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MAE112HW7

# MAE112HW7 - MAE 112 Propulsion Homework Assignment#7 Due...

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1 MAE 112 Propulsion Homework Assignment #7 Due: March 5, 2010 1. Consider an ion rocket with a 1200 volt drop in potential between the accelerating electrodes placed 60 centimeters apart. Xenon of atomic weight 54 is the propellant. The charge to mass ratio is 7.34 x 10 5 coulombs per kilogram. One volt equals one newton- meter per coulomb. The cross-sectional area is 125 cm 2 . 0 = 8.85 x 10 -12 (coulomb) 2 /newton-meter. Determine the (a) exit velocity, (b) specific impulse, (c) maximum beam current, (d) thrust at maximum beam current, and (e) mass flow at maximum beam current. (f) What are the thrust and the mass flow if the rocket operates on one-half of the maximum current? 2. Design an arc jet that produces 200 1bf of thrust. Give maximum chamber temperature and pressure. Describe propellant choice. Give mass flow of propellant, throat area, exit velocity, and exit pressure. 3. Helium has the ionization potential of ε = 24.48 electron volts. (1 ev = 1.602x10 -19 joules.) The Saha equation, adjusted for degeneracy in the helium states, gives 3/ 2 / 3 (2 ) 4 kT electron

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