Apollo Pintle Injector Print

Design

To land on the Moon, the Lunar Module's descent engine had to throttle smoothly from full power down to a gentle hover. TRW solved it with a variable-area pintle injector. Oxidizer (nitrogen tetroxide) flowed down the centre and out past a fixed pintle as a ring of individual sprays. Fuel (Aerozine 50) left the faceplate as a thin cylindrical sheet, and the oxidizer sprays broke it up and mixed with it. A movable sleeve, linked to the flow control valves, changed the size of both openings at the same time, so the mixture stayed right at every thrust setting.

The engine throttled between 10% and 60% of its 10,500 lbf maximum, or ran at full thrust; the range between 65% and 92.5% was avoided to protect the nozzle. On Apollo 13 the same engine pushed the crippled spacecraft back towards Earth. The pintle injector design later went into SpaceX's Merlin engines.

This print is the fine-line edition of the drawing: the engine in half-section, with Detail A showing the fixed pintle, the movable sleeve and the two propellant paths.

Item

Printed on heavyweight matte paper with a smooth, glare-free finish that suits fine line work. Shipped in protective packaging. Frame not included.

Care instructions

- Keep out of direct sunlight to protect the print