduce to only one turbo pump. It's just not going to happen, with good reason.

SpaceX is confident that 27 turbo pumps will work when the Falcon Heavy debuts.

Offline Prober

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Re: multiple combustion chamber Merlin
« Reply #21 on: 10/29/2011 04:12 am »
Realistically, though, if a multi-chamber rocket design is pursued - SpaceX would design a larger thrust chamber anyway.

Unless you propose a 9 chamber design with the current Merlin 1D thrust chamber... :) Which would be pointless, since we know the 9 engines do work together.

And since SpaceX was confident enough to put 9 turbo pumps in a stage, I don't see why they would ever feel the urgent need to reduce to only one turbo pump. It's just not going to happen, with good reason.

Cluster three turbo pumps on one shaft.  That would reduce the parts and if designed right give you more power.

Before Jim says it won't work.  Let me say P&W understands pumps real well ...watch the video

« Last Edit: 10/29/2011 04:49 am by Prober »
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Offline sdsds

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Re: multiple combustion chamber Merlin
« Reply #22 on: 10/29/2011 05:55 am »
It seems just possible that SpaceX could create a "Falcon 16" by putting 16 Merlin-sized combustion chambers under a larger core, with each of four sets of turbomachinery powering a cluster of four combustion chambers....  A totally hypothetical triple-core "Falcon 16 Heavy" version might even deliver more than 70 tons to LEO.
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Offline krytek

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Re: multiple combustion chamber Merlin
« Reply #23 on: 10/29/2011 10:05 am »

And since SpaceX was confident enough to put 9 turbo pumps in a stage, I don't see why they would ever feel the urgent need to reduce to only one turbo pump. It's just not going to happen, with good reason.

SpaceX is confident that 27 turbo pumps will work when the Falcon Heavy debuts.

Those are great points. So lets say (hypothetically) we want to have a single first stage core with 27 engines. What would be the advantage(if any) of say 9 cluster engines (3 chambers per cluster) vs  27 separate M1d engines?
« Last Edit: 10/29/2011 10:06 am by krytek »

Offline Jim

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Re: multiple combustion chamber Merlin
« Reply #24 on: 10/29/2011 12:32 pm »
Realistically, though, if a multi-chamber rocket design is pursued - SpaceX would design a larger thrust chamber anyway.

Unless you propose a 9 chamber design with the current Merlin 1D thrust chamber... :) Which would be pointless, since we know the 9 engines do work together.

And since SpaceX was confident enough to put 9 turbo pumps in a stage, I don't see why they would ever feel the urgent need to reduce to only one turbo pump. It's just not going to happen, with good reason.

Cluster three turbo pumps on one shaft.  That would reduce the parts and if designed right give you more power.

Before Jim says it won't work.  Let me say P&W understands pumps real well ...watch the video



Not the same thing.  Jet engine compressors are not liquid propellant pumps.  Also, there is the matter of seals, which jets don't have to worry about.

Also, your example doesn't show a single shaft, it has multiple nested shafts.

