Exit area is not given A rocket motor operates steadily as s

Exit area is not given

A rocket motor operates steadily as shown below. The molecular weight of the exhaust gas is 26 and has k = 1.4. Compute the exhaust velocity and temperature, and the diameter of the exhaust nozzle.

Solution

Exit gas: Molecular weight 28, thus

Rgas 49700/28 1775 ft2/(s2 °R). Then,p exit= P/RT =15(144)psf/(1775)(1100+460)=0.000780slug/ft2

for mass conservation the exit mass flow must be equal to fuel+oxygen entering=0.6 slug/sec

m exit= 0.6slug/sec p_e A_eVe   =(0.000780)(pi)/4(5.5/12)² V_e = solve for Ve=4660ft/sec

exit

e

A V (0.00078)

V ,

s

Ans

s

e e

4

e

e

12