Oh, Nomadd is right, they only tested the power pack, right? No interpropellant seal, no main propellant flow, no main propellant flow related failure modes. So how could the failure be related to the interpropellant seal?So again: how about stopping to spread FUD?
FFSC has the potential to be much more reliable than both ORSC which the BE-4 uses and FRSC as it eliminates the interpropellant seal which is a potential serious failure mode. The failure of the BE-4 powerpack may have been caused by unwanted propellant mixing causing an explosion. Such a failure would not have happened if BO had selected FFSC for BE-4. Hopefully they will learn their lesson and use FFSC for their next engine after BE-4 which NA will use. FFSC at BE-4's Pc should be extremely reliable.
Quote from: DJPledger on 09/10/2017 07:21 pmFFSC has the potential to be much more reliable than both ORSC which the BE-4 uses and FRSC as it eliminates the interpropellant seal which is a potential serious failure mode. The failure of the BE-4 powerpack may have been caused by unwanted propellant mixing causing an explosion. Such a failure would not have happened if BO had selected FFSC for BE-4. Hopefully they will learn their lesson and use FFSC for their next engine after BE-4 which NA will use. FFSC at BE-4's Pc should be extremely reliable.Quite true in theory.However I've seen quite a few Aerojet design studies in the archives and they really did love the FFSC cycle (along with really high O/F ratios) Yet when Congress (through the USAF) put money on the table what did they go for?BTW the SSME was an FRSC and in flight I don't think it ever suffered an interpropellant seal failure.What FFSC would have done would have eliminated one of those large 300lb GHe tanks, radically improving the T/W ratio. BTW part of their size was because the seal leakage was about 3-4x what it was forecast to be. Modern seal designs (EG the brush) can deliver the leakage rates that the SSME was originally expected to have, using the simplistic models available at the time of its initial specification.
IIRC, The SSME used a continuous flow of GHe through the turbine shaft cavities to expel preburned H to mitigated the leakage. It is one of the many reasons the engines needed extensive refurbishment between each mission and increased total weight of the orbiter due to the additional helium and tanks required. Refurbishment is not a concern with the RS-25s going into the SLS for obvious reasons. While many rocket designs utilize helium purges to remove explosive gases during shutdown, for example, it does not seem likely any modern engine developer would wish to include this type of interseal redundancy scheme.
https://twitter.com/JeffBezos/status/908124621391618050The tweet has nothing to do with space, but I think that's a (partially assembled) BE-4 in the background.
No such thing as a "regular" staged combustion engine. Either fuel rich, oxidizer rich, or full flow. Fuel rich, all of the fuel goes through the turbine and a small amount of it is burned with a small amount of the oxidizer, that combustion spins the pump to push oxidizer through the engine while the hot gassified fuel goes into the main combustion chamber and burns with the still liquid oxidizer. Ox rich is basically the same but the other way around. With both of these, you need an interpropellant seal because both propellants are going through the same turbopump, just on different sides, and if they interact before getting to the combustion chamber, boom. Full flow staged combustion has 2 totally separate turbopumps, where all of the fuel goes through one pump and all of the oxidizer goes through the other, excepting the tiny amount of the opposite needed by each for combustion in the turbopumps (hence, full flow), and both propellants are fully gassified when they go into the chamber. Since the propellants go through totally separate pumps, theres no need for a seal. Dual expander engines don't need a seal either for a similar reason, though to date no such engine has flown
Time for a bump. With less than a week to IAC 17, if there is significant progress (good news) on BE-4, I would expect to hear early next week. If nothing to report, I will start to be concerned. They did start the test program hardware rich.
Quote from: testguy on 09/23/2017 07:27 pmTime for a bump. With less than a week to IAC 17, if there is significant progress (good news) on BE-4, I would expect to hear early next week. If nothing to report, I will start to be concerned. They did start the test program hardware rich.I think we all hope to see something new from Blue. What I think we are all worried about is that they had to make a design change that sent all of the extra hardware to the scrap bin. (i.e. maybe switching from hydrostatic bearings to more conventional ball and roller bearings like the ssme turbomachinery uses.)Like has been stated before, only time will tell.C
Quote from: ChaoticFlounder on 09/24/2017 03:34 pmQuote from: testguy on 09/23/2017 07:27 pmTime for a bump. With less than a week to IAC 17, if there is significant progress (good news) on BE-4, I would expect to hear early next week. If nothing to report, I will start to be concerned. They did start the test program hardware rich.I think we all hope to see something new from Blue. What I think we are all worried about is that they had to make a design change that sent all of the extra hardware to the scrap bin. (i.e. maybe switching from hydrostatic bearings to more conventional ball and roller bearings like the ssme turbomachinery uses.)Like has been stated before, only time will tell.CThere is no need to be worried as BO have more than enough money to afford a redesign of the BE-4 and they are not in any particular rush to do anything. Hopefully we will get something new on BE-4 during IAC2017.
But its a problem for ULA, which needs to downselect engine for Vulcan ASAP.
Quote from: ChaoticFlounder on 09/24/2017 08:32 pmQuote from: Rebel44 on 09/24/2017 08:04 pmBut its a problem for ULA, which needs to downselect engine for Vulcan ASAP.You are right, it's times like these that big boy decisions get made and we get to see what Tory Bruno is made of .P.S. - I don't doubt his ability one bit, I'm watching and hope I can learn something about leadership from this...Don't put too much stock on that. He's just as human, and the ULA "parents" are about as coldly pathological as any. He cares about the survival of ULA long term, which was why attempting BE-4 was an extremely good idea, but there's only so long that he can wait before "falling back" to AR-1 becomes necessary.The "parents" believe they can twist AJR's arm enough, for a marginally successful ULA. Perhaps they will learn to become immune to "iocane poison"?
Quote from: Rebel44 on 09/24/2017 08:04 pmBut its a problem for ULA, which needs to downselect engine for Vulcan ASAP.You are right, it's times like these that big boy decisions get made and we get to see what Tory Bruno is made of .P.S. - I don't doubt his ability one bit, I'm watching and hope I can learn something about leadership from this...
Meyerson: we have made “measurable progress” on BE-4 engine this year, with more engines in the pipeline. #IAC2017