A∗ Nozzle throat area Ae Exhaust nozzle area c∗ Exhaust characteristic speed cp Specific heat at constant pressure cv Specific heat at constant volume CD Discharge coefficient Cf Thrust coefficient d External diameter first stage d2 External diameter second stage e Combustion chamber thickness ee Insulator thickness eh Specific heat ep Pyrolyzed thickness et Insulator thickness f First stage combustion chamber safety factor g0 Normalized acceleration at Sea level ISP Ideal specific impulse at Sea level Isp Simplified ideal specific impulse Ispdelivered Delivered specific impulse k Average specific heats in the mixture kcombustion Specific heat in the combustion chamber knozzle Specific heat in the nozzle outlet Me Exhaust Mach number Meff Effective molecular weight mP roducts (g) Gaseous products mol ms Mass per area mSystem System mass m∗ Throat ideal mass flow m∗ Throat average mass flow p Maximum internal pressure P∗ Throat pressure P0 Combustion chamber pressure Pa Atmospheric pressure Pburst Burst pressure Pe Exhaust nozzle pressure Qa Ablation heat R Universal constant of perfect gases T∗ Throat temperature T0 Combustion chamber temperature Ta Ablation temperature tburnout First stage burnout time Te Exhaust temperature va Ablation speed