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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 crosssectional area is 125 cm
2
.
0
= 8.85 x 10
12
(coulomb)
2
/newtonmeter.
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 onehalf 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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This note was uploaded on 03/13/2010 for the course MAE 19070 taught by Professor Larue during the Winter '09 term at UC Irvine.
 Winter '09
 LaRue

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