AbstractA coupling frame of speed gain and maintain was suggested to assess the flight performance of hypersonic cruise vehicles (HCV). The optimal cruise speed was obtained by analyzing the flight performance measured by the ratio of initial boost mass to generalized payload. The performance of HCVs based on rockets and air-breathing ramjets was studied and compared to that of a minimum-energy ballistic trajectory under a certain flight distance. It is concluded that rocket-based HCVs flying at the optimal speed are a very competitive choice at the current stage.