I wouldn't be surprised if they started messing around with LOX/LH2 just to get familiar with it. Do something like a small Kestrel-sized LOX/LH2 engine for starters, just to try and learn all the subtleties that you can never pick up just from textbooks. And then if that works out, work their way up to bigger Merlin-sized LOX/LH2 upper stage engines.~Jon
Would expanding the first stage and creating a Falcon 12 or even a Falcon 16 be practicle?
I would like to see this team keep doing what it knows best, which appears to be pintle injector kerosene engine development. After vacuum Merlin, it would seem to me a good idea to look at higher-thrust booster kerosene engines. Would it, for example, be cost effective to replace the nine Merlin 1C engines on the Falcon 9 first stage with four engines, or three, or two, or one.
Well, I agree that making a scaled up Merlin that would allow them to keep the engine count down to like 5 or so would be a big win.
Quote from: jongoff on 02/18/2009 07:22 pmWell, I agree that making a scaled up Merlin that would allow them to keep the engine count down to like 5 or so would be a big win. I doubt that they would create another engine that had less than 2x the thrust of their current one. No I predict that any 'big Merlin' would have at least 5x-10x thrust.
It might not be as sexy as designing a F1 class engine or a hydrogen upper stage engine, but I think that if they can get the 9 engine configuration to work, they should incrementally improve the merlin engine:
Quote from: rklaehn on 02/18/2009 08:36 pmIt might not be as sexy as designing a F1 class engine or a hydrogen upper stage engine, but I think that if they can get the 9 engine configuration to work, they should incrementally improve the merlin engine:Merlin already went through several improvement iterations and is expected to be uprated again by over 20% in thrust. That's about at the margins it's thought to be able to handle. There's only so much you can squeeze out of a given engine.
I was thinking mostly about non performance-related improvements. For example, if they could show that their containment system really works under most conditions, that would go a long way to show that they really have engine-out capability. And since a merlin has never been fired after being immersed in salt water, I am sure there are a lot of improvements in that area as well.
I really don't see the point of building a big merlin. If the 9 engine configuration can not be made to work reliably, spacex will not design any new engines. And if it can be made to work, why should they change?
The question is, if you wanted to increase performance, especially on high delta-V missions, would it be cheaper to develop a LH2 engine or just scale up an all-kerolox booster? It seems to me introducing LH2 into the equation would give SpaceX more trouble than it's worth.
To reduce costs/increase reliability they'll do another, bigger Kerolox. Staged combustion is nothing like pintel injector designs, and runs counter to the whole methodology that works for them. All they need is a bigger Merlin.
Quote from: nooneofconsequence on 02/18/2009 09:15 pmTo reduce costs/increase reliability they'll do another, bigger Kerolox. Staged combustion is nothing like pintel injector designs, and runs counter to the whole methodology that works for them. All they need is a bigger Merlin.1.Why should going to one engine increase reliability? You think the engine out capability won't work because engines will explode so violently that they take out their neighbors despite the kevlar shields?2.When was the last time a liquid engine failed explosively? (This is not a rhetorical question. I am genuinely interested :-)
If you just want to increase performance to LEO, then LH2 is probably not worth it. I am not even sure if it is worth it for GTO. But as soon as you want to go to escape trajectories, LH2 really starts to be superior. Since elon wants to go to mars, he will want a LH2 stage as soon as possible.It is a shame that lockheed probably does not want to do business with spacex. A falcon topped off with a wide body centaur would be a fantastic vehicle with 100% american engines. And duplicating the technology lockheed has with the centaur would take spacex a long time.
You can add parts (more engines, more for crossfeeds, more for ...) or you can remove parts (remove engines). More parts, more potential for failure. Less parts, less chances for failure. QC/QA works much better.
When Mr. Musk first announced Falcon 5, he talked about a possible future upgrade that would have included an RL10 powered second stage.
Quote from: nooneofconsequence on 02/18/2009 09:41 pmYou can add parts (more engines, more for crossfeeds, more for ...) or you can remove parts (remove engines). More parts, more potential for failure. Less parts, less chances for failure. QC/QA works much better.That's one way to spin it. The other way would be added redundancy and engine-out capability, limited as it is.Consider what appears to be a common cause for engine loss - foreign object debris in the LOX tank. Ingest the particle into the turbopump and it's trashed. If it's the only one in your stage you just bought the farm. If that same particle was ingested into a smaller turbopump in one of several engines, it doesn't necessarily mean loss of mission. As far as in-flight liquid failures go (let's be fair and not count test stand abuse and development tests), I inquired about that here already and it appears the last explosive failure was back in the prehistoric days of the space age or something like that.
When was the last time a liquid engine failed explosively on an operational launcher? (This is not a rhetorical question. I am genuinely interested :-)
Any anomaly lessens trust in a vehicle. You can't forstall the extent of damage to a vehicle. That you get lucky and make it to proper orbit isn't the shining success you want, since people will think it a fluke.
Last case of FOD and exploding liquid fueled boosters was just last year.
Don't talk about test stand abuse - the only place for a engine failure IS THE TEST STAND! These things are weapons, plain and simple. Expecting that you can tolerate a small "boom!" in a skyscraper of high explosive not to go off is simply nuts!Any parts you add to increase "reliability" can themselves become unreliable.
Well, there was the SeaLaunch failure a couple of years ago, and there was the 1990 Zenit failure: