LR91 is a rocket motor that is used in the 2nd stage of the Titan-23G space launcher. This motor uses two liquid propellants: nitrogen tetroxide (N0,) and Aerozine 50 (a 1:1 mixture of hydrazine (NH) and dimethyl- hydrazine (CH,N)). Assume that it is an ideal rocket motor with a nozzle expansion ratio (^/Ath) of 49, combustion chamber pressure and temperature are 5.6 MPa and 3400K. The exhausted gaseous products of the combustion have y = 1.3 and R = 390.4 1/(kg-K). Determine: a) The altitude at which the nozzle is designed for optimal expansion? b) If the nozzle exit diameter is 1.6 m, determine the nozzle throat diameter, mass flow, and the ideal thrust at the optimal altitude? 6.1-9.2 m Payload 7.3m 21.4m 2nd stage (LR91 motor) 1st stage (LR67 motor)