There are four major
components
to any full scale rocket; the
structural system
or frame, the
payload system, the
guidance system, and the
propulsion system.
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 stability for the rocket,
and to control the rocket during maneuvers.
The
motion
of any object in flight is a combination of the
translation
of the center of gravity and the
rotation
of the object about its
center of gravity.
Many different
methods
have been developed to control rockets in flight.
All of the control methods produce a
torque
about the rocket's
center of gravity
which causes the rocket to rotate
in flight. Through an understanding of the
forces
acting on the rocket and the resulting
motion,
the rocket guidance system can be programmed to
intercept targets, or to fly
into orbit.
A
stable
rocket is one which naturally returns to its flight configuration
when it is perturbed from that configuration.
For simple rockets flying within the atmosphere, stability is
assured
if the
aerodynamic forces
acting through the
center of pressure
are kept below the rocket center of gravity.
Fins located at the bottom of the rocket, or
weight added to the top of the rocket help to
establish this condition.
For complex rockets, or for rockets flying above the atmosphere,
stability can be provided by the guidance system, using
the same methods employed for maneuvers.
On this slide, we show a picture of a Atlas rocket
at the left and a picture of the Space Shuttle at
the right.
The Atlas rocket was developed in the late 1950's
and used small vernier rockets on the sides
of the missile to provide maneuvering and balance.
The Space Shuttle was designed in the late 1970's and
employed the more modern
gimbaling
of the main engines to provide for control during launch.
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