Author Topic: Blue Origin's BE-4 Engine  (Read 1148958 times)

Offline edkyle99

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Re: Blue Origin's BE-4 Engine
« Reply #80 on: 10/03/2016 12:27 am »
Not to mention BE-4's much lower chamber pressure gives a lot more confidence in its potential reliability.
I agree.  Reliability, not ISP or any other number, will largely determinate if these engines make the history texts or merely the footnotes. 

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Offline Space Ghost 1962

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Re: Blue Origin's BE-4 Engine
« Reply #81 on: 10/03/2016 12:43 am »
Not to mention BE-4's much lower chamber pressure gives a lot more confidence in its potential reliability.
I agree.  Reliability, not ISP or any other number, will largely determinate if these engines make the history texts or merely the footnotes. 

Reliability has nothing to do with confidence. Reliability is an intrinsic in a manufactured design that is proven on a test stand and confirmed with tear down and measurement. Over and over again. Test history. Flight history. Revisions.

Nothing you determine in the short term.

Offline arachnitect

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Re: Blue Origin's BE-4 Engine
« Reply #82 on: 10/03/2016 02:18 am »
Not to mention BE-4's much lower chamber pressure gives a lot more confidence in its potential reliability.
I agree.  Reliability, not ISP or any other number, will largely determinate if these engines make the history texts or merely the footnotes. 

Reliability has nothing to do with confidence. Reliability is an intrinsic in a manufactured design that is proven on a test stand and confirmed with tear down and measurement. Over and over again. Test history. Flight history. Revisions.

Nothing you determine in the short term.


...and there is little test history -and no flight history- of FFSC engines.

Offline Dante80

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Re: Blue Origin's BE-4 Engine
« Reply #83 on: 10/03/2016 02:29 am »


...and there is little test history -and no flight history- of FFSC engines.

Yes. And the same is true more or less for large methalox ORSC engines.

In the end though, one thing for me is clear. Raptor will be completed later than BE-4, and will probably also have a more complex and arduous development program. I get the vibe that Raptor is designed like a Ferrari, and  BE-4 like a Hummer... ;)

Not that it matters really. Both engines are designed for mass production, and hopefully both are going to have long and successful histories (fingers crossed). Those comparison stories (my rocket engine is better than yours!) are pretty boring I think.
 
« Last Edit: 10/03/2016 02:33 am by Dante80 »

Offline baldusi

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Re: Blue Origin's BE-4 Engine
« Reply #84 on: 10/03/2016 03:44 pm »
I don't believe that BE-4 was developed to Raptor's specifications. Also, we have companies that have lasted a 100 years exactly for avoiding the bleeding edge (e.g. Ford). I love Raptor's technology, but I wouldn't presume to know how the future will develop just because one technology appears superior to the other.
In fact, if you asked me which engine could be the best step to make a Raptor engine, I would say that BE-4 is quite probably the best bet. You have things like the RD-0164, that could probably match Raptor.
But KBKhA had a lot of experience on the expander cycle and ORSC. Only Aerojet Rocketdyne had that experience, and they wouldn't even start to think about something like that without a 3B contract from the US Government.

Offline Oli

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Re: Blue Origin's BE-4 Engine
« Reply #85 on: 10/03/2016 05:08 pm »
BO said it's doing a medium performance version of a high performance architecture. For reliability/reusability. SpaceX does a very high performance version of a very high performance architecture.

By the way, do we know why BO chose ORSC? It seems they want to avoid FRSC, which would preclude a FFSC architecture.
« Last Edit: 10/03/2016 05:08 pm by Oli »

Offline baldusi

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Re: Blue Origin's BE-4 Engine
« Reply #86 on: 10/03/2016 05:16 pm »
BO said it's doing a medium performance version of a high performance architecture. For reliability/reusability. SpaceX does a very high performance version of a very high performance architecture.

By the way, do we know why BO chose ORSC? It seems they want to avoid FRSC, which would preclude a FFSC architecture.

Well, the decision is very easy from a thermodynamics POV. The power to your turbines is (basically) specific heat * mass flow. Do the numbers for methalox and you get more power with ORSC. They wanted a cheap engine, and so they went with a single turbine.
Nothing prevents them from then developing a full flow engine on that base. In fact, it would be "relatively" easy. The FRSC circuit is the easiest.

Offline Space Ghost 1962

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Re: Blue Origin's BE-4 Engine
« Reply #87 on: 10/03/2016 08:24 pm »
Not to mention BE-4's much lower chamber pressure gives a lot more confidence in its potential reliability.
I agree.  Reliability, not ISP or any other number, will largely determinate if these engines make the history texts or merely the footnotes. 

Reliability has nothing to do with confidence. Reliability is an intrinsic in a manufactured design that is proven on a test stand and confirmed with tear down and measurement. Over and over again. Test history. Flight history. Revisions.

