Quote from: rpapo on 08/09/2016 02:10 pmQuote from: Jim on 08/09/2016 01:58 pmNot a really relevant parameter for comparison. Try installed T/W. Compare Atlas V thrust section to F9 thrust section. Installation wise, I bet RD-180 kick Merlins butt all over town. Atlas V/RD-180 had no need for 9 feed lines.But they can't throttle down to what is effectively less than 10% thrust either. Yes, I appreciate the KISS principle in rocket design, but they could never have pulled off the booster landings with only one or two very powerful engines.Neither can Merlin. But what does throttling or landing have to do with the BE-4?
Quote from: Jim on 08/09/2016 01:58 pmNot a really relevant parameter for comparison. Try installed T/W. Compare Atlas V thrust section to F9 thrust section. Installation wise, I bet RD-180 kick Merlins butt all over town. Atlas V/RD-180 had no need for 9 feed lines.But they can't throttle down to what is effectively less than 10% thrust either. Yes, I appreciate the KISS principle in rocket design, but they could never have pulled off the booster landings with only one or two very powerful engines.
Not a really relevant parameter for comparison. Try installed T/W. Compare Atlas V thrust section to F9 thrust section. Installation wise, I bet RD-180 kick Merlins butt all over town. Atlas V/RD-180 had no need for 9 feed lines.
Actually, almost all methane engine designs proposed so far had lower ISP than high-ISP kerosene engines
Quote from: baldusi on 08/09/2016 01:48 pmIn fact, the thing I find most impressive is that people says that the tolerances on that engine are ridiculously loose.Yet several years ago there were people on here calling RD-180 a "ticking time bomb". Whether it was due to its ox-rich staged combustion cycle, a distrust toward its country of origin and their manufacturing practices and whether it was coming from experts in the field or forum "experts", I don't know, but it was pretty amusing.
In fact, the thing I find most impressive is that people says that the tolerances on that engine are ridiculously loose.
Please correct me if I'm wrong but haven't the various proposed Russian crew launch vehicle using the RD-170 family engines lowered the chamber pressure to increase safety?
Regarding BE-4, here is what we know so far. Propellants: LNG/LOXThrust: ~ 550,000 lbfChamber pressure: 1,950 psiCycle: ORSC (single shaft)Isp:<311s SL, <338 vac. (for the booster variant in Vulcan)TWR: <78Re-usability: 25 complete missions, minimum.
Suggest that a full scale Raptor on a test stand is within a month or so.Have not heard Bezos brag about a full scale BE4 making it to a test stand, is he behind Musk? Will Musk beat Bezos to the test stand with a engine for respective next vehicles?Pretty sure AR1 is at least 18+ months out and not sweating.Can anyone contradict this please?Oh, and could we somewhere do an engine comparative between the three and their best known stats. Thank you.
http://www.parabolicarc.com/2016/03/11/be4-engine-testing-update-jeff-bezos/
Is it possible to do staged combustion with a pintle?
Apologies in advance if I'm in the wrong place.That looks like a thrust plate, while Merlin is a pintle. I didn't find any information about what Raptor has.Is it possible to do staged combustion with a pintle?Thanks!
Quote from: Ronsmytheiii on 03/12/2016 12:43 pmhttp://www.parabolicarc.com/2016/03/11/be4-engine-testing-update-jeff-bezos/Apologies in advance if I'm in the wrong place.That looks like a thrust plate, while Merlin is a pintle. I didn't find any information about what Raptor has.Is it possible to do staged combustion with a pintle?Thanks!
Quote from: scanline on 09/06/2016 05:46 amApologies in advance if I'm in the wrong place.That looks like a thrust plate, while Merlin is a pintle. I didn't find any information about what Raptor has.Is it possible to do staged combustion with a pintle?Thanks!Don't think the current Merlin has a pintle injector. Could be wrong but pintles don't work to well with high chamber pressures (1000+ psi?), too much prop hitting the side wall leading to hot spot on the chamber wall. Suppose could get round this with greater local cooling, transpiration/film etc. Also seem to remember there was some IP issues with Mr Muellers former employer, so they switched to some variant of coax swirl.
Pintle preburner, interesting. The CFD picture they released of the preburner in their mailing list looked more "traditional" and text with it talked about injector elements. Along RD-170 lines, swirl injectors burning at normal mixture rations then diluted with extra oxygen. Assuming the picture is representative of what they are really working on of course.