CFD investigation of the VLM-1 interstage

Abstract

The Hot Separation staging method is supposed to provide an e cient separation of the rocket stages. Nevertheless, it requires a non-conventional con guration of the interstage that includes a grid and a plume de ector for the lower stage. The Brazilian launcher VLM-1 is designed to employ this staging method and therefore, aerodynamic studies have to be accomplished in order to investigate the ow eld within the interstage. The aim of the presented work is the prediction of the drag coe cient of the VLM-1, considering all rocket components. Three main numerical studies have been performed applying the ow solver TAU for the Qmax and Hot Separation trajectory point which correspond to a Mach number of 1.55 and 2.16, respectively. The rst analysis concerns the estimation of the drag coe cient for each component of the launcher, considering the contribution of the body, ns and base for a closed con guration of the rocket (without interstage) for the in ow conditions with an angle of attack of 3:3 . The other two are parametric studies performed for a 2D-axisymmetric model. One is aimed to identify the best de ector geometry, inducing the highest drag on the rst stage at the Hot Separation trajectory point. The last study investigates the in uence on the drag of the di erent interstage clearance and grid models, comparing the results also with the one obtained for the open con guration (open interstage, without grid). These studies have been performed for a non-viscous ow. In order to estimate the inaccuracies introduced by the hypotheses taken, two extra studies have been accomplished for both 3D and viscous simulations. The results of these studies have been analyzed separately. On the one hand, the de ector study has shown that the best con guration, among the ones studied, is the conic de ector with the lowest volume. On the other hand, the drag coe cient for all rocket con gurations has been analyzed in order to combine the results and to predict the drag of the VLM-1 for the angles of attack of 0:0 and 3:3 at both trajectory points. The drag prediction has been accomplished taking into account also the results for the 3D and viscous simulations. From these estimation, three main conclusions have been made. First, the VLM-1 with interstage grid provides a drag coe cient more similar to the one for the closed interstage con guration than to the one for the open interstage without grid. Second, the clearance length has a low in uence on the drag coe cient for the interstage con gurations with grid. Third, the higher the number of elements of the interstage grid, the lower is the drag coe cient.