Computational fluid dynamics study for stability analysis of an unmanned aircraft mass simulator with rocket-assisted take-off

Abstract

This paper presents the stability analysis of a high speed unmanned aerial system mass simulator fitted with a rocket-assisted take-off (RATO) system. Flight stability characteristics from rocket ignition to rocket burnout were analyzed using computational fluids dynamics methods to determine the viability of a proposed RATO system as an alternative to other launching methods, as well as traditional take-off. The RATO system used in this analysis is a quad-motor, recoverable design that was developed for testing experimental low-cost solid rocket fuel alternatives. This stability analysis was performed as a critical risk reduction measure for live-fire testing of this RATO system with various propellants. Static longitudinal stability was analyzed, initially using fundamental kinematics, and quickly progressing to the use of computational fluid dynamics to determine the influences of aerodynamic forces. In addition, a proprietary in-house program developed specifically to analyze various launching mechanisms was utilized to estimate the flight trajectory of the mass simulator given the kinematic and computational fluid dynamics analysis results. The analysis has shown that, with the proposed RATO system mounting geometry, the vehicle can achieve and maintain stable flight. This study concludes that the approach laid out within provides a means of adequately analyzing the aerodynamic effects on longitudinal static stability of an unmanned aircraft mass simulator during RATO launch through the use of computational fluid dynamics.