EDIT: I agree that SpaceX really needs to transition into operations mode.
While I'm glad there is a useful growth head in basic designs, I'm concerned that everything they do requires upgrades. Seems like a recipe for endless R&D spending spree without operations volume to back it up. If they started ramping Merlins up after launching 8 F-9s, it would seem more comfortable.P.S. I'm also afraid that an endless procession of one-off rockets, each a little different, cannot be good for expected reliability and insurance premiums.
Why do they need to move turbopump prodution away from a mature and experienced producer to their own internal "start-up" to become "operational"? Save money, OK. Guaranteed to be just as reliable? Well, how many 1D flights do they need before they've proved that?
How about a little history of the Merlin engine and its evolution.First is the Merlin 1a, an all-ablative (that includes the combustion chamber, throat and nozzle), gas generator turbopump fed hydrocarbon engine with a pintle injector. It flew twice, failing on its first flight (F1 f1) due to a fuel leak and subsequent fire. The next flight (F1 f2) it performed nominally and was then retired. SpaceX had planned to add a higher performance turbopump, increasing overall thrust, for use on Falcon 9 launches. This is the Merlin 1b, but before it was ever used, SpaceX decided ablative was too much of a hassle, and switched to a regenerativley-cooled design. This is the Merlin 1c. It has a channel wall cooled combustion chamber and throat, and a tube wall cooled nozzle. It first flew on F1 f3, and was de-tuned to provide the same thrust as a Merlin 1a (so as not require a redesign of the Falcon 1) and even though it performed nominally (and 19 Merlin1c since), the failure to account for the residual thrust inherent to its design doomed this mission as well. This new regen configuration allows for a higher chamber pressure (and therefore more thrust) but its early generation turbopump, manufactured by Barber-Nichols, under performs for this task. Ever since the switch to regen, SpaceX's publicly announced plan was to eventually replace this tubopump with one optimized for the-now-regen cooled design, and to increase the diameters of propellant feedlines accordingly (but AFAIK no changes to tank sizes). They reffered to this as BLOCK II. BLOCK II is Merlin 1d, they only recently starting calling it such.Now that there is some evidence that SpaceX has decided to bring turbopump design and production in-house, and that Max Vozhoff has stated that Merlin 1d will have "a lower part count" (read: simpler, optimized) perhaps this explains their decision to rename the Merlin 1c BLOCK II as Merlin 1d.To add to the confusion, we have Falcon9 BLOCK II. To over simplify: Falcon9 + Merlin 1d = Falcon9 BLOCK II (again, AFAIK, no tank stretch)And that is why Merlin 1d and Falcon 9 BLOCK II are the "low hanging fruit" on the SpaceX family tree, NOT Falcon 1e. Falcon 1e = Merlin 1d + new first stage + new fairing + needs better launch site.Once SpaceX gets Falcon 9 BLOCK II, then they are that much closer to Falcon Heavy common core. That leaves the launch site, Vandenberg. Build it for Falcon Heavy but make it backward-compatible for Falcon 9 and even Falcon 1e, and then decide if the time is right to put F1e on the front burner again.Anyone thinking "Falcon 1e is dead" or "Merlin 2 is alive" is staring at the tea leaves too hard...
...The truth is that high quality production is not that difficult to do. It's expensive and requires a very strict QA. In particular, you have to be very picky about the suppliers. Some times, might be even cheaper to do it yourself than to do all the necessary controls to your supplier....
Amen to that. A lot of the trouble with LM and Orion was that Ares kept downgrading its performance. if LM had been doing Orion and Ares then they maybe could have mitigated the impact of such tweaks or atleast had more information up front about the limitations of the stick design.The nice thing about a vertically integrated rocket designer is that the information you have about each piece of technology is better understood and there should be less bluffing about capability between departments under a single roof no?
P.S. I'm also afraid that an endless procession of one-off rockets, each a little different, cannot be good for expected reliability and insurance premiums.
Quote from: Robotbeat on 03/20/2011 07:42 pmEDIT: I agree that SpaceX really needs to transition into operations mode.The good thing is that since they are assuming at this point that COTS 2 & 3 are being combined, the Dragon/Falcon mission in a few months will likely be 95% the same vehicle/payload that flies for the next 2-3 years.If that doesn't streamline production, SpaceX is in big trouble.
No surprise here. Your first few are always *unique*. Where I'd be scared is if successive contract missions aren't largely the same.If they aren't, you can't accumulate meaningful flight history - it becomes meaningless.
Ever since the switch to regen, SpaceX's publicly announced plan was to eventually replace this tubopump with one optimized for the-now-regen cooled design, and to increase the diameters of propellant feedlines accordingly (but AFAIK no changes to tank sizes). They reffered to this as BLOCK II. BLOCK II is Merlin 1d, they only recently starting calling it such.Now that there is some evidence that SpaceX has decided to bring turbopump design and production in-house, and that Max Vozhoff has stated that Merlin 1d will have "a lower part count" (read: simpler, optimized) perhaps this explains their decision to rename the Merlin 1c BLOCK II as Merlin 1d.
So first stage changes are all about engine upgrades to the best of my knowledge. No vehicle changes have been mentioned. 2nd stage remains as is - no changes identified there, are there?
Oh, and, wasn't Merlin 1d sea level thrust targeted to be 125 klbf for years already - as per F9 page?
I was thinking, 600kN vs current 423kN is is almost 42% extra thrust. What would be the performance of a 7 Merlin 1D Falcon? Or just taking the center engine, that would give you almost the expected thrust of the 556kN nominal Merlin with just eight engines.I don't think they can lengthen the first stage much. Much less widen it (because of transport issues). So what do you do with the extra trust? ...
But why couldn't they stretch the first stage?
Quote from: Robotbeat on 03/21/2011 03:19 pmBut why couldn't they stretch the first stage?The VTS3 support structure seems to be sized for current tank height, as is the Cape hangar. Lengthening the stage more could provide road transportation problems as well.I did a BOTE calculation based on the rough volume of the current stage and RP-1/LOX typical densities. I got about 270 t of propellant load with I'd guess lower than 10% uncertainty. That would mean the tank is already maxed out in propellant load.