Hot Air Balloons Work
On the 19th of September 1783, Pilatre de Rozier, a scientist, launched the first hot air balloon called ‘Aerostat Reveillon’. The passengers were a sheep, a duck and a rooster and the balloon stayed in the air for a grand total of 15 minutes before crashing back to the ground. The first manned attempt came about 2 months later on the 21st of November, with a balloon made by 2 French brothers, Joseph and Etienne Montgolfier. The balloon was launched from the center of Paris and flew for a period of 20 minutes. The birth of hot air ballooning!
Recently, balloon envelopes have been made in all kinds of shapes, such as hot dogs, rocket ships, and the shapes of commercial products. Hot air balloons work with buoyancy. You’ve heard people say “hot air rises,” right? Well, the air inside the balloon is heated up by the propane, and lifts the balloon off the ground because the air inside the envelope is hotter than the air outside of the balloon. It can be a little tricky to steer, as you can mostly only really control the balloon going up and down, but can raise and lower the balloon in a way that catches small wind currents as a way of ‘steering.’
THE PARTS OF A HOT AIR BALLOON
A hot air balloon consists of a bag called the envelope that is capable of containing heated air. Suspended beneath is a gondola or wicker basket (in some long-distance or high-altitude balloons, a capsule), which carries passengers and (usually) a source of heat, in most cases an open flame that runs on propane. The heated air inside the envelope makes it buoyant since it has a lower density than the relatively cold air outside the envelope. The deflation port at the top of the envelope allows hot air to escape at a controlled rate, slowing the rise of the balloon or allowing descent.
As with all aircraft, hot air balloons cannot fly beyond the atmosphere. Unlike gas balloons, the envelope does not have to be sealed at the bottom since the air near the bottom of the envelope is at the same pressure as the surrounding air. In today’s sport balloons, the envelope is generally made from nylon fabric and the mouth of the balloon (closest to the burner flame) is made from fire resistant material, such as Nomex.
Refer to the diagram at the left for more details.