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

S.3 Basic Equation of Thrust
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Basic rocket propulsion equations are based on Newton Law of Motion
For constant propellant exhaust velocity ve at thruster nozzle outlet, and with thrust force F
collinear to ve, gives the
The Basic Equation for Force of Thrust
o
v m F = [N]
e
From the Law of Conservation of Momentum follows:
v m m v ⋅ ∆ − = ⋅ ∆ [Ns]
e
which is the change of momentum of spacecraft. This implies the change of momentum of
the expelled propellant.