“It’s a long way from taking on Blue Origin or SpaceX, but UK startup Orbex is confident enough to show off its Prime Rocket’s second stage. Inside the engineering prototype’s shell is what it claims is the “world’s largest” 3D printed rocket engine, which is also designed to run on bio-propane, a renewable fuel source. The rocket itself is made of a carbon fiber and aluminum composite that’s supposed to be 30 percent lighter than any other vehicle in its category…”

Source: http://www.impactlab.net/2019/02/15/take-a-look-at-the-worlds-largest-3d-printed-rocket-engine/