Author Topic: Should SpaceX aim for a 330,000 lbs engine rather than am F1 class engine?  (Read 53343 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.

Offline 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.

Offline QuantumG

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Human spaceflight is basically just LARPing now.

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
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Offline 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.

Human spaceflight is basically just LARPing now.

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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Offline go4mars

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Merlin 2 and BFR seem like they would be pretty useful for taking thousands and thousands of colonists and/or vacationers to Mars. 

If you make a definitive statement, please either back it up with a link/source, or state it as an opinion. 
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Offline Jim

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Merlin 2 and BFR seem like they would be pretty useful for taking thousands and thousands of colonists and/or vacationers to Mars. 

In what scifi book or movie?

Get real.  Not going to happen in anybody's lifetime who is on this forum.   It will be a long time before there will be a base on mars and a heck of a lot longer before it can sustain colonists much less vacationers. 

There are dreams and then there is reality.
« Last Edit: 06/29/2012 01:58 am by Jim »

Offline Brian Copp

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The NK-33 would seem to meet most of those requirements. I'm not sure how many of them are in existence, or if SpaceX could find a way to manufacture them in house.

Offline Jason1701

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The NK-33 would seem to meet most of those requirements. I'm not sure how many of them are in existence, or if SpaceX could find a way to manufacture them in house.

Kuznetsov built about 200, of which Aerojet has 40. SpaceX would develop its own staged-combustion engine rather than use old Russian ones, I'm sure.

Offline dwightlooi

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The NK-33 would seem to meet most of those requirements. I'm not sure how many of them are in existence, or if SpaceX could find a way to manufacture them in house.

Kuznetsov built about 200, of which Aerojet has 40. SpaceX would develop its own staged-combustion engine rather than use old Russian ones, I'm sure.

It's called the AJ26. SpaceX's competitor Orbital Sciences Corp uses two of these on each of their Antares Rocket (aka Taurus II) to launch the Cygnus ISS supply capsule. Their upper stage is solid.

Offline Idiomatic

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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.

It doesn't matter what you think. Musk has said he is interested in ISRU.

Offline hrissan

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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.

What you suggest is just repeating that stupid moonshots. Ok, after you spend lots of money for your mission, what's left beyond "we were there!!!"?

Producing just 10 kg fuel and oxidizer ISRU would advance technology much more than "fly one man do no science and get him back". :)

Offline CapitalistOppressor

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Merlin 2 and BFR seem like they would be pretty useful for taking thousands and thousands of colonists and/or vacationers to Mars. 

In what scifi book or movie?

Get real.  Not going to happen in anybody's lifetime who is on this forum.   It will be a long time before there will be a base on mars and a heck of a lot longer before it can sustain colonists much less vacationers. 

There are dreams and then there is reality.

^^ 100% true.

However, as much as boundaries exist and reflect reality progress is made only when we bump up against those boundaries, wonder whats on the other side and then start pushing.

As to the substance of what go4mars said, I don't think a BFR is necessary if you want to send lots of people to Mars.  What is necessary are rapid and efficient reusable orbital class launchers at both ends of the pipeline, with logistics on Mars to support that. Once you have that, the process of actually moving people economically from one planet to the other is relatively straightforward.

But, as Jim pointed out that sort of end to end capability is likely something none of us will live to see.  Making a Mars exploration mission affordable in the near term is a much more reachable goal.

Offline QuantumG

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However, as much as boundaries exist and reflect reality progress is made only when we bump up against those boundaries, wonder whats on the other side and then start pushing.

Progress is made by the unreasonable man.
Human spaceflight is basically just LARPing now.

Offline go4mars

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as Jim pointed out that sort of end to end capability is likely something none of us will live to see.
You seem to have an apt moniker.  Jim's statement is opinion (clearly).  Not everyone shares it.  What would his grandad have said about the possibility of men walking on the moon if you asked him in 1935?

Luckily, capatilists tend to offend the status quo from time to time through success.

I don't think a BFR is necessary if you want to send lots of people to Mars.
Why do us earthlings have different sizes of airplanes?  Couldn't everything on earth be shipped one at a time, and if it's too big to move that way, just build it from tinier pieces that you can ship separately? 

What is necessary are rapid and efficient reusable orbital class launchers at both ends of the pipeline, with logistics on Mars to support that.
Yup.  But there are economies of scale.  What are millionaire tourists/colonists more likely to shell out for:  Living in a tiny barebones tuna can for many years, or living in a bigger tuna can with a few more creature comforts? 
« Last Edit: 06/30/2012 04:30 am by go4mars »
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Offline CapitalistOppressor

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as Jim pointed out that sort of end to end capability is likely something none of us will live to see.
You seem to have an apt moniker. 

What can I say, I am a proud to believe in capitalism :)

As to the rest of my response to Jim, I personally don't expect to live to see thousands of colonists heading to Mars.  I'd be thrilled to see hundreds, and think its achievable in the next ~30 years I expect to live. 

Even if we meet Elon's cost goals for transportation to Mars in that time frame, I doubt it would be prudent to send thousands of colonists before we have debugged the local living arrangements and built up a local infrastructure capable of absorbing large numbers of new arrivals.

But Jim seems to have strong opinions about long term possibilities, so being new to the forum it seemed prudent to emphasize a near term goal that I feel completely confident arguing about as opposed to emphasizing an aspirational goal which is 20 steps away.

Offline MP99

SpaceX has a certain amount of experience with launchers and a cargo capsule that can be entered from ISS once it's berthed.

They hope to have a crew-capable capsule fairly soon which is OK for a crew for a day or so each way to / from ISS, and powered landings. Maybe a reusable launcher.

It's a massive step from that to them building spacecraft and Mars ground infrastructure that can keep a crew alive for two years. Nevermind doing it for thousands of people.

cheers, Martin

Offline beb

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I was under the impression that the DoD was looking for a 500,000 lb thrust engine, hence Aerojet's interest in developing an AJ-26-500. If SpaceX is going to build a new 1st stage engine that would seem to be the proper goal. Reduces Falcon 9 to three engines. But seriously, it looks as if SpaceX engine development days are behind them. It's now a case of getting these rockets out the door and launched.

Offline edkyle99

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I was under the impression that the DoD was looking for a 500,000 lb thrust engine, hence Aerojet's interest in developing an AJ-26-500. If SpaceX is going to build a new 1st stage engine that would seem to be the proper goal. Reduces Falcon 9 to three engines. But seriously, it looks as if SpaceX engine development days are behind them. It's now a case of getting these rockets out the door and launched.
Agreed about the 500K - that is the thrust that has nearly been demonstrated, per nozzle, for RD-180, which makes it likely a useful modularized thrust value.  But from a SpaceX perspective, a more important number is cost per pound of thrust, which would give the real useful value.

As for SpaceX engine development, I would suggest that it would be in the national interest for this successful rocket engine team to keep working, to keep pushing the boundaries.

 - Ed Kyle
« Last Edit: 06/30/2012 03:20 pm by edkyle99 »

Online oldAtlas_Eguy

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The test teams would be organized into RP-1 test team and Hydrazine test team. Each team would do both developmental and acceptance testing on the prop type engines. Doing development testing is not a great extra expense for testing because most of these teams’ time is doing acceptance testing, so costs and overhead for development is very low. A new prop type engine development such as methane would entail a significant overhead and practically a new test team and infrastructure.

The design teams would be organized similarly into prop types of RP-1 and Hydrazine. Each team does both developmental work and support operations with failure and problem analysis since they know the engines best. A new prop type would need a new design team or could be an augmented growth of an existing team. Currently the RP-1 design team would be finishing up the M1D development work on M1DVAC variation as well as any problem resolution encountered during the first sets of production M1D testing. The Hydrazine design teams would be continuing the development work on the Super Dracos as well as support for the production engines on the US and Dragon.

A methane or LH2 SC engine would be a higher developmental expense than doing a RP-1 development. In fact a SC RP-1 development would be costs would be almost lost in the existing support costs.

Offline go4mars

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Quote from: CapitalistOppressor
What can I say, I am a proud to believe in capitalism :)
Good.  I was trying to point out that such a pessimistic view could be interpreted as oppressive to capitalists. 

Thanks for the further elaboration.
« Last Edit: 07/01/2012 01:48 am by go4mars »
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Offline Karloss12

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Yeah, but Wikipedia says that there is low level on going development of the Merlin 2.  :-)

The reasons I think this development would exist:

-is to keep the skilled design team working and as a result maintain the nations engine design skills base.  (These peoples skill will degrade quickly if there is nothing for them to atleast analyse.)

