Author Topic: Should SpaceX aim for a 330,000 lbs engine rather than am F1 class engine?  (Read 17164 times)

Offline dwightlooi

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There have been talks about a "Merlin II" engine in the 1.2~1.7 million lbs thrust class. The only justification for such an engine is to reduce the recurring cost of launching F9s and FHs, as well as reduce the total number of engines used in possible Super HEavy Lift vehicles to some sane number.

However, to this regard a 330,000 lbs class engine might actually be an optimal compromise. Let's call this (hypothetical) engine the "Griffon" and look at what it does:-

Griffon 1A
Fuel: RP-1/LOX
Isp (SL): 278 secs
Isp (Vac): 312 Secs
Dry Mass: 2,200 lbs
Thrust-to-Weight Ratio: 150:1
Thrust (SL): 313,000 lbs
Thrust (Vac): 330,000 lbs

* A F1.1 core will need 4 engines instead of 9 (56% reduction in engine count)
* A FH will need 12 engines instead of 27
* In a cross fed FH you can have 100% cross feed via adjacent feeding
* A 110 ton class LV will need 27 engines (no more than the current FH)
* All the above configurations will have reasonable engine out capability which a single engine core will lack
* The engine will still be small enough that the components can be made on standard CnC mills like the Merlin 1
* The engine is a good match for an enlarged FH upper stage whereas an F1 class engine is not


The idea achieves three ends while offering a greater than 50% reduction in engine count. Keep the engine small enough such that the components can be fabricating using common CnC mills and be compatible human muscle handling -- preferably the same equipment and procedures used for Merlin 1s. Concentrating on efficient mass production may actually be cheaper than building a smaller number of very big engines which may be difficult to construct because of special machinery and handling requirements. Also, because will still have a quartet of engines on the Falcon 9 and twelve on an FH a good degree of engine out capability is maintained. Finally, the FH can really use an expanded upper stage 2~3 times heavier than the F9. An engine with about 2.3 times the Merlin 1D's thrust is a good match for such an upper stage.


Offline Lee Jay

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Keep the engine small enough such that the components can be fabricating using common CnC mills ...

Since I've seen CnCs as small as my microwave and as big as my house, I'm wondering on what this statement is based.

Offline Idiomatic

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Merlin 2 has probably been mostly abandoned for the time being. It makes reusability impossible in the way they seem to want to do it. Throwing away all of their plans for the next ~5ish years.

If they build another launcher it would probably be a scaled up everything falcon 9. Maybe a 5. It would have to have a central engine at least assuming they keep their current reusability configuration. Which, if they get working, they will be loathe to give up.

A Hawk9 made up of Griffons could work though. But we aren't talking anytime in the short term.

Online QuantumG

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Merlin 2 has probably been mostly abandoned for the time being.

It was never in the cards.

One maverick, who has now left the company, gave one presentation about his personal ideas once, and then got publicly disavowed, get over it.

« Last Edit: 06/28/2012 01:19 AM by QuantumG »
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Offline FinalFrontier

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There have been talks about a "Merlin II" engine in the 1.2~1.7 million lbs thrust class. The only justification for such an engine is to reduce the recurring cost of launching F9s and FHs, as well as reduce the total number of engines used in possible Super HEavy Lift vehicles to some sane number.

However, to this regard a 330,000 lbs class engine might actually be an optimal compromise. Let's call this (hypothetical) engine the "Griffon" and look at what it does:-

Griffon 1A
Fuel: RP-1/LOX
Isp (SL): 278 secs
Isp (Vac): 312 Secs
Dry Mass: 2,200 lbs
Thrust-to-Weight Ratio: 150:1
Thrust (SL): 313,000 lbs
Thrust (Vac): 330,000 lbs

* A F1.1 core will need 4 engines instead of 9 (56% reduction in engine count)
* A FH will need 12 engines instead of 27
* In a cross fed FH you can have 100% cross feed via adjacent feeding
* A 110 ton class LV will need 27 engines (no more than the current FH)
* All the above configurations will have reasonable engine out capability which a single engine core will lack
* The engine will still be small enough that the components can be made on standard CnC mills like the Merlin 1
* The engine is a good match for an enlarged FH upper stage whereas an F1 class engine is not


