Aerospike nozzle performance study and its contour optimization

Abstract

Because aerospike nozzle can meet the need of Single-Stage-To-Orbit (SSTO), it has already attracted common attention. To understand the performance of aerospike nozzle, a series of simulation tests on aerospike nozzle unit, which employed solid propellant, were completed. Results indicate that the thrust of aerospike nozzle decreases at beginning and then increases with an increase of backpressure, which is different from traditional bell nozzle. The experimental and numerical results indicate that the resultant force direction of the aerospike nozzle unit may change in a large range during the flight. A full travel optimization method, a parametric optimization essentially, is put forward in this paper, which is performed keeping maximizing total impulse and not restricted to a certain rated altitude. The process of building optimization model including computational procedure of the optimization is presented in detail. Introduction The multi-purpose low-cost reusable SingleStage-To-Orbit (SSTO) earth-orbit transportation system is a strong trend of aerospace technology development. To this system, the aerospike nozzle engine is critical. The aerospike nozzle has already attracted an increasing common attention. That is owing to its outstanding advantages: the automatically compensation ability of altitude performance, which can meet the need of SSTO. Also, in comparison with the conventional bell * PH.D. student, School of Astronautics, BUAA f Professor, School of Astronautics, BUAA Copyright © 2001 by the American Institute of Aeronautics and Astronautics Inc. All right reserved. nozzle it has shorter structure, lighter weight, flexible structure combination, and uniform load distribution, using turbine exhaust gas effectively to form the spike flow. In recent years the aerospike nozzle was widely studied experimentally and theoretically in many countries. Especially in the United States, the aerospike nozzle has been studied since 1960's and the technology level of approaching to practical flights has been reached '. In Europe, an Advanced Rocket Propulsion Technology (ARPT) program is undergoing, under which a number of investigations on aerospike nozzle have been performed In Japan, a reusable launcher demonstrator powered by aerospike engines is being studied . All these experimental studies employed the entire aerospike or plug nozzle, either clustered or linear, --' and the performance analysis also was as a whole 1. A whole aerospike nozzle testing is beneficial to gain an understanding of the performance and characteristic of the aerospike nozzle engine. But some characteristics of the nozzle itself, for example, how the thrust vector of the aerospike nozzle unit changes with flight altitude, were ignored owing to the symmetry of aerospike nozzle. In order to facilitate a fully understanding of the nozzle characteristics, in the study reported here an aerospike nozzle unit as shown in Fig.l was employed, and a specially designed testing setup was fabricated. Generally, an aerospike or plug nozzle is designed for a certain rated pressure ratio, which is linked to a certain area ratio. In the case of an ideal aerospike or plug nozzle, to fully determine the plug contour, the definition of the rated pressure ratio or area ratio and mass flow rate should be sufficient. For the portion around the exit lip of internal nozzle America Institute of Aeronautics and Astronautics (c)2001 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization. it can be done based on a Prandtl-Meyer expansion and the contour followed the streamline 1<- in this paper a full travel optimization method is put forward, essentially a parametric optimization, which is performed keeping maximizing total impulse and not being restricted to some rated altitude.