Numerical investigation on the safe stage-separation mode for a TSTO vehicle

Abstract

The TSTO (two-stage-to-orbit) model is one of the most feasible candidates for the next generation aerospace vehicle with its efficiency on aerodynamics and propulsion obtained by each stage vehicle in the entire flight envelope. But it must face the problem of the two-body separation that determines the success of the orbital flight. The mechanism of the stage-separation process for the parallel arrangement mode is not yet fully grasped at present. To address this critical issue, a type of large lift-body, like-scale, parallel arrangement TSTO vehicle with the turbo-based combined cycle engine (TSTO-TBCC model) was adopted to investigate the stage aerodynamic interference and separation process by numerical simulation method with dynamic overset grid technology. And the influence of flap pre-deflection, angle of attack, and flying Mach number on the safety of stage-separation was mainly explored. The results indicate that, it is difficult to achieve a safe stage-separation model for the present TSTO-TBCC at the balance state between aerodynamic lift and gravity. The method to change flap pre-deflection is of limited usefulness in improving the safety of the stage-separation. When the flap pre-deflecting angle |δf| is increased from 5° to 30°, the separation between stages always failed. Meanwhile the method of reducing the angle of attack has a higher efficiency, and a safe stage-separation model can be achieved at an angle of attack −2°. For the flight Mach number of 3.0 to 6.0 under the condition of approximately equal dynamic pressure trajectory, the two stages of TSTO-TBCC can be safely separated only when the angle of attack is reduced to −2°. Since the increment of lift produced by the change of the Mach number is lower than the increment of the angle of attack by 1°, the safety of the stage-separation for TSTO-TBCC is not sensitive to the flight Mach number.