Alan Higashi, Age 10, of San Leandro, Calif., for his question:
What is a wind tunnel?
One of the biggest wind tunnels is near San Francisco at moffet Field. It is a huge testing room, big enough to hold a jet fighter. At one end of the big barn, a mighty, man made wind can be turned on and off. Experts test the plane in the wind tunnel to learn whether it can stand the stormy stresses of real flight.
Dozens of experts work to design a new plane. Models and metals are tested and retested. The wind tunnel is one of the toughest tests. It may be a few inches wide or bigger than a barn. At one end of the tunnel is a metal grill, and behind the grill are fans and motors to turn them. The motors may have enough power to drive 2000 cars.
The man made wind can come roaring down the tunnel like a hurricane or sighing like a soft breeze. It can be Wet or dry, hot or icy cold. These are some of the conditions a plane will meet when it takes to the air. Small tunnels are used to test a streamlined Wing or some other part of the plane. Big tunnels are used to test jets and propeller planes, guided missiles and every satellites.
A finished plane may go into a wind tunnel before the test pilot takes it up for its first trip. It is propped there on supports and clamped dorm so that it does not blow away. Instruments are fixed 'co its wings and its sides, its nose and its tail. The instruments are connected to more instruments outside the Wind tunnel. The experts can read these outside gadgets and learn how the plane is holding up under the stormy stresses inside.
Wind is moving air, and on a breezy day there are sheltered spots and breezy corners. One side of a house may be calm and sheltered while a high flying flag rippies like a wavy sea and, in a corner; perhaps the breezes are waltzing a whirlwind.
The moving air must blow over some objects and around others. Its tricky antics are following the laws of aerodynamics. A fast plane pushes ahead, and the moving air around it must follow the same rules as the wind. These aerodynamics are tested in a wind tunnel.
A plane is streamlined to let the air flow around it. Cushions of dense air pile up under the plane to help it lift and stay aloft. When it reaches the speed of sound, walls of air pile up in front, and the plane smashes through with a sonic boom. All these tricks of aerodynamics are studied when a plane is tested in a roaring wind tunnel.