the problem there being that Merlin 2 costs a hell of a lot to develop for performance goals that have been largely achieved with Merlin 1D, and on top of that it's not compatible with SpaceX's vertical landing reusability architecture. Which, even if you don't credit it with high chances of success (can't blame you), is certainly a strong priority for SpaceX. They won't do anything that requires reusability, but at this point they won't do anything that precludes it.
As far as Grasshopper, you may be pleasantly shocked by what they accomplish. As far as future development, Musk has hinted openly at a nuclear based engine way off in the future. I think that's where they are ultimately going. Merlin 2 maybe, Raptor maybe but not likely.
Raptor could be next up for development, maybe. That's something we both can agree on. As far as Merlin 1d we've seen the tests and it seems to be coming along nicely. My thoughts are what to achieve AFTER Merlin 1d. SpaceX engineers are going to have some time on their hands after 1d is completed and in service. Let's hope they push the envelope.
as we all know staged combustion hydro-lox engines are EXTREMELY hard to design. ... particularly and upper stage engine that would need to be capable of multiple re-starts.
Quotethe problem there being that Merlin 2 costs a hell of a lot to develop for performance goals that have been largely achieved with Merlin 1D, and on top of that it's not compatible with SpaceX's vertical landing reusability architecture. Which, even if you don't credit it with high chances of success (can't blame you), is certainly a strong priority for SpaceX. They won't do anything that requires reusability, but at this point they won't do anything that precludes it.Performance targets for the upgraded falcon 9 and FH which were planned anyway. M1D was always the plan. Merlin 2 would be for a larger falcon rocket, it would be based on the falcon 9 but likely would use only one merlin 2 on the first stage, and potentially raptor or a merlin2 based mvac on the second stage.
As for Merlin2, there is a desire to try and reduce the number of engines on the FH. This is because it would appear that ultimately SpaceX wants to acquire government contracts for that vehicle for things that might normally fly on DIVH and/or things that are to heavy for that. The way things appear right now, the idea of having 27 engines be them 1c's or 1ds on your inital stage is probably a turn off to these sorts of contracts, because its not viewed as reliable, and indeed it remains to be seen if it will be reliable or not.
In addition, m2 development is not as expensive as you seem to think
As to other propulsion projects, they are all shelved as far as I can tell because they have no need for things like methane engines, nuclear, ect unless they start doing large scale deep space missions to other planets.
And again, regarding the full re-usability stuff, I want to stress that I honestly do not think they will ultimately go forward with that once they discover how hard it is to fly back stages when testing begins later this year, if it begins this year that is.
Quote from: FinalFrontier on 05/30/2012 04:35 pmas we all know staged combustion hydro-lox engines are EXTREMELY hard to design. ... particularly and upper stage engine that would need to be capable of multiple re-starts. Given that, any chance they'd 'buy in' an existing engine (even if they only buy the basic design, and develop/produce it themselves)?Noel
It would also be ungodly expensive to develop a nuclear stage.
Quote from: FinalFrontier on 05/30/2012 04:35 pmas we all know staged combustion hydro-lox engines are EXTREMELY hard to design. ... particularly and upper stage engine that would need to be capable of multiple re-starts. Given that, any chance they'd 'buy in' an existing engine (even if they only buy the basic design, and develop/produce it themselves)?
