The search for optimum configurations for re-entry vehicles

Abstract

This paper describes an investigation to identify possible optimum re-entry vehicle configurations. The criteria for selecting the optimum re-entry vehicle shapes are based on aerodynamic stability, nosetip/frustum boundary-layer transition onset and propagation, asymmetric nosetip shape change induced trim, minimization of reentry dispersion, and booster sizing/weight limitation. The numerical results indicate that a highly oblate nose shape (e.g., a flat-faced nose or 5x1 ellipse) has a better performance potential when compared to a spherical nose using the above criteria. For the aft body, only biconic shapes are considered and the optimum bicone is believed to have the following characteristics: Oj ~2$2 and Rb ~2Rj where 07, 62 are the fore and aft cone angles, respectively, Rj the local radius at bicone juncture, and Rb the re-entry vehicle base radius. Under these restrictions, improvement in re-entry vehicle aerothermodynamic performance, e.g., small Xc p variation with A/a, and a> minimum ablated nosetip downstream influence may be achieved with possibly no degradation in frustum boundary-layer transition performance. Consideration also is given to the disadvantages of using these suggested optimum re-entry vehicle configurations.