Turbine D
The question is, how do you know (100% positively sure) the bond has been made? Perhaps today there is adequate inspection technology to survey the bonds and detect abnormalities now, but then inspection technology wasn't as advanced as today. The plane never got a chance to work, the contract (funding) by the US government was cancelled before any planes were built.
They did test the engine though
unmanned transport
Because to my knowledge, the USA holds the patent on diffusion bonded titanium fan blades. I may be wrong and someone please correct me if so.
I didn't know we did