Quote from: FinalFrontier on 05/30/2012 04:35 pmQuotethe problem there being that Merlin 2 costs a hell of a lot to develop for performance goals that have been largely achieved with Merlin 1D, and on top of that it's not compatible with SpaceX's vertical landing reusability architecture. Which, even if you don't credit it with high chances of success (can't blame you), is certainly a strong priority for SpaceX. They won't do anything that requires reusability, but at this point they won't do anything that precludes it.Performance targets for the upgraded falcon 9 and FH which were planned anyway. M1D was always the plan. Merlin 2 would be for a larger falcon rocket, it would be based on the falcon 9 but likely would use only one merlin 2 on the first stage, and potentially raptor or a merlin2 based mvac on the second stage.Even assuming M2 gets built this makes no sense. If one M2 could get a rocket off the ground, then one M2 will give the upper stage a really bad mass fraction and way too much acceleration. It's bad engineering.Quote from: FinalFrontier on 05/30/2012 04:35 pmAs for Merlin2, there is a desire to try and reduce the number of engines on the FH. This is because it would appear that ultimately SpaceX wants to acquire government contracts for that vehicle for things that might normally fly on DIVH and/or things that are to heavy for that. The way things appear right now, the idea of having 27 engines be them 1c's or 1ds on your inital stage is probably a turn off to these sorts of contracts, because its not viewed as reliable, and indeed it remains to be seen if it will be reliable or not.This is a reasonable motivation for M2, however given the development costs quoted (~$1B) I recall SpaceX angling to get a government contract to develop the thing and I don't think they will without that. Being able to bid on more launches would be nice, however they're already booked solid and scrambling to fulfill the existing contracts. If they can deliver F9 reliably and on time, that'll carry them through the decade.As a speculative venture, full reusability is a bigger deal long term than DoD launches, is something SpaceX is prepared to self-fund, is potentially achievable with variants of existing vehicles and engines, and is not well served by M2 because of the extremely large size.Quote from: FinalFrontier on 05/30/2012 04:35 pmIn addition, m2 development is not as expensive as you seem to thinkMarkusic: "(Merlin 2) could be qualified in three years for $1 billion.".The question then becomes why you think it's less expensive than SpaceX does - if they're wrong, it's probably in the other direction.Quote from: FinalFrontier on 05/30/2012 04:35 pmAs to other propulsion projects, they are all shelved as far as I can tell because they have no need for things like methane engines, nuclear, ect unless they start doing large scale deep space missions to other planets.The case for methane has at least as much to do with the favorable design attributes (similar density to LOX simplifying pumping, non-coking) as the ISP. It's a good fuel for a company without a big heritage investment.Quote from: FinalFrontier on 05/30/2012 04:35 pmAnd again, regarding the full re-usability stuff, I want to stress that I honestly do not think they will ultimately go forward with that once they discover how hard it is to fly back stages when testing begins later this year, if it begins this year that is.That is entirely possible, but that's different than arguing they are prepared to commit to engines that will rule it out before this has been demonstrated. You think it won't work, and there's a good chance you're right, but as far as they're concerned Reusability Is The Goal. So they're not going to design engines around expendability. That's what you'd do with your view reusability won't work.
The question then becomes why you think it's less expensive than SpaceX does - if they're wrong, it's probably in the other direction.
As a speculative venture, full reusability is a bigger deal long term than DoD launches, is something SpaceX is prepared to self-fund, is potentially achievable with variants of existing vehicles and engines, and is not well served by M2 because of the extremely large size.
Even assuming M2 gets built this makes no sense. If one M2 could get a rocket off the ground, then one M2 will give the upper stage a really bad mass fraction and way too much acceleration. It's bad engineering.
That is entirely possible, but that's different than arguing they are prepared to commit to engines that will rule it out before this has been demonstrated. You think it won't work, and there's a good chance you're right, but as far as they're concerned Reusability Is The Goal. So they're not going to design engines around expendability. That's what you'd do with your view reusability won't work.
Firstly, I think you overestimate the difficulty involved in building extremely large rocket engines. The published range of values for Merlin 2 sea level thrust would make it literally the largest and most powerful single-chamber gas generator rocket engine in history. The F-1 had massive problems achieving combustion stability, and there seems to be no evidence yet of a general solution to those difficulties.
Quote from: FinalFrontier on 05/30/2012 05:03 pmIt would also be ungodly expensive to develop a nuclear stage.Not only that, aren't nuclear engine heavy as heck - in addition to all the pipes, pumps etc that you have on a regular 'chemical' engine, you'd need a complete reactor? High ISP and high thrust, sure, but also heavy - not sure what the application is?Noel
Regarding the above, I think you mean understate
The same is true of raptor, but if you have newer documentation suggesting that its moved forward (beside the LH2 tank car thing at the test site) then please post it, as that's the whole point of thread: trying to find out if it went forward or not.
Quote from: jnc on 05/30/2012 05:33 pmQuote from: FinalFrontier on 05/30/2012 04:35 pmas we all know staged combustion hydro-lox engines are EXTREMELY hard to design. ... particularly and upper stage engine that would need to be capable of multiple re-starts. Given that, any chance they'd 'buy in' an existing engine (even if they only buy the basic design, and develop/produce it themselves)?Very unlikely - and certainly not from any of the existing large engine producers like PwR. The cost is just too high - they can make it themselves for cheaper if needed.
Quote from: FinalFrontier on 05/30/2012 06:00 pmRegarding the above, I think you mean understate Thanks, I edited it.Quote from: FinalFrontier on 05/30/2012 06:00 pmThe same is true of raptor, but if you have newer documentation suggesting that its moved forward (beside the LH2 tank car thing at the test site) then please post it, as that's the whole point of thread: trying to find out if it went forward or not. See Elon's AIAA conference keynote address in August 2011 (). He said that he expected to unveil a "super-efficient" staged combustion engine "later this year or next year".I don't think that the LH2 tank car at the test site can be taken as evidence that SpaceX are doing anything with LH2.