[zippy5]

I feel the opposite. My understanding is that BE-4 is hydrogen based rocket engine which really has never been executed successfully before where raptors are methane. Blue origin is going from 0 to 1 and space x is going from n to n+1. Obviously the short term results are going to be worse than Space X but I’m not convinced their engines will be worse.

That being said obviously ULA made the wrong deal since it’s not clear they will alive long enough to benefit from interplanetary refueling.

[CarVac]

BE-4 is methane too, and hydrogen has been done zillions of times before, including by Blue themselves (BE-3).

[nickik]

> BE-4 is hydrogen

BE-4 and Raptor are both Methalox:

A type of binary rocket fuel composed of liquid oxygen (lox) oxidizer and liquid methane combustible.

> which really has never been executed successfully before

A staged combustion cycle that is used by BE-4 has seen flight with kerolox (RP1 and oxygen) engines. Mostly Russian engines such as the historic NK-33 and current versions like the RD-180. In this version the pre-burner that drives the turbine uses very little fuel and a lot of oxygen and in the combustion chamber you mix gaseous oxygen with liquid fuel.

A staged combustion cycle has also been achieved in the US with the SSME or RS-25, the engine on the Space Shuttle. This engine was staged but in a very different way then. Important to know that this is a fuel rich engine, meaning that to drive the turbine (or rather turbines in this case) burn a little bit of oxygen with a lot of fuel leading to gaseous fuel and liquid oxygen being mixed in the main combustion chamber.

There has never been a flown version of either of these engines types using methalox.

SpaceX Raptor is even another step beyond either of these, refereed to as 'Full-Flow Staged'. In this version you have one fuel-rich and one ox-rich pre-burner and you end up mixing gaseous fuel with gaseous oxygen. This allows for much better mixing of propellants and thus a higher combustion rate and thus a higher efficiency.

> Blue origin is going from 0 to 1 and space x is going from n to n+1. Obviously the short term results are going to be worse than Space X but I’m not convinced their engines will be worse.

I think I explain above that this is incorrect understanding.

The BE-4 is a considerable worse engine then the Raptor. The Raptor is blowing it away in all key comparative metrics by a huge amount, if far more reusable, has a higher throttling range and is far cheaper to build.

The Raptor is evolving considerable faster then the BE-4, as Raptor 2.0 is already as far in development as BE-4 initial version. The Raptor 2.0 as a sea-level engine will almost match thrust of the BE-4 while being a far smaller engine.

It has to be understood that the BE-4 delivered to ULA will be considerably less capable then what they promised with BE-4. The removed a lot of features that are not needed by ULA in order to get this done. In order to fly their own New Glenn rocket, they will need to evolve the engine considerably.

The Raptor also has a Vacuum version, refereed to as RVac. In the initial presentation about NewGlenn, they presented a vecuum version of the BE-4 but that was scrapped very early.

In summation, BE-4 is a really nice engine but its at a technology level that is still below some of the Russian engines like the RD-180. The Raptor is a true next generation engine.

> That being said obviously ULA made the wrong deal since it’s not clear they will alive long enough to benefit from interplanetary refueling.

I am not sure what you are talking about. ULA has no interest in interplanetary travel and ULA will be around for quite some time.

Also, the BE-4 is strictly an engine used to launch from earth and only for the first stage, so your comment about interplanetary refueling makes no sense.

Maybe you are mixing up the BE-4 with the BE-3U, an upper stage engine they are also developing.