The article discusses systems with a given characteristic. A throwing device of a fundamentally new principle of action based on elastic hinges is considered. In it, energy is stored in elastic hinges. The hinge is a structure in which an elastic element (spring or air spring) moves between the guides of the design shape. This paper presents a design in which an elastic hinge can rotate more than 180 degrees. The characteristic of the entire system has a working section with almost constant traction. In the propellant device according to the invention, the flexible string has been replaced by two rigid rods, which allows the pulling force to be exerted on a longer working section. Calculations of the shape of the hinge guides in the case of a spring and in the case of a pneumatic spring are given. It is shown that in the case of a pneumatic spring, there is the possibility of a given change in the characteristics of the entire system. The possibility of using a system with a given characteristic as an aero finisher.