# The temperature at which flesh burns

• Writing: Input Wanted
I'm putting together an idea about a weapon (insert hand-wavy science here) that fires extremely high temperatures a very short range (100 feet or so). A Heat Shotgun, if you will.
The idea is that this weapon, with a single blast, could turn the majority of a human sized creature to literal cinders and ash in a couple seconds.

What kind of temperature are we talking about here?
I assume that if you had some flesh softer than human (say about the consistency of an octopus?) it could be a lower temperature?
If I connected an insulated conductive cable away from the gun and to a portable heat sink, would there be a problem conducting the heat away from the gun in that way?

## Answers and Replies

Simon Bridge
Science Advisor
Homework Helper
Think heat not temperature .... this is an energy weapon.
Humans are soggy creatures, to turn a human to ask you first have to dry it out.
You can work out the power required to vaporize all the water in a human body ... in a few seconds.
Drying out then burning to ash would take longer ... a cooler approach is just to set the body-fat on fire. For this you are looking for the "flash point" ... won't burn up the person in seconds but they will catch fire. (316-370C ... smoke from hot fat catches fire)

Hm. interesting, but my thought is how to destroy a human-sized creature in an extremely fast manner so that its extremely infectious flesh can no longer infect others.

Just setting the thing on fire isn't going to be enough - think the Blob whose size and shape is about that of an adult human, and its vulnerable to fire.
And it's fairly intelligent
And it wants to infect you

Vaporizing the water in a body like this would simply make it explode and scatter the infectious flesh everywhere, no?

Simon Bridge
Science Advisor
Homework Helper
Complete combustion of around 75kgs of material in a few seconds is an explosion.
If this is an ET vulnerable to fire, then just pick the flash point for the material closest to its composition... that would start it burning.
However, you want it to burn quickly... it is not just temperature that governs burn speed.

If you want a realistic fire vulnerability, then you need to figure what form it takes.
Maybe its a colony that lives in pools of ethanol? Maybe its a cloud of dry spores that breath out hydrogen gas?

Why is it vulnerable to fire? Technically speaking, all creatures are vulnerable to fire.

Like Simon said, you can not take all of the energy contained in 75kg of human, release it all at once, and not have it explode. If biohazard is the issue, you'd want to burn the bodies slowly and thoroughly.

Ryan_m_b
Staff Emeritus
Science Advisor
Humans are mostly water, hitting one with enough energy to boil of that water is going to result in an explosion of steam. If explosions aren't your thing how about a radiological weapon? A neutron bomb or similar could kill off all life in an area without harming infrastructure, though secondary activation might be a problem.

Alternatively just make up something, so long as it's internally consistent it doesn't matter what you choose. For example: a "hyper-disruptor", fires a blast of exotic material that converts matter into energy that is released into hyperspace.

A man would have to boil inside to explode. How to heat the interior of a man first?

Also, how can a man be stopped by fire?

A man burnt to death may die of fluid loss through burnt skin, and of infections of burn wounds, over several days. If a fire causes mortal burn wounds to skin but fails to immediately cook deep muscles and brain beneath, the burnt man might be conscious and actively moving - if in serious pain - for hours, to escape the fire or to fight the fire and the foes causing the fire.

So, in which ways can a fire stop a man immediately?

Hm. okay, so it sounds like the idea of a heat ray just isn't what I'm looking for, unless I add a lot of hand wavy woo-woo stuff.

So let's look at a way to kill a human-sized creature down to the cellular level in a second or less.
If I have a strong enough, focused burst of radiation, would that be enough to kill a human creature in a second or less?

Or maybe think about this in a different way...

I have a creature. A normal specimen has equivalent mass of your average adult human.
Their flesh is fairly soft, they are boneless and are shapeshifters. In their "normal" state, they're a pile of goop.
That goop is actually billions of microcreatures, with a hive mind. These microcreatures, should you get spattered with a drop's worth of them, can "eat" you, making more of them.

How do you kill this?
You must not spray gobbets of infectious flesh everywhere (projectiles and conventional explosives are out)
You must kill it all the way down to effectively the cellular level (a drop of microcreatures can end you)
You must kill it quickly (a few seconds at most) they move fast, and have a habit of making sharp claws and stabbing or cutting their victims, leaving their flesh behind to take over the body.

Thoughts?

A logical move would be to use microwaves at a wavelength which penetrates a few dm of flesh.

