the only use case I can think of for the rocket body 3d printing, combined with methane engines, is a something weird: fly to mars with a 3d printer and some te

the only use case I can think of for the rocket body 3d printing, combined with methane engines, is a something weird: fly to mars with a 3d printer and some technology to extract iron from the sand and methane from the atmosphere and build multiple rockets there to fly something useful back to Earth. But that's such a big leap of imagination.