Hi all, I’m new here; my name is Kris aged 53 in Norfolk, UK. I’ve been in engineering design all my life so they few theories and ideas I may submit for comment do have some sound basis. Anyway, today lesson (for you to teach me) concerns Jet Thrust and ducted fan motors. I understand that thrust measurement is not strictly ‘pressure’ but the ‘equal & opposite reaction’ to the combustion of the fuel in a jet engine? Well as I see it the fuel combusts causing massive expansion in the confined space of the engine housing with it’s only direction for expansion being via the outlet. The expansion causes Force in all directions; the engine housing is subject to this force but no reaction can be caused on the lateral periphery but a reaction to the force exiting the outlet can be caused on the front of the engine being axially opposite. Therefore in space where there is no atmosphere to inhibit progress it is the ‘equal & opposite reaction that causes the space craft to move. Am I correct so far? Ok from here lets go to the aircraft jet. Similar things happen but progress is aided by the engine outlet force coming up against the atmosphere thereby giving this force something to push against. Therefore if this pressure is pushing against the atmosphere, which is under pressure from gravity, it must be causing a greater pressure in the atmosphere locally? So, am I right in saying that the engine must cause pressure as a result of the thrust? Right now to my question; Radio Control Ducted Fan (jet) Engines. As I see it thrust from this engine is mechanically rather than combustion induced and is more simply ‘pushing’ air out the rear. From this, propulsion is the effect of pressure caused between the propeller and the atmosphere and NOT equal and opposite reaction and is not thrust in the true sense as this system would be totally ineffectual in space? So is it true to say that a Ducted Fan Motor can and does produce pressure as in a ‘Bouncy Castle’ inflation system? How much pressure remains to be measured but is the theory sound? I shall await your theory shredding eagerly.