Take Flight With Science!
- Monday, January 26, 2009
At some time in our lives, we all wish we could “sprout” wings and fly. People have been curious about flight for thousands of years. In ancient times, myths and legends involving winged horses and humans abounded, and today inventors and scientists continue to pursue the invention of flying machines.
The first “flying” objects invented by man were kites. The ancient Chinese have been credited with this invention. Their original kites were made of silk stretched upon a bamboo frame. Legend has it that the first kite was created when a farmer living in ancient China tied a string to his hat to keep the wind from blowing it away. However, the earliest written account we have about kite flying was recorded around 200 B.C. According to historical records, Chinese General Han Hsin of the Han Dynasty flew a kite over the walls of a city he was attacking in order to measure how far his army would have to tunnel to reach past the defenses. Knowing this distance, his troops tunneled inside the city, surprised their enemy, and were victorious.
The Study of Aerodynamics
Leonardo da Vinci was one of the first people to study and analyze basic principles of aerodynamics and flight. He began observing birds and their flight in his youth and sketched what he observed.
Da Vinci designed a number of flying machines, including a flying machine with flapping wings, called an “ornithopter.” The wings were powered by the “pilot.” Unfortunately, humans don’t possess the strength to keep such a machine in the air. Even though he was not able to build his ornithopter, Da Vinci addressed many key concepts related to flight, such as the structure of wings, carrying surfaces, landing gear, and devices for directional control. He even sketched the earliest concept of a helicopter, which he called the “aerial screw.” He was truly a designer and inventor ahead of his time!
Sir Isaac Newton contributed greatly to the study and understanding of flight and aerodynamics. In 1655 he proposed three laws of motion, which today explain why a plane flies:
- If an object is not moving, it will not start moving by itself.
- If an object is moving, it will not stop or change direction unless something pushes it.
- When an object is pushed, it will move farther and faster when it is pushed harder.
- Observe birds and study their wing structure. Check out the drawings on this webpage www.biology-resources.com/drawing-bird-wing.html. Based on your child’s personal observation and research, have him draw his own sketches.
- Look at sketches of da Vinci’s ornithopter.
- Use drinking straws and tape to design and build an ornithopter wing. Cover it with tissue paper when the frame of the wing is complete.
Airborne at Last!
The first successful human flight was made in a hot air balloon. In 1783, two French brothers by the name of Montgolfier created a giant balloon made of paper and linen. They filled it with hot air and sent two friends into the sky above Paris. The balloon is reported to have traveled 5 miles.
Hot air balloons work because the air around us is made of molecules. In cold air, the molecules do not move much and are close together. As air is heated, molecules move around more and have more space between them and therefore start to rise. This is why hot air is used to fill a hot air balloon.
- Use the spiral cutout in the activity file found at http://www.treaureboxpres.com/TOSFlightActivities.pdf to make a paper spiral with a string attached to one end. Have an adult light a candle and hold the spiral over the flame. The spiral will start to twirl as the hot air from the candle rises. The air molecules warmed by the flame are farther apart and move more; therefore they rise, causing the spiral above to spin.
- Blow up a balloon. Cover it completely with paper maché. After the paper maché has dried, paint the outside of your hot air balloon and pop the balloon (optional). Using a single hole-punch, punch three holes around the top of a small paper or plastic cup. (This will serve as the gondola for your hot air balloon.) Using three pieces of string or chenille stick, thread one through each hole in the gondola. Attach the gondola to the hot air balloon with tape. Paint your balloon.
- Label the parts of a hot air balloon (http://www.treaureboxpres.com/TOSFlightActivities.pdf).
The Physics Behind Flight
George Cayley was one of the first men to study and analyze aerodynamic forces, including lift and drag. He discovered that a curved aerofoil shape created more lift on an airplane wing than a flat plate. In 1804 he built his first model monoplane glider.
Cayley’s findings are based on earlier work by Daniel Bernoulli. In the early and mid-1700s, Bernoulli studied fluid flow, pressure, density, and velocity. Cayley understood that great power would be needed for flight, so he tried to build an internal combustion engine using gunpowder! He discovered that air has pressure and that the faster air moves, the less pressure it exerts. Cayley also realized that air also moves in a stream over the wings.
Applying these insights to flight, when an airplane wing flies through the air, the air divides and flows over and under the wing. The air going over the top travels faster to reach the trailing edge of the wing. Because the air traveling over the wing is moving faster, it exerts less pressure on the wing than the air below. The air under the wing is pushing up more than the air above is pushing down. This is called “lift.” Airplanes are heavier than air. They fly because of the aerodynamic force generated by the flow of air over the lifting surface.
Flight is made possible by four forces:
- Weight caused by gravity pulls everything down toward the ground.
- Drag is the backward and downward movement.
- Lift is upward motion caused by air moving over the wings.
- Thrust is the forward force. It is produced by an engine as it overcomes the force of drag.
The Wright Brothers and Beyond
Orville and Wilbur Wright grew up in Ohio with parents who supported their creative and mechanical thinking. Their first endeavor together was a printing business. In their early twenties, they printed their own newspaper on a printing press they constructed from a tombstone and buggy parts!
