Ready, Set, ... Jet!

If you looked at the history of flight links in the last entry, you may have noticed that many of the earliest "flying machines" were actually gliders, which flew without power. Like a modern glider, they needed help getting going. The importance of the Wright Brothers' invention was that their airplane had an engine, and could take off from the ground.

Modern airplanes usually use either propellers or jets to move. Let's talk about jet engines here. Jet engines work by blowing gas out through a small hole called a nozzle. Air is sucked into the front of the engine by a fan. The air is then mixed with fuel and ignited. The hot gas, which is at high pressure, comes rushing out the back, pushing the jet engine (and whatever it is attached to) forward.

You can make a simple jet engine with things you may have around the house.

What you'll need:

Balloon

Tape

Drinking straw

Long piece of string

Blow the balloon up and just hold the empty end closed. Tape the drinking straw to the balloon as shown in the picture. Let the air out of the balloon.

Now find a place to tie the string that lets you stretch it out to its full length. Try a doorknob in a fairly large room. Tie one end of the string, then thread the string through the drinking straw. Stretch the string out, keeping the balloon near your end. Blow the balloon up and hold the end closed again. Make sure that the string is straight, then let go of the balloon. As the air rushes out, the balloon will take off along the string. How far can you make it go?