It’s true. But there is a very complex science behind this flight method
If you've seen the heartwarming Disney film Up, then you have a slight idea of what we're about to discuss. If like us, you can’t get over that magical moment when the house was lifted by hundreds of colorful balloons and even managed to travel to a distant land then keep on reading. We’re about to explain why being carried off by a helium balloon up in the sky is certainly possible.
A flying house tied to helium balloons might be near impossible to recreate in real life, although lifting something lighter, such as a single human, is perfectly achievable. A performer and magician, David Blaine, will attempt to prove the concept on Sep. 2, after 10 years of preparations. He wants to soar in the sky and fly in Arizona by holding onto balloons.
All he needs is a lot of helium balloons. How many you may ask? Well, Blaine just has to use this helium balloon calculator to figure it out. We wish him good luck, and we're keeping our fingers crossed.
Why do helium balloons float?
Before we determine how many helium balloons can lift a person, let's start with a bit of theory. Why do these balloons float in the first place? It happens because they are filled with helium—a gas lighter than air.
You probably already know the phenomenon of buoyancy. For instance, an inflatable mattress floats on water, because the air it's filled with is lighter. The same principle applies here. As the density of helium is lower than air, a balloon filled with helium gas will start moving up.
The density of helium is equal to 0.1785 grams per liter while the density of air is about 1.25 grams per liter. Leaving some tolerance for the weight of the balloon and the string, we can approximate that every liter of helium has a lifting force of one gram.
There are a few more gases that are lighter than air such as hydrogen, ammonia, or methane. They are not commonly used in balloons as they are easily flammable. Nevertheless, you can change the gas type in this helium balloons calculator to compare between them and helium.
How many balloons to lift a person?
Let's get on with the calculations. As you have just learned, the lifting force of helium is approximately one gram per liter. It doesn't seem like much, that's why you will need a lot of balloons to start flying!
1. Determine your weight - for instance, 75 kg. This number should include everything that will be flying, so your clothing as well. Every gram counts.
2. Choose the size of the balloons. Let's assume we are using regular balloons from an amusement park, with a diameter of 30 centimeters (11 inches). In the advanced mode, you can enter a custom size of the balloon.
3. Calculate the volume of a balloon. We will assume that the balloons are perfectly spherical and use the sphere volume formula:
V₀ = 4/3 * π * r³ = 4/3 * π * (30/2)³ = 14137 cm³ = 14.137 liters
Now, convert your weight to grams:
75 kg = 75000 g
4. Now, we'll find out how much helium we need. If you're performing these calculations by hand, you can surely use the lifting force of one gram per liter, yet our helium balloons calculator uses a more precise value of 1.0715 g/L:
V = 75000 / 1.0715 = 69995 liters
5. Finally, divide the total volume of helium needed by the volume of one balloon to find out how many balloons lift a person:
n = V / V₀ = 69995 / 14.137 = 4951
You will need roughly five thousand balloons to fly. It's quite a lot, isn't it? If, however, you chose balloons that are 12 feet in diameter, you would only need three of them to lift you up.
In the video below, a group of scientists tried to lift themselves with monster balloons (a diameter of 98" or 2.5 m). In the end they used 18 balloons, which approximately held 96,000 liters of helium. It looks like they almost achieved it.
A real-life Up house
We mentioned in the beginning that recreating the memorable Up moment is near impossible. But a team from National Geographic have tried and accepted the challenge in 2011. They constructed a special lightweight house and lifted it up in the air using 300 eight-foot-tall balloons. The house soared 10,000 feet into the sky and flew around for approximately one hour.
If you don't believe us, here's the actual video footage to change your mind