Heat exchange injector for use in a rocket engine

A heat exchange injector assembly suitable for use in a rocket engine, the heat exchange injector assembly comprising:

• a liquid oxidizer post extending between a first end and a second end having a length therebetween, and comprising an inner surface and an outer surface;
• an elongate multi-passage swirl element disposed in the liquid oxidizer post adjacent the inner surface and extending a substantial portion of the length of the post between a third end and a fourth end to form a double helical flow passage extending along the multi-passage swirl element and the liquid oxidizer post;
• and
• a fuel sleeve disposed about the outer surface of the liquid oxidizer post and extending between a fifth end and a sixth end to form an annular flow passage extending along the fuel sleeve and the liquid oxidizer post;
• wherein the annular flow passage extends parallel along a length of the double helical flow passage between the third end and the fourth end to facilitate heat transfer between the annular flow passage and the double helical flow passage.