Experimental Investigation of Poly(methyl Methacrylate) Cooling Beds for Warm Gas Generator Applications

Abstract

Throttleable solid propulsion systems are sometimes supplied using solid gas generator systems. Solid propellants, such as ammonium perchlorate-based composites, have been extremely useful for boost propulsion, but flame temperatures generally exceed material limitations of valve-controlled thrusters. The objective of this research is to experimentally investigate the use of a solid propellant flowing through a deflagrating cooling bed to lower gas temperatures for warm gas controllable thrusters. A nonaluminized, ammonium perchlorate solid propellant generated hot combustion gases that flowed through a polymethyl methacrylate (PMMA) coolant chamber. The cooling chamber contained a PMMA center-perforated cylinder as a cooling material. Experiments were conducted in a constant pressure chamber and in laboratory-scale solid rocket motors at pressures up to 600 psi. The results showed that as the mass flux of the hot gases increased, so did the regression rate of the coolant material. The initial and final PMMA profiles of the cooling material were used to develop a PMMA regression rate correlation as a function of average gas flux. The average mass flux ranged from 0.067 to [Formula: see text], whereas the regression rate ranged from 0.008 to 0.044 in./s. The net cooling effect ranged from 510 to [Formula: see text]. The Nusselt number correlations are also presented for the warm gas generator.