START-UP ABILITY OF UAVs ON TASK

Besides low cost, easy manufacturability, light weight, long operation time, and high durability, miniature UAVs need restart capability during flight.

Small unmanned air vehicles (UAVs) are today extensively used for a wide range of applications, from amateur to military applications. Many UAVs use electrical energy for the thrust generation, making them flexible, simple, safe, and quiet. The main drawback of this traction strategy is the low energy density of batteries compared to energy stored in the liquid form, as well as the speed and flight range of the vehicle. This is the point where turbines make their entrance.

However, micro turbines used for the bigger UAVs are complex and expensive. The small dimensions require small clearances to maintain reasonable efficiencies. On the other hand, the rotating parts should be able to expand due to the high temperature. As the scale of turbo machinery is reduced, the compressor efficiency decreases and, therefore, the efficiency non-linearly drops with its size when it is utilized in a micro-propulsion system, resulting in efficiencies of about 30 to 50% lower than for big turbines.