The propulsion system that will take the Orion spacecraft beyond the moon and back is nearing completion, NASA reported.

A major flight hardware assembly at United Launch Alliance’s Decatur, Ala., facility was finished about a week ago. The Boeing-designed interim cryogenic propulsion stage, the piece in question, is a liquid oxygen/liquid hydrogen system that will give Orion an extra push on the first unmanned flight of the spacecraft with the brand-new Space Launch System. This proving-ground mission for deep-space flight will test the rocket’s endurance beyond the moon and back. The unmanned launch is expected sometime in 2018.  

With this flight hardware portion complete, the ICPS has more steps to go, including avionics installation at the Decatur facility. The system will the travel by barge and road to the Delta Operating Center in Cape Canaveral for avionics and system-level testing. Final delivery to NASA is expected in mid-2017.