The Competition of the Methalox engines

[Robotbeat]

Agreed totally. I think the reason Blue may have gone for staged combustion is because they thought they could handle it and that it was a necessary long term investment in what they wanted to achieve anyway.


Additionally, they were shooting for competing with RD-180 (although I’m not sure if that was a consideration early enough to influence their choice). A gas generator methalox engine might actually have no greater Isp than the RD-180 but would have the density penalty of methalox (kerolox is denser).

If you have effectively unlimited funding (as Blue kind of has) it’d feel way too tempting to choose staged combustion over gas generator.

EDIT: The TQ-12 is a gas generator first stage methalox engine for Landspace. It has a vacuum Isp of just 337s, the same or slightly lower than RD-180’s 338s Isp. It’s tough to see ULA wanting to switch to methalox if they have to take a performance hit.

[edzieba]

At the time BO started BE-4 development (2011) Raptor was still a notional Hydrolox staged-combustion engine, and only moved to Methalox in 2012. BO were in the position where they had the 'head start' in development, a cycle that was flight-proved (albeit not with that particular propellant), and likely assumed that if they were having a hard time with a 'mere' ORSC engine, the harder FFSC Raptor would take even longer. The wild spec changes of the early Raptor and the initial sub-scale testing probably strengthened that idea. By the time Raptor emerged as an engine sufficiently advanced to fly vehicles on - albeit one still in development - BO were locked into BE-4's design and had a supplier contract forcing them to deliver on the 2014-era specifications.
Reneging on the ULA supply contract is not even worth considering as an option, so they're stuck building BE-4 as it stands. And if they're building it, they may as well use it for New Glenn, even if they think a different design would be better in the long run, because they need something ASAP.

[JayWee]

At the time BO started BE-4 development (2011) Raptor was still a notional Hydrolox staged-combustion engine, ...

Is it even possible to do hydrogen FFSC or was it FRSC ?

[meekGee]

...
Blue on the other hand almost seems like they got an inverted Pareto principle on the BE-4… An ORSC engine with only 134 bar (only about 20% higher than Merlin FT) of chamber pressure is like 80% of the engineering hassle of Raptor with 20% of the benefits…

Asymmetrical warfare...

This too should have been a very short thread.

[trimeta]

...
Blue on the other hand almost seems like they got an inverted Pareto principle on the BE-4… An ORSC engine with only 134 bar (only about 20% higher than Merlin FT) of chamber pressure is like 80% of the engineering hassle of Raptor with 20% of the benefits…

Asymmetrical warfare...

This too should have been a very short thread.

Perhaps the real question should be "how well do each of these engines meet the needs of their respective projects?", rather than directly comparing them to each other. Although there's no particular reason such a question would belong in the Blue Origin subforum in particular.

[edzieba]

At the time BO started BE-4 development (2011) Raptor was still a notional Hydrolox staged-combustion engine, ...

Is it even possible to do hydrogen FFSC or was it FRSC ?

It was FRSC.

[Lemurion]

...
Blue on the other hand almost seems like they got an inverted Pareto principle on the BE-4… An ORSC engine with only 134 bar (only about 20% higher than Merlin FT) of chamber pressure is like 80% of the engineering hassle of Raptor with 20% of the benefits…

Asymmetrical warfare...

This too should have been a very short thread.

Perhaps the real question should be "how well do each of these engines meet the needs of their respective projects?", rather than directly comparing them to each other. Although there's no particular reason such a question would belong in the Blue Origin subforum in particular.

I'm not sure why it had to be in this subforum either.

Speaking to your question, which I agree is far more relevant, I would say that both Raptor and Archimedes appear to be meeting the requirements of their respective projects fairly well. I'm less convinced regarding BE-4 as it has to balance ULA's requirements for Vulcan against Blue's internal requirements for New Glenn.

[ZachF]

At the time BO started BE-4 development (2011) Raptor was still a notional Hydrolox staged-combustion engine, ...

Is it even possible to do hydrogen FFSC or was it FRSC ?

FFSC is possible on hydrolox, it’s just not as huge of a performance boost as the hydrogen requires like 80% of the pump power anyway.

