AGARD Standard Model

In this study, the OEM is used for estimation of the aerodynamic derivatives of AGARD standard ballistic model (SBM) from the data available in the open literature. For this SBM, the hybrid model with aerodynamic forces represented in the wind axis and the moments in the body axis coordinate systems was used [23]. The SBM is composed of a blunt nose cone with a cylindrical midsection followed by a 10° flare. This axis-symmetric, uninstrumented model is solid in construction. The free-light tests were performed at Mach number 2.0 in the NASA Ames pressurized ballistic range facility. The model, as it flew the down range, was photographed by 22 fully instrumented orthogonal shadowgraph stations. The trans­lational and angular motions were acquired in Earth-fixed orthogonal coordinates based on analysis of the film records. The NASA method was based on the LS/Gaussian LS differential approach. The V-a, b and the body axis models were used. The available data for V, x, y, z, U, w in a short flight duration were not uniformly sampled and hence a cubic spline interpolation was used to generate uniform data sets. The flow angle trajectories were generated using a = U + tan_1(dz/dx) and b = —■f + tan_1(dy/dx). Table 9.9 shows a comparison of some of the aerodynamic derivatives.

Due to the axis-symmetry property of the AGARD SBM, the static stability derivatives in longitudinal and lateral axes are the same except for the polarity.