Fins, attached to the side of a rocket below its center of gravity, help to maintain a stable flight path after the rocket is launched, according to the National Aeronautics and Space Administration, or NASA. Rockets have been equipped with fins since their invention in China during the 1200s. Rocket fin use continues in the 21st century, to aid stability and lift.
Fins are added to a rocket to increase its stability during flight. When a rocket is in flight, exhaust gases from the burning fuel do not always escape in a uniform fashion. Where the gases escape in a less-than-perfect way, the rocket can be forced to move in a sideways motion instead of traveling in a straight path. A rocket’s fins act against the air flowing over the exterior of the rocket, forcing it to move back to its intended direction.
A rocket can take one of a number of forms, including use solely as an engine or as a vehicle for transportation. The space shuttle, which transports people and equipment into space, uses rocket engines to achieve flight and movement. Rockets burn fuel that produces hot gases; the escaping gases push against the vehicle and the atmosphere to create propulsion. The force produced by the engine creates lift, which is controlled by the aerodynamic drag of the rocket.
During flight, a rocket rotates on its center of gravity according to its aerodynamic configuration, including the fins. A rocket in flight is inclined to an angle as it forces its way through the atmosphere, creating a lift force generated through the body of the rocket, according to NASA. The fins are designed to act against aerodynamic alterations that may influence the rocket’s movement along its intended flight path.
Rocket fins restore stability during flight. When a rocket’s propulsion is pushed to one side, it spins and, if uncorrected, becomes uncontrolled. Rotation causes the nose to rotate away from the tail and destabilize the rocket. The fins and the rocket design are configured to stabilize rotation, to maintain the required direction.