US Government As Represented by the Secretary of the Army

Douglas L May

William M Chew

Leo K Asaoka

Darren M Thompson

Jay S Lilley

Elemental silicon is a solid high energy material which provides an advane when added to gel, hybrid, and ducted rocket fuels by increasing both specific impulse, lsp, and density specific impulse, .rho.*lsp. The quantity added depends on the specific applications for which the formulation will be used. The usual concentration ranges from about 0.5% to about 70% by weight. The important parameters to consider during formulation are particle size, concentration, combustion efficiency, physical properties, and plume signature. Comparisons for 50% solid fuel loading in a gel bipropulsion system predicts a maximum lsp of 286 lbf.s/lbm as compared to 267 lbf.s/lbm for carbon--a 7% increase. The .rho.*lsp produced by silicon is 14.5 lbf.s/cubic inch as compared to 13.7 lbf.s/cubic inch produced by carbon--a 7% increase. A 25% solid loading in solid fuel-gas generators for the hybrid rocket produced a maximum lsp of 278 lbf.s/lbm as compared to 267 lbf.s/lbm produced by carbon--a 4% increase. The .rho.*lsp produced by silicon is 14.8 lbf.s/cubic inch as compared to 14.1 lbf.s/cubic inch produced by carbon--a 5% increase. Another advantage for silicon loaded gel fuels is the large 'plateau' in the performance versus oxygen/fuel curves, and, resulting in a less stringent oxidizer-to-fuel ratio (O/F) control in an operational system.

Silicon as a high energy additive for fuel gels and solid fuel-gas

A propulsion system is disclosed comprising a glycidyl azide polymer (GAP) olid fuel generator (SFGG) that produces fuel-rich hot gases which are combusted in a combustion zone of a combustion chamber of a solid fuel ducted rocket. A basic embodiment comprises an airbreathing engine wherein a ducted member scoops air in from the atmosphere for hypergolic reaction with the fuel-rich hot gases for propulsion during a sustain stage of a flight. An augmentation of the basic embodiment is achieved by combusting the fuel-rich GAP SFGG effluent with inhibited red fuming nitric acid (IRFNA) gel oxidizer to produce higher thrust during the boost and dash stages of a flight. During the high thrust stages, the air ducts of the ducted member are closed and IRFNA gel is injected into the combustion chamber to react with the fuel-rich hot gases from the GAP SFGG. The resulting higher pressure in the combustion chamber gives the missile a correspondingly greater thrust than during the lower pressure airbreathing sustain stage of flight.

Solid fuel ducted rocket with gel-oxidizer augmentation propulsion

A gel/solid bipropellant propulsion system employs fuel-rich combustion gs from a solid gas generator and an oxidizer gel in a highly efficient combustion chamber wherein the fuel-rich combustion gases and the oxidizer gel are each metered through a vortex injector into a combustion chamber to produce a hypergolic reaction. The solid gas generator (SSG) has a preferred composition of glycidly azide polymer (GAP). The GAP SSG is composed of GAP diol and/or triol polymerized with a di-or tri-function isocyanate, such as isophorone diisocyanate. The gel/solid bipropellant propulsion system comprises the SSG in combination with an oxidizer storage/extrusion vessel system, a combustion chamber system, and a system controller which controls initial ignition of the SSG to produce fuel rich combustion gas which pressurize the system. The system controller monitors pressures and flow rates of fuel and gel oxidizer. System shut-down is achieved by closing valves in fuel-rich combustion gases supply line, gel oxidizer supply line, and a pressurization line to gel oxidizer storage/extrusion vessel. A blow-down line is opened to de-pressurize the SSG container which extinguishes the SSG. When start up is desired, a reignition shut-off valve is reopened which permits the injection of the gel oxidizer from the line retained under pressure and achieves reignition of the SSG.

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Huntsville, AL, United States of America

Douglas L May