Author Topic: Blue Origin's BE-4 Engine  (Read 143101 times)

Offline rpapo

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Re: Blue Origin's BE-4 Engine
« Reply #40 on: 08/09/2016 02:53 PM »
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.
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?
I wasn't speaking of the BE-4 at all (and therefore was off topic).  I was referring to your comment about the greater plumbing requirements for the Merlin, or rather for the set of nine of them.  Their use case is different, so the comparison is not entirely fair.
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Re: Blue Origin's BE-4 Engine
« Reply #41 on: 08/09/2016 02:55 PM »
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.
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?
It was originally developed for Blue Origin's own vehicle. The deal with ULA came after.
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Offline Oli

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Re: Blue Origin's BE-4 Engine
« Reply #42 on: 08/09/2016 04:26 PM »
Actually, almost all methane engine designs proposed so far had lower ISP than high-ISP kerosene engines

I don't think so, which ones?

Offline Dante80

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Re: Blue Origin's BE-4 Engine
« Reply #43 on: 08/09/2016 04:37 PM »
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.

Even if you account for the extra weight for more feed lines and such, the thrust assembly should still be lighter (per kN installed). And we are talking about double the thrust here as per the coming uprate (so you would have to compare the assembly with something like the RD-171 based Zenit assembly).

The public info I have for RD-180 is a weight of 5,480 kg, and for the 9 Merlins the weight is around 4,230 kg with the actuators installed.
« Last Edit: 08/09/2016 04:46 PM by Dante80 »

Offline baldusi

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Re: Blue Origin's BE-4 Engine
« Reply #44 on: 08/09/2016 04:42 PM »
In 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.
Those were the MSFC that used that to dismiss anything not done by them (actually, their contractors under their supervision). That's how they stated with a straight face that Atlas V was risky while Ares I was the safest ever. Look what happened when they were taken out and the industry was left to decide.
Some went with gas generator (Space), but the rest went with ORSC. In fact, for the next step, SpaceX and KBKhA went with gas-gas implementations. There is a reason BE-4 is that, when it could have been fuel rich, for example.
Yes, the expansive energy of an ORSC turbine failure is something like 20 to 50 times that of a gas generator. But propulsion failure is LOM if you don't have engine out capabilities (and in many cases, even engine out won't cut it). No matter how "minimal" the catastrophic failure. LAS will (quite probably) save your crew exactly the same as long as the engine is turned off.
So I don't pay much attention to those naysayers. The rocket technology wars have a clear winner and the hero of that battle was the RD-180. BE-4 is probably more indebted to the RD-170 than to any other engine family.

Offline notsorandom

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Re: Blue Origin's BE-4 Engine
« Reply #45 on: 08/09/2016 06:53 PM »
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?

Offline baldusi

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Re: Blue Origin's BE-4 Engine
« Reply #46 on: 08/10/2016 12:17 AM »
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?
The RD-180V when it was designed for the Rus-M, used lower pressures. But that was due to the worse particle cleanness standard for the tanks on the Russian industry. The Atlas V version only added electronics for extra fault detection.
In fact, the RD-191 actually increased it so slightly. And RD-181 is actually same as RD-191. So they sort of increased it. Yes, the RD-0162/4 (KBKhA project) used lower chamber pressure. But was quite an increased when compared to previous models of the design bureau. And I'm kind of suspect of Voronezh's quality wrt NPO Energomash.

Offline Steven Pietrobon

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Re: Blue Origin's BE-4 Engine
« Reply #47 on: 08/10/2016 06:19 AM »
Regarding BE-4, here is what we know so far.

Propellants: LNG/LOX
Thrust: ~ 550,000 lbf
Chamber pressure: 1,950 psi
Cycle: ORSC (single shaft)
Isp:<311s SL, <338 vac. (for the booster variant in Vulcan)
TWR: <78
Re-usability: 25 complete missions, minimum.

If sea level thrust Fs = 2446.5 kN and the exit diameter of the BE-4 is De = 1.886 m (as measured from posted drawings), then the vacuum thrust is Fv = Fs + π De²/4 Pa = 2729.6 kN where Pa = 101.325 kPa is the sea level surface pressure. This means that if the Sea Level Isp is Is = 311 s, then the vacuum Isp must be Iv = Is*Fv/Fs = 347 s, quite a bit higher than the RD-180.