Nothing you determine in the short term.


...and there is little test history -and no flight history- of FFSC engines.
True also for the SSME when it was chosen for the Shuttle.

As for the RD270, 24 tests of (I think) 7 engines. Was at the time the most powerful engine on Earth.

Did not continue because the huge (super Proton) LV it was designed for was discontinued. In favor of N1, out of fear of a launch catastrophe for so much hypergolic propellant.

Oh, yeah BE-4 and AR-1 are first American ORSC engines too here. No American ORSC engines have ever been flown.

And ... some claim that FFSC, while more complex, is less risky because your dual preburner sides of the closed loop can be smaller and run at a lower relative pressure. So the true risk is in the injectors/combustion chamber.

If you have recent experience upping same in a prior engine, perhaps this is not such a big deal?

However, if you're dependent on materials technology to hold up for ORSC, it might take a while to perfect the recipe to reach enough of a preburner flow rate to match enough of a chamber pressure, without your parts being consumed in the process? The NK33 had considerable teething pains, along with its follow-on.

Have to consider ... what to be relentless about ... to achieve a reliable engine.

add:

Don't think I've ever been aware of any engine program ... that ever set out to design an unreliable engine  ::)

Would also think, that if you needed to gang large numbers of them together, rely on them for HSF, and require them to function with reuse, performing a function similar to the LM Ascent engine ... that reliability would be a significant requirement  :o

RS68's (and Merlin 1A) had ablative nozzles. As such, expendible limited life components ... so you might say limited reliability yield, I suppose ...

add:

Afraid we'll never know the truth about NK-33's reliability. Too much has happened to obscure it. And it appears to be in no one's interest to clarify that which remains to any great degree. Too many half truths ...
« Last Edit: 10/03/2016 10:04 pm by Space Ghost 1962 »

Offline pippin

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Re: Blue Origin's BE-4 Engine
« Reply #88 on: 10/03/2016 09:44 pm »
Well, NK-33 only had half the chamber pressure of Raptor so I'd say Raptors OR loop alone will probably be just as challenging as NK-33's from a materials perspective, especially considering that while the pressure differential and power output in the turbine might be comparable to NK-33 the actual pressure will still be twice as high.
« Last Edit: 10/03/2016 09:46 pm by pippin »

Offline Dante80

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Re: Blue Origin's BE-4 Engine
« Reply #89 on: 10/04/2016 12:08 pm »
BO said it's doing a medium performance version of a high performance architecture. For reliability/reusability. SpaceX does a very high performance version of a very high performance architecture.

By the way, do we know why BO chose ORSC? It seems they want to avoid FRSC, which would preclude a FFSC architecture.

I think they went for it since it would be a better choice than FRSC, as far as the propellant mix is concerned. FRSC cycles are almost completely devoted to Hydrolox engines.

Offline baldusi

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Re: Blue Origin's BE-4 Engine
« Reply #90 on: 10/04/2016 02:19 pm »
BO said it's doing a medium performance version of a high performance architecture. For reliability/reusability. SpaceX does a very high performance version of a very high performance architecture.

By the way, do we know why BO chose ORSC? It seems they want to avoid FRSC, which would preclude a FFSC architecture.

I think they went for it since it would be a better choice than FRSC, as far as the propellant mix is concerned. FRSC cycles are almost completely devoted to Hydrolox engines.
That is because with hydrolox you get something like 3 times more power to turbines by using FRSC than ORSC. On methalox, I think it was something like 30% more power by doing ORSC.
BTW, it is important to understand that instead of getting 30% more power you can decrease the delta-t by 30% and get cooler turbines. Both a big improvement for useful life and material reliability.

Offline baldusi

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Re: Blue Origin's BE-4 Engine
« Reply #91 on: 10/04/2016 02:34 pm »
Well, NK-33 only had half the chamber pressure of Raptor so I'd say Raptors OR loop alone will probably be just as challenging as NK-33's from a materials perspective, especially considering that while the pressure differential and power output in the turbine might be comparable to NK-33 the actual pressure will still be twice as high.
NK-33 was a breakthrough for the West. But the first ORSC Russian rocket engine was OKB-1's S1.5400, which powered the Molnyia rocket third stage, and was operation by 1960.
And the RD-270 has a Pc of 26.4MPa, only surpassed by Raptor.
And the RD-253 had a T/W of 125 and the original design (which was actually supposed to be used on the N-1) was from 1960.
The "famous" T/W of the NK-33 is actually a lie. It was for a fixed engine with no TVC. If you calculated the T/W for RD-253 in that way, it would be 200. And when Aerojet added a TVC, it ended up with a T/W of 77.
In that sense, the best operative engine in the world, right now, is the RD-170 family and (you might argue) the Merlin 1D. But the RD-170 has been operative for more than 30 years.

