A Superposition Approach to Aerodynamic Modelling of a Capturing Device used for In-Air Capturing of a Reusable Launch Vehicle

Abstract

This study will focus on a detailed aerodynamic analysis of the capturing device used in an innovative reusable launcher recovery concept called "In-Air Capturing". The idea involves capturing of a Reusable Launch Vehicle (RLV) mid-air and towing it back to launch site using an aircraft. For the capture, a device is released from the aircraft when the RLV is in vicinity. The preliminary design of this device includes a 2 m long fuselage and four large fins for agility. It is capable of pitching, yawing and rolling by symmetrically deflecting horizontal, vertical and all flaps respectively. However, for 6DOF movement, the flaps must be deflected asymmetrically in the presence of angle of attack and sideslip angle. This entails the requirement for a large dataset to effectively define the aerodynamics of the system. While a broad dataset can be generated using theoretical methods, the resulting large data tables with acceptable accuracy may not be sufficient. It is possible to achieve even better accuracy through Computational Fluid Dynamics (CFD), but the computational effort required to generate the complete aerodynamic dataset is infeasible. An alternative approach to achieve a good balance in accuracy and computation time can be used by taking advantage of the axisymmetric geometry. Thus, the paper proposes a way in which numerical CFD data for symmetric flap deflections are superimposed to achieve asymmetric flap datasets. The relative deviation of this method is compared against data generated using the semi-empirical tool Missile Datcom and validated using additional CFD calculations. Anomalies and sources of possible inaccuracies are also identified.