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A system for controlling a position of jet engine exhaust mixing tabs includes a plurality of exhaust mixing tabs spaced apart from one another and extending from a lip of an exhaust nozzle of a jet engine nacelle adjacent a flow path of an exhaust flow emitted from the exhaust nozzle. Each of the e

A system for controlling a position of jet engine exhaust mixing tabs includes a plurality of exhaust mixing tabs spaced apart from one another and extending from a lip of an exhaust nozzle of a jet engine nacelle adjacent a flow path of an exhaust flow emitted from the exhaust nozzle. Each of the exhaust mixing tabs are constructed to be controllably deformable from a first position adjacent the flow path to a second position extending into the flow path of the exhaust flow in response to a control signal applied to each of the exhaust mixing tabs. In the first position, the exhaust mixing tabs either have no affect on the thrust produced, or increase the momentum (thrust) of the exhaust flow exiting from the exhaust nozzle. In the second position, that is, the "deployed" position, the exhaust mixing tabs are deformed to extend into the flow path. In this position the exhaust mixing tabs promote mixing of the exhaust flow with an adjacent air flow. This results in the attenuation of noise generated by the jet engine.

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What is claimed is: 1. A system for controlling a position of jet engine exhaust mixing tabs, said system comprising: a plurality of exhaust mixing tabs extending from a lip of at least one nozzle of an engine nacelle; a plurality of shape memory alloy (SMA) tendons attached at opposing ends to eac

What is claimed is: 1. A system for controlling a position of jet engine exhaust mixing tabs, said system comprising: a plurality of exhaust mixing tabs extending from a lip of at least one nozzle of an engine nacelle; a plurality of shape memory alloy (SMA) tendons attached at opposing ends to each exhaust mixing tab, wherein the SMA tendons are adapted to constrict when activated by heat, the constriction causing the exhaust mixing tabs to deploy into an exhaust flow emitted from the nacelle nozzle, the deployment causing the exhaust flow to intermix with adjacent air flow; and a plurality of tubular SMA tendon sleeves attached to and contouring with an inner surface of each exhaust mixing tab, each sleeve enclosing one of the SMA tendons in a 'slip-fit' fashion such that an air gap exists between each sleeve and the respective SMA tendons, each sleeve adapted to retain the respective SMA tendons when the SMA tendons are activated to deploy the respective exhaust mixing tabs. 2. The system of claim 1, wherein each exhaust mixing tab comprises an outer layer adapted to return the exhaust mixing tabs to a non-deployed position when the SMA tendons are deactivated. 3. The system of claim 1, wherein each exhaust mixing tab comprises a compliant coating disposed across an inner surface of each exhaust mixing tab. 4. The system of claim 1, wherein the engine nacelle nozzle comprises a by-pass fan exhaust nozzle. 5. The system of claim 1, wherein the engine nacelle nozzle comprises an engine turbine exhaust nozzle. 6. The system of claim 1, wherein the engine nacelle nozzle comprises a by-pass fan exhaust nozzle and an engine turbine exhaust nozzle. 7. The system of claim 1, wherein the SMA tendons are activated by heat generated by the exhaust flow emitted from the nacelle nozzle. 8. The system of claim 1, wherein the SMA tendons are deactivated by being exposed to air having a temperature substantially cooler than the exhaust flow emitted from the nacelle nozzle. 9. The system of claim 1, wherein the SMA tendons are activated by heat generated by connecting the SMA tendons to an electrical current source. 10. The system of claim 9, wherein the SMA tendons are deactivated by disconnecting the SMA tendons from the electrical current source. 11. The system of claim 1, wherein the SMA tendons are attached to an inner surface of at least one exhaust mixing tab in a 'parallel line' pattern. 12. The system of claim 1, wherein the SMA tendons are attached to an inner surface of at least one exhaust mixing tab in a 'fan-like' pattern. 13. A method for varying a position of jet engine exhaust mixing tabs, said method comprising: activating a plurality of shape memory alloy (SMA) tendons enclosed in a plurality of tubular SMA tendon sleeves in a 'slip-fit' fashion, and attached to a plurality of exhaust mixing tabs extending from a lip of at least one nozzle of an engine nacelle, each tendon sleeve attached to and contouring with an inner surface of each exhaust mixing tab, and each SMA tendon attached at a first end to an inner side forward edge of the respective exhaust mixing tab and attached at a second end along an inner side aft portion of the respective exhaust mixing tab offset from an aft edge of the respective exhaust missing tab; wherein the SMA tendons constrict when activated and pull on the aft portion to cause the exhaust mixing tabs to deploy into an exhaust flow emitted from the nacelle nozzle, thereby intermixing the exhaust flow with adjacent air flow. 14. The method of claim 13, wherein the method further comprises returning each exhaust mixing tab to a non-deployed position utilizing outer layer of the respective exhaust mixing tabs to generate a biasing force that returns the exhaust mixing tabs to the non-deployed position when the SMA tendons are deactivated. 15. The method of claim 13, wherein activating the SMA tendons comprises activating the SMA tendons attached to the exhaust mixing tab extending from the lip of at least one of a by-pass fan exhaust nozzle and a turbine exhaust nozzle. 16. The method of claim 13, wherein activating the SMA tendons comprises utilizing heat generated by the exhaust flow emitted from the nacelle nozzle to activate the SMA tendons. 17. The method of claim 16, wherein the method further comprises deactivating the SMA tendons by exposing the SMA tendons to air having a temperature substantially cooler than the exhaust flow emitted from the nacelle nozzle. 18. The method of claim 13, wherein activating the SMA tendons comprises connecting the SMA tendons to an electrical current source to generate heat to activate the SMA tendons. 19. The method of claim 18, wherein the method further comprises deactivating the SMA tendons by disconnecting the SMA tendons from the electrical current source. 20. The method of claim 13, wherein activating the SMA tendons comprises disposing the SMA tendons to the inner surface of the exhaust mixing tabs in a 'parallel line' pattern. 21. The method of claim 13, wherein activating the SMA tendons comprises disposing the SMA tendons to the inner surface of the exhaust mixing tabs in a 'fan-like' pattern. 22. A jet engine nacelle having variable position exhaust mixing tabs, said nacelle comprising: at least one exhaust nozzle comprising a plurality of exhaust mixing tabs extending from a lip of the nozzle; plurality of sleeves attached to and contouring with an inner surface of each exhaust mixing tab; a plurality of shape memory alloy (SMA) tendons, each SMA tendon disposed within a respective one of the sleeves, each SMA tendon attached at a first end to a forward edge of the respective exhaust mixing tab and attached at a second end along an aft portion of the respective exhaust mixing tab offset from an aft edge of the respective exhaust missing tab; and wherein the SMA tendons are adapted to constrict when activated by heat and pull on the aft portion to cause the exhaust mixing tabs to deploy into an exhaust flow emitted from the nozzle, thereby intermixing the exhaust flow with adjacent air flow. 23. The nacelle of claim 22, wherein each sleeve encloses one of the SMA tendons in a 'slip-fit' fashion such that an air gap exists between each sleeve and the respective SMA tendons, each sleeve adapted to retain the respective SMA tendons within the sleeves when the SMA tendons are activated to deploy the respective exhaust mixing tabs. 24. The system of claim 22, wherein each exhaust mixing tab comprises an outer layer adapted to return the exhaust mixing tabs to a non-deployed position when the SMA tendons are deactivated. 25. The system of claim 22, wherein the nacelle further comprise a compliant coating disposed across an inner surface of the exhaust nozzle and each exhaust mixing tab, the compliant coating covering the sleeves and providing an aerodynamically smooth inner surface. 26. The system of claim 22, wherein the exhaust nozzle comprises at least one of an engine by-pass fan exhaust nozzle and an engine turbine exhaust nozzle. 27. The system of claim 22, wherein the SMA tendons are adapted to: activate when exposed to heat generated by the exhaust flow emitted from the nozzle; and deactivate when exposed to air having a temperature substantially cooler than the exhaust flow emitted from the nozzle. 28. The system of claim 22, wherein the SMA tendons are adapted to: activate when heated by connecting the SMA tendons to an electrical current source; and deactivate when the SMA tendons are disconnected from the electrical current source. 29. The system of claim 22, wherein the SMA tendons are attached to an inner surface of at least one exhaust mixing tab in a 'parallel line' pattern. 30. The system of claim 22, wherein the SMA tendons are attached to an inner surface of at least one exhaust mixing tab in a 'fan-like' pattern.