> I would bet 30% of Spacex's innovation lies in that one engine. Musk often points out that the stage 0 work is harder (and I suspect more innovative) than th

> I would bet 30% of Spacex's innovation lies in that one engine. Musk often points out that the stage 0 work is harder (and I suspect more innovative) than the rocket (and engine) design. He also often mentions that fabrication is even harder. I.e., all the processes, tools, machines, etc. used to build all those engines and rockets is harder still than stage 0 -- one might even call it stage -1. It's possible that Raptor is not even closed to "30% of Spacex's innovation" :)