-If the bundle of 9 x Merlin 1 engines proves to be reliable but more importantly much less expensive then the equivalent engine on completion rocket then both Elon and various government agencies may be interested in SpaceX developing an equally inexpensive Merlin 2.

As to what it would be used for, I don't know.

If 100 Falcon 9's were to fly without a single engine failing (That's 900 successful Merlin 1 engines.) then that would give SpaceX some confidence in developing a Merlin 2 engine.  But it would never be used for a Falcon 9 or Heavy as the cost of the rockets would become higher due to them no longer being reusable.

The SLS core stage uses Liquid Hydrogen.  So not an option there.

A possible use would be for a replacement to the SLS Solid rocket strap-ons.

If reliability and complete reusability is acheived and becomes the norm then large Merlin 2's don't fit anywhere.  I don't think the larger Merlin 2 has been filed away.  I think it was only ever a slide show for bidding for the SLS and uless there is an idea for overcoming the re-usabilty issue it is now dead.

If the Falcon Heavy proves very successful in every way, in ten years I can see SpaceX having the Falcon 9 as it currently is with 9 x Melin 1D's lifting 12 Tonne, The Falcon Heavy having 9 x Griffon's (lifting ~50 Tonne) and the Falcon SLS with the same configuration as the Merlin Falcon Heavy but with 27 Griffons lifting 150+ Tonne.  This way you keep all the reliability and re-usability and therefore low cost.  But Elon has to achieve his goal of re-usability and a lot of politics has to happen as well, so of course only a dream for now.

Offline ArbitraryConstant

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Yeah, but Wikipedia says that there is low level on going development of the Merlin 2.  :-)
Following the links, it doesn't seem to be new information, just someone else who saw the original presentations and hasn't gotten over it.

Offline Karloss12

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Yeah, but Wikipedia says that there is low level on going development of the Merlin 2.  :-)
Following the links, it doesn't seem to be new information, just someone else who saw the original presentations and hasn't gotten over it.

I wasn't taking it seriously.

But just as Falcon 1 was a test stand that gave lessons for creating the Falcon 9, I don't see why many lessons can't be learnt from the Falcon 9 to produce a single core rocket with 9 x 330,000 lb engines to replace the Falcon Heavy.  It would have all of the reliabilty of the current F9.

And if the current Falcon heavy does get a dozen flights before being replaced, a lot of lessons would have been learnt about producing a three core 27 x 330,000 lb rocket.

I think if the F9 And FH are very successful then SpaceX could produce enough revenue to fund most of the development of the 9 x 330,000 lb engines rocket (that replaces the FH).

The 27 x 330,000 lb rocket would never have a commercial customer.  But if SpaceX can be very reliable and financially competitive with the 9 x 330,000 lb then they could give NASA confidence that the 27 x 330,000 lb rocket would be less expensive then the SLS and finance a test flight.

This seems like the simplest credible path to producing a Falcon Super Heavy that would be able to take large amounts of equipment to mars as per Elon's dream.  The FH(Merlin) is to small especially with all the ~10 Tonnes of added weight that needs to be added to it to make it reusable and less expensive.
« Last Edit: 07/08/2012 05:03 pm by Karloss12 »

Offline ArbitraryConstant

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But just as Falcon 1 was a test stand that gave lessons for creating the Falcon 9, I don't see why many lessons can't be learnt from the Falcon 9 to produce a single core rocket with 9 x 330,000 lb engines to replace the Falcon Heavy.  It would have all of the reliabilty of the current F9.
Ah, ok. Yeah, you aren't the only one thinking along these lines.

Offline Jim

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But just as Falcon 1 was a test stand that gave lessons for creating the Falcon 9, I don't see why many lessons can't be learnt from the Falcon 9 to produce a single core rocket with 9 x 330,000 lb engines to replace the Falcon Heavy.  It would have all of the reliabilty of the current F9.


No it wouldn't.  It would be a new rocket with no flight experience.

Falcon 1 to 9 is not the same as FH to this not going to exist rocket.

Offline Jim

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The 27 x 330,000 lb rocket would never have a commercial customer.  But if SpaceX can be very reliable and financially competitive with the 9 x 330,000 lb then they could give NASA confidence that the 27 x 330,000 lb rocket would be less expensive then the SLS and finance a test flight.

This seems like the simplest credible path to producing a Falcon Super Heavy that would be able to take large amounts of equipment to mars as per Elon's dream.  The FH(Merlin) is to small especially with all the ~10 Tonnes of added weight that needs to be added to it to make it reusable and less expensive.

Again no.  cost has nothing to do with it. Otherwise, SLS would not exist.

Offline Idiomatic

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I believe he meant that it would have the same features which add to reliability as the F9. Not that it would be exactly the same. Obviously new engines and a new scale will be a bit different.

True that SLS isn't really too concerned about cost. But it would be MCH harder to sell SLS to congress if they can buy a rocket from SpaceX that costs 1/4 as much with the same capabilities. That would be a political nightmare for SLS supporters.

Offline ArbitraryConstant

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Again no.  cost has nothing to do with it. Otherwise, SLS would not exist.
The SLS doesn't exist.

The probability of SLS block >1 ever flying is nil.
« Last Edit: 07/08/2012 05:46 pm by ArbitraryConstant »

Offline Jim

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Again no.  cost has nothing to do with it. Otherwise, SLS would not exist.
The SLS doesn't exist.

The probability SLS block >1 ever flying is nil.

Same goes for this vehicle

Offline Idiomatic

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True, but SpaceX making a Super heavy lift vehicle is probably about as likely or more likely than NASA doing so in the next 5~10 years.

Offline Downix

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I believe he meant that it would have the same features which add to reliability as the F9. Not that it would be exactly the same. Obviously new engines and a new scale will be a bit different.

True that SLS isn't really too concerned about cost. But it would be MCH harder to sell SLS to congress if they can buy a rocket from SpaceX that costs 1/4 as much with the same capabilities. That would be a political nightmare for SLS supporters.
SpaceX is not designing a rocket with the same capabilities as SLS. They are designing one to meet the Ariane 5 or Delta IV Heavy. The FH is nowhere close to competing with SLS, especially for the mission. SpaceX has shown no desire to develop the systems needed. LEO performance is a bad metric. To GTO, SLS can throw 10* as much, and to the moon the difference is even more extreme.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline Lurker Steve

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I believe he meant that it would have the same features which add to reliability as the F9. Not that it would be exactly the same. Obviously new engines and a new scale will be a bit different.

True that SLS isn't really too concerned about cost. But it would be MCH harder to sell SLS to congress if they can buy a rocket from SpaceX that costs 1/4 as much with the same capabilities. That would be a political nightmare for SLS supporters.

Except that Congress is ALREADY SOLD ON SLS. Forget the argument that a LV the size of SLS isn't needed. We certainly can't afford our government to support 2 launchers with the limited number of missions that need a LV this large.

Offline Idiomatic

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Except that Congress is ALREADY SOLD ON SLS. Forget the argument that a LV the size of SLS isn't needed. We certainly can't afford our government to support 2 launchers with the limited number of missions that need a LV this large.


If it ends up on the chopping block in 5 years time. Or if they ask for additional funding that is more than the cost of a SpaceX vehicle that is near completion. Or if the cost per individual launch after both are completed is less via SpaceX. But yeah, unlikely.

I believe he meant that it would have the same features which add to reliability as the F9. Not that it would be exactly the same. Obviously new engines and a new scale will be a bit different.

True that SLS isn't really too concerned about cost. But it would be MCH harder to sell SLS to congress if they can buy a rocket from SpaceX that costs 1/4 as much with the same capabilities. That would be a political nightmare for SLS supporters.

SpaceX is not designing a rocket with the same capabilities as SLS. They are designing one to meet the Ariane 5 or Delta IV Heavy. The FH is nowhere close to competing with SLS, especially for the mission. SpaceX has shown no desire to develop the systems needed. LEO performance is a bad metric. To GTO, SLS can throw 10* as much, and to the moon the difference is even more extreme.

SpaceX likely has some papers, maybe even blueprints for a super heavy lift vehicle at this point. They've stated repeatedly that they intend to build a shl vehicle. It is only a matter of when and how they'll pay for it. Of course the FH is not competitive with the SLS. (Though, with an upgraded 2nd stage engine, it could be competitive in GTO vs the smallest SLS). I was talking about a currently non-existant super heavy, just like the SLS.