Their interests eventually turned to bicycles and then gliders. Using their ingenuity, they constructed a wind tunnel in which to test their glider ideas and designs. Between 1900 and 1902 they built and tested several gliders, and in 1902 they successfully flew a glider 620 feet at Kitty Hawk, North Carolina. However, they didn’t stop there. The Wright Brothers returned home in 1902 to add a propeller and engine to their design. On December 17, 1903, Orville Wright flew 120 feet in a machine-propelled airplane.
Over the next one hundred years, airplane design advanced rapidly, and space travel became the next frontier for aviation. In fact, while the Wright brothers were testing their gliders, a young boy named Robert Goddard was writing school papers about space travel and proposing ways to propel a rocket into space.
Robert Goddard is known as the Father of Rocketry. In college he earned two patents, one for a rocket using solid and liquid fuel, and the other for a multi-stage rocket. He went on to pioneer combustion chambers and more complex rockets. Goddard also developed systems for steering rockets and using gyroscopes.
- Enjoy making paper airplanes, including (1) an airplane that flaps its wings, (2) gliders, and (3) a boomerang copter. An extensive collection of printables can be found at this site: www.ss42.com/pt-planesfly.html.
- Find out when the Space Station and any orbiting shuttles are visible at this website: http://www.nasa.gov/mission_pages/shuttle/main/index.html.
Accepting the Challenge
Space travel is entering a new era. Recently the X PRIZE Foundation offered a $10,000,000 prize to the first non-government organization to launch a reusable manned spacecraft into space twice within two weeks. Burt Rutan and his team at Scaled Composites were the first team to accomplish the goal with their SpaceShipOne. Rutan invented an ingenious way of getting SpaceShipOne back to Earth safely, with a unique “feathering” system.
When any object falls through our atmosphere, it is moving at a very fast rate. When the object falls, friction is created. Friction causes heat. Have you ever seen a “shooting star”? These meteors are rocks that have fallen into the Earth’s atmosphere from space. They are going so fast that a large amount of friction and heat are created, which causes the rock to burn up. To us, these meteors look like “shooting stars.”
Hold your hands against your face. Now, rub your palms together for ten to twenty seconds. Then hold your palms up to your face. Your palms will feel warm against your skin. This is because the friction created heat. The Space Shuttles built by NASA have special tiles on the underside to keep the Space Shuttles from burning up when they travel back home through the Earth’s atmosphere. Mr. Rutan, however, invented a way to slow SpaceShipOne down by using drag only.
Have you ever put your hand out a car window and faced your palm toward the front of the car? You would have felt the air pushing against your palm. This is how drag works to slow down SpaceShipOne. The wings and tail booms fold up. This causes enough drag to slow down SpaceShipOne and keep it from getting too hot from friction. Mr. Rutan calls this “carefree reentry.”
Activity: Build a model of SpaceShipOne using the template and instructions in this file www.deepspringspress.com/TOSFlightActivities.pdf.
Activities: The following activities will demonstrate to your child the concept of air pressure and lift.
- Make an aerofoil shaped wing. You'll need paper, tape, thread, and a needle. Cut a piece of 8½ x 11 paper in half horizontally to make a piece 8½ x 5½. Hold the paper so the 8½-inch side is at the bottom. Fold the left (5½-inch) side in about 3 inches. Roll the other 5½-inch side in and under the folded flap on the other side. Tape the flap to the top of the wing. It should form a bulge with a rounded edge on one side and the folded crease on the other.
Tape the ends of the paper together so that it creates a wing shape (flat on the bottom and curved on the top). Thread the needle. About a third of the way back from the rounded edge of the wing, push the thread through the top and bottom of the wing. Remove the needle from the thread. Hold both ends of the thread. Blow air over the front end of wing. Low pressure is created when the air flows over the wing. This causes the wing to rise.
- Gather two empty 1-liter plastic soda bottles with caps, a nail, and two balloons. Punch a hole in one of the bottles about an inch from the bottom. Insert an un-inflated balloon into each bottle, and stretch the opening of the balloon over the opening of the bottle. Try to blow up each balloon. What happens?
The balloon in the bottle without the hole does not inflate, because the air in the balloon is at the same pressure as the outside air and the air in the bottle. As you blow into the balloon, air pressure in the lungs is greater than the air pressure in the balloon. Next, punch a hole in the bottle and try to blow up the balloon. When you blow up the balloon, the air in the bottle flows out the hole, so the pressure in your lungs exceeds the pressure of the air in the bottle, which allows the air to continue to flow and inflate the balloon. If you cover the hole again, the expansion of the balloon decreases the volume of the air in the bottle, and the pressure is increased. The pressure in the bottle then increases to equal the pressure of the air in your lungs, making it impossible to blow more air into the balloon.
The history of flight is rich with ingenuity and creativity, which makes it a topic that is easy to blend into your history, science, and literature studies. Listed below are some additional sites and resources to enrich your flight unit study.
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