Re: Under jet engine
The patent is attached.
Its basically a gas generator and a reaction chamber. The chemicals proposed as the fuel for this system are pretty exotic, stuff like lithium borohydride LiBH4 or molten magnesium. Mechanix Illustrated notwithstanding, this system would have made much more sense as a propulsion system in weapon than a submarine. And even there, I have my doubts. It looks very hard to get right, compared to other options.
Zwicky was much better known as an astronomer than as a propulsion engineer, probably for good reason.