Offline Downix

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Except that Congress is ALREADY SOLD ON SLS. Forget the argument that a LV the size of SLS isn't needed. We certainly can't afford our government to support 2 launchers with the limited number of missions that need a LV this large.


If it ends up on the chopping block in 5 years time. Or if they ask for additional funding that is more than the cost of a SpaceX vehicle that is near completion. Or if the cost per individual launch after both are completed is less via SpaceX. But yeah, unlikely.

I believe he meant that it would have the same features which add to reliability as the F9. Not that it would be exactly the same. Obviously new engines and a new scale will be a bit different.

True that SLS isn't really too concerned about cost. But it would be MCH harder to sell SLS to congress if they can buy a rocket from SpaceX that costs 1/4 as much with the same capabilities. That would be a political nightmare for SLS supporters.

SpaceX is not designing a rocket with the same capabilities as SLS. They are designing one to meet the Ariane 5 or Delta IV Heavy. The FH is nowhere close to competing with SLS, especially for the mission. SpaceX has shown no desire to develop the systems needed. LEO performance is a bad metric. To GTO, SLS can throw 10* as much, and to the moon the difference is even more extreme.

SpaceX likely has some papers, maybe even blueprints for a super heavy lift vehicle at this point. They've stated repeatedly that they intend to build a shl vehicle. It is only a matter of when and how they'll pay for it. Of course the FH is not competitive with the SLS. (Though, with an upgraded 2nd stage engine, it could be competitive in GTO vs the smallest SLS). I was talking about a currently non-existant super heavy, just like the SLS.
It is less than non-existant, it is paper-only. SLS at least has physical systems we can point to, touch, and leverage. A theoretical Falcon SuperHeavy has no such things. 

And I have long argued that the creation of the Heavy was a dumb idea rather than a hydrolox upper stage engine. The money spent on Merlin 1D could have given them far more with a hydrolox Merlin (Call it the Circie) allowing them to compete for the larger GTO market. Even with the weaker Merlin-1C, a Falcon Heavy with this engine for the upper stage would out-lift the FH as it is now.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline ArbitraryConstant

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The SLS doesn't exist.

The probability SLS block >1 ever flying is nil.
Same goes for this vehicle
Under present circumstances I would agree.

A big engine would cause me to revise that assessment up a bit, but as of now there is no such engine that we know of and no reason to strongly expect one.

Except that Congress is ALREADY SOLD ON SLS. Forget the argument that a LV the size of SLS isn't needed. We certainly can't afford our government to support 2 launchers with the limited number of missions that need a LV this large.
If a three-core version would qualify as SLS-class, I'm pretty sure a single-stick version would be able to find a day job with commercial launches.

And yes, the government is already committed to SLS. That doesn't mean it's going to fly, or that hard questions aren't going to be asked over multiple administrations as efforts to reanimate the Shuttle's corpse continue.

Offline ArbitraryConstant

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And I have long argued that the creation of the Heavy was a dumb idea rather than a hydrolox upper stage engine. The money spent on Merlin 1D could have given them far more with a hydrolox Merlin (Call it the Circie) allowing them to compete for the larger GTO market.
??? They've signed customers for GTO launches on single-stick Falcon 9 v1.1.
« Last Edit: 07/08/2012 07:54 pm by ArbitraryConstant »

Offline Karloss12

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But just as Falcon 1 was a test stand that gave lessons for creating the Falcon 9, I don't see why many lessons can't be learnt from the Falcon 9 to produce a single core rocket with 9 x 330,000 lb engines to replace the Falcon Heavy.  It would have all of the reliabilty of the current F9.


No it wouldn't.  It would be a new rocket with no flight experience.

Falcon 1 to 9 is not the same as FH to this not going to exist rocket.

Sorry Jim, I mean the 9 x 330,000lb core would have the same philosophy of reliability and re-usability designed into it as the F9.  It would of course require 3 successful flights to actually be as reliable as the current F9.

In up sizing the F9 in this way most of the experience and skills and design 'methods' and 'techniques' would be re-used (of course with some improvements and mods).  Maybe half of this up sized core would use existing skills and techniques from the F9.  The remaining gaps in the design would of course require new learning and developing new design techniques.

In fives years time when the F9 and FH are flying flawlessly, the dragon capsule is conducting crewed flights and the F9 core stage has landed to be rapidly refueled and re-used for the first time, will Elon just layoff the hundreds of people that were his R&D/design employees.  (All that would be left is the Raptor to be developed.)

Elon has some dream of creating a new civilisation on Mars.

A reusable FH will lift less than 40 Tonnes after the addition of re-usability equipment.  No where near enough to get a single person to and from Mars, let alone get all the equipment and people to mars to create a community (which I think will ultimately fail).

He seems a bit more intelligent then to just go with the flow and make up new designs as he goes along.  So unless he is telling fibs or is just spreading propaganda, then he will have a longer term plan.  This is the most logical common sense scenario that I can think of that uses the experience and skills that SpaceX already has.

When F9 and FH are completely re-usable, capital will become available to develop the 9 x 330,000lb core with little or no government funding.  And it will potentially be more reliable as it has one third of the moving parts as the current FH.  It will also have the same profitable commercial viability as the FH.  It possibly wont need government money.  Even if it did, the government get cheaper launches in return.

If it proves its reliability and is 1/4 the price of the Delta IV and the designed but unflown 27 x 330,000lb heavy lifter has a price tag of 1/4 of the SLS, I think this will be equivalent to allot of political clout for Elon's political lobbyists.

So I think I’ve come up with a credible scenario where SpaceX can develop a completely commercially viable replacement (single 9 x 330,000lb core) for what is projected to be the commercially viable FH.  The lessons learnt from flying the FH and a bit of political will power could slap 2 more of these cores on either side of this single core to replace the SLS with a 27 x 330,000lb super heavy.  As a result freeing up government cash to spend on more interesting space science.

It all hinges on the F9 1st stage being re-usable to generate enough capital to develop the the 330,000lb engine and core and Elon being serious about going to Mars.

Congress is SOLD on SLS but I do remember about 5 years ago congress being SOLD on Constellation.
« Last Edit: 07/08/2012 08:05 pm by Karloss12 »

Offline Jim

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In fives years time when the F9 and FH are flying flawlessly, the dragon capsule is conducting crewed flights and the F9 core stage has landed to be rapidly refueled and re-used for the first time,


if, if, if.....

Offline Karloss12

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In fives years time when the F9 and FH are flying flawlessly, the dragon capsule is conducting crewed flights and the F9 core stage has landed to be rapidly refueled and re-used for the first time,


if, if, if.....

Yes, lots of gaps needing to be filled.

The other option is Elon connecting equipment in LEO with many FH launches.  But I don't think so.

Has anyone else got a more logical common sense scenario?

Offline MikeAtkinson

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He seems a bit more intelligent then to just go with the flow and make up new designs as he goes along.  So unless he is telling fibs or is just spreading propaganda, then he will have a longer term plan.  This is the most logical common sense scenario that I can think of that uses the experience and skills that SpaceX already has.

Musk is much too intelligent to have a plan. What he has is a goal and a roadmap. Think of it as a road trip from New York to the west coast, there are multiple routes, you might have to make a diversion and the destination may change (more specific Los Angeles, or different Texas). Where the roadmap analogy breaks down is that multiple roads may be traveled on at the same time, and by the time you are half way to the destination that has changed to one further away.

So SpaceX are probably exploring multiple paths to their stated destination (cheap Mars colonization). There are several we know about and probably a lot more we don't. Just because they are exploring a road doesn't mean they will go down it. Even if they go down it, that doesn't mean it will lead directly to their destination.

Quote
So I think I’ve come up with a credible scenario where SpaceX can develop a completely commercially viable replacement (single 9 x 330,000lb core) for what is projected to be the commercially viable FH.  The lessons learnt from flying the FH and a bit of political will power could slap 2 more of these cores on either side of this single core to replace the SLS with a 27 x 330,000lb super heavy.  As a result freeing up government cash to spend on more interesting space science.

That seems to be one road. It is fairly obvious, so SpaceX have probably explored it. Maybe they are discovered a roadblock, maybe they think other roads are better (for whatever reason), maybe they'll take it but it will turn out to be a dead end.

Offline Lurker Steve

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The SLS doesn't exist.

The probability SLS block >1 ever flying is nil.
Same goes for this vehicle
Under present circumstances I would agree.

A big engine would cause me to revise that assessment up a bit, but as of now there is no such engine that we know of and no reason to strongly expect one.

