I’ve been reading up on this a bit. Apparently, the Vulcan Centaur is the ULA’s new rocket which replaces Russian RD-180 engines with BE-4s they sourced from Blue Origin. Blue Origin themselves are working on their New Glenn rocket which will use these engines. It’s interesting that the ULA (United Launch Alliance: Boeing and Lockheed’s rocket company) got to try them out first.

It’s also interesting that they are powered by methane. If I’m not mistaken, this is the first successful launch of a methane rocket? SpaceX’s Starship also uses methane engines. Apparently, they have a number of advantages over the more traditional kerosene. For example, they don’t leave any residue that can gunk up the works and affect reusability. I am not an expert on any of this, however, so feel free to correct me.