# How much energy would be required to vaporise a giant reptilian monster?

At the climax of my story, the main antagonist transforms into a gigantic and nigh-unkillable monstrosity that resembles an unholy hybrid of a crocodile, Mosasaurus and Dimetrodon. After a long and destructive battle, he is finally killed when my deuteragonist unleashes a powerful energy beam from her sword (Excalibur-style) that destroys the antagonist by completely vaporizing him and overtaxing his healing factor. This form that the antagonist takes is basically a scaled up saltwater crocodile (with a tail fluke akin to that of Mosasaurus hoffmanni along with a head and sail-like structure on its back similar to that of Dimetrodon angelensis) measuring 80 meters long from snout from tail.

Although, I was unable to calculate this creature's weight, a combination of basic investigative skills and the wonderful accessibility of Google Search enabled me to find out the density of an adult crocodile is 948 kg/m^3. It is to my understanding that vaporization is basically when a substance in a liquid state changes into a gaseous state due to an increase in temperature and/or pressure (please feel free to correct me if I am mistaken).

How much energy would be needed to achieve such a feat?

• wont need any of that, the monster would collapse under its own weight before it even started (would be funny if you added that in your story) – Creed Arcon Jun 26 '18 at 5:15
• Just a warning: Vaporizing this thing will likely wipe out everything around the creature in a significant radius, including your hero and the city they're trying to save – Sydney Sleeper Jun 26 '18 at 5:17
• A good place to start is to assume the creature is made entirely out of pure water. Indeed, depending on how you handwave the regeneration mechanism, flashing all the water in the creature to steam should end it regardless, as body chemistry ceases to react and cellular structures explode. – Sean Boddy Jun 26 '18 at 5:42
• handwave the energy amount. Just make sure that the energy field is contained around the target, or the heat and the steam wave will kill people and melt things all around. – Valerio Pastore Jun 26 '18 at 5:52
• Vaporizing is going from liquid into gas, going from solid straight into gas is called Sublimation, just thought that might be useful to know – Blade Wraith Jun 26 '18 at 6:45

According to this source, the energy needed to vaporize the human body (leaving skeleton) is 1.42 $\times$ 10$^8$ Joules, or the equivalent of 28 kg of TNT. The density of a human is 985 kg/m³. 75840 kilos of croc $\approx$ 77 times the human body. 28 times 77=2156 kilos of TNT. So, 2156 kilograms of TNT to vaporize your monster.

• Someone once linked this site on the stack here and its too awesome and fitting to not share it here again ^^ – Nicolai Jun 27 '18 at 16:00
• Check your math - last time I checked, most humans weren’t 1000 kilos lol – Dubukay Jul 19 '18 at 15:56

You are partially correct.

When you deal with reactive matter (and organic matter is highly reactive with respect to oxygen), vaporizing it in the sense of changing its physical status from solid to liquid to vapor/gas is going to be tricky.

But I assume your goal is not to make research on the phase transitions at ambient pressure of a monster size alligator, but simply take rid of the beast.

If you make a comparison with human body, on average the cremation of a body uses 110 liters of fuel, usually natural gas. In a first approximation you can use the same density for the two bodies, so just scale up for the weight of the beast.

This would account for $110 \ liter \ of \ fuel/0.01 \ m^3$ that is $11000 \ l/m^3$.