With the X3 looking remarkably like a modernised Fairy Rotodyne the question arises to what powers the rotor. The drawing shown has no anti torque tail rotor which suggests that the rotor is powered, when required, by blade tip jets although these are not shown in the drawing.
The Fairy Rotodyne had a significant noise problem caused by the original single flame tube tip jets. I understand that a solution had been designed which reduced the noise from 113 db to 96 db at 600 ft. I assume that this new tip jet design had been tested and the 96 db noise level had been confirmed but, I believe the project was cancelled before the new tip jets were test flown.
The new tip design was a unit that was made up of 9 x small flame tubes in a one piece combustion chamber with each flame tube exhausting through cold air mixing noise silencing exhaust nozzle. The unit was 4 ft long and no doubt quite slim and light weight to enable them to be fitted into the blade tip without creating unacceptable loadings on the blade.
In the USA, Darpa has sponsored research which is being carried by the Groen brothers but this has stopped due to company financial problems and to the inability to reduce the noise to an acceptable level. Darpa has now transferred that research to Georgia University who have apparantly some expertise in this field. The only picture of results of the Darpa financed research is what appears to be a single piece flame tube and what is possibly an exhaust nozzle, I'm not sure if this is a standalone unit or part of a multi tube unit.
My questions are;
1) Was the original noise reducing units developed during the Rotodyne period ever tested in a ground test stand and if so were they ever tested on the aircraft itself?
2) Are the Darpa financed quiet tip jets a new design or, are they working on a modernised version of the original multi flame tube with air mixing exhaust nozzles?