Using Pc = 13,445 kPa, an area ratio of Ar = (1.886/0.4)² = 22.22 and nozzle efficiency of 0.9418 (the same as the RD-180), the USAF Isp program gives an Iv = 337 s and Is = 302 s, which is less than the RD-180 with Iv = 338.4 s and Is = 311.9 s.
« Last Edit: 08/10/2016 07:42 AM by Steven Pietrobon »
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Re: Blue Origin's BE-4 Engine
« Reply #48 on: 08/29/2016 05:48 PM »
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.

Offline jongoff

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Re: Blue Origin's BE-4 Engine
« Reply #49 on: 08/29/2016 10:39 PM »
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.

Do we have more details on this Raptor engine going to the test stands than the one sentence from Gwynne's SmallSat talk? I know people are interpreting this as a fully-integrated, flight-like Raptor engine, but has SpaceX actually said that, or are we possibly reading things into that statement that they never explicitly claimed.

As for BE-4 status, I think the goal was to have the full-scale engine into testing this year, so ULA could make a downselect decision between AR-1/BE-4.

It's possible that SpaceX has caught up and passed Blue Origin with Raptor, but we're basing a lot off of a single sentence from a talk (unless there've been more details released since then).

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Offline scanline

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Re: Blue Origin's BE-4 Engine
« Reply #50 on: 09/06/2016 05:46 AM »
http://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!


Offline Steven Pietrobon

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Re: Blue Origin's BE-4 Engine
« Reply #51 on: 09/06/2016 06:06 AM »
Is it possible to do staged combustion with a pintle?

I don't see why not. Using a pintle is a method of injecting the propellants into the combustion chamber. Staged combustion is a method of pressuring the propellants before injection. I would have thought those two operations (injection and pressurisation) would be fairly independent of the method used.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline Nomic

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Re: Blue Origin's BE-4 Engine
« Reply #52 on: 09/06/2016 08:22 AM »
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!

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.

Offline baldusi

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Re: Blue Origin's BE-4 Engine
« Reply #53 on: 09/06/2016 05:59 PM »
http://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!
One characteristic of Raptor is that it is a full flow cycle. Thus, it needs three injectors: LOX-rich preburner, CH4-rich preburner and Main Combustion chamber preburner.
The preburners need to mix two liquids, but have a very un balance ratio (sometimes 50:1 O/F). When Muller worked on the TR-107 (I think), he used a pintle on the ORSC preburner (the RP-1 was injected in liquid form). So I would speculate that both preburners are pintle injectors.
Regarding the MCC injector, that's anybody's guess. Pintle should work fine, you are working with hot gases, so mixing should be a lot easier than with liquids. And the inertia is a lot less, too. But you need a big section because gas is a lot less dense than liquid (depending staged combustion on pressure 2 to 8 times less). Without knowing the subject, I would get the impression that Raptor could use pintle just fine.
But Raptor will also use a lot of 3D printing. Pintle are beautiful for machining on a lathe. But 3D printing is better suited for coaxial injectors.
In the end, it is anybody's guess, for now.

Offline baldusi

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Re: Blue Origin's BE-4 Engine
« Reply #54 on: 09/06/2016 06:01 PM »
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!

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.
As far as I understand it, you just have to change the mixing angle somewhat to take into consideration the higher pressure. And I think that the IP issues were resolved the old fashion way (i.e. licensing).

Offline Nomadd

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Re: Blue Origin's BE-4 Engine
« Reply #55 on: 09/06/2016 06:19 PM »
 I remember in the beginning, Musk wasn't too happy with the combustion efficiency with the "bloody pintle"

Offline mheney

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Re: Blue Origin's BE-4 Engine
« Reply #56 on: 09/06/2016 07:37 PM »
Let's keep this on the BE-4.  There are plenty of other places for discussing SpaceX engines ...

Offline baldusi

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Re: Blue Origin's BE-4 Engine
« Reply #57 on: 09/07/2016 01:10 AM »
Well, I wonder if they used a pintle injector in the preburner. Simplest, cheapest and most reliable.

Offline Nomic

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Re: Blue Origin's BE-4 Engine
« Reply #58 on: 09/07/2016 08:59 AM »
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.

Offline baldusi

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Re: Blue Origin's BE-4 Engine
« Reply #59 on: 09/07/2016 08:04 PM »
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.
Quite probable that they are pretty standard, then.

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