Steam-Expansion in Resonant Cavity Propulsion

[venomousbird]

I recall reading about a new propulsion that was supposed to have a much higher efficiency than any previous method. The basic idea was to let superheated steam pour through a valve into a specially shaped resonant cavity, at which point, there was apparently an interesting reaction between the steam and water that shot the boat forward, similar to a ramjet. Has anybody heard anything about this?

[daiquiri]

Guess you're talking about this:
http://www.boatdesign.net/forums/jet-drives/what-happened-pursuit-marine-drive-project-24676.html
;)

[jehardiman]

Here are the plans for that steam cyclic impluse propulsion system (http://www.sciencetoymaker.org/boat/) that are free on the internet. You can use steam to replace combustion in valved pluse-jet techchnology (http://en.wikipedia.org/wiki/Pulse_jet_engine) or ramjet technology (http://en.wikipedia.org/wiki/Ramjet)using steam expansion and increased impluse mass over air.

All old hat and viable theory, but almost impossible to implement with flow and thermal losses compared to direct combustion. It is probabily better to use a monopropellant such as Otto fuel to generate the steam directly in the chamber, but that is not a commerically viable system given the problems with monopropellants.