A novel method for increasing the rate of jet mixing by the production of streamwise vortices has been developed. An analytic description of this hypermixing effect is obtained with an eddy viscosity whose length and velocity scales are proportional to the vortex size and rotational speed. The predictions of this analysis are compared with experimental results for the growth of hypermixing jets, and the generalization to other shear flows is discussed. Tests of an improved hypermixing nozzle show that the length of the thrust augmenting ejec- tor developed at ARL can be almost halved, with no loss in augmentation. through the shroud. The primary jet is decelerated as it mixes with the secondary flow, causing the average static (and total) pressure in the duct to rise. Since the primary flow is only a fraction of the secondary flow, the mixing section may be considered to act an an elongated actuator disk, or fan. Because of the increased static pressure in the diffuser section, the inlet-diffuser venturi develops a net lip thrust. It is this force that augments the thrust of the primary jet. When integrated with the wing into a lift propulsion system, the ejector acts like a jet flap to increase the cir- culation lift during transition. Since ejectors can be used to augment and deflect the engine thrust during takeoff and landing, their use permits the installation of a smaller engine for more efficient cruise. The lowered exhaust velocities and acoustic shielding provided by the walls of the duct offer im- portant advantages in the area of noise reduction, as well. The application of ejector thrust augmentation to V/STOL aircraft has, therefore, been an active research goal for several decades. However, complete mixing of the primary jet and secondary entrainment flow is required to achieve significant levels of augmentation. In the past this has meant that an ejector must include a long mixing duct. Ejectors shor- tened to meet aircraft size and weight limitations could not generate sufficient thrust to make the concept practical. The performance of short ejectors can be increased by ac- celerating the rate of entrainment by the primary jet (hyper- mixing). The hypermixing nozzles developed at ARL produce a system of streamwise vortices in the primary flow. These vortices serve to entrain additional fluid, so that a more fully mixed flow is obtained within a shorter distance. In the present article an eddy viscosity for hypermixing jets is presented, and tests of an improved nozzle, which has made large reductions in ejector length possible, are reported.