Yes, and that is in fact not my perspective, I only mentioned the ratio in order to illustrate that the fuel weight is substantial. The right condition is of c

Yes, and that is in fact not my perspective, I only mentioned the ratio in order to illustrate that the fuel weight is substantial. The right condition is of course J/kg for the fuel + engine + propeller/shroud/etc. package, and also taking into account cooling drag and frontal area. >Yes, if you compare a slightly modified off-the-shelf automotive piston engine produced in millions, to a small batch jet engine, then yes, the former is cheaper. However, if you need your drone to be both very fast and fly very far (and these two are very important in military context), then off the shelf automotive piston engines are really not an option, and instead you need to invest in something very custom, which would destroy the per-unit cost advantage of piston over jet, and that’s ignoring benefits like smaller form factor allowing for much bigger payload (extra 100 kg available for warhead does make a difference). The problem is that jet turbines of the required efficiency and weight are actually expensive. They have high temperatures internally, and continuously, and have all these blades and bearings. I think it might be feasible to make them much more cheaply than they can be manufactured today, but a Wankel engine can be mass produced with present technology and is not incredibly bad.