Dang indeed. That is crazy. Kudos to those firefighters!
Any pics of the outside of these trucks?
ETA: I found some. I guess theyre called brush trucks. Pretty much a BIG truck with firefighting accessories. How do the tires not melt? https://unruhfire.com/brush-trucks/
Earth, water, air all have density. Meaning we can create a vehicle that can be lower destiny than the (Earth, water, air) our vehicle is riding in.
Fire doesn't have density. So we can't make a vehicle lighter than fire as fire has no density to begin with.
A rocket you say? Doesn't qualify. The rocket (when in the atmosphere) is providing lots of expanding gasses which creates a difference in air pressure pushing the vehicle forward. The rocket (when in the vacuum of space) is providing lots of expanding gasses at high velocities that we throw out of one side of the rocket causing the rocket to be thrown equally and oppositely the other direction. We have lots of engine in space which done have fire at all (nitrogen cold gas thrusters come to mind).
While fire itself may not have mass or density, the materials involved in the fire (fuel and oxygen) do have density.
In the context of a rocket engine, the combustion process involves the ejection of high-speed exhaust gases, which have mass and therefore contribute to the overall density of the vehicle.
We're in agreement on the physics of rocket propulsion. However, "fire" is essentially defined as a chemical oxidation reaction. The reaction itself doesn't have mass. While fuel and oxidizer undergo the oxidation reaction, it isn't the reaction itself providing the propulsion, its the mass and velocity of the combustion products.
This is why the "natural element" definition is old and out-of-date. Any discussion of "fire" as an element is a philosophical or literary exercise, not a scientific one.