By Kyle Hill. The craziest part of BioShock Infinite isn’t the idea of combining a first-person shooter with jingoism, religious purity, and intense xenophobia. It’s the idea of floating an entire city.
Within the first twenty minutes of BioShock Infinite, you are introduced to Columbia, a city above the clouds, above the “Sodom” below. It’s founder, Father Comstock, sought refuge from the invading “foreign hoards,” and he found the sky. Like BioShock Infinite’s predecessor, the original BioShock, an entire city is constructed in a nearly unthinkable environment with the help of delightfully steampunk 1912 technology.
In Columbia, apartment buildings, skyscrapers, bridges, boutiques and boardwalks are all hovering above the Earth with the aid of rockets and blimps. The game’s floating vistas are gorgeous.
But I wanted to know if you could actually float a city like that. Let's start with what it would take to float one building and work from there, as any suitably mad engineer would.
If you take a detour from shooting and shocking your way through this BioShock adventure, you’ll notice that all the places you see, everywhere you tread, are held up by a combination of fans, rockets, and balloons. Let’s begin with rockets.
The Saturn V rocket is one of the largest rockets ever devised. At full burn, this monster can belch out enough fire and exhaust to produce 1.7 million pounds of thrust. That’s more than enough to help a shuttle escape the pull of Earth’s gravity, but is it enough to hold up a building?
It’s hard to find any real estimates of the weight of a city, as you may imagine, so let’s take a large building to estimate the plausibility of lifting it. If a Saturn V rocket could hold it up, perhaps it’s not so ridiculous to hold up a city with many of them. Take the Empire State building. It weighs a staggering 330 million kilograms. With a bit of unit conversion, the math shows that we would need more than 420 Saturn V rockets to lift it. And what a sight that would be. The burn from the engines would light up the sky, even at night. The scream of the fuel would surely cause a mass exodus of concerned homeowners from the world below.
Imagine what we would need to float an entire city on rockets like this. We would have to lift museums and monuments, not to mention roads and the concrete beneath them. Supplying that many rockets would require a fuel reservoir on a scale we have never even dreamed of. Rockets are out of the question.
But what about balloons? They don’t have the copious exhaust or noise or fuel requirement. Could helium carry the heft of Columbia?
Again we could use the weight of the Empire State building to estimate some of the beginning considerations an incredulous engineer would have to consider. Helium floats in air because it is less dense. (We should use helium instead of the lighter hydrogen, if we have learned anything from the Hindenburg disaster, especially with all the shooting going on.) Let go of a party balloon and it rushes up a gradient of lower density into the sky. This density difference produces lift. As an engineering rule of thumb, one cubic meter of helium can lift about one kilogram of mass. So how much helium would it take to lift New York’s landmark?
A lot. It turns out that there isn’t enough helium in the world to make Columbia fly. The math puts it at around 330 million cubic meters of helium. In terms of volume, that’s around the same volume of oil transported in all the oil tankers worldwide each year. In terms of blimps, we would need 1650 Hindenburgs to keep the Empire State building aloft. And seeing that worldwide helium production is around 30,000 metric tons per year (extracted from the ground and created by radioactive decay), the amount of helium to lift just this solitary skyscraper would be more than twice the worldwide annual production.
Now consider what using balloons would mean for a whole floating city. By my math, there are 150 trillion cubic meters of helium in Earth’s atmosphere. If Columbia weighs, in total, 10,000 times heavier than one skyscraper (a very conservative estimate), then the amount of helium needed to keep it in the air would be 2% of all the helium on the planet. As helium escapes from the city’s balloons due to maintenance and failure (and perhaps your own handiwork in the game), it would need to be replaced delicately and immediately. Before you know it, one city has completely drained the atmosphere of one of the universe’s most abundant elements.
And we haven’t even mentioned the stability of these structures, or just how vomit-inducing it would be to live in a building that is constantly bobbing up and down among the clouds.
Though using a system of rockets or balloons to lift a whole city is nigh impossible, there could be some workarounds. Maybe the brilliant minds inhabiting the city could devise a clever application of quantum levitation. Operating within the game’s own canon, perhaps more supernatural elements are at work. Either way, for us still stuck living on the ground, it looks like it will be a long time before you can lean out the window and have your head in the clouds.
Kyle Hill is a research fellow with the James Randi Educational Foundation and science writer who contributes to Scientific American, Wired, Nature Education, and Popular Science. He writes daily at the Science-Based Life blog, and you can follow him on Twitter under @Sci_Phile.