Offline baldusi

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Re: multiple combustion chamber Merlin
« Reply #25 on: 10/29/2011 12:45 pm »
Replacing a multiple engines with a multichamber one, gives better reliability. Engine out might protect you against some failures, but not against others (look at the Zenit 2 RD-170 explosions). So overall, it would be better from that POV. At least, according to NASA methodologies.
There are two other good points, that I can think of. The first, is that a multichamber setup is shorter. Specially if you want to land vertically, this might save some mass. But the bigger one is what happens if you have a family of engines. Currently, the RD-171M, RD-180 and RD-191 have something like 70% commonality. This allows NPO Energomash to have great economies of scale, and produce very different engines (from thrust POV) with the same tooling.
If SpaceX developed a new engine with 3MN, for example, they could use a dual chamber version for Falcon 9, and a four chamber version for some heavy engines (at 12MN it would be on SRB territory thrust). But their is a game of price. And as I stated before (and against the perception of some other posters here  ;)), SpaceX's strategy is one of minimizing the number of different components, and making those cheap in great numbers.
Just to put an example, at 5.6MN of SL thrust, the Falcon 9 with Merlin 1D will have the most thrust of the EELV class cores, also it's one of the longest, for it's width. But not the best performance. They don't care about putting extra thrust and fuel to get the same performance if it can be done cheap.
What many have misinterpreted on my methane SC thread, is that I think that the only way that SpaceX will get away from the Merlin 1D will be with something that gives better performance at the same cost. That's was why I proposed methane staged combustion engine. Which I did some rough numbers and was even superior to Merlin+Raptor.
But here they would need a reason. Clearly Falcon 9 will stay with nine engines, given the way their reusability efforts is going. Since they are concentrating on that, I don't see them proposing anything bigger than the Falcon Heavy for a decade. The only need that I see for a bigger thrust engine, is the SLS booster.
As I said before, NASA doesn't like multiple engines, much less multiple chamber multiple engines. Their risk models kills them. If you look at the reasons they used to justify that Ares I was the only acceptable solution given the "horrible" reliability of the EELV, you'll see that they stated that the RD-180 had twice the failure rate of any other engine in the study. So, I could see them proposing something akin to a Merlin 2, for that reason. Given the relatively low pressure, and all that, they should be able to show pretty good safety numbers. Which I still think will be a driver on the competition. I've seen picture of the "possible" LRB for SLS, and cad something like 7 chambers. Which sort of exactly what you would expect if they used AJ-500. So, they might accept that this time, if enough safety can be paper demonstrated. But I think that's the card that the SRB folks will play. The only was for SpaceX to differentiate itself from AeroJet would be to actually have two or three chambers.

Offline pippin

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Re: multiple combustion chamber Merlin
« Reply #26 on: 10/29/2011 10:03 pm »
One drawback of that common-parts strategy is that for the small versions T/W gets really bad.

Offline Lars_J

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Re: multiple combustion chamber Merlin
« Reply #27 on: 10/29/2011 11:13 pm »
Baldusi - give it up. They are not going to use AJ-500 or any russian engine.

And they are not going to do multi-chambered engines when they have no problem putting nine engines on a single rocket stage. Multi-chamber designs add plumbing complexity, and are harder to transport and test. Mass production does have its benefits.

When they need a larger engine, I think they'll make as large of a thrust chamber they can, and then just duplicate that engine 2, 3, 4 or more times to get the thrust they wanted.
« Last Edit: 10/29/2011 11:24 pm by Lars_J »

Offline clongton

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Re: multiple combustion chamber Merlin
« Reply #28 on: 10/30/2011 12:50 am »
Baldusi - give it up. They are not going to use AJ-500 or any russian engine.

They already are - The RD-180; built in Russia by Russians using a Russian design and flown as the MPS on the DoD Atlas-V. The AJ-500 is more American than the RD-180 in spite of its Russian heritage. The design is an American improvement on the Russian design and it is an American manufactured engine.

This "sickness" of NIH has got to stop. There are lots of smart people in the world and only some of them are American. There are even some in (OMG) Russia. If you are reading this on a computer then you are using AC power supplied to us courtesy of Serbian Nikola Tesla. AC power is not an American invention and yet we are utterly dependent on it. This "sickness" of NIH has got to stop.
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Offline Lee Jay

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Re: multiple combustion chamber Merlin
« Reply #29 on: 10/30/2011 01:08 am »
If you are reading this on a computer then you are using AC power supplied to us courtesy of Serbian Nikola Tesla.

He was an American citizen working in Colorado Springs, Colorado.

Offline clongton

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Re: multiple combustion chamber Merlin
« Reply #30 on: 10/30/2011 01:12 am »
If you are reading this on a computer then you are using AC power supplied to us courtesy of Serbian Nikola Tesla.

He was an American citizen working in Colorado Springs, Colorado.