Even though Methalox requires slightly higher pump power for the oxygen as the methane, you could have probably designed a higher chamber pressure FRSC engine with less of an engineering headache as ORSC (no hot oxygen-rich gas).

I’m not sure if FFSC is possible with kerolox as you’d probably get coking problems on the kerosene side.

[Zed_Noir]

<snip>
I’m not sure if FFSC is possible with kerolox as you’d probably get coking problems on the kerosene side.

Is there any practical way to reduce the kerosene coking? Presuming a higher than usual development budget.

[zubenelgenubi]

Moderator:
Thread moved to Commercial Space Flight General board.

[Purona]

SpaceX needed a high thrust, high isp engine. An engine that worked well at both Sea Level and in a Vacuum. A Full Flow Staged Combustion engine was the right choice for them

Blue Origin just needed a first stage booster engine that could serve the, at the time, payloads and future payloads for LEO/GTO/Direct GEO. The Version 1 BE-4 engine with two variants and the version 2 BE-4 engine with a single variant serves those payloads.

There was no need for Blue Origin to build a full flow staged combustion engine when the BE-4 is perfectly capable of serving every mission so far while being reusable .... on paper.

At the moment the BE-4 doesn't need to be more powerful it needs to be more reusable, reliable, cheaper and easier to maintain

[rakaydos]

Looks like moving this thread to a more active forum was it's death knell.

[CorvusCorax]

Theres an old Be4 vs Raptor thread in the SpaceX section that despite all odds did not end up getting axed. It's not been active lately, but it has some interesting comparison data, at least on  the two main contestants.

https://forum.nasaspaceflight.com/index.php?topic=47513.0

[Tywin]

Is the BE-4 the most powerful methalox engine now?

https://twitter.com/torybruno/status/1533912186225049600

[trimeta]

Is the BE-4 the most powerful methalox engine now?

https://twitter.com/torybruno/status/1533912186225049600

That tweet was deleted, and corrected with the following, which suggests that its thrust hasn't changed from previously reported. Which has always been higher than the proposed thrust for Raptor...although Raptor 2 is closing in on that value.

https://twitter.com/torybruno/status/1534158256431681536

[edzieba]

550klbf = 2.5MN (or ~250 tonnes-force to be awkward).
For comparison, latest Raptor 2 number was "245 tons", which could be 245 tonnes or 222 tonnes (so 2.4MN or 2.18MN respectively).

Just use Newtons, please!

[edzieba]

550klbf = 2.5MN (or ~250 tonnes-force to be awkward).
For comparison, latest Raptor 2 number was "245 tons", which could be 245 tonnes or 222 tonnes (so 2.4MN or 2.18MN respectively).

Just use Newtons, please!

emphasis mine
Just a small typo
245 tons or 222 tonnes

Nope, I meant what I wrote. 245 tonnes (metric tons) = 222 tons (long tons), but it seems that the US uses a different ton (short tons) which would be 270 tons (short tons). ::EDIT:: Argh, other way around: 245 short tons = 222 tonnes, but 245 long tons = 250 tonnes. I hate non-SI units!

Another reason to use Newtons when the same phoneme can mean 3 entirely different units!

[JayWee]

Musk said in the ED interview he likes tones because he can see t/w immediately. So I suspect he meant metric tones.

[Robotbeat]

Note that power is thrust times exhaust velocity (i.e. basically Isp in proper units), so we can't tell if BE-4 is more powerful or not without that Isp figure. It's too close.

[Hog]

550klbf = 2.5MN (or ~250 tonnes-force to be awkward).
For comparison, latest Raptor 2 number was "245 tons", which could be 245 tonnes or 222 tonnes (so 2.4MN or 2.18MN respectively).

Just use Newtons, please!

emphasis mine
Just a small typo
245 tons or 222 tonnes

Nope, I meant what I wrote. 245 tonnes (metric tons) = 222 tons (long tons), but it seems that the US uses a different ton (short tons) which would be 270 tons (short tons). ::EDIT:: Argh, other way around: 245 short tons = 222 tonnes, but 245 long tons = 250 tonnes. I hate non-SI units!

Another reason to use Newtons when the same phoneme can mean 3 entirely different units!

Apologies, I thought you were attempting to convert tonnes to tons, but incorrectly wrote tonnes twice, the error was in my comprehension.