. . . The aircraft he was standing beside in the picture burned, of all things,
coal oil!
Might be the same type of aircraft......
Just a thought.
This makes some sense as a test craft. The FW 190F that the Smithsonian restored had a few gallons of coal-based gasoline in its tanks when the NASM team started tearing it down.
Note also that the photo shows the rig attached right over where the normal droptank rack would be attached anyway. The fully-enclosed attachment between the fairing and the pipe is a few inches behind the small propeller, and there is a lack of a clear ram intake into the rig. If you were going to make smoke, would it make sense to drain from the aircraft's internal fuel or oil?
Given the location of the pipe along the fuselage, it would be pretty improbable that this is some kind of reactive thrust system, especially because of the rudder proximity.
Just trying to confuse the situation