Except that Congress is ALREADY SOLD ON SLS. Forget the argument that a LV the size of SLS isn't needed. We certainly can't afford our government to support 2 launchers with the limited number of missions that need a LV this large.
If a three-core version would qualify as SLS-class, I'm pretty sure a single-stick version would be able to find a day job with commercial launches.

And yes, the government is already committed to SLS. That doesn't mean it's going to fly, or that hard questions aren't going to be asked over multiple administrations as efforts to reanimate the Shuttle's corpse continue.

The very hard questions that will be asked of those NASA administrators, is why they are breaking the law ? Remember that the LAW says NASA is to build a HLV with an eventual capability of at least 130 tons using Shuttle and Constellation technology where practice-able. Dropping the internal NASA program and funding a SpaceX development may just bring up another Contempt of Congress charge.

SpaceX should definately look to keep their development engineers busy developing. But they should at a product that has potential for enough sales volume to at least cover the costs of development. For instance,a cluster of 4 - 330k lbs engines in a 3.3 or 5m core probably doesn't have enough thrust to compete and win against the other likely entries to the SLS advanced booster competition.

How about keeping those engineers busy by developing a better upper-stage engine ? Maybe if they cut the roots with the original Merlin, they could start with a semi-clean sheet of paper and build a LH2/LOX vacuum engine, or maybe a second stage that used multiple Merlins to enable higher energy orbits.

Offline krytek

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A bit OT but...

There's some kind of law that requires the US government to use a commercial alternative to a government service if available (or something along those lines).

Do you believe NASA be forced to drop SLS if a comparable performance commercial SpaceX launcher is available?

Offline ArbitraryConstant

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Dropping the internal NASA program and funding a SpaceX development may just bring up another Contempt of Congress charge.
Well, that's not quite what I'm saying. I know NASA is thoroughly boxed in.

What I'm saying is that the probability of SLS flying is very low. And once it has failed of its own accord, when it is being debated once again, Falcon Heavy will very likely already be a fait accompli.

Offline Downix

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And I have long argued that the creation of the Heavy was a dumb idea rather than a hydrolox upper stage engine. The money spent on Merlin 1D could have given them far more with a hydrolox Merlin (Call it the Circie) allowing them to compete for the larger GTO market.
??? They've signed customers for GTO launches on single-stick Falcon 9 v1.1.
For Delta II class payloads. They lack the performance for even Atlas V 401 class payloads. And their price is no better than for D2, so now that the cancellation of the older Delta has been put on hold, Falcon now has lost its edge.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline ArbitraryConstant

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And I have long argued that the creation of the Heavy was a dumb idea rather than a hydrolox upper stage engine. The money spent on Merlin 1D could have given them far more with a hydrolox Merlin (Call it the Circie) allowing them to compete for the larger GTO market.
??? They've signed customers for GTO launches on single-stick Falcon 9 v1.1.
For Delta II class payloads. They lack the performance for even Atlas V 401 class payloads.
It's pretty damn close, and >2x Delta II to GTO.

Offline Downix

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And I have long argued that the creation of the Heavy was a dumb idea rather than a hydrolox upper stage engine. The money spent on Merlin 1D could have given them far more with a hydrolox Merlin (Call it the Circie) allowing them to compete for the larger GTO market.
??? They've signed customers for GTO launches on single-stick Falcon 9 v1.1.
For Delta II class payloads. They lack the performance for even Atlas V 401 class payloads.
It's pretty damn close, and >2x Delta II to GTO.
Not even close. According to the Falcon 9 user guide, the Falcon 9 v2.0 gets 2.3 metric tons to the same GTO orbit Delta II gets 2.2 metric tons using the same margins. Atlas V 401 gets 4.7 metric tons under the same profile. If you use a lower apogee orbit on F9 or change the inclination you can make it look less, but that is marketing and not the truth. To the same orbit, F9 compares well against D2, but not AV.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline Jason1701

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F9 v2.0 does not exist.

Offline vigleik

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Not even close. According to the Falcon 9 user guide, the Falcon 9 v2.0 gets 2.3 metric tons to the same GTO orbit Delta II gets 2.2 metric tons using the same margins. Atlas V 401 gets 4.7 metric tons under the same profile. If you use a lower apogee orbit on F9 or change the inclination you can make it look less, but that is marketing and not the truth. To the same orbit, F9 compares well against D2, but not AV.

Falcon 9 gets 4850kg to GTO, according to their website. The Falcon 9 user guide is old, it probably has v1.0 (block2?) numbers rather than v1.1 numbers.

Offline go4mars

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And I have long argued that the creation of the Heavy was a dumb idea rather than a hydrolox upper stage engine. The money spent on Merlin 1D could have given them far more with a hydrolox Merlin (Call it the Circie) allowing them to compete for the larger GTO market. Even with the weaker Merlin-1C, a Falcon Heavy with this engine for the upper stage would out-lift the FH as it is now.
We don't know exactly how much 1d development cost, or what the cost improvement per engine is for 1d versus 1c. 

Also, you are suggesting that it is heavy instead of hydrolox instead of suggesting that it is heavy then hydrolox. 
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Offline Downix

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Not even close. According to the Falcon 9 user guide, the Falcon 9 v2.0 gets 2.3 metric tons to the same GTO orbit Delta II gets 2.2 metric tons using the same margins. Atlas V 401 gets 4.7 metric tons under the same profile. If you use a lower apogee orbit on F9 or change the inclination you can make it look less, but that is marketing and not the truth. To the same orbit, F9 compares well against D2, but not AV.

Falcon 9 gets 4850kg to GTO, according to their website. The Falcon 9 user guide is old, it probably has v1.0 (block2?) numbers rather than v1.1 numbers.
To a lower orbit than being discussed here. Comparing a GTO with apogee of 10k at 28 degrees against a GTO with apogee of 40k at 15 degrees is intellectually dishonest. I used the published figures to keep it fair. If I use my own skill, Falcon looks even worse against Atlas V.
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Offline Downix

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And I have long argued that the creation of the Heavy was a dumb idea rather than a hydrolox upper stage engine. The money spent on Merlin 1D could have given them far more with a hydrolox Merlin (Call it the Circie) allowing them to compete for the larger GTO market. Even with the weaker Merlin-1C, a Falcon Heavy with this engine for the upper stage would out-lift the FH as it is now.
We don't know exactly how much 1d development cost, or what the cost improvement per engine is for 1d versus 1c. 

Also, you are suggesting that it is heavy instead of hydrolox instead of suggesting that it is heavy then hydrolox. 
They chose a path which pushed hydrolox behind many other pieces. The development behind Heavy was to give them the GTO performance to compete against Ariane, Delta and Proton. They could have achieved this with less development and schedule risk by focusing on the hydrolox.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline 2552

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Not even close. According to the Falcon 9 user guide, the Falcon 9 v2.0 gets 2.3 metric tons to the same GTO orbit Delta II gets 2.2 metric tons using the same margins. Atlas V 401 gets 4.7 metric tons under the same profile. If you use a lower apogee orbit on F9 or change the inclination you can make it look less, but that is marketing and not the truth. To the same orbit, F9 compares well against D2, but not AV.

Falcon 9 gets 4850kg to GTO, according to their website. The Falcon 9 user guide is old, it probably has v1.0 (block2?) numbers rather than v1.1 numbers.

Also, the lowest 35,786km apogee GTO performance listed for F9 Block 2 (on page 23 of the F9 user's guide) is 2,972kg to a 15deg 35,786km GTO, which would require a combined plane change/GTO transfer burn. A 28.5deg GTO is listed as 4,536kg. The highest performance 35,786km apogee GTO I can find for Delta II in DeltaIIPayloadPlannersGuide2007.pdf (under General Performance Capability, table 2-4) is 2,171kg to a 28.7deg inclination GTO, no plane change required. And that's using a Star48B 3rd stage, which F9 doesn't use.

I do wish SpaceX would put up a more recent user's guide though.

Falcon 9 gets 4850kg to GTO, according to their website. The Falcon 9 user guide is old, it probably has v1.0 (block2?) numbers rather than v1.1 numbers.
To a lower orbit than being discussed here. Comparing a GTO with apogee of 10k at 28 degrees against a GTO with apogee of 40k at 15 degrees is intellectually dishonest. I used the published figures to keep it fair. If I use my own skill, Falcon looks even worse against Atlas V.

Unless I'm wrong, F9 user's guide lists performance to 10,000km apogee 28.5deg GTO as 7,002kg. Performance to 100,000km apogee 15deg GTO is listed as 2,348kg.
« Last Edit: 07/09/2012 02:30 am by 2552 »

Offline Idiomatic

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The f9 user guide is really outdated, don't know why it is being discussed when we have better data from nasa.