The idea achieves three ends while offering a greater than 50% reduction in engine count. Keep the engine small enough such that the components can be fabricating using common CnC mills and be compatible human muscle handling -- preferably the same equipment and procedures used for Merlin 1s. Concentrating on efficient mass production may actually be cheaper than building a smaller number of very big engines which may be difficult to construct because of special machinery and handling requirements. Also, because will still have a quartet of engines on the Falcon 9 and twelve on an FH a good degree of engine out capability is maintained. Finally, the FH can really use an expanded upper stage 2~3 times heavier than the F9. An engine with about 2.3 times the Merlin 1D's thrust is a good match for such an upper stage.



Not necessary or doable in the short term wrt Re-usability plans.

This was/is an ongoing discussion (sort of) on another thread here:

http://forum.nasaspaceflight.com/index.php?topic=29035.0


There has been nothing discussed about Merlin2 by SpaceX since 2010. Also it was not this small in any regard, it was listed as an F1 class thruster in power, although possibly a good bit smaller in mass. It is currently shelved as far as anyone can tell, and was never developed beyond the concept/option stage because SpaceX had already decided to move back towards full re-usability, and were well into Merlin1D development. This engine would be for future vehicles and a BEO program, be it private or otherwise and as such its not needed anytime soon.
« Last Edit: 06/28/2012 01:30 AM by FinalFrontier »
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Offline Idiomatic

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Merlin 2 has probably been mostly abandoned for the time being.

It was never in the cards.

One maverick, who has now left the company, gave one presentation about his personal ideas once, and then got publicly disavowed, get over it.



I was trying to play nice.

Online QuantumG

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When someone is wishing for a pony, there's little to be gained by suggesting a unicorn would be ever better.. ya know, unless it's sarcasm.

Offline FinalFrontier

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I was trying to play nice.

Oh, sorry.

Out of curiosity are you referring to Vozhoff or Tom Markusic?
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Offline Prober

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Keep the engine small enough such that the components can be fabricating using common CnC mills ...

Since I've seen CnCs as small as my microwave and as big as my house, I'm wondering on what this statement is based.

off the shelf or non custom designed CNC's
I have not failed. I've just found 10,000 ways that won't work. ~ by Thomas Alva Edison

Online QuantumG

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Out of curiosity are you referring to Vozhoff or Tom Markusic?

Yeah, true. I was talking about Vozoff but Markusic actually did put "Merlin 2" in his powerpoint slides too.

When someone is wishing for a pony, there's little to be gained by suggesting a unicorn would be ever better.. ya know, unless it's sarcasm.

Offline Lars_J

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Merlin 2 has probably been mostly abandoned for the time being.

It was never in the cards.

I do believe it was in the cards - but only as a part of a SpaceX bid for SLS contract(s).

Offline CapitalistOppressor

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Merlin 2 has probably been mostly abandoned for the time being.

It was never in the cards.

I do believe it was in the cards - but only as a part of a SpaceX bid for SLS contract(s).

Yes, except SpaceX had roughly zero chance of winning those contracts, as was quickly made apparent to them.  "Never in the cards" thus was a true statement before SpaceX even realized it.

Offline CapitalistOppressor

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There have been talks about a "Merlin II" engine in the 1.2~1.7 million lbs thrust class. The only justification for such an engine is to reduce the recurring cost of launching F9s and FHs, as well as reduce the total number of engines used in possible Super HEavy Lift vehicles to some sane number.

