Re the jet engine claim, if Rossi is seeing prompt charged particles, this could have led him to speculate about the possibility of a jet engine. If the Papp engine was real, it is not difficult to imagine that it was powered by having prompt charged particles (e.g., alpha particles) momentarily ionize the working gas, which would lead to an abrupt expansion. The working gas in the case of the Papp engine was confined, but that need not be the case.
It is true that little in the way of prompt charged particles have been observed in LENR. But that says little about what Rossi may be seeing. Eric