2018 年 66 巻 1 号 p. 15-23
An external nozzle is one of the altitude compensating nozzle for a wide range operating airframe like RLV (Reusable Launch Vehicle). This paper explores the possibility of simplifying thrust calculations of the external nozzle for a series of flight operations. We focused on a replacement of some 2D thrust calculations with a method at a low computation cost in thrust performance evaluation along a trajectory of RLV equipped with the external nozzle. The replacement is determined by threshold conditions of jet Mach number and slip line angle. Since strict calculation of the threshold conditions takes expensive computational cost, calculating models of the threshold conditions were constructed. These models were able to predict the threshold conditions with an error of 4% or less. Then, the models were applied to the calculation for 2604 nozzle shapes and 191 points along a trajectory of TSTO (Two Stage To Orbit) booster. Thrust calculations of 86% conditions were replaced by the method with low computational cost, so that the models proposed in this work demonstrated the achievement of simplification.