Doesn't matter. He already had the outlines of AC power when he came here. His deal with Edison was supposed to pay him enough to be able to fund it but Edison screwed him. He brought AC with him from Serbia.
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Offline Lars_J

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Re: multiple combustion chamber Merlin
« Reply #31 on: 10/30/2011 01:40 am »
Baldusi - give it up. They are not going to use AJ-500 or any russian engine.

They already are - The RD-180; built in Russia by Russians using a Russian design and flown as the MPS on the DoD Atlas-V.

"They" as in SpaceX.

Quote
This "sickness" of NIH has got to stop. There are lots of smart people in the world and only some of them are American. There are even some in (OMG) Russia.

WTH? My post had nothing to do with NIH. Just what makes sense for SpaceX.

Besides, the opposite of NIH - "outsource all of it" makes no sense either. There is inherent value in having domestic knowledge and expertise in engine design & production.

And I find the "all LV's should use Russian or rebranded Russian engines" crowd ( such as Baldusi) just as eyebrow raising.

Offline kevin-rf

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Re: multiple combustion chamber Merlin
« Reply #32 on: 10/30/2011 01:55 am »
When they need a larger engine, I think they'll make as large of a thrust chamber they can, and then just duplicate that engine 2, 3, 4 or more times to get the thrust they wanted.

But what if they need 4.5 times ;)
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Offline clongton

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Re: multiple combustion chamber Merlin
« Reply #33 on: 10/30/2011 01:33 am »
Baldusi - give it up. They are not going to use AJ-500 or any russian engine.

They already are - The RD-180; built in Russia by Russians using a Russian design and flown as the MPS on the DoD Atlas-V.

"They" as in SpaceX.

Sorry. Should have said "we". It would have been more specific to my point. There is a lot of "we will never use a Russian engine on "our" flagship launcher" being passed around lately. Personally I don't care who makes the engine so long as it is the best engine for the task *and* the supply chain is reasonably secure. That's why I like the Merlin, the SSME *and* I like the AJ-500. I don't care if the AJ-500 has Russian heritage or not - it's a good engine. The Russians did some awesome design work and Aerojet is doing some truly awesome adaptation. The RD-180 is a really good engine and I have no problem with it on an American launcher. My only question wrt the RD-180 is the security of the supply chain. Lock that up and I'll buy them all day long. Built in Russia? So what! It's a good engine.

I concur with having domestic capability and I would prefer it but I would not hamstring my program by ignoring a foreign-built engine if it's the best one for the task. If a domestic company wants to take over that business let it do what Aerojet did; take the engine and make it their own by making it an even better engine and manufacturing it here at home.
« Last Edit: 10/30/2011 01:36 am by clongton »
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Offline ugordan

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Re: multiple combustion chamber Merlin
« Reply #34 on: 10/30/2011 10:02 am »
If we have to split hairs on Tesla...

He brought AC with him from Serbia.

Close, but not quite. He was a Serb by nationality, but he never actually lived in Serbia. Born in Croatia, after finishing high school he went around Europe (Austria, Hungary...) for a while before finally coming to the U.S. and becoming a citizen.

Offline clongton

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Re: multiple combustion chamber Merlin
« Reply #35 on: 10/30/2011 10:32 am »
If we have to split hairs on Tesla...

He brought AC with him from Serbia.

Close, but not quite. He was a Serb by nationality, but he never actually lived in Serbia. Born in Croatia, after finishing high school he went around Europe (Austria, Hungary...) for a while before finally coming to the U.S. and becoming a citizen.

Ok, the hair is properly split, thank you, although I will note that he is generally noted as being Serb.

But I hope you get my point. This phobia against all things foreign (NIH) is dubious at best. The United States is a nation of immigrants. Almost everybody here came from somewhere else either directly or via their immediate ancestry. For example I am English, Irish, French and Norwegian.  My wife is English, Irish and Scott. That makes my kids English, Irish, French, Norwegian and Scott. My next door neighbor is 2nd generation Mexican while his wife is an immigrant from Holland. My neighbor across the street immigrated from Italy and his wife is 2nd generation Canadian. My neighbor up the hill immigrated from Croatia while his wife is 2nd generation Turk. My neighbor on the other side and his wife immigrated from China. And so on and so on. We all came here from over there, somewhere else. Everything we invent is invented by someone who came here from somewhere else. Or they finish their work after arriving here, like Tesla. He laid the foundation for AC power in Europe, long before he came to America. He came here to get funding to finish it and his other projects, because there was no funding in Europe, ended up being screwed by Thomas Edison and becoming an American citizen.

