**9. Distance between state of art and goals**

From the analysis of the several prototypes and from the documentation available in literature and on the web it can be noticed as all the groups of search are to the state of prototype. Regarding the prototype of the MIT they have been found problems of rotors failure in operating conditions. The group design by the Belgian researchers seem to be at the more advanced state, but they are not available data of any application. The Japanese model has been introduced to meeting a NATO and lacks recent news. For the Italian model the problem, currently resides in leading the system to a rotational speed, by means of generator/ electric motor, sufficient to prime the combustion. Problems have been found in the bearings behaviour and their limited lifetime
