Status: Hardware. Date: 2000-2004. Thrust: 378.04 kN (84,987 lbf). Specific impulse: 300 s. Specific impulse sea level: 270 s. Burn time: 169 s.
SpaceX Merlin engine was developed internally at SpaceX, but drew on pintle injector concepts developed at TRW for the lunar module descent stage engine. Propellant was fed via a single shaft, dual impeller turbopump operating on a gas generator cycle. The turbo-pump also provided the high pressure kerosene for the hydraulic actuators, which then recycled into the low pressure inlet. This eliminated the need for a separate hydraulic power system and eliminated thrust vector control failure through loss of hydraulic fluid. A third use of the turbo-pump was to provide roll control by actuating the turbine exhaust nozzle. SpaceX completed development in early 2005. The Merlin 1A, was a high pressure 342,650-newton at sea level thrust engine that was turbo-pump fed with a gas generator cycle. SpaceX began development on the Falcon V Merlin 1B upgrade engine (378,250 newtons at sea level) in 2005. The company expected to complete a Falcon V stage hold down firing with all M1B engines by the end of 2005. The next major engine development was Merlin 2, where SpaceX would aim for a significant increase in thrust and chamber pressure. Merlin 2 would serve as an exact scale version of the F-1 class (>6,675,000 newtons or 1.5 million pounds-force thrust) engine that SpaceX intended to start developing in a few years. However these plans were superseded by development of the Merlin 1C for the Falcon 9.
Thrust (sl): 317.700 kN (71,422 lbf). Engine: 760 kg (1,670 lb). Propellant Formulation: Lox/RP-1. Thrust to Weight Ratio: 94.