The world's first passenger-carrying hot air balloon flew over France in 1783. Join Richard Ambrose and Jonny Phillips as they explain how today's hot air balloons become light enough to leave the ground.
Hot-Air Balloons
Transcript JONNY PHILLIPS: Now we all know what a balloon is. It's basically a flexible bag filled with air or some kind of gas. And we often associate them with kiddies' parties, but believe you me there's a lot more to the story of balloons than cakes and clowns. Rich what are you doing? Come down.NARRATOR: Today, balloons of all shapes and sizes are used for all sorts of things, from lighting up sporting events to advertising.Doctors use them to open arteries of patients with heart disease.Surgeons can use them to stretch skin, allowing women to have bigger silicone implants.Film companies use them for lighting and providing birds eye views of football games. And scientists use them to gather vital information from the Earth's atmosphere, and even occasionally send them into space. Oh, and they're also quite fun to fly and are, in fact, man's oldest form of manned-air transport.In 1783 one hundred and twenty years before the Wright brothers took to the skies, the world's first passenger carrying hot air balloon flew over France.It managed to climb to around 500 meters and travelled more than 3 kilometres before landing in a forest.So what did the passengers think? Well, it was hard to tell, because the passengers on this historic flight were a sheep, a chicken and a duck.RICHARD AMBROSE: Of course it wasn't long before humans followed where those intrepid farmyard animals led and balloons were taking to the skies across the world.NARRATOR: So how do hot air balloons become light enough to leave the ground? Well, as you've probably guessed, the clues in the name.JOHNNY: As air is heated it begins to expand, becoming less dense and more buoyant than the colder air surrounding it and so it begins to rise.RICHARD AMBROSE: And we've got a little demonstration involving a toaster for you.JONNY PHILLIPS: Now, if you just take a cereal packet and place it over the toaster, and this is to keep the heat from the plastic bag from burning it, we don't advise doing this at home.ON SCREEN TEXT: DO NOT ATTEMP AT HOMEJONNY PHILLIPS: And then, turn the toaster on.RICHARD AMBROSE: Power it upJONNY PHILLIPS: And the hot air rising should lift the bag.RICHARD AMBROSE: In a hot air balloon this rising air produces lift and given enough heat it will eventually lift the balloon off the ground or over the toaster in this case. Success.RICHARD AMBROSE: Our first flight, Jonny.NARRATOR: But to lift anything significant, you do need to heat an awful lot of air. Which is why a typical hot air balloon will have a volume approaching 7000 cubic meters.JONNY PHILLIPS: Although ballooning has been around for a very long time, hot air balloons as we know them today, with their wicker baskets, propane burners, and teardrop shapes are really a relatively recent invention, dating in fact from the 1960s.NARRATOR: The first ones were funded by the US Navy, but the public loved them too and the sport of hot air ballooning was back in the public eye more than 170 years after it's invention.RICHARD AMBROSE: The real breakthrough came with the addition of lightweight propane burners, I've got one here. Watch this it's impressive.NARRATOR: In a modern hot air balloon the liquid propane enters these coils where it's heated up and turns into a gas.RICHARD AMBROSE: WowNARRATOR: The advantage of burning hot gas is that it produces a much bigger flame and dramatically increases the efficiency of the burners.JONNY PHILLIPS: Heating the air inside the balloon and letting it cool down is the main way that the pilot has of controlling altitude. But it's not the only way, they can also open a flap at the top of the balloon, called a parachute valve, which allows air to escape quickly, which in an emergency could be a lifesaver.However, in terms of direction the balloon is really at the mercy of the wind, but the wind blows in different directions at different altitudes, so by going up and down the pilot does have some control over where they end up.