Epic Games’ immensely popular Fortnite: Battle Royale isn’t known for its realism, especially with its fantastical weapons and magical building mechanics. At the start of every match, players skydive out of the beloved Battle Bus, a blue school bus flying through the air via a hot air balloon. It isn’t always easy to reconcile Fortnite with real-life physics, but at least one hot air balloon expert thinks the Battle Bus isn’t entirely implausible.

Inverse spoke with the owner and chief operator at Air-istocrat Balloon Rides, Gary Fehr, about how hot air balloons function and whether or not a real-life Battle Bus is possible. Weirdly enough, he says, it’s totally possible — within the world of Fortnite anyway, because you’d need to work some science fiction magic to make the Battle Bus follow the real-world rules of physics.

“The basic principle here is that the hotter it is outside, the more heat you need inside the balloon to create enough lift,” Fehr tells Inverse. Hot air balloons function by heating a certain volume of a gas — usually hydrogen — inside the balloon using a propane fuel source, he explains.

A volume of 1,000 cubic feet of hydrogen, for instance, can generate 75 pounds of lift. Applying more heat generates more lift: “When you burn hotter, you’d get lift quicker. It’s the difference between stepping on the gas pedal halfway or all the way,” he says. In theory, if you’ve got enough volume in your balloon or a strong enough balloon to withstand a specific amount of heat, then you’ve got a flying bus.

But how much lift would the Battle Bus hot air balloon need to generate?

Battle Bus in 'Fortnite: Battle Royale'
How much does the Battle Bus defy the laws of physics in 'Fortnite'?

Judging from the looks of it, the Battle Bus is a Type C or “conventional” school bus that’s been painted blue. By its classification, all Type C school buses weight at least 10,000 pounds, but Scapt.org claims that most weigh somewhere between 23,500 and 29,500 pounds. Let’s call the weight of the Battle Bus a cool 26,500.

Considering it has a set of wheel clamps, then it’s probable that its traditional combustion engine might’ve been removed, so we don’t have to account for the additional weight of the hot air balloon engine. And don’t forget the 90 to 100 passengers that skydive out the back and try to kill each other! According to Livestrong, the average weight for an average-height male hovers around 190 pounds; women of average height weigh around 135 pounds. So if the Battle Bus has a full load of 100 players, half male and half female, then we’re talking an additional 16,250 pounds in human weight.

That’s a grand total of 42,750 pounds — about 21 tons — which means the balloon will need to generate more lift than that. (This is why zeppelins and blimps have HUGE balloons.)

The balloon Gary Fehr flies has a volume of 120,000 cubic feet and has a maximum lift capacity of 3,200 pounds — which is less than 2 tons. Fehr’s balloon is an estimated 73 by 54 feet.

To carry 21 tons? “You’d need a couple million cubic feet as just a guess,” Fehr said. “Unless …”

Here’s where the much-needed science fiction kicks in.

How does such a small balloon lift such a heavy bus in 'Fortnite'?
How does such a small balloon lift such a heavy bus in 'Fortnite'?

Let’s say the Battle Bus is 45 feet long. That would make its balloon around 25 feet in diameter at the rounded top, which is way smaller than Fehr’s balloon.

“You could always make up a fake gas that’s lighter than hydrogen and use a gas balloon,” Fehr theorized. “If it has half an atom instead of one, for example, that would give it twice the lift of hydrogen.” Alternatively, Fehr also suggested a fuel source different from the usual propane. If only you could find something like that in Fortnite, right?

As noted on Reddit, the engine atop the Battle Bus has the V-Bucks symbol on it, which actually stands for Vindertech, the company in the world of Fortnite that manufactures the many advanced weapons you see in the game. Supposedly, the Battle Bus engine runs on a substance called “BluGlo”, which is basically a supernatural power source with undetermined properties.

“If you have a unique fuel source like this BluGlo, then just convert that energy into enough heat,” Fehr said. “If damage to balloon fabric wasn’t an issue, then a smaller balloon could actually work. In a typical hot air balloon you’re going to lose a lot of radiant heat, so you’ll need a special indestructible material with no holes in it that’s really well-insulated.”

So in short, the only way to make an Battle Bus happen — down to the exact size — is an indestructible balloon and an impossible fuel source.

Totally doable in a world this crazy, right?