Aerodynamic coefficients of the first reentry stage of the reusable ballistic rocket Neptun in supersonic flow employing the air brakes as control surfaces

The aerodynamic coefficients of the first reentry stage of Neptun employing the air brakes as control surfaces were determined experimentally in the 30 x 30 sq cm supersonic wind tunnel of the DFVLR for ranges of Mach number 2.25 greater than free stream Mach greater than 4.15 and angles of incidence -3 greater than alpha greater than 5 deg. Attention was fixed mainly on the gliding flight properties which are of importance for recovery and which are compared with those of a typical lifting reentry body (ERNO LB1). Results show that with reference to the maximum attainable range the lifting body possesses a gliding flight behavior better by an order of magnitude than that of the ballistic reentry body. Typical values of the lift-drag ratio are approximately 0.1 for Neptun W1 and approximately 1.5 for ERNO LB1. In contrast, the static longitudinal stability of the ballistic flight vehicle is superior to that of the lifting body. The latter can only be maintained on a descending glide path in a trimmed flight state with the aid of aerodynamic control surfaces.