Abstract: A new method of calculation that reflects actual situation of the dynamic pressure encountered by seat-man system, particularly at supersonic speeds is presented. Bason on large scale analyses and calculations, a semi-empirical mathematic expression of correction coefficient K of dynamic pressure exerting on seat-man systems is presented and the methods of selecting ε and f (ε) are proposed. For selecting ε and f (ε), only experimental data of drag coefficient at four different Mach numbers are needed. As a principle, the selection of experimental values of drag coefficients is free when the experimental values are of high precision, otherwise its root-mean-square error might be considerable. The present method is not only applicable for the calculation of drag coefficient of large blunt bodies such as seat-man system within arbitrary Mach number range, but also good for other large blunt bodies as well, and its root-mean-square error is less than 0 05. In addition, when the experimental values are expressed as semi-empirical mathematical equation it is convenient for computer programming or simulation under other situations.

Key words: ejection seats, dynamic pressure, Mach number, wind effects