Author Topic: Blue Origin's BE-4 Engine  (Read 124356 times)

Offline mn

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Re: Blue Origin's BE-4 Engine
« Reply #420 on: 09/11/2017 04:24 PM »
....The seafloor is littered with Atlas/RD-180 stages, grabbing one on the sly would be easy, and maybe even legal...

Matthew

Finding a living person who worked on these engines might be easier and might even give better results ;)

Offline Nomadd

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Re: Blue Origin's BE-4 Engine
« Reply #421 on: 09/11/2017 04:33 PM »
We've all been discussing whether Blue's BE-4 or Aerojet's AR-1 will be the Vulcan's engine... assuming that both will have successful development programs.  It is possible that neither will develop a reliable ORSC engine in the next five years (or ever).

Maybe that's why ULA is buying RD-180s to cover Atlas-V flights out to mid-2020s...
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.
Do you have any information about the reason for their failure or are you just spreading FUD?
It's kind of obvious that a failure caused by interpropellant seal wouldn't have happened is there was no such seal.
« Last Edit: 09/11/2017 04:33 PM by Nomadd »

Online Ictogan

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Re: Blue Origin's BE-4 Engine
« Reply #422 on: 09/11/2017 04:34 PM »
We've all been discussing whether Blue's BE-4 or Aerojet's AR-1 will be the Vulcan's engine... assuming that both will have successful development programs.  It is possible that neither will develop a reliable ORSC engine in the next five years (or ever).

Maybe that's why ULA is buying RD-180s to cover Atlas-V flights out to mid-2020s...
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.
Do you have any information about the reason for their failure or are you just spreading FUD?
It's kind of obvious that a failure caused by interpropellant seal wouldn't have happened is there was no such seal.
But is there any information on whether the failure had anything to do with the interpropellant seal?

Offline pippin

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Blue Origin's BE-4 Engine
« Reply #423 on: 09/11/2017 06:16 PM »
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?

« Last Edit: 09/11/2017 09:08 PM by Chris Bergin »

Offline envy887

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Re: Blue Origin's BE-4 Engine
« Reply #424 on: 09/11/2017 08:44 PM »
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?

Nomadd's point was that FFSC by design cannot possibly have an inter-propellant seal failure, since it does not have such a seal.

AIUI the powerpack testing necessarily requires the interpropellant seal, since the powerpack includes the oxidizer rich turbine driving both pumps.

Offline john smith 19

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Re: Blue Origin's BE-4 Engine
« Reply #425 on: 09/11/2017 11:02 PM »
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.
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.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline Space Ghost 1962

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Re: Blue Origin's BE-4 Engine
« Reply #426 on: 09/12/2017 01:24 AM »
Suggest different ambitions for chamber pressure drove the BO/SX design choices.

For SX, the ambition was for a high chamber pressure from the very start, to gain a very compact engine with higher than Merlin TWR. For more power, they'd scale the entire engine to meet requirement.

For BO, the ambition was for a low chamber pressure so as to have a 'good enough", quick win to get engines into a vehicle quickly. Then, like with Merlin's relentless cycle of improvements, they'd push up the chamber pressure on subsequent revisions of uprating.

The choice of the higher chamber pressure drove the need for FFSC. The lower pressure engine could be simpler in design, so bearings and other considerations could take into account less wear in operation, thus the selection of ORSC. Perhaps they did not see the interpropellant seal as much of a challenge? Possibly because the propellant's nature offered the expectation of manageable partial combustion mass flows, less chaotic than kerolox/hydrolox?

This is where scaling makes things less predictable in practice.

Offline mgeagon

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Re: Blue Origin's BE-4 Engine
« Reply #427 on: 09/12/2017 02:55 AM »
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.
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.

Offline john smith 19

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Re: Blue Origin's BE-4 Engine
« Reply #428 on: 09/12/2017 06:26 PM »
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.
This is one of those "in theory no, in practice yes" problems that most real engines do have to do.

Rocket engine design 101.
IRL nearly all big engines are driven by propellants pressurized by a pair of pumps.
Those pumps are nearly always driven by turbines.
Those turbines are nearly always driven by a stream of combustion gases which, for either performance or thermal management reasons is rich in one of the propellants. Therefore the seal between that turbine, and the opposite propellant whose pump it's driving, is always a criticality 1 failure point.  :(

That said Soyuz uses a turbopump propelled by an Oxygen rich steam flow from the breakdown of Hydrogen Peroxide (so possible issue with it pumping fuel) and the RL10 uses "hot" GH2 (actually about -58c, which is hot by the standards of LH2 :) ) but the LOX pump is driven through a gearbox.

The key issues with these systems are a) What's the pressure difference between the 2 sides (ihigher is tougher)  and b)Can the interseal space be vented, and if so where to?

In reality I'm not sure I've ever heard of an engine RUD traced to a seal leak. What it does do is add mechanical complexity and the need for either inert gas gas or a vacuum (well a low pressure region to suck the inter seal gap into) source. Only things like the dual expander "Broadsword" of Masten or the GHe drive of SABRE avoid these problems but most people (especially the Russian ORSC engines) cope with them without a major problem
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline su27k

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Re: Blue Origin's BE-4 Engine
« Reply #429 on: 09/15/2017 03:50 AM »
https://twitter.com/JeffBezos/status/908124621391618050

The tweet has nothing to do with space, but I think that's a (partially assembled) BE-4 in the background.

Offline mgeagon

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Re: Blue Origin's BE-4 Engine
« Reply #430 on: 09/15/2017 08:12 AM »
https://twitter.com/JeffBezos/status/908124621391618050

The tweet has nothing to do with space, but I think that's a (partially assembled) BE-4 in the background.

Combustion chamber, nozzle and bell. Could be headed to "one" of the powerpacks for mounting. Might be a good sign that testing is underway again.

Offline ChaoticFlounder

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Re: Blue Origin's BE-4 Engine
« Reply #431 on: 09/15/2017 11:36 PM »
A couple things:

First, do we know from Blue Origin any information other than "a powerpack failed on the test stand?"

Second, can you give clarity on what defines the line between a "Full Flow" Staged Combustion engine and a "Regular" Staged Combustion engine?

Third, turbine drive engines will usually have an "interpropellant seal" somewhere, save FFSC designs that I have seen to date.  Merlin should have one, F-1 had one, SSME has one, RL-10 should have one somewhere.  To my knowledge, it is not possible to get a perfect seal.  Even valves that are stationary have a minute leak rate.  It gets a little more difficult when you have a shaft spinning at 15,000 RPM and this is what drives the need for the inert gas.

C

Oh, edited to attach some interesting info about some things that can go wrong...
« Last Edit: 09/15/2017 11:50 PM by ChaoticFlounder »

Offline brickmack

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Re: Blue Origin's BE-4 Engine
« Reply #432 on: 09/16/2017 04:41 AM »
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

Offline ChaoticFlounder

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Re: Blue Origin's BE-4 Engine
« Reply #433 on: 09/16/2017 05:54 AM »
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

Eh, have a look at the presentation attached below.  It seems that around 76% (which surprised me, i thought it was less) of the fuel goes to the two preburners and the rest is used for cooling and then ends up in the MCC (PDF Page 25-26, Labeled Page 19-20).  I'm saying this because you said "all".

The reason I keep talking about the SSME here is it is a FRSC engine and it has 2 high pressure turbo pumps which run on the FRSC cycle, 1 LPHTP that runs on expander, and 1 LPOTP that runs off of high pressure lox discharge from the HPOTP.  What I haven't seen made very clear in the forums above is that FFSC and FRSC / ORSC are more similar than they are different.  Staged combustion (FRSC / ORSC) can come in a myriad of pump combinations as seen above and is not limited to a one-shaft turbopump like BO chose to use.  That was a design choice they chose to make.

Also, there is an interesting bit in the attached PDF on shaft seals (PDF Page 70-71, Labeled Page 64-65).  This will give you an idea of the general design intent of it and how one may go about it.  I can speculate BE-4 may have a similar architecture, it may not... same goes for Space X's Merlin...

Let me know if you have any questions or if I didn't explain something well.

C


Offline yokem55

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Re: Blue Origin's BE-4 Engine
« Reply #434 on: 09/16/2017 01:52 PM »
This article on the study done to convert the SSME to FFSC in the early 80's makes for an interesting, although one-sided, comparison of FFSC and FRSC.

http://www.eaglehill.us/programs/journals/spaevo/2015a1/

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