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The Aero Club
WATER ROCKET
Flight of Water Rocket
INTRODUCTION
• A water rocket is a
type of model rocket
using water as its
reaction mass.
PRINCIPLE
It is based on the NEWTONS THIRD LAW
OF MOTION.
WORKING
• Prior to launch, the body of the rocket is
filled with water to some desired amount,
typically about 40% of the volume.
• Air is pumped into the bottle rocket to
pressurize the bottle and thrust is
generated when the water is expelled from
the rocket through the nozzle at the
bottom.
Ideal Rocket Equation
Water rocket stability
• As the rocket accelerates away
from the launch pad, the
velocity increases and the
aerodynamic forces on the
rocket increase.
• The wind introduces an
additional velocity
component perpendicular to
the flight path
• The addition of this component
produces an effective flow
direction
• Since the effective flow is
inclined to the rocket axis, an
aerodynamic lift force is
generated by the rocket body
and fins.
• During the flight of a
model rocket small
gusts of wind, or
thrust instabilities can
cause the rocket to
"wobble", or change
its altitude in flight.
• Whenever the rocket
is inclined to the
flight path, a lift
force is generated
by the rocket body
and fins
• The aerodynamic
drag remains fairly
constant for small
inclinations.
• Lift and drag both
act through the
center of pressure
cp of the rocket
• A restoring force exists
for the model rocket
because the center of
pressure is below the
center of gravity.
• If the center of pressure
is above the center of
gravity, the lift and drag
forces maintain their
directions but the
direction of the torque
generated by the forces is
reversed. This is called a
de-stabilizing force
THANKS
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NOW….
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