Managing heat dissipation in a magic wand

Question

Backstory

You won't believe it, but I'll tell you anyway. I'm a Level 6¹ wizard. If you think about it, wands aren't all that hard to use. Point, invoke, joyfully watch your enemy burn in the fires of Reetath. I've watched wizards do it all my life.²

So, when I stumbled across a fairly new-looking wand,³ I picked it up. Wands are fairly generic, right? They all shoot little darts, lightning bolts, fireballs... We've all heard the stories.⁴ So I wanted to see what I could do! I visited the local library and asked the librarian⁵ what the word was for "fireball." Then skipped⁶ to an open field (I wasn't looking to roast a cow or anything), pointed my new wand at some unsuspecting tree, and said Lamboobalar!

The next thing I remember was waking up in my mom's house⁷ with my hand wrapped up to my elbow and wishing someone would hit me behind the ear with a hammer. It hurt! And what I want to know is, what'd I do wrong?

World Rules

• Wands are a bit like magical rifles. Fire a bullet through a rifle and the barrel heats up. Fire enough bullets fast enough and the barrel becomes burning hot! No matter what you cast with your wand, the more powerful the spell or the faster you cast the hotter the little honker will get.
• Magic is the funniest thing. The wand must be held. Not touched by skin necessarily, but held. If you set a wand on a table and scream Wapatay! the wand will happily sit there and ignore you. If you pick up the table, it'll still ignore you. But! grasp it with some chopsticks or with a gauntlet and BOOM! pink mist!⁸
• As a bit of a reference point, casting the fireball spell generates enough heat to cause 3^rd degree burns on the unprotected hand and wrist. Using the wand to magically rap someone's knuckles, causing them to drop their sword, would only cause noticeable heat if you were paying attention. Casting the dread Sheeeaaaaah