Abstract: A new electrothermal fluid motor connected to an electrically controlled energy source for uniformly heating a unique reticulated heat exchanger, which together with an expansion fluid fills a chamber, having a mechanical energy output consisting of a jet flow or a change of force, pressure, or motion, has achieved elimination of internal convection and consequent start-up wall losses found in prior art devices, resulting in improved efficiency and response-time reduction. Typically, the heat exchanger has millions of heating elements, interconnected in a network of distorted dodecahedron cells, each with thirty shared heating elements of triangular cross-section, giving a shock resistance of thousands of g's and thousands of degrees centigrade, a void space of about 97%, and an average thermal diffusion distance of about 100 microns. The preferred energy source is electrical resistance heating, but induction, electrostatic, or radiation-absorption heating may be used.