Low Cost, Fluidic, Hot Gas Throttling Valve for Solid Fuel Propulsion Systems

A fluidic, tab-actuated, vortex valve is proposed to throttle solid propellant hot gasses. conventional approaches are expensive due to the need for close tolerances and exotic materials and reliability is poor due to the mechanical complexity. DRT's valve, operated by a simple vortex-tripping tab has been demonstrated in high speed pulsing of drilling mud in bore-hole telemetry systems and can vary its effective outlet area by more than 3:1. Combined with the burn rate pressure sensitivity of a solid propellant gas generator, 10:1 flow/thrust modulation can readily be achieved. An alternate concept, for those cases where the mass flow rate does not depend on chamber pressure, would use a chamber-pressure-bleed controlled, vortex valve designed to have an effective area variation in excess of 20:1, if desired. (A pressure reduction upstream of the vortex chamber would be needed to ensure a control pressure higher than the vortex supply pressure.) Actuation would be achieved using very low cost NASA-developed Rainbow piezo-electric benders to modulate the tab position or, in the case of flow-controlled valve, the control flow. These benders, capable of displacing 0.5 mm with several pounds of force in less than 200us, would cost less than $5 in production quantities. Projected production cost of the complete valve assembly, fabricated from molybdenum or TZM, including a PC interface is anticipated to be less than $1000 in quantities of 1000. In Phase I, an Inconel, brassboard system will be designed, built and tested on cold gas and the necessary hardware and software to support five hot gas tests will be provided to MICOM for evaluation. Analysis for a flight worthy system to be designed in Phase II will also be conducted.