If you use fire, then you char the surface of skin, but because of poor hear conduction the heat would take time to penetrate to deep muscles. Whereas microwaves could penetrate the flesh and cook the skin and deep muscles simultaneously.

jim mcnamara
Mentor
I assume you want to safely stop the opponent quickly and sanitarily.

Microwaves will not solve the problem of exploding. Chicken eggs are a lot like most animals on Earth - a water resistant covering with >80% water inside.

This is what will happen with anything short of an incredible amount of energy. Time to heat up - then boom. More energy and the boom happens earlier. A very large amount of energy would simply vaporize the blob in a bigger explosion, spreading disease everywhere.

Hyperspace or some alternate dimension is your best choice for an instant non-infectious removal. You could also opt for something like: UV light is instantaneously fatal to Mr Blob. But then you still have the infectious blob to clean up.

I assume you want to safely stop the opponent quickly and sanitarily.

Microwaves will not solve the problem of exploding. Chicken eggs are a lot like most animals on Earth - a water resistant covering with >80% water inside.

This is what will happen with anything short of an incredible amount of energy. Time to heat up - then boom. More energy and the boom happens earlier. A very large amount of energy would simply vaporize the blob in a bigger explosion, spreading disease everywhere.
Will it explode? And then to what?
A man is killed by heatstroke to less than 45 degrees. Any part of man, including skin, is killed at 50 degrees.
Suppose that an egg is heated with a smaller amount of microwaves - so that the near end is heated to 80 degrees, and far end to 60 degrees.
No part of the egg reaches 100 degrees, so no part boils or explodes. But every part is heated to 60 degrees or more, so every part is cooked.

Ryan_m_b
Staff Emeritus
Science Advisor
Will it explode? And then to what?
A man is killed by heatstroke to less than 45 degrees. Any part of man, including skin, is killed at 50 degrees.
Suppose that an egg is heated with a smaller amount of microwaves - so that the near end is heated to 80 degrees, and far end to 60 degrees.
No part of the egg reaches 100 degrees, so no part boils or explodes. But every part is heated to 60 degrees or more, so every part is cooked.

The OP's premise is that this fictional alien shapeshifter can infect, grow, eat and become you if a "drop" of it survives to touch you. A microwave weapon would have to ensure that every single part of the creature was heated to the point of cell death, which seems a little unlikely to me (but perhaps it's not with a big enough field-of-fire and energy source).

Perhaps a two shot solution of burning and irradiation would work. Pull the trigger on your energy weapon and it fires a burst of microwaves sufficient to cook (and yeak explode) the enemy but also releases tens of gy of radiation. Any small parts of the organism that did survive should die after a few days of radiation sickness. Of course the problems with that are:

1) Powering such a weapon

2) Not being killed yourself by such a weapon

3) Not being killed by the remnants of said alien that, whilst taking a fatal dose of radiation, might still be able to kill you in time.

A microwave weapon would have to ensure that every single part of the creature was heated to the point of cell death, which seems a little unlikely to me (but perhaps it's not with a big enough field-of-fire and energy source).
It also seems to me that just microwaves would take too long to heat it up enough to kill it without exploding it. If the creature is charging, you'll only have a couple seconds to cook it to death.

Perhaps a two shot solution of burning and irradiation would work. Pull the trigger on your energy weapon and it fires a burst of microwaves sufficient to cook (and yeak explode) the enemy but also releases tens of gy of radiation. Any small parts of the organism that did survive should die after a few days of radiation sickness.
oo, I kind of like this...

Of course the problems with that are:
1) Powering such a weapon
2) Not being killed yourself by such a weapon
3) Not being killed by the remnants of said alien that, whilst taking a fatal dose of radiation, might still be able to kill you in time.
Right - to respond
1. Aliens can be fairly advanced, so conceivable that humans have co-opted an alien power source to build the weapons.
2. I'll look up this "tens of gy of radiation", but it's reasonable that the humans could have a radiation-resistant/safe suit, right? I can research radiation safety.
3. If the suit is solid enough, and fairly combat-capable, and has good seals, the remnants of the organism shouldn't be that much of a problem - they could just quarantine the area and move on.

If you have teleportation technology in your world, then perhaps you can fire something that locks onto it and teleports it into a furnace for safe destruction.

How mobile is the "infectious" alien when dismembered/scattered?
How would you go about destroying a swarm of bees, wasps or gnats, if killing just most of them means the survivors will decide to scatter and sting you?