As an ideal propulsion system for hypersonic flight in near space and wide speed range and large airspace flight of aerospace vehicles， the combined propulsion system has high aviation and aerospace application value. Based on the analysis of the current combined propulsion schemes in the United States， this paper makes a preliminary discussion and estimate on its technical development and trend. The potential military applications are analyzed by taking several typical combined power aircraft as examples. Some suggestions for the development of combined propulsion system in China are proposed.

U.S. military unmanned aerial vehicles （UAVs） play an important role in military operations. There is an increasing trend for the total number of the UAVs and their intelligent level. To seize the high ground in the domain of the unmanned intelligent warfare， the US army are carrying out a series of new research projects. This paper analyzes the operational characteristics as well as the advantages and disadvantages of the U.S. military's in-service UAV equipment. According to the latest development of the intelligent technology in software and hardware， the projects of Carrier-Based Aerial-Refueling System， Loyal Wingman， Golden Horde， Project Maven， Advanced Battle Management System are analyzed in detail. The new characteristics and pattern of these intelligent military equipment are presented. The implications and suggestions for tackling the development of unmanned intelligent equipment are proposed in terms of the air combat theory， capabilities and techniques， as well as the equipment system.