Theoretical Conditions for Burning in Solid Propellant Slots

Solid propellants suffer from a lack of active burning rate control. Active control could be capable of throttling propellant gas generation rates in applications ranging from adaptable airbags or other gas generators to solid rocket motors. In this study, we have investigated the concept of altering the burning behavior of solid propellants via surface area modification in the form of an adjacent slot. The conditions for burning in an adjacent slot to occur are considered, and several theoretical relationships are developed and presented between pressure and slot width for the threshold condition for penetration. The derivations assumed several different threshold criteria. Most considered convective heat transfer and applied an ignition threshold, whereas one derivation examined the quenching of a flame propagating into a slot. The resulting expressions were then applied to existing literature data and contrasted. The results showed that the derived equations fit the literature data well with our equation from the flame quenching derivation having the highest average R squared value.