I’ve tried to find out more info on this thing and discovered it’s not the only one around. They run on hydrogen peroxide (H2O2). There is no engine. The H2O2 is pumped up to the rotor and down to the tips where a catalyst (silver, in this case) causes it to decompose into high pressure steam which then shoots out the little nozzles and causes the rotors to spin. It sounds like the perfect, non-polluting solution to everything but hydrogen peroxide is notoriously dangerous if handled wrong. The Germans used it in WWII on some experimental stuff and, while it did work, there were enough accidents that it hasn’t been tried in any major way since. Still pretty neat, though.