Note: I wrote this for FS 101 at Allegheny College, a first-year seminar that taught critical thinking in the style of MythBusters, and I also presented it as a speech. Lightly formatted for the web, otherwise as submitted. I was proud of this one.
Introduction
In 2009, Pixar's movie Up hit the big screen and fascinated audiences with its fantastical depiction of a house flying through the sky (Peterson, 2009). For some scenes, Pixar animated over twenty thousand standard party balloons, but it has been estimated that the actual number of balloons needed to lift a house is much higher and even in the millions (Allain, 2009). Stepping back from the original animation, a question is proposed; is there some combination of variables that make it possible to lift a house off the ground using gas-filled balloons?
When breaking down the physics of the house there are four key forces to take note of (Glossop, 2011). The first force is the buoyancy of the balloons which will generate lift. The buoyancy of the gas in the balloons is the sole force that will be acting to lift the house off the ground so it will be the focus of most of the experiments. The second force is the weight of the balloons. The third force is the tension of the tethers, which come in a variety of sizes, each with a certain break load that determines how much tension can be applied steadily without the rope snapping (Merriam-Webster, 2021). Finally, the fourth force is the weight of both the tethers and the house. The weight of the house in the film was approximated to be around one hundred thousand pounds or about forty-five thousand kilograms (Madrigal, 2009). Another significant variable of the house is its center of gravity, which must be in the middle to evenly distribute the weight among the balloons and tethers.
In the past, similar experiments have been conducted, with one instance using an A-frame, a lightweight version of the house, and large latex helium-filled balloons (Terrell, 2011). This experiment was able to lift over four thousand pounds about ten thousand feet into the atmosphere. The most obvious difference between this experiment and the current one is the large gap in weight, one house being four thousand pounds and the other much heavier at one hundred thousand pounds. To still accomplish the goal of lifting the full-scale house off the ground, it will be necessary to investigate how to alter certain variables to find the most efficient rig with the highest likelihood of success.
The first variable to test is the gas. There are two possibilities, hydrogen and helium. Hydrogen is the lighter of the two and would have greater buoyancy, but it is extremely flammable, one good example being the Hindenburg disaster (BTH Management, 2009). Helium is by far the safer alternative, is commonly used for party balloons, and is used in the film, making it more accurate to the myth (Peterson, 2009). The second variable is the balloon material: latex (the standard party balloon, used in the film), mylar, chloroprene (the large Cloudbuster), and polyethylene, the type NASA uses in its weather balloon program, one of which has lifted up to three thousand six hundred kilograms (Rand, 1992). Balloon size and tether type and size round out the variables, each with the same tension: bigger is not automatically more efficient, because size adds weight.
The testing area matters as much as the rig. The outside temperature and, more importantly, the air pressure must stay constant between experiments, because any variation may alter the fill rate of the balloons and even the amount of gas they can hold. It may be necessary to build an entire static testing area. All in all, I hypothesize that the most efficient way of lifting a house into the air would be to use hydrogen gas in large polyethylene balloons using two 36 mm nylon tethers.
Materials and Method
Experiment One, the balloon type: fill balloons of each material (latex, mylar, chloroprene, polyethylene) at a slow, constant rate with helium and then hydrogen, measuring the gas held just before each pops. The material that withstands the most gas before popping is the most efficient, and is used from this point forward.
Experiment Two, the balloon size: using the winning material, fill balloons of one, three, six, and twelve feet in diameter and measure how much weight each can lift without touching the ground, its carrying capacity. Comparing carrying capacity to size gives a ratio for the most efficient size, and if the balloons scale proportionally, points toward an even larger balloon for the final build.
Experiment Three, the tethers: connect a chosen tether size to a one hundred thousand pound weight and a crane, then attempt to lift it, adding tethers of the same size until it lifts, using a tension gauge to confirm the load is distributed within the expected break load (Rubio-Gomez, 2021). Repeat for each size. The size whose required number weighs the least overall is the most efficient.
Experiment Four, the final build: the number of balloons needed is found by dividing the weight of the house by how much a single balloon of the chosen size, material, and gas can carry. Build a to-scale house, attach the calculated tethers, fill and attach the balloons. If the house lifts off the ground, the experiments were successful.
Conclusion
One factor to consider is the foundation, or lack thereof, which may make the model house unstable, since the weight of a house usually rests on its foundation (Madrigal, 2009). Steel beams, like the ones house movers use to support a house without a foundation, could stand in, as long as their weight is factored out (NFPC, 1990). Another concern is that in the actual movie the house is ripped off its foundation, which would require far more force; it has been predicted that the number of standard party balloons needed would be around one hundred million (Glossop, 2011), which is extremely unrealistic to replicate.
Overall, the main difficulty will be overcoming the environmental factors, because every minute detail of the gas and the air must be controlled. Despite trying to achieve all the best possible components, it is still not likely that the gas will be able to overcome the weight of the house with a realistic number of balloons. The space the balloons and gas take up may simply be too large in relation to the house. To the dismay of Pixar and science fans alike, the physical limitations of the real world are just too strict, and it will likely not be possible to float the full weight of a house off of the ground.
Selected References
- Allain, R. (2009). More on the Movie Up! Wired.
- Glossop, T., Jinks, S., and Hopton, R. (2011). How Many Balloons Does It Take to Lift a House. Physics Special Topics, 9(1).
- Madrigal, A. (2009). How Pixar's Up House Could Really Fly. Wired.
- Rand, J. L. (1992). Balloons. Aerospace America.
- Terrell, M. (2011). Strange Planet: Real Life Up House. National Geographic.
- Zell, H. (2015). Types of Balloons. NASA.
- Peterson, B., Docter, P., and Rivera, J. (2009). Up. Walt Disney Studios.