# Using fire magic to levitate (hot air balloon style)

A magician has the ability to produce, control, contain and extinguish fire anywhere near his body, as much as necessary and has enchanted himself and any object, for example clothing, on himself to not burn at all (he can lowkey control temperature of objects very near to his body using those enchantments and controls heat flow into his clothes.) All this to say the fire won't be of harm to him, or anyone near him who is also enchanted, if he so chooses.

Is it possible for him to take a cloth, small enough to carry on his person and similarly immune to burning, heat up the air inside it while holding it in the form of a parachute, and levitate himself (and perhaps someone else) out of a sticky situation?

• Is this magician trying to fly with the cloth, or leap off a cliff and slow his descent? Commented Jan 20, 2021 at 21:37

The cloth won't be that small if it has to rely just on the lifting power of hot air.

Let's look at the best case scenario, where the volume in the cloth is completely devoided of air, the cloth doesn't let any air leak in and can withstand the outer pressure. This means that a cubic meter of that void will have a lifting force equivalent to the weight of the displaced air, which means about 12 N. This means that to lift a 100 kg load the magician would need a volume of about $$1000/12 \approx 84 \ m^3$$.

Assuming it is a sphere, it would make a cloth covering 92 $$m^2$$, which is about the size of a decent sized apartment.

Considering that in reality the volume won't be empty, the magician would need an even larger cloth.

Let's say the magician can reduce the density of air by half, a volume of 168 $$m^3$$ would be needed, with a surface of 147 $$m^2$$.

It looks highly unpractical.

• I actually made it about 300m^2 but even so, it is definitely impractical. +1 Commented Jan 20, 2021 at 13:30
• Although it's probably still implausible, the calculation presented is for cancelling out the momentum, while a (hot air) parachute as requested by the author doesn't do this. It just reduces the terminal velocity. Commented Jan 20, 2021 at 14:51
• To add to the answer, it's possible to get a rough visual estimate of the size by looking at photos of a past incident where a person flew using helium weather balloons: en.wikipedia.org/wiki/Lawnchair_Larry_flight Commented Jan 20, 2021 at 21:07
• @Trioxidane: It sounds to me more like the question is about holding the cloth and flying away on an updraft, Revali's Gale style, not about slowing a descent. Commented Jan 20, 2021 at 21:35
• @user2357112supportsMonica I missed the word levitate. You're probably right. Commented Jan 21, 2021 at 8:27

I don't think so.

I don't have most of the math in me so I searched. According to this article, lifting a person even with helium takes a lot of volume. For a small, 100 pounds teenager:

Therefore each cubic foot of helium could lift 0.069 pounds. In order to lift 100 pounds (which would include the weight of your load, the balloon, and the helium) you would need 1449 cubic feet of helium. This would require a balloon with about a 15.5 foot diameter. If instead you used small spherical (one foot diameter) balloons (which holds about 0.526 cubic feet of gas), it would take over 2754 of them to lift the 100 pounds.

Therefore a handful of small balloons will not lift you off the ground.

I don't think your firebender would be able to carry a cloth able to hold that much helium folded in his pocket. Also that calculation is for helium, which is much lighter than even hot air. Actual air would require more space, which is why balloons that do carry people are so large.

You could always throw realism aside and handwave it though. In the Avatar series of animations, people who could do fire magic could propel themselves in the air, Ironman style. At certain times they could even achieve true flight.

Their weight is scientifically supported by the Rule of Cool. I imagine they could carry someone on their backs if plot necessitated it.