Low Observable (LO) operations are thwarted when contrails are formed. It is essential that means be sought to automatically detect and once detected, eliminate this visual signature so that the operational advantage of reduced radar cross section and infra-red signatures can be fully exploited for obtaining combat advantage. A passive, exhaust system design is proposed which provides extremely high level of supersaturation in the exhaust flow by a unique non-uniform flow field design technique. This technique has been successfully applied for greatly reducing plume infra-red and acoustic signatures of an LO aircraft; the application to simultaneously reduce contrail visibility is unique. Preliminary analysis indicates minimal impact on performance and other signatures. Analysis by the Los Alamos National Laboratory indicates that for this type of nozzle design, homogeneous condensation will dominate over heterogeneous condensation for typical turbofan exhaust massflow (species), and an extremely large number of very small droplets will form. General Electric's plume visibility code calculates (1) the growth of the water droplets in the plume as external flow mixes with it, and (2) the visibility of the condensed water trail (contrail). GE's analysis indicates that for the initial water droplet distribution indicated by Los Alamos code, the contrail will be invisible to human eyes as well as to passive contrail detection system using CCD camera with advanced real time image processing.Anticipated benefits/potential applications:Commercial aircraft have neither the engine cycle nor free expansion exhaust nozzle required for passive contrail suppression. Also, contrail visibility is not a problem to their effectiveness.