Offline ArbitraryConstant

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From the Falcon 9 v1.1 thread there's a NASA performance estimator... I saw LEO and C3 there but not GTO.

Note additionally that just being wrong isn't intellectually dishonest. When I posted previously it didn't even occur to me to consider different apogees, I thought they all just went to 35786 km.

Given additional checking however, it does seem like F9 v1.1 is competitive with Atlas V 401 and maybe even heavier versions for GTO, for similar inclinations and apogees. The claim that an LH2 stage was necessary for this kind of performance does not appear to be borne out by these numbers.

Merlin 1D is a huge upgrade.
« Last Edit: 07/09/2012 03:01 am by ArbitraryConstant »

Offline Downix

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Not even close. According to the Falcon 9 user guide, the Falcon 9 v2.0 gets 2.3 metric tons to the same GTO orbit Delta II gets 2.2 metric tons using the same margins. Atlas V 401 gets 4.7 metric tons under the same profile. If you use a lower apogee orbit on F9 or change the inclination you can make it look less, but that is marketing and not the truth. To the same orbit, F9 compares well against D2, but not AV.

Falcon 9 gets 4850kg to GTO, according to their website. The Falcon 9 user guide is old, it probably has v1.0 (block2?) numbers rather than v1.1 numbers.

Also, the lowest 35,786km apogee GTO performance listed for F9 Block 2 (on page 23 of the F9 user's guide) is 2,972kg to a 15deg 35,786km GTO, which would require a combined plane change/GTO transfer burn. A 28.5deg GTO is listed as 4,536kg. The highest performance 35,786km apogee GTO I can find for Delta II in DeltaIIPayloadPlannersGuide2007.pdf (under General Performance Capability, table 2-4) is 2,171kg to a 28.7deg inclination GTO, no plane change required. And that's using a Star48B 3rd stage, which F9 doesn't use.
We lack detail on the launch margins used by F9, so I have to assume it is raw numbers or MRS rather than refined, which drops the total payload.

Using Schillings, I get a total payload of the F9 1.1 to 2,841 metric tons to the GTO orbit I tend to use (185 x 42164 km, 28 deg) while with Delta II I get 2,149 kg to the same. Atlas V 401 I get 5238 kg, still almost twice Falcon 9 to the same orbit.
Quote
I do wish SpaceX would put up a more recent user's guide though.
Fully agreed here, as it references a model not in use, which may never be in use at this rate.
Quote
Falcon 9 gets 4850kg to GTO, according to their website. The Falcon 9 user guide is old, it probably has v1.0 (block2?) numbers rather than v1.1 numbers.
To a lower orbit than being discussed here. Comparing a GTO with apogee of 10k at 28 degrees against a GTO with apogee of 40k at 15 degrees is intellectually dishonest. I used the published figures to keep it fair. If I use my own skill, Falcon looks even worse against Atlas V.

Unless I'm wrong, F9 user's guide lists performance to 10,000km apogee 28.5deg GTO as 7,002kg. Performance to 100,000km apogee 15deg GTO is listed as 2,348kg.
Again, that is without any detail on the margins used, while the margins for Delta II are well documented, although not in the users guide but elsewhere. And this is for a model of Falcon which is not actually in service to boot.

The main reason why I would have focused on Hydrolox instead of 1D is due to this factor. With a Hydrolox Merlin engine, still gas generated mind you, I can get Falcon 9's performance at close to 6 metric tons, comparing very well against Atlas. This is with the older 1C main engine and no tank stretch or changes to the first stage. This would give them more variety, more capability, as they could switch between the kerolox and hydrolox upper stages depending on need. I'd mentioned earlier that I would have used Falcon 1 first stages as boosters to the F9 to further improve performance, much how SRB's enhance the EELV's, but I would further use the F1's upper stage to improve GTO/GSO performance as well, like how the Star improves the GTO/GSO performance for both Delta II and Atlas V. It would require less development, and open up more markets, than the path they chose which has given them a vehicle which shall suffer from the same issues that hurt the Ariane 5, too large for the majority of payloads. They assume that their lower price will encourage doubling-up, but that was argued before with Ariane as well, and yet they still lose out to other launch vehicles better optimized to the particular need.
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Offline Downix

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From the Falcon 9 v1.1 thread there's a NASA performance estimator... I saw LEO and C3 there but not GTO.

Note additionally that just being wrong isn't intellectually dishonest. When I posted previously it didn't even occur to me to consider different apogees, I thought they all just went to 35786 km.

Given additional checking however, it does seem like F9 v1.1 is competitive with Atlas V 401 and maybe even heavier versions for GTO, for similar inclinations and apogees. The claim that an LH2 stage was necessary for this kind of performance does not appear to be borne out by these numbers.

Merlin 1D is a huge upgrade.
I cannot validate the chart, every scenario I run it through does not have a curve which matches this line in any way shape or form. The 1D might have gained more impulse, it might be using a new undisclosed upper stage, lots of variables. I cannot put my faith in it without those numbers at this time.
« Last Edit: 07/09/2012 03:13 am by Downix »
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Offline vigleik

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Not even close. According to the Falcon 9 user guide, the Falcon 9 v2.0 gets 2.3 metric tons to the same GTO orbit Delta II gets 2.2 metric tons using the same margins. Atlas V 401 gets 4.7 metric tons under the same profile. If you use a lower apogee orbit on F9 or change the inclination you can make it look less, but that is marketing and not the truth. To the same orbit, F9 compares well against D2, but not AV.

Falcon 9 gets 4850kg to GTO, according to their website. The Falcon 9 user guide is old, it probably has v1.0 (block2?) numbers rather than v1.1 numbers.
To a lower orbit than being discussed here. Comparing a GTO with apogee of 10k at 28 degrees against a GTO with apogee of 40k at 15 degrees is intellectually dishonest. I used the published figures to keep it fair. If I use my own skill, Falcon looks even worse against Atlas V.

I don't understand how you can use those outdated numbers (or your own skill?) and conclude that I'm intellectually dishonest.

Here's a like for like comparison, using Nasa's numbers (http://elvperf.ksc.nasa.gov/elvMap/staticPages/launch_vehicle_info1.html). With a standard GTO orbit, 28.5 degrees, Falcon 9 v1.1 actually gets 5755kg. More than what they claim on their website. Atlas V (401) gets 4365kg. 40000km at 15 degrees gives 3530kg for Falcon 9 versus 2835kg for Atlas V.

Of course Falcon 9 v1.1's real world performance remains to be seen, but I don't think any of us (who are allowed to talk) know more than Nasa about Falcon's expected performance.

Offline Downix

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Not even close. According to the Falcon 9 user guide, the Falcon 9 v2.0 gets 2.3 metric tons to the same GTO orbit Delta II gets 2.2 metric tons using the same margins. Atlas V 401 gets 4.7 metric tons under the same profile. If you use a lower apogee orbit on F9 or change the inclination you can make it look less, but that is marketing and not the truth. To the same orbit, F9 compares well against D2, but not AV.

Falcon 9 gets 4850kg to GTO, according to their website. The Falcon 9 user guide is old, it probably has v1.0 (block2?) numbers rather than v1.1 numbers.
To a lower orbit than being discussed here. Comparing a GTO with apogee of 10k at 28 degrees against a GTO with apogee of 40k at 15 degrees is intellectually dishonest. I used the published figures to keep it fair. If I use my own skill, Falcon looks even worse against Atlas V.

I don't understand how you can use those outdated numbers (or your own skill?) and conclude that I'm intellectually dishonest.

Here's a like for like comparison, using Nasa's numbers (http://elvperf.ksc.nasa.gov/elvMap/staticPages/launch_vehicle_info1.html). With a standard GTO orbit, 28.5 degrees, Falcon 9 v1.1 actually gets 5755kg. More than what they claim on their website. Atlas V (401) gets 4365kg. 40000km at 15 degrees gives 3530kg for Falcon 9 versus 2835kg for Atlas V.

Of course Falcon 9 v1.1's real world performance remains to be seen, but I don't think any of us (who are allowed to talk) know more than Nasa about Falcon's expected performance.
You used a website number without any qualifying information to back it, that is what is dishonest. I am not saying you are the dishonest one, but that the comparison is.

