There are four major components to any full scale rocket;
structural system or frame, the
payload system, the
guidance system, and the
The guidance system of a rocket includes very sophisticated
sensors, on-board computers, radars, and communication equipment.
The guidance system has two main roles during the launch
of a rocket; to provide
for the rocket,
and to control the rocket during maneuvers.
Many different methods
have been developed to control rockets in flight.
On this slide we look at four of these methods. The
of any object in flight is a combination of the
of the center of gravity and the
of the object about its center of gravity,
which is also called the
center of mass.
All of the control methods produce a
about the rocket's
center of gravity
which causes the rocket to rotate
in flight. Through an understanding of the
acting on the rocket and the resulting
the rocket guidance system can be programmed to
intercept targets, or to fly
Early rockets and current air-to-air missiles typically use
movable fins at the rear of the rocket.
The movable fin adjusts the amount of the
on the rocket. The aerodynamic force acts through the
center of pressure
which is normally not located at the center of gravity.
The difference in location generates the torque about the
center of gravity, or center of mass.
On the figure, the trailing edge of the fin facing us
has been colored magenta and
has been deflected to the right. The resulting aerodynamic force
would move the nose of the rocket to the right.
Most modern rockets rotate, or
the nozzle to produce the control torque.
In a gimbaled thrust system, the exhaust
of the rocket can be swiveled from side to side. As the nozzle is moved,
the direction of the
is changed relative to the
center of gravity
of the rocket.
On the figure the rocket nozzle is colored magenta
and has been pivoted to the right. The resulting thrust
force would move the nose of the rocket to the right.
Some older rockets, like the Atlas missile, used small
additional rocket engines at the bottom of the main rocket
to generate the control torque. The small control rockets were
called vernier rockets.
In the figure, the right vernier rocket engine is colored
magenta and has been fired to
cause the nose of the larger rocket to move to the right.
Because of the additional weight for the fuel and plumbing,
vernier rockets are not used much any more.
On some early rockets, like the V2 and Redstone rocket, small
thrust vanes were placed in the exhaust stream of the main rocket
to deflect the thrust and produce a control torque. In the figure,
a thrust vane has been colored magenta and is deflected to the
right. This causes the exhaust stream to be deflected and the nose
of the rocket would move the right.
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