GROUND SCHOOL
Aerodynamic Flight and Modern Aerospace Craft
Aerospace craft of the 24th century are equipped with anti-gravity,
repulsor lifts, and in some cases warp field generators. This means that
in most cases, lift created by air flow over a wing surface is no longer
needed to maintain flight. However, to understand the principles of aerodynamic
flight (that which is concerned with lift generated by air flow) will help
you understand some of the design in many of the SFMC's aerospace craft,
especially the tactical ones.
Four Primary Forces
A craft in flight is the center of a continuous battle of forces.
The conflict of these forces is the key to all maneuvers performed. There
is nothing mysterious about the forces in question. They are defined and
well documented. The direction in which each acts can be calculated, and
the aircraft is designed to take advantage of each. These four forces are
known as lift, weight, thrust, and drag.
Lift is the force that acts in an upward direction to support the craft in the air. It counteracts the effects of weight, and is generated by air flow over a lifting surface, such as an aircraft wing. Rotary wing aircraft, commonly known as helicopters achieve lift by rotating a set of small wings rapidly, generating lift (hence the name "rotary wing aircraft").
Weight is the force of gravity acting downward on the craft and everything in the craft, including the crew, cargo and fuel. Lift must be greater than or equal to weight if flight is to be sustained.
Thrust is the force developed by the craft's engines, and it acts in the direction of motion. Thrust must be greater than or equal to the effects of drag for flight to begin or be sustained.
Drag is the force that tends to push against the craft. Drag is caused by the disruption of the airflow around the nacelles, the fuselage, and all protruding objects on the craft. Aerodynamic shapes reduce drag, and therefore allow for increased thrust. This is why the tactical aerospace craft employed by the SFMC retain much of the aerodynamic styling of older aircraft. Motion will become zero if the drag on the craft becomes greater than the thrust being applied by the aerospace craft's engines.
Newton's Laws of Motion
According to Newton's First Law of Motion (Inertia), an object
at rest will remain at rest, or an object in motion will remain in motion
at the same speed and in the same direction, until an outside force acts
on it. For a craft to taxi, hover or fly, a force must be applied to it.
It would remain at rest without an outside force. Once the craft is moving,
another force must act on it to bring it to a stop. It would continue in
motion without an outside force. This willingness of an object to remain
at rest or continue in motion is referred to as inertia, and is most notable
in space (where there is little atmosphere or gravity to create drag or
weight).
The second law of motion (Force) states that if an object moving with uniform speed is acted upon by an external force, the change of motion (acceleration) will be directly proportional to the amount of force and inversely proportional to the mass of the object being moved. The motion will take place in the direction in which the force acts. Simply put, this means that an object being pushed by 10 pounds of force will travel faster than it would have if it were pushed with 5 pounds of force. A heavier object will accelerate more slowly than a lighter object when an equal force is applied.
The third law of motion (Action and Reaction) says that for every action, there is an equal and opposite reaction. This law can be demonstrated with a balloon. If you inflate a balloon with air and release it without securing the neck, as the air is expelled the balloon will move in the opposite direction of the air rushing out.
Bernoulli's Principle
This principle states that when a fluid flowing through a tube
reaches a constriction or narrowing of the tube, the speed of the fluid
passing through the constriction is increased and the pressure of the fluid
is decreased. It is the shape of the aircraft wing and the motion of air
over it that creates lift. Air flowing across the flat bottom of a wing
has a higher pressure, since it travels a shorter distance. Air flowing
across the curved top of a wing must travel farther (and therefore faster),
decreasing pressure above the wing, creating lift.
Material on this page ruthlessly plagerized from the SFMC's Aerospace Branch Manual by Matt Kelley and available from SFMC Academy.
WebPage designed & maintained by Kevin "MAC" Nulty
