The basic principles of the Fastrac design (namely, a pintle injector and ablatively cooled chamber) lived on in SpaceX's Merlin 1A engine, which used a turbopump from the same subcontractor.[18] The Merlin-1A was somewhat larger with a thrust of 77,000 lbf (340 kN) versus 60,000 lbf (270 kN) for Fastrac. The same basic design was capable of much higher thrust levels after upgrading the turbopump. Variants of the Merlin-1D achieve 190,000 lbf (850 kN) of thrust as of May, 2018,[19] though the combustion chamber is now regeneratively cooled.[20]