However, to this regard a 330,000 lbs class engine might actually be an optimal compromise. Let's call this (hypothetical) engine the "Griffon" and look at what it does:-

Griffon 1A
Fuel: RP-1/LOX
Isp (SL): 278 secs
Isp (Vac): 312 Secs
Dry Mass: 2,200 lbs
Thrust-to-Weight Ratio: 150:1
Thrust (SL): 313,000 lbs
Thrust (Vac): 330,000 lbs

* A F1.1 core will need 4 engines instead of 9 (56% reduction in engine count)
* A FH will need 12 engines instead of 27
* In a cross fed FH you can have 100% cross feed via adjacent feeding
* A 110 ton class LV will need 27 engines (no more than the current FH)
* All the above configurations will have reasonable engine out capability which a single engine core will lack
* The engine will still be small enough that the components can be made on standard CnC mills like the Merlin 1
* The engine is a good match for an enlarged FH upper stage whereas an F1 class engine is not


The idea achieves three ends while offering a greater than 50% reduction in engine count. Keep the engine small enough such that the components can be fabricating using common CnC mills and be compatible human muscle handling -- preferably the same equipment and procedures used for Merlin 1s. Concentrating on efficient mass production may actually be cheaper than building a smaller number of very big engines which may be difficult to construct because of special machinery and handling requirements. Also, because will still have a quartet of engines on the Falcon 9 and twelve on an FH a good degree of engine out capability is maintained. Finally, the FH can really use an expanded upper stage 2~3 times heavier than the F9. An engine with about 2.3 times the Merlin 1D's thrust is a good match for such an upper stage.



This represents a good sized development cost that leads to a hefty capital investment that leads to no ROI unless a market develops for a BFR, which itself would need to be developed at substantial cost.

As pointed out, Merlin 2 is deader than dead which makes the comparison suspect.

Reduction of engine count just doesn't seem to be a worthy goal for the existing launchers.  N1 blew up 40 years ago.  Sensors and avionics are light years better now, and are likely more than capable of gracefully managing existing M1d clusters indefinitely with low LoV rates.

F9 works.  F9v1.1 will probably work better.  FH is probably going to work as well.  No need to muck with any of that unless you are Elon Musk and want to retire on Mars.  To me the best hypothetical engine development thread around is the Methane staged combustion engine.  It makes a ton more sense to me than a Griffon concept.

Offline dwightlooi

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F9 works.  F9v1.1 will probably work better.  FH is probably going to work as well.  No need to muck with any of that unless you are Elon Musk and want to retire on Mars.  To me the best hypothetical engine development thread around is the Methane staged combustion engine.  It makes a ton more sense to me than a Griffon concept.

Not sure about retiring to Mars, but if you simply want to go there Methane is not such a great fuel. Yes, it is higher impulse than RP-1, but it is also less dense which partially cancels that out. It is also paired with LOX which is still cryogenic which means heavy tanks, insulated tanks, refrigeration units or some combination of the aforementioned. I am also complete dubious about making any kind of fuel or oxidizer or fuel on mars. Doing that in a dusty environment with minimal resources and limited power, all of which you have to transport millions of miles through space and land on the red planet is immediately a red flag for me.

I'll stick to hydrazine and its derivatives with Nitrogen Tetroxide. Just live with the 310~320 Isp and build your mission around that. Build a bigger stack in LEO if you have to. Bring everything, produce nothing, but keep the mission as spartan as possible. Fly one man, land one man, do no science and get him back.

Offline FinalFrontier

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Merlin 2 has probably been mostly abandoned for the time being.

It was never in the cards.

I do believe it was in the cards - but only as a part of a SpaceX bid for SLS contract(s).

Yes, except SpaceX had roughly zero chance of winning those contracts, as was quickly made apparent to them.  "Never in the cards" thus was a true statement before SpaceX even realized it.


They did conduct a concept study into it, which continued until sometime near the end of 2010. No hardware was ever made for it as far as anyone knows.


That concept is shelved somewhere in hawthorne, but if they found they needed the engine, I am sure it would be developed.


SpaceX is a private company, as such they don't develop things unless they need them. But that doesn't mean they don't come up with concepts for potential future markets like every other company in the world does.



Its not dead, its in a filing cabinet for when/if its needed. Dead would be comparable to things like NASA throwing away engines like Fastrac, and the big TRW engine. Of course those were well beyond the simple concept design stage when they were left behind.
« Last Edit: 06/29/2012 01:36 AM by FinalFrontier »
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