Quote from: Antares on 08/28/2010 07:45 pmThe only one of those things other companies haven't used is Ethernet.One interesting aspect of wat Beal did, pressure-fed first stages, was not adopted by SpaceX. They did try cheap composite ablative nozzles, but upgraded to regenerative nozzles later. It would also be interesting to see someone field an operational orbital launcher with a kerosene peroxide first stage. Blue Origin presumably intends to do that eventually, but not with a minimum cost expendable.
The only one of those things other companies haven't used is Ethernet.
Yeah... SpaceX certainly gave ablative engines a shot. (weren't F1 #1 and #2 launched with an ablative Merlin?) And now they seem to use regen engines whenever they can. All 12 regen engines that have flown (12?) appear to have run flawlessly.
Jon (or anyone else who knows), this may be going slightly off-topic, but you may be a good person to ask: Whenever people come up with new ideas for low-cost launch vehicles that drastically will lover the $$$/lb to orbit, most of those proposals seem to have ablative engines in common. But what is the actual ratio of successful production engines that are ablative vs. regen? (RS-68 comes to mind as a recent example, but is it the exception to the rule?
Also, with your work dealing with primarily reusable engines (I assume), isn't regen pretty much required? How would you accomplish an ablative reusable engine?
for engines like RS-68 I have a hard time seeing what the big deal is with doing a regen extension, especially since the TP's and injectors were designed for such an assumption originally.
Quote from: jongoff on 09/12/2010 02:05 amfor engines like RS-68 I have a hard time seeing what the big deal is with doing a regen extension, especially since the TP's and injectors were designed for such an assumption originally.The RS-68 FTP was designed for the additional flow resistance of pushing fuel through a regen nozzle the size of the existing nozzle?
I wouldn't be quite so sure that ablative nozzles are really cheaper than regen ones....
Actually, for pressure fed engines, I can't think of too many regen cooled systems other than Masten's.
But starting with something simple is logical enough. It's what von Braun did. It's what the New Space companies are doing. Didn't you guys start with IPA/LOX, ablative, pressure-fed, blow-down because it was a good place to start, only adding regenerative cooling later?
This is a SWAG, but I think part of the reason that SpaceX went regen was that the business case for building the ablative in-house didn't close. The unit price might've been cheaper, but they would have needed the capital to work with that particular material when nothing else in their product line needs it. Or, they would have had to contract it out, which they don't seem to like.
Nope, we never did ablative at Masten. We went straight from heatsink firings (to dial in injector and chamber geometry stuff) to regen cooled. Mind you, nobody but Ian Moore thought it would work the first time. But it did.
And also all of our systems have been regulated pressure systems. They do blow down a bit near the end of the run, but the first 1/2-2/3 of the flight is at a constant tank pressure.
High pressure pintle injectors and ablative chambers are a risky mix.
Quote from: jongoff on 09/13/2010 07:52 pmNope, we never did ablative at Masten. We went straight from heatsink firings (to dial in injector and chamber geometry stuff) to regen cooled. Mind you, nobody but Ian Moore thought it would work the first time. But it did.Interesting. Did you use a double wall or something a bit more advanced? Or is that an impertinent question?
QuoteAnd also all of our systems have been regulated pressure systems. They do blow down a bit near the end of the run, but the first 1/2-2/3 of the flight is at a constant tank pressure. Am I confusing this with what Paul Breed did or am I just misremembering what I read?
Anyway, thanks for all that information! Straight from the horse's mouth, it doesn't get much better than that. One of the great things about continuous integration.
Quote from: jongoff on 09/13/2010 07:55 pmHigh pressure pintle injectors and ablative chambers are a risky mix.That's a very interesting piece of information. Wasn't the Apollo LM ascent engine designed for maximum simplicity in order to maximise safety? Would it have been better to use a regeneratively cooled engine? And was this known in the sixties?