For a solid propellant rocket motor with a sea level thrust of 207,000 lbf, determine: (a) the (constant) propellant mass flow rate and the specific impulse I at sea level, (b) the altitude for optimum nozzle expansion as well as the thrust and specific impulse at this optimum condition, and (c) at vacuum conditions. The initial total mass of the rocket motor is 50,000 Ibm and its propellant mass fraction is 0.90. The residual propellant (called silvers, combustion stops when the pressure falls below the deflagration limit) amounts to 3% of the burnt propellant. The burn time is 50 seconds, the nozzle throat area (4) is 164.2 in2 and its area ratio (A/A) is 10. The chamber pressure (pi) is 780 psia and the pressure ratio (pi/p2) across the nozzle is taken as 90.0. Neglect any start/stop transients and use the altitude data attached. a) m = 873 lbm/sec, 237 sec.
b) 13.900 ft, F-216.900 lof. 1,-248.5 sec.
c) F = 23 1,000 lbf Isp = 295 sec. 2 0.