SBIR-STTR Award

High performance combustion power systems for small untethered submersible vehicles will be sought by comparing proven methods with modern alternatives, Including advanced cryogenics and solid-state storage of hydrogen and oxygen. A large list of potentially attractive combinations of reactants, converters, and exhaust collection processes will be examined from two viewpoints. First, the chemical issues will be considered, calculating gravimetric and volumetric energy densities for the aggregate of fuel, oxidizer and any chemical species required to process the exhaust stream. Containers for reactants and products will be Included in the weight and volume estimates so that the effects of cryogenic dewars, pressure vessels, hydrides, oxides, etc., Are accounted for. The second issue in the selection process will be mechanical equipment evaluation Including a variety of engines, and exhaust processing equipment. Each system will be characterized by its net efficiency, weight and envelope volume. The best chemical options will be paired up with appropriate mechanical equipment and at least three systems will be compared in detail to form the final conclusions of the study. The best alternative will be built and tested in phase ii and demonstrated at full-scale in the reynolds aluminaut in phase III.

The Phase I study examined methods for storing and converting chemical energy for propulsion of submersible vehicles. Liquid oxygen and hydrogen, generated from the reaction of solid chemicals with water, were found to offer the highest energy density in a neutrally buoyant volume. Closed cycle internal combustion engines were found to be superior to fuel cells in terms of cost, reliability, size and weight, but less efficient and noisier. Phase II offers experimental proof of two enabling features of the proposed power system: 1) the hydrogen generation process, similar in concept to that used for many years to fill weather balloons, can be carried out in external storage bladders suitable for deep submersibles, 2) hydrogen engines in sealed pressurized engine compartments can rival the efficiencies of fuel cells. A successful demonstration of (1) is equally useful for hydrogen engines or fuel cells. Most of the work in Phase II is directed toward designing the hydrogen generator. A smaller portion of the Phase II effort will go toward proving (2). A successful result leaves noise as the only advantage of fuel cells over internal combustion engines. Noise experts are optimistic about the possibility of silencing the hydrogen engine.