Flying model rockets is a relatively
and inexpensive way for students
to learn the basics of forces and
the response of vehicles to external forces.
Like an airplane in flight,
a model rocket is subjected to the
forces, lift and drag.
The relative magnitude and direction of the forces
determines the flight trajectory of the rocket.
On this slide we show the events in the flight of a single stage
Throughout the flight, the weight of a model rocket is fairly constant;
only a small amount of solid propellant is burned relative to the weight of
the rest of the rocket. This is very different from
full scale rockets
in which the propellant weight is a large portion of the vehicle weight. At
the thrust of the rocket engine is greater than the weight of the
rocket and the net force accelerates the rocket away from the pad. Unlike
full scale rockets, model rockets rely on aerodynamics for
stability. During launch, the velocity is
too small to provide sufficient stability, so a launch rail is used.
Leaving the pad, the rocket begins a
Thrust is still greater
than weight, and the aerodynamic forces of lift and drag
now act on the rocket. When the rocket runs out of fuel, it enters a
The vehicle slows down under the action of the weight and drag since
there is no longer any thrust present. The rocket eventually reaches some
maximum altitude which you can
using some simple length and angle measurements and
The rocket then begins to fall back to earth under the power of gravity.
rocket has been coasting, a delay "charge" has been slowly burning in the
rocket engine. It produces no thrust, but may produce a small streamer of smoke
which makes the rocket more easily visible from the ground. At the end of
the delay charge, an ejection charge is ignited which pressurizes the body tube,
blows the nose cap off, and deploys the parachute.
The rocket then begins a
under parachute to a recovery.
The forces at work here are the weight of the vehicle and the drag of the
After recovering the rocket, you can replace the engine and fly again.
On the graphic, we show the flight path as a large arc through the sky.
Ideally, the flight path would be straight up and down; this provides the
highest maximum altitude. But model rockets often turn into
the wind during powered flight because of an effect called
weather cocking. The effect is the result
of aerodynamic forces on the rocket and cause the
to be slightly less than the optimum.
Types of Rockets:
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