And you are right there, we do not know the final numbers. However my initial point remains, if they had gone Hydrolox instead of upgrading both the main engine *and* the main stage, they would have been at the same performance curve, but with less development and given them a leg up on future developments at the same time.
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Offline QuantumG

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Hydrolox.. less development.. yeah... what's the weather like on your planet?

Human spaceflight is basically just LARPing now.

Offline ArbitraryConstant

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Using Schillings, I get a total payload of the F9 1.1 to 2,841 metric tons to the GTO orbit I tend to use (185 x 42164 km, 28 deg) while with Delta II I get 2,149 kg to the same. Atlas V 401 I get 5238 kg, still almost twice Falcon 9 to the same orbit.
Schillings emphatically denies that it represents real world performance, particularly given whatever undisclosed parameters you used.

SpaceX is advertising 4850 kg to GTO, and the only information available that contradicts that is the NASA numbers that suggest more like >5000 kg to anything below 60000 km. Presumably SpaceX is giving themselves a little margin so aren't stuck with instantaneous launch windows for everything, and can potentially use different launch sites, but their number seems like a reasonably reliable minimum under the circumstances.

I cannot validate the chart, every scenario I run it through does not have a curve which matches this line in any way shape or form. The 1D might have gained more impulse, it might be using a new undisclosed upper stage, lots of variables. I cannot put my faith in it without those numbers at this time.
I don't think the situation requires faith on your part because nobody's asking you to book payloads based on these numbers. And the people that are booking launches have contracts that don't require faith from them either.

The available information supports the provisional conclusion that F9 v1.1 single-stick supports payloads larger Delta II, or even Atlas V 401, to GTO.
« Last Edit: 07/09/2012 04:45 am by ArbitraryConstant »

Offline Lurker Steve

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And the people that are booking launches have contracts that don't require faith from them either.


The companies that have booked payloads on F9 are going ENTIRELY on faith right now. There have been 3 F9 launches so far. How have they demonstrated the lift capability of the F9 ? By dropping off a few cubesats and a half-empty Dragon capsule ? How many tonnes did that block of cheese weigh ?

Without evidence, customers just need to have the "faith" to believe the SpaceX sales pitch. Most of these same customers are also praying that SpaceX might someday get around to launching their satellites. Who has faith that the SpaceX fairing will work the first time ?
 

Offline ArbitraryConstant

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The companies that have booked payloads on F9 are going ENTIRELY on faith right now.
Don't they get refunds if SpaceX doesn't meet the required schedule and performance?

Offline Lurker Steve

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The companies that have booked payloads on F9 are going ENTIRELY on faith right now.
Don't they get refunds if SpaceX doesn't meet the required schedule and performance?

Only if they get the lawyers involved.

Offline go4mars

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They chose a path which pushed hydrolox behind many other pieces. The development behind Heavy was to give them the GTO performance to compete against Ariane, Delta and Proton. They could have achieved this with less development and schedule risk by focusing on the hydrolox.
[/b]
The part in bold is the part I am skeptical of. 
I suspect they assumed hydrolox to have greater development and operational cost and complexity as well as increased timeframe compared to parallel stages.  Crucial decisions for a fledgling company.
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Offline Downix

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They chose a path which pushed hydrolox behind many other pieces. The development behind Heavy was to give them the GTO performance to compete against Ariane, Delta and Proton. They could have achieved this with less development and schedule risk by focusing on the hydrolox.
[/b]
The part in bold is the part I am skeptical of. 
I suspect they assumed hydrolox to have greater development and operational cost and complexity as well as increased timeframe compared to parallel stages.  Crucial decisions for a fledgling company.
That is possible indeed. However, their later focus on developing a staged combustion methane engine dismisses that claim, due to the greater complexities of both ORSC *and* Methane.
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Offline ugordan

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due to the greater complexities of both ORSC *and* Methane.

Wasn't the whole point of a methane SC engine that you can do a fuel rich preburner without worrying about coking?

Offline Downix

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due to the greater complexities of both ORSC *and* Methane.

Wasn't the whole point of a methane SC engine that you can do a fuel rich preburner without worrying about coking?
If they are going fuel rich it would make things easier, but not by much. Staged Combustion is a complex beast, and it makes little sense to me to be persuing it when they have one of the most efficient GC systems made. Exploit their strength I say. Perfection is the enemy of good enough.
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Offline ArbitraryConstant

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If they are going fuel rich it would make things easier, but not by much. Staged Combustion is a complex beast, and it makes little sense to me to be persuing it when they have one of the most efficient GC systems made. Exploit their strength I say. Perfection is the enemy of good enough.
Don't LOX/LH2 engines tend to need two independent turbopumps because of the highly different densities, even with GG engines like J2 and RS-68?

That's on top of the density problem and ground handling costs. A new SC engine might be costly to develop, but I suspect not quite so much as it would be at other companies, and I think SpaceX has a good chance of making it inexpensive to manufacture. Conversely, LH2 would add costs with every flight, and its own development costs as well.

You might argue the costs for dealing with LH2 are minor, but I would respond that Musk has no desire to see costs stay that high.

Offline hkultala

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[offtopic]


However my initial point remains, if they had gone Hydrolox instead of upgrading both the main engine *and* the main stage, they would have been at the same performance curve, but with less development and given them a leg up on future developments at the same time.

Are you seriously claiming that developing totally new engine with a totally different fuel than previous designs AND developing a totally new much bigger second stage would be "less development" than developing a new turbopump and some other small changes for an existing engine and stretching the existing first stage a bit?

[/quote]
« Last Edit: 07/09/2012 08:32 am by hkultala »

Offline ChefPat

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Wow, did this thread get waaaaay off topic.
Playing Politics with Commercial Crew is Un-American!!!

Offline Rocket Science

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Wow, did this thread get waaaaay off topic.
Pat, what else is new? :D

~Robert
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Offline Downix

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Wow, did this thread get waaaaay off topic.
Pat, what else is new? :D

~Robert
I don't see it. The topic is "Should SpaceX aim for a 330,000 lbs engine rather than am F1 class engine?" and I am discussing kinds of engine to be developed, so keeping to the topic at hand.
« Last Edit: 07/09/2012 02:00 pm by Downix »
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Online dunderwood

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If the question is '330k vs 1500k' thrust levels, then 'hydrogen vs methane' fuel seems a bit off topic.

Offline Downix

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If the question is '330k vs 1500k' thrust levels, then 'hydrogen vs methane' fuel seems a bit off topic.
Only if taken out of context. I pointed out that I'd rather see them focus on a higher energy engine than a higher thrust engine at this point, and gave my reasons as to why.
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Offline go4mars

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I pointed out that I'd rather see them focus on a higher energy engine than a higher thrust engine at this point, and gave my reasons as to why.
Just for clarity, do you think it would be faster and less expensive to build and operate a raptor stage? Or a bigger better hydrocarbon solution?


I see FH and V1.1 as pretty much maximum size for road transportable.  It is also for that reason that I think raptor may be a third stage instead of a second stage (density of H2), and that V 2.0 will be LNG first and second stage (also of highway diameter), but reusable (3rd stage raptor not reusable at this diameter).  As to a 330000 pound RP-1 Merlin, I don't see it as likely.  The engine could be developed at Hawthorne and tested in Texas, but a stage would be too large until they have either a coastal manufactory, or one in close proximity to their launch pad.  If that is the case, and they need new transportation solutions anyway, I think Elon is more likely to just go straight to building a BFR.  I think his BFR might be a giant version of the FH V2.0 (which may have methane SC engines in the size range you propose and likely less than 9 of them), with a scaled-up hydrolox 3rd stage (which can re-enter at Earth from Mars return speeds).  It depends partly on how important an intermediate sized engine is.    Thousands of colonists will need a far larger engine IMO.
« Last Edit: 07/09/2012 05:15 pm by go4mars »
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Offline Karloss12

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I pointed out that I'd rather see them focus on a higher energy engine than a higher thrust engine at this point, and gave my reasons as to why.
Just for clarity, do you think it would be faster and less expensive to build and operate a raptor stage? Or a bigger better hydrocarbon solution?


I see FH and V1.1 as pretty much maximum size for road transportable.  It is also for that reason that I think raptor may be a third stage instead of a second stage (density of H2), and that V 2.0 will be LNG first and second stage (also of highway diameter), but reusable (3rd stage raptor not reusable at this diameter).  As to a 330000 pound RP-1 Merlin, I don't see it as likely.  The engine could be developed at Hawthorne and tested in Texas, but a stage would be too large until they have either a coastal manufactory, or one in close proximity to their launch pad.  If that is the case, and they need new transportation solutions anyway, I think Elon is more likely to just go straight to building a BFR.  I think his BFR might be a giant version of the FH V2.0 (which may have methane SC engines in the size range you propose and likely less than 9 of them), with a scaled-up hydrolox 3rd stage (which can re-enter at Earth from Mars return speeds).  It depends partly on how important an intermediate sized engine is.    Thousands of colonists will need a far larger engine IMO.


