Air is Stuff
Air is not just empty space—it has substance, or mass. Air has molecules that are constantly moving. Because air has mass, Earth’s gravity attracts it and gives it weight. Because…
Gravity Keeps Us Down to Earth
WHAT IS GRAVITY? Gravity holds us to the surface of the Earth and keeps our atmosphere wrapped around our planet. An object’s weight is a measure of the gravitational force…
Gravity & Air
Understanding the basics—gravity and air—is key. To rise above it all, you have to face some facts: You must grapple with gravity no matter how or where you fly, because…
We Aren’t Built to Fly
WE JUST AREN’T BUILT TO FLY Birds inspired our first attempts to fly, but our progress was limited until we learned that we could not fly like them. Thanks to…
The Four Forces
FOUR FORCES AFFECT THINGS THAT FLY: 1. Weight is the force of gravity. It acts in a downward direction—toward the center of the Earth. 2. Lift is the force that acts at a right…
Forces of Flight
Understanding how things fly begins by learning about the Four Forces of Flight. When an airplane flies, the wing is designed to provide enough Lift to overcome the airplane’s Weight, while the engine…
Shaped for Space
HOW DOES SPACE AFFECT STRUCTURE? If a spacecraft flies only in space and not through an atmosphere, it does not have to deal with drag. Its shape and configuration can…
Hypersonic Vehicles
WHAT HAPPENS TO VEHICLES AT HYPERSONIC SPEEDS? A vehicle designed to fly at hypersonic speed (more than five times the speed of sound) or to reenter the atmosphere must be…
Materials
WHAT KINDS OF MATERIALS ARE USED TO MAKE AIRCRAFT? Several materials can be used for major structures—wings, fuselage, or landing gear, for example—on different types of aircraft. Airplane rivets. ● Wood…
Weight and Strength
HOW DOES AN AIRCRAFT BALANCE WEIGHT AND STRENGTH? Finding a safe compromise between low weight and high strength is critical when creating an aircraft. Aircraft structures must be light yet…
