They are currently developing a larger engine, Raptor, which is intended for their Mars project and possibly for an upper stage for the Falcon family.  But it&#x27;s not a plug-and-play replacement for the Russian RD-180. (Nor is Blue Origin&#x27;s BE-4, which is what ULA currently plans to use to effectively replace the RD-180 -- but only by building a substantially new Rocket, the Vulcan, around the BE-4, to replace their current Atlas V.)<p>BTW, as others have noted, &quot;heavy lift&quot; is more often used to characterize whole rockets than individual engines -- and the current American leader in that category (until SpaceX finally launches Falcon Heavy) is the Delta IV heavy, powered by three RS-68s, each of which nearly matches the thrust of an RD-180.  (And yet isn&#x27;t a drop-in replacement for numerous reasons, starting with use of different fuels.)