Design method based on the quasi two-dimensional method of characteristics (MOC) was proposed for the three-dimensional (3-D) rectangular cross-section asymmetrical nozzle with lateral expansion. The corresponding asymmetrical nozzle design program based on MOC was obtained. Then

according to different lateral expansion laws

a series of asymmetrical nozzles were designed by using this method. And comparisons were made between these nozzles and the optimal configurations designed by optimization method. The comparisons show that:the up and down ramps of asymmetrical nozzles designed by the two methods are basically coincident and the pressure distributions on the expansion ramp are consistent

verifying the reliability of quasi-two-dimensional method of characteristics; the difference in thrust between the MOC design and the optimization design is lower than 0.60% and in lift is lower than 8.07%. This design method can reduce the time spent by the design from 30.5h to 2h

presenting a satisfactory approach for the preliminary design.