Abstract: To address the challenge of predicting transitional flow characteristics of aerospace vehicles in rarefied gas environments at high altitudes, the multiscale discrete velocity method coupled with a steady implicit algorithm was employed to conduct numerical simulations of transitional flows over high-speed flight vehicles. Numerical simulations were performed for typical three-dimensional geometries, including 9^\circ blunted cone, 70^\circ blunted cone, Apollo 6 reentry capsule, and X-38 vehicle, under transitional flow conditions. The results demonstrate that the present method accurately captures the non-equilibrium effects and primary flow features in transitional flow regimes. Comparisons with reference data from the direct simulation Monte Carlo(DSMC) method and relevant experimental measurements show good agreement for key aerodynamic parameters, including lift and drag coefficients, surface pressure coefficient, and heat flux coefficient. A comparative analysis for the X-38 vehicle case indicates that, under the conditions considered in this study, the MDVM with the steady implicit algorithm produces results comparable to those of the DSMC method, while showing certain advantages in computational efficiency and potential for engineering applications. The simulation results validate the effectiveness and accuracy of the multiscale discrete velocity method, providing methodological support for aerodynamic characteristic prediction and aerodynamic design of vehicles operating in transitional flow regimes.