I hope you get my point. NIH is a distinction of dubious value. Instead of shunning it, we should embrace it. It is who we are. Like the AJ-500. The design foundation came from Russia. They designed a very good engine. Aerojet took that design and made the AJ-26 out of it. Now there is the AJ-500. It started in Russia, yes, but it is now an American engine, just like everything else we build here. The Russians could figure it out but right now they can't build it. It is no more Russian today than AC current is Serbian. Back to the point of the topic, it is an American engine. The AJ-500 is no more Russian than the Merlin is South African.

But we stray off topic so let's let this one aspect of the discussion lie on the table.
« Last Edit: 10/30/2011 10:42 am by clongton »
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Offline HappyMartian

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Re: multiple combustion chamber Merlin
« Reply #36 on: 10/30/2011 11:20 am »
....
The United States is a nation of immigrants. Almost everybody here came from somewhere else either directly or via their immediate ancestry.
....

Amen.
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Offline baldusi

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Re: multiple combustion chamber Merlin
« Reply #37 on: 10/30/2011 09:00 pm »
Baldusi - give it up. They are not going to use AJ
Are you aware that my "they" was NASA's SLS team? I meant that since they used the multichamber "unreliability" excuse to take out the RD-180 of the competition, the only way to accept LRB would be with a gigantic engine.
But that drawing sort of made me assume that they (NASA) had talked with AeroJet and using them as LRB baseline. I also assumed that they will keep the same animosity to multiple engines of before. So, the only chance I saw of SpaceX making an engine more powerful than the Merlin 1D in the near term was explicitly for that competition.
And given that AeroJet appears to be working on an 7 x AJ-500 solution, SpaceX would have to make something with something like 8MN of thrust to differentiate itself. In other word, I only expect them to make a big chamber, not multi chamber high thrust engine, and explicitly for NASA's. Not for them for the next decade.

Offline Robotbeat

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Re: multiple combustion chamber Merlin
« Reply #38 on: 11/02/2011 08:50 pm »
For goodness sake, it's pretty obvious that SpaceX isn't just going to randomly start using a Russian-built engine. SpaceX has got some of the best industry experience in making a rocket engine using modern manufacturing technology, and they've probably built more turbopump rocket engines in the last couple years than any other rocket engine manufacturer in the last couple years (likely as much as all others COMBINED). They've tested dozens, launched dozens successfully, and are set to launch hundreds within the next few years. They definitely have made more than 50 already.

EDIT:I may be jumping in here, but if we ARE talking about using a Russian engine for SLS, WHY are we talking about it in this thread?
« Last Edit: 11/02/2011 08:52 pm by Robotbeat »
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Offline baldusi

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Re: multiple combustion chamber Merlin
« Reply #39 on: 11/02/2011 09:36 pm »
We are not about SpaceX using Russian engines, please! The original question was about using the same technological solution. In other words, that SpaceX designs and builds a multi chambered engine.
Then I speculated that: first, NASA hates multi chamber, due to the way they calculate the statistics and certain bias. Second AeroJet's proposal for SLS will have seven AJ-500, which is derived from Russian technology, but purely American engine. Third, there's no reason for SpaceX to do a vehicle more powerful than the Falcon Heavy for the next decade, at least, and that they need the multiple engine solution, so no more powerful engine from them for their own use. And fourth, that since AeroJet came with the full support of Alabama's senators, the only chance that SpaceX had at SLS booster's competition was to take advantage of the multi chamber bias at NASA and do a huge chambered one.
So, no Russian engine, not buying engines from others. Just speculation of what would they need a faster engine, and for the only realistic reason, multi chamber is out of the picture.

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