3d printing rocket parts and liquified natural gas could also dramatically lower launch costs

Reusable rockets could greatly lower rocket launch costs but two other significant emerging technologies are 3D printing and liquified natural gas rocket fuel. Liquefied natural gas, which is a commercially available form of methane, could have several advantages as a rocket fuel.
Blue Origin has said its wide availability and low cost would enable an "extended engine development test program." Methane is also clean, meaning it’s less likely to clog fuel lines inside the engine. That would reduce the type of rigorous cleaning needed to clear those particulates and make it easier for reusability, said Ann Karagozian, UCLA professor of mechanical and aerospace engineering.
The gas also self-pressurizes, which could eliminate the need for tank-pressurization systems. The combination could enable a simple, reliable design that is easy to manufacture. It could be a game changer. SpaceX is also developing a liquid-oxygen-and-methane staged combustion engine called Raptor.
3D printing: Additive manufacturing, commonly known as 3D printing, can substantially reduce the time and cost of producing rocket parts.
Take the main oxidizer valve body in one of the SpaceX Falcon 9 rocket engines, for example. The part, which controls the flow of oxygen into the engine, was produced through 3-D printing in less than two days and launched on a Falcon 9 in 2014. That marked the first time that SpaceX flew a 3-D printed part. Normally, that process would have taken months, the company said in a blog post at the time.
SpaceX said that compared with a traditionally cast part, the printed valve body had "superior strength, ductility and fracture resistance." After undergoing a rigorous test program, the 3D printed part was qualified to fly interchangeably with cast parts on all Falcon 9 missions, the company said.
Additive manufacturing has been used for individual parts and components up to SpaceX’s SuperDraco engine chamber for the Dragon Version 2 spacecraft and Aerojet’s demonstration rocket engine. The SuperDraco engine chamber was printed in Inconel, a superalloy. The engines will power a launch escape system.