Aren't you jumping the gun.

"The key to Relativity Space’s success is none other than an unassuming piece of machinery: the 3D printer." Success in raising money is important but real success is actually delivering payloads to orbit at a lower cost. Another note-if you are reusing your rocket how fast and simply you can make them becomes less important.

Regarding:

"The finished product retains the rough bumpy texture of 3D printed items but can be machined down to look indistinguishable from regular metal. And the texture does add 5–10% more mass to the rocket, but this doesn’t put the 3D printed rockets at an aerodynamic disadvantage compared to their traditional counterparts." Mixing mass fraction with aerodynamic performance is flawed reasoning. Do you understand how much money, time and effort a rocket designer would be willing to expend to reduce the dry mass of his rocket 5-10%? It is considerable. In addition to the penalty imposed by the bumpy texture, 3D printed materials have lower material properties than friction stir welded high strength alloys. I am pretty sure the mass penalty for 3D tanks vs. other flight proven fabrication techniques is much more than the stated 5-10%. I wish them success but almost all of the new space startups over promise and under deliver. Even the legacy rocket builders over promise and under deliver. Don't believe anyone's hype.

TEK