Mathematical and Computational Fluid Dynamic (CFD) Analysis of a Low Altitude Rocket Stability for Varying Fin Root Chord

One of the major components in determining the stability of a model rocket is the rocket fin. In order to define the static stability of the model rocket, the relative positions of the centre of gravity and centre of pressure (CP) needs to be calculated first. The centre of gravity depends on the mass distribution of the rocket meanwhile the centre of pressure analysis requires the pressure distribution over the surface of the rocket body. This induces a much more challenging problem as in order to obtain the pressure distribution, wind tunnel testing is required. This present study aims to analyze the centre of pressure of model rocket using mathematical equations as well as computational fluid dynamics (CFD) with varying fins root chord. Mathematical prediction using theoretical Barrowman’s equation as well as OpenRocket software and CFD are used to obtain the centre of pressure as well as the static stability of the designed model rocket. Wind tunnel testing is not necessary as CFD analysis is able to provide the centre of pressure of the rocket. The data from all approaches was then compared and analyzed. It is found that the centre of pressure results from the theoretical Barrowman’s equation and CFD shows the same trend of linear increase in CP as the root chord increases. The stability obtained from the Barrowman’s equation ranging between 3.0 to 3.4 cal and OpenRocket at 2.91 to 3.27 cal shows percentage error of less than 5%. It is also found that the stability of the rocket using CFD analysis shows unstable rocket with stability range of 0.45 to 0.55 cal.