InjectorPintle Typeby TRW (original), SpaceX (Merlin), various
Typical Specifications
Throttle Ratio
Up to 10:1
Combustion Stability
Inherently stable (single element)
Pressure Drop
15u201325% of chamber pressure
Operating Principle
One propellant flows through the central pintle element and is directed radially outward through slots or holes, while the other propellant flows as an annular sheet around the pintle. The two streams impinge and atomize for combustion.
The pintle injector is a type of rocket engine injector that uses a central post (pintle) to spray one propellant radially outward into an annular sheet of the other propellant. Originally developed by TRW for the Apollo Lunar Module Descent Engine, it enables deep throttling capability. SpaceX adopted the pintle design for all Merlin engines due to its simplicity and throttleability.
Materials
Used In Engines
Common Failure Modes
Pintle erosion, thermal fatigue of pintle tip, coking/deposits on injection surfaces, flow instability at low throttle
Recent Innovations
Enables throttle ratios up to 10:1, inherently resistant to combustion instability, single-element design simplifies manufacturing, SpaceX mass production adaptation
