Keep the engine small enough such that the components can be fabricating using common CnC mills ...
Merlin 2 has probably been mostly abandoned for the time being.
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 1AFuel: RP-1/LOXIsp (SL): 278 secsIsp (Vac): 312 SecsDry Mass: 2,200 lbsThrust-to-Weight Ratio: 150:1Thrust (SL): 313,000 lbsThrust (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 notThe 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.
Quote from: Idiomatic on 06/28/2012 01:13 amMerlin 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.
Quote from: Idiomatic on 06/28/2012 01:27 amI was trying to play nice.Oh, sorry.
Quote from: dwightlooi on 06/28/2012 01:02 amKeep 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.
Out of curiosity are you referring to Vozhoff or Tom Markusic?
Quote from: Idiomatic on 06/28/2012 01:13 amMerlin 2 has probably been mostly abandoned for the time being.It was never in the cards.
Quote from: QuantumG on 06/28/2012 01:17 amQuote from: Idiomatic on 06/28/2012 01:13 amMerlin 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).
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.
Quote from: Lars_J on 06/28/2012 02:27 amQuote from: QuantumG on 06/28/2012 01:17 amQuote from: Idiomatic on 06/28/2012 01:13 amMerlin 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.
Merlin 2 and BFR seem like they would be pretty useful for taking thousands and thousands of colonists and/or vacationers to Mars.
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.
Quote from: Brian Copp on 06/29/2012 02:11 amThe 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.
Quote from: CapitalistOppressor on 06/28/2012 10:56 amF9 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.
Quote from: go4mars on 06/29/2012 01:47 amMerlin 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.
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 Jim pointed out that sort of end to end capability is likely something none of us will live to see.
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.
Quote from: CapitalistOppressor on 06/29/2012 11:38 pmas 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.
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.
What can I say, I am a proud to believe in capitalism
Yeah, but Wikipedia says that there is low level on going development of the Merlin 2. :-)
Quote from: Karloss12 on 07/08/2012 12:25 pmYeah, 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.
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.
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.
Quote from: Jim on 07/08/2012 05:39 pmAgain 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.
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.
Quote from: Idiomatic on 07/08/2012 05:43 pmI 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.
Quote from: Lurker Steve on 07/08/2012 06:23 pmExcept 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.Quote from: Downix on 07/08/2012 06:14 pmQuote from: Idiomatic on 07/08/2012 05:43 pmI 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.
Quote from: ArbitraryConstant on 07/08/2012 05:43 pmThe SLS doesn't exist.The probability SLS block >1 ever flying is nil.Same goes for this vehicle
The SLS doesn't exist.The probability SLS block >1 ever flying is nil.
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.
Quote from: Karloss12 on 07/08/2012 04:54 pmBut 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.
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,
Quote from: Karloss12 on 07/08/2012 08:03 pmIn 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.....
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.
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.
Quote from: Jim on 07/08/2012 05:47 pmQuote from: ArbitraryConstant on 07/08/2012 05:43 pmThe SLS doesn't exist.The probability SLS block >1 ever flying is nil.Same goes for this vehicleUnder 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.Quote from: Lurker Steve on 07/08/2012 06:23 pmExcept 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.
Dropping the internal NASA program and funding a SpaceX development may just bring up another Contempt of Congress charge.
Quote from: Downix on 07/08/2012 06:52 pmAnd 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.
Quote from: ArbitraryConstant on 07/08/2012 07:51 pmQuote from: Downix on 07/08/2012 06:52 pmAnd 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.
Quote from: Downix on 07/09/2012 12:28 amQuote from: ArbitraryConstant on 07/08/2012 07:51 pmQuote from: Downix on 07/08/2012 06:52 pmAnd 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.
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.
Quote from: Downix on 07/09/2012 01:27 amNot 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.
Quote from: Downix on 07/08/2012 06:52 pmAnd 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.
Quote from: vigleik on 07/09/2012 01:53 amFalcon 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.
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.
Quote from: vigleik on 07/09/2012 01:53 amQuote from: Downix on 07/09/2012 01:27 amNot 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.
Quote from: Downix on 07/09/2012 02:17 amQuote from: vigleik on 07/09/2012 01:53 amFalcon 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.
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.
Quote from: vigleik on 07/09/2012 01:53 amQuote from: Downix on 07/09/2012 01:27 amNot 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.
Quote from: Downix on 07/09/2012 02:17 amQuote from: vigleik on 07/09/2012 01:53 amQuote from: Downix on 07/09/2012 01:27 amNot 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.
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.
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.
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.
Quote from: Lurker Steve on 07/09/2012 05:07 amThe 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?
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.
Quote from: Downix on 07/09/2012 02:21 amThey 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.
due to the greater complexities of both ORSC *and* Methane.
Quote from: Downix on 07/09/2012 05:59 amdue 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.
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.
Wow, did this thread get waaaaay off topic.
Quote from: ChefPat on 07/09/2012 12:45 pmWow, did this thread get waaaaay off topic.Pat, what else is new? ~Robert
If the question is '330k vs 1500k' thrust levels, then 'hydrogen vs methane' fuel seems a bit off topic.
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.
Quote from: Downix on 07/09/2012 03:46 pm 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.
Quote from: Rocket Science on 07/09/2012 12:59 pmQuote from: ChefPat on 07/09/2012 12:45 pmWow, did this thread get waaaaay off topic.Pat, what else is new? ~RobertI 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.
Quote from: dunderwood on 07/09/2012 02:30 pmIf 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.
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.
Quote from: Downix on 07/09/2012 03:46 pm 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?
Quote from: FOXP2 on 07/09/2012 07:42 pmMinor 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.
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.
Back to the 330,000 lbs engine such as one with the following specs:-Griffon 1AFuel: RP-1/LOXIsp (SL): 278 secsIsp (Vac): 312 SecsDry Mass: 2,200 lbs
Thrust-to-Weight Ratio: 150:1Thrust (SL): 313,000 lbsThrust (Vac): 330,000 lbsThe 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.
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 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?
I think SpaceX is more likely to build something like Briz-M than Centaur.
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.
Quote from: dwightlooi on 07/11/2012 10:08 pmPropulsive 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.
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.
Quote from: hkultala on 07/11/2012 07:25 amI 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.