SpaceX Merlin 1D

The SpaceX turbopump was an entirely new, clean sheet design contracted to Barber-Nichols, Inc. in 2002 who performed all design, engineering analysis, and construction; the company had previously worked on turbopumps for the RS-88 (Bantam) and NASA Fastrac engine programs. The Merlin 1A turbopump used a unique friction-welded main shaft, with Inconel 718 ends and an integral aluminum RP-1 impeller in the middle. The turbopump housing was constructed using investment castings, with Inconel at the turbine end, aluminum in the center, and 300-series stainless steel at the LOX end. The turbine was a partial-admission (i. e. , working fluid is only admitted through part of the rotation of the turbine; an arc not the whole circumference) impulse design and turned at up to 20,000 rpm, with a total weight of 150 lb. [citation needed]