Good point on the transportability.

But the rest of what you say is equivalent to SpaceX scrapping allot of what it has learnt and done in the last 5 years and then start from scratch.

He doesn't have the cash to start a new rocket from scratch.  And there are plenty of opportunities to evolve and improve the already successful system that SpaceX already has.  A new upper stage Raptor seems like the component containing new technology that makes commercial sense for SpaceX to start exporing.

I can't see the government writing a cheque for a BFR unless SpaceX has already intergrated some of the BFR's core components into its profitible commercial operations.
« Last Edit: 07/09/2012 06:58 pm by Karloss12 »

Offline Rocket Science

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Wow, did this thread get waaaaay off topic.
Pat, what else is new? :D

~Robert
I don't see it. The topic is "Should SpaceX aim for a 330,000 lbs engine rather than am F1 class engine?" and I am discussing kinds of engine to be developed, so keeping to the topic at hand.
I'm just being light hearted Nate. :)
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Offline ArbitraryConstant

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If the question is '330k vs 1500k' thrust levels, then 'hydrogen vs methane' fuel seems a bit off topic.
Only if taken out of context. I pointed out that I'd rather see them focus on a higher energy engine than a higher thrust engine at this point, and gave my reasons as to why.
I guess I'm just not seeing it.

The Merlin 1D upgrades resulted in improved ISP, wildly improved thrust, and actually cut costs. Even if performance was flat I wouldn't be surprised if it was worth it for reduced costs alone. But on top of that it increases GLOW without strapons or other mods, which is a pretty big win in its own right because first stage growth is usually a lot harder than that, and the increased performance to GTO and LEO is substantial. All this with an engine that's still pretty simple by most standards. Completely apart from any other upgrades they might attempt, low hanging fruit optimizations for the first stage such as this make unimpeachable sense.

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Minor point by why has SpaceX not used the exhaust from the gg to provide film cooling for part of the nozzle? It would reduce the amount of nozzle that needs active cooling. I understand that for a single engine the gg exhaust is useful for roll control, but with multiple engines it really does nothing.   

Offline Robotbeat

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Minor point by why has SpaceX not used the exhaust from the gg to provide film cooling for part of the nozzle? It would reduce the amount of nozzle that needs active cooling. I understand that for a single engine the gg exhaust is useful for roll control, but with multiple engines it really does nothing.   
They already do some film cooling.
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Offline Downix

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I pointed out that I'd rather see them focus on a higher energy engine than a higher thrust engine at this point, and gave my reasons as to why.
Just for clarity, do you think it would be faster and less expensive to build and operate a raptor stage? Or a bigger better hydrocarbon solution?
Between those two, the better hydrocarbon solution easily. However I was not discussing the raptor, a staged combustion engine. I was discussing a GG derived from the Merlin, which would serve several purposes. If the Raptor is the aim goal, this GG hydrolox would give the operational experience necessary first. It would give a performance curve similar to what the hydrocarbon engine upgrade should do as well. The thing to me is that they are no closer to having the necessary support structure for Raptor after this upgrade, which means those hurdles still have to be addressed and by addressing them later rather than sooner, inertia threatens to take over the program and that is the last thing I want to see happen.
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Offline FOXP2

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Minor point by why has SpaceX not used the exhaust from the gg to provide film cooling for part of the nozzle? It would reduce the amount of nozzle that needs active cooling. I understand that for a single engine the gg exhaust is useful for roll control, but with multiple engines it really does nothing.   
They already do some film cooling.

Well then they could do more with the gg exhaust in trade for active cooling.

Perhaps the cost of building the manifold for pumping the exhaust gas around the nozzel bell for an engine their size is more than simply making the whole thing actively cooled.     

Offline dwightlooi

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Back to the 330,000 lbs engine such as one with the following specs:-

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

The advantages are.

(1) The idea is not to use it to build a bigger Falcon rocket. The idea is to use it to reduce the number of engines needed for each 3.6m Falcon core from 9 to 4.

(2) The 330,000 lbs thrust level also enables the Falcon heavy to fly 2.5 times as heavy an upper stage as the current design using the same 330,000 lbs engine. Not resorting to multiple engines eliminates the problems with having to forgo a high expansion ratio nozzle or needing an expanded diameter interstage.

(3) Having 4 engine also gives nearly as good a level of practical engine out capability as having nine.

(4) It is more manufacturable and easier to handle during assembly than a monster engine in the 1.5~2.0 million lbs thrust class.

I don't know why this got carried off into a discussion about Delta payloads or cryogenic LH2 uppers. As far as combustion cycles goes though, it may be beneficial for SpaceX to look at the Tap-Off Cycle (TOC) as an alternative to the Gas Generator Cycle. TOC uses a main combustion chamber bleed to drive the turbo pump instead of having a separate gas generator. This simplifies the engine making it lighter and reducing the parts count. It also makes air start and multiple restart setups easier and more reliable because you don't have to start multiple combustion chambers at differing timings. Efficiency is lower, but only slightly (probably no more than about 5 isp). But personally I believe that simple, reliable and cheaper is better than high performance.

Offline QuantumG

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Because no-one wants to talk about your made-up pretend engine.
Human spaceflight is basically just LARPing now.

Offline go4mars

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GG hydrolox would give the operational experience necessary first. It would give a performance curve similar to what the hydrocarbon engine upgrade should do... they are no closer to having the necessary support structure for Raptor after this upgrade, which means ...by addressing them later rather than sooner, inertia threatens to take over the program and that is the last thing I want to see happen.
Thanks for the elaboration.  Many factors at play in that decision.  They are probably approaching the point where proto-typing hydrolox is beginning to make sense from a business perspective IMO (available for flights in a few years).  But the momentum you allude to might not be all bad.  In fact, it seems to me that they could use a little more corporate momentum.  Although Elon is in his 40's, his track record has demonstrated comfort with risk.  He knows that some ideas could be dead ends but I don't think it will shy him away from continuing to test new ideas.  I think we'll see in the next year whether he can succeed at allowing operational momentum while not crushing the drive to radically improve things.   An intended oxymoron.  I think he'll strike a fine  balance; unless he bores the innovators.  That's where maximum use of robots helps.  ;)
« Last Edit: 07/11/2012 04:59 am by go4mars »
Elasmotherium; hurlyburly Doggerlandic Jentilak steeds insouciantly gallop in viridescent taiga, eluding deluginal Burckle's abyssal excavation.

Offline hkultala

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Back to the 330,000 lbs engine such as one with the following specs:-

Griffon 1A
Fuel: RP-1/LOX
Isp (SL): 278 secs
Isp (Vac): 312 Secs
Dry Mass: 2,200 lbs

The mass is quite optimistic

Something like >1500 kg for the vacuum version though?

Quote
Thrust-to-Weight Ratio: 150:1
Thrust (SL): 313,000 lbs
Thrust (Vac): 330,000 lbs

The advantages are.

(1) The idea is not to use it to build a bigger Falcon rocket. The idea is to use it to reduce the number of engines needed for each 3.6m Falcon core from 9 to 4.

I consider this a disadvantage. 4 engines would mean
* Reusable version could not land with one engine, as the T/W would be too big, and the engine alignment would also be problematic for this
* It would have worse engine-out capability than falcon 9.

Quote
(2) The 330,000 lbs thrust level also enables the Falcon heavy to fly 2.5 times as heavy an upper stage as the current design using the same 330,000 lbs engine. Not resorting to multiple engines eliminates the problems with having to forgo a high expansion ratio nozzle or needing an expanded diameter interstage.

Not so simple. They would not need multiple engines currently either.

Second stage does not need T/W of >1. Actually second stage T/W can be many times smaller than 1, when staging high(and FH is definetely staging high). They can already use quite heavy second stage. Atlas V-551 lifts 18,814 kg to LEO with just 99 kN of second stage engine thrust. That's 34% of FH payload, with about 15% of the thrust of FH.
Putting second centaur (552) increases the payload to 20520 kg. That's 38% of FH payload, with 30% of the thrust. And the 552 is meant for only LEO launches, as it  won't help at all for BEO missions.

