Propulsion system integration and thrust vectoring aspects for scaled jet UAVs

Abstract

Scaled UAV configurations of planned aircraft is well suited for the trial of new aeronautical technologies in flight. These systems offer a significant potential for minimizing costs and complexity. For these reasons project Sagitta has been started with the support of the company Cassidian, namely, to build a scaled demonstrator of a full-scale configuration in order to prove the concept of those technologies. Among others, new technologies with respect to the propulsion system of the demonstrator shall be examined. The demonstrator has a flying wing configuration without vertical stabilizers and is powered by two jet engines. Due to the requirements for a low radar cross section for the full-scale configuration, the propulsion system shall have an adequate integration, leading to a curved propulsion duct, in order to integrate the engines as good as possible in the wing. In order to support lateral stability of the scaled configuration, thrust vectoring functionalities shall be implemented into the nozzle system. These aspects induce difficulties with respect to the integration and challenges with the scaling effects regarding the full-scale configuration. Other important issues of such propulsion integration are the total pressure losses in the inlet and nozzle duct, the thermal loads induced by the engine and the required power for the thrust vectoring concept. For the thrust vectoring system, fluidic concepts have been considered due to their potential for weight, complexity and maintenance effort reduction. Such systems have been mostly tested under laboratory conditions; therefore, a flying demonstrator would suit well for a flight trial of the technology. The presented paper will concentrate on the overall integration aspects of the propulsion system and the initial assessment of promising thrust vectoring solutions.