Advanced rocket nozzles

Abstract

Several nozzle concepts that promise a gain in performance over existing conventional nozzles are discussed in this paper. It is shown that significant performance gains result from the adaptation of the exhaust flow to the ambient pressure. Special attention is then given to altitude-adaptive nozzle concepts, which have recently received new interest in the space industry. Current research results are presented for dual-bell nozzles and other nozzles with devices for forced flow separation and for plug nozzles with external freestream expansion. In addition, results of former research on nozzles of dual-mode engines such as dual-throat and dual-expander engines and on expansion-deflection nozzles are shown. In general, flow adaptation induces shocks and expansion waves, which result in exit profiles that are quite different from idealized one-dimensional assumptions. Flow phenomena observed in experiments and numerical simulations during different nozzle operations are highlighted, critical design aspects and operation conditions are discussed, and performance characteristics of selected nozzles are presented. The consideration of derived performance characteristics in launcher and trajectory optimization calculations reveal significant payload gains at least for some of these advanced nozzle concepts.