Also, Delta-IV Heavy lifts > 22 tons(maybe something like 24 tons with RS-68A) to LEO with 110kN thrust. That's 41-45% of FH payload, with 17% of the payload.


And replacing 600 kg engine with 1500 engine means 900 kg more mass to orbit - mass that's not part of the payload.

And, most FH launches are for BEO, not LEO.

Quote

(3) Having 4 engine also gives nearly as good a level of practical engine out capability as having nine.

Any basis for this claim?
« Last Edit: 07/11/2012 07:44 am by hkultala »

Offline FOXP2

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If it losses one engine now it losses 11% of thrust, with four engines it would loss 25% thrust if one goes out. Assuming a worse case scenario of the rocket losing that engine right after life off, the rocket would need to be built and missions setup around utilizing only 75% of its thrust capacity.   

Offline ArbitraryConstant

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The thing to me is that they are no closer to having the necessary support structure for Raptor after this upgrade, which means those hurdles still have to be addressed and by addressing them later rather than sooner, inertia threatens to take over the program and that is the last thing I want to see happen.
I think the question this suggests is: is LH2 inevitable or necessary? Is it the end state of any space program as you seem to suggest, or do other approaches have potential?

AFAICT the SpaceX stable of vehicles can handle any commercial payload to any commercial orbit, at least assuming Falcon Heavy works. Which would suggest for near to mid term commercial launches they aren't really missing much, except for what Falcon 1 could have done if it had continued.

An LH2 US would be necessary to nudge the GTO performance up to Proton territory in single stick configuration, but they can get the necessary performance from Falcon Heavy with no new fuels, or engines, or stages. They don't even need crossfeed, and it's not even clear bringing LH2 to the party would be cheaper.

But say LH2 was cheaper for that niche. I think that assumes a steady state for the launch business that SpaceX isn't aiming for and doesn't want. At best you're talking about saving a few million on a 8-9 figure launch cost. They might be wrong about whether it can be done, but SpaceX wants it to be 6-7 figures. GTO will be a low volume sideshow not worth specializing for if that happens.

Skepticism would be a sensible default position to take on this, except they've actually bent metal towards that goal on their own dime.

They might be wrong, but Falcon Heavy is sufficiently competitive with no new engines or stages for that to be a survivable mistake even if they are.
« Last Edit: 07/11/2012 04:32 pm by ArbitraryConstant »

Offline dwightlooi

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I consider this a disadvantage. 4 engines would mean
* Reusable version could not land with one engine, as the T/W would be too big, and the engine alignment would also be problematic for this
* It would have worse engine-out capability than falcon 9.

(3) Having 4 engine also gives nearly as good a level of practical engine out capability as having nine.

Any basis for this claim?

Propulsive landing is not necessary for re-usability. Honestly, I think grasshopper is a pipe dream. Doing everything with engine thrust simply uses too much propellant and too risky in the sense that an engine failure will result in a 30~80 ton object partially fueled with RP-1/LOX crashing down on the launch site. In the end, I believe that if they achieve 1st stage re-usability, they use engine thrust to reduce the re-entry velocity to about Mach 4~5 from about Mach 9~10 only. As long as the stage survives re-entry and slows down to sub-sonic speeds via atmospheric drag, they'll use parachute(s) to slow it down sufficiently for a water landing -- like they originally intended to do. In this model, the engine does not need to be on the centerline. It just has to be gimballed so the thrust goes through the CG (very much like SSMEs). Besides, there is no reason to fire just one engine they can fire two or all four.

The thing about engine out capability is that with 4 engines you can lose an engine through about 50~70% of the 1st stage flight envelope depending on how close to the limit the payload happens to be. With 9 engines you can lose an engine through about 60~80% of the flight envelope. It is worse with 4 but not horribly worse. Besides, most engine failures happen either during the initial start and throttling to full thrust, or late in the burn. The former is mitigated by the 2 second hold down, the latter is fine with either 4 or 9 engines.

Offline spectre9

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I think SpaceX is more likely to build something like Briz-M than Centaur.

Super Draco hypergolic stage?

Why even bother with new engines?

Offline Jim

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I think SpaceX is more likely to build something like Briz-M than Centaur.


Huh?  There is no data to suppose that and actually data that says the opposite.

Offline hkultala

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Propulsive landing is not necessary for re-usability. Honestly, I think grasshopper is a pipe dream. Doing everything with engine thrust simply uses too much propellant and too risky in the sense that an engine failure will result in a 30~80 ton object partially fueled with RP-1/LOX crashing down on the launch site.


How does this differ to landing aeroplanes?

That they still maintain some manouverability even without engines?

And it's not doing _everything_ with engine thrust. Atmospheric drag helps a lot also.

Quote
In the end, I believe that if they achieve 1st stage re-usability, they use engine thrust to reduce the re-entry velocity to about Mach 4~5 from about Mach 9~10 only. As long as the stage survives re-entry and slows down to sub-sonic speeds via atmospheric drag, they'll use parachute(s) to slow it down sufficiently for a water landing -- like they originally intended to do. In this model, the engine does not need to be on the centerline. It just has to be gimballed so the thrust goes through the CG (very much like SSMEs). Besides, there is no reason to fire just one engine they can fire two or all four.

Elon wants "rapid reusability". That means not needing to spend lots of time and money to recover and fix/refurbish boosters that have been on salty sea water.

And in other to do propulsive landing, capability to thrust down to T/W of 1 is needed.

Offline FOXP2

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Propulsive landing is not necessary for re-usability. Honestly, I think grasshopper is a pipe dream. Doing everything with engine thrust simply uses too much propellant and too risky in the sense that an engine failure will result in a 30~80 ton object partially fueled with RP-1/LOX crashing down on the launch site.


How does this differ to landing aeroplanes?

That they still maintain some manouverability even without engines?

And it's not doing _everything_ with engine thrust. Atmospheric drag helps a lot also.

Well do wings weigh more than propellent? Also we might give points to propulsive landing for not needing a runway.


Quote
Elon wants "rapid reusability". That means not needing to spend lots of time and money to recover and fix/refurbish boosters that have been on salty sea water.

I have to disagree with his strategy then, parachute landing would be a technologically safer avenue, making the falcon 9 partially reusable even if you have to spend weeks refurbishing would save money for the development of a more radical propulsive landing system later.   


Offline douglas100

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There's another thread for discussing re-usability.
Douglas Clark

Offline Karloss12

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I consider this a disadvantage. 4 engines would mean
* Reusable version could not land with one engine, as the T/W would be too big, and the engine alignment would also be problematic for this
* It would have worse engine-out capability than falcon 9.

(3) Having 4 engine also gives nearly as good a level of practical engine out capability as having nine.

Any basis for this claim?

Propulsive landing is not necessary for re-usability. Honestly, I think grasshopper is a pipe dream. Doing everything with engine thrust simply uses too much propellant and too risky in the sense that an engine failure will result in a 30~80 ton object partially fueled with RP-1/LOX crashing down on the launch site. In the end, I believe that if they achieve 1st stage re-usability, they use engine thrust to reduce the re-entry velocity to about Mach 4~5 from about Mach 9~10 only. As long as the stage survives re-entry and slows down to sub-sonic speeds via atmospheric drag, they'll use parachute(s) to slow it down sufficiently for a water landing -- like they originally intended to do. In this model, the engine does not need to be on the centerline. It just has to be gimballed so the thrust goes through the CG (very much like SSMEs). Besides, there is no reason to fire just one engine they can fire two or all four.

The thing about engine out capability is that with 4 engines you can lose an engine through about 50~70% of the 1st stage flight envelope depending on how close to the limit the payload happens to be. With 9 engines you can lose an engine through about 60~80% of the flight envelope. It is worse with 4 but not horribly worse. Besides, most engine failures happen either during the initial start and throttling to full thrust, or late in the burn. The former is mitigated by the 2 second hold down, the latter is fine with either 4 or 9 engines.

Elon says "It really comes down to what the staging Mach number would be.  For an expendable Falcon 9 rocket, that is around Mach 10. For a reusable Falcon 9, it is around Mach 6, depending on the mission." and goes on to say "The payload penalty for full and fast reusability versus an expendable version is roughly 40 percent,"

Sounds like an attempt at FH side core recovery to me.  A logical first step to recovering other equipment.

I would expect there would be more then one landing pad and the concrete to fill the crater costs about $500 per cubic metre.

Anyway, if the F9 can be recovered then a 9 x 330,000 core could replace the FH.  It all depends on recovery though.

But I see how your pessimism about SpaceX's current plan to achieve rapid recovery produces your idea.

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