Offline Chris Bergin

Re: Blue Origin's BE-4 Engine
« Reply #92 on: 10/04/2016 08:09 pm »
Thread is about BE-4. Please use this thread only for that engine (or it annoys people and they send report to mod alerts).
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Offline Oli

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Re: Blue Origin's BE-4 Engine
« Reply #93 on: 10/05/2016 05:48 am »
BO said it's doing a medium performance version of a high performance architecture. For reliability/reusability. SpaceX does a very high performance version of a very high performance architecture.

By the way, do we know why BO chose ORSC? It seems they want to avoid FRSC, which would preclude a FFSC architecture.

Well, the decision is very easy from a thermodynamics POV. The power to your turbines is (basically) specific heat * mass flow. Do the numbers for methalox and you get more power with ORSC. They wanted a cheap engine, and so they went with a single turbine.
Nothing prevents them from then developing a full flow engine on that base. In fact, it would be "relatively" easy. The FRSC circuit is the easiest.

Thanks!

I found this explanation in a paper (http://www.rocket-propulsion.info/resources/articles/LPRE.pdf):

Quote
For  staged  combustion  cycles,  the  pressure  cascades
resulting  from  thrust  chamber  cooling  and  turbopump
power  requirements  are  compared  in  Figure  8  taking
LOX-methane  as  example.  The  pumping  requirements
are  lower  for  the  cycle  using  a  oxidizer-rich  preburner,
because no fuel is rerouted to the preburner after passing
through  the  thrust  chamber  cooling  channels.  The  small
amount of fuel required for the preburner is delivered by
a low-powered kick stage.

The    fuel-rich    cycle    results    in    higher    fuel-pump
requirements and requires an additional LOX-kick-stage,
while  the  ox.-rich  cycle  results  in  similar  lower  pump
requirements    without    a    kick-stage.    The    preburner
pressure is also lower in the ox.-rich cycle. However, the
oxygen-rich environment of the preburner gas may cause
additional complexity for the turbines as well as for hot-
gas lines and valves.

Is this what you meant?
« Last Edit: 10/05/2016 05:52 am by Oli »

Offline baldusi

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Re: Blue Origin's BE-4 Engine
« Reply #94 on: 10/05/2016 12:32 pm »
Looking at it from another side, but yes. They are talking about the results.

Offline TrevorMonty

Re: Blue Origin's BE-4 Engine
« Reply #95 on: 10/05/2016 01:46 pm »
There is a fuel difference between BE4 and Raptor. BE4 is designed to use LNG while Raptor uses liquid methane (99% ?). How it affects engine design I'm not sure.

"Natural gas consists almost entirely of methane (CH4), the simplest hydrocarbon compound. Typically, LNG is 85 to 95-plus percent methane, along with a few percent ethane, even less propane and butane, and trace amounts of nitrogen"

With a large RLV fuel price starts to become significant part of operating costs. Blue have decided to use lower performing engine with cheaper fuel.

Offline spacenut

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Re: Blue Origin's BE-4 Engine
« Reply #96 on: 10/05/2016 02:10 pm »
LNG and liquid methane are essentially the same thing.  During liquification, some impurites are drawn out.  LNG is about 95% methane.  At least it was with the company I worked for.  I've never heard of 85% unless it is at the well head and there it is separated out for 95% injected into transmission lines around the country. 

During chill down, some impurities like propane and butane can be separated out.  Propane liquifies at only about 10 lbs. leaving the methane.  Butane is similar.  Nitrogen will be heavier and settle to the bottom of methane in gas state.  Not that hard to separate during liquification of methane.  It might do it naturally during the process. 

Offline Dante80

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Re: Blue Origin's BE-4 Engine
« Reply #97 on: 10/05/2016 02:49 pm »
There is a fuel difference between BE4 and Raptor. BE4 is designed to use LNG while Raptor uses liquid methane (99% ?). How it affects engine design I'm not sure.

I might be wrong, but SpaceX may need neat methane due to their goal of chilling it more.

Offline AncientU

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Re: Blue Origin's BE-4 Engine
« Reply #98 on: 10/05/2016 04:36 pm »
There is a fuel difference between BE4 and Raptor. BE4 is designed to use LNG while Raptor uses liquid methane (99% ?). How it affects engine design I'm not sure.

I might be wrong, but SpaceX may need neat methane due to their goal of chilling it more.

I've been assuming all along that they'll purify the LNG to avoid separation/icing from the heavier elements.
"If we shared everything [we are working on] people would think we are insane!"
-- SpaceX friend of mlindner

Offline baldusi

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Re: Blue Origin's BE-4 Engine
« Reply #99 on: 10/05/2016 05:55 pm »
I think I remember Bezos stating that he said LNG to make things simple for the layman, but they were going to use liquid methane.

 

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