S.1 Spacecraft Propulsion Systems Chapter 1: Introduction to ...

Kinetic energy in the expelled mass
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Electric propulsion leads to higher exhaust velocities achieved by chemical propulsion (ve
< 5000 m/s), by this saving mass of propellant.
Power Input
Since power is the major constrain for electric thrusters on spacecraft, the following example will
illustrate the impact of power on limiting of thrust levels for electric propulsion.
The power input to a thruster system is:
ve
P = F [W]
2η
F
2η
= P [N]
ve
With the assumption:
P = 1000W power input
η = 1 (to simplify)
ve = 30 000 m/s typically for electric thrusters
The resulting thrust will be:
2 ⎡W ≡ Nm / s⎤
F = 1000 = 0.
067
30000 ⎢
⎣ m / s ⎥
⎦
[ N ]
Conclusion: Thrust levels of electric propulsion will be