Propulsion and Flight Performance Evaluation of Dual-Bell Nozzles

Abstract

We performed an analytical study of propulsion and flight performance of dual-bell nozzles, to e xplore possible application of this advanced-nozzle concept to the current and near-term launch vehicles. With the help of a new nozzle-flow separation model, we evaluated performance gains to be obtained by using dual-bell nozzles during the ascent flight of expen dable and single -stage candidate vehicles. To evaluate the vehicle -level flight performance, we performed flight simulation analyses using a trajectory optimization program, thereby incorporating weight penalty. The weight increase was calculated by heat transfer analysis through the nozzle wall. The present analysis indicates a significant performance gain of this advanced nozzle concept. The tradeoffs between propulsion performance gain and weight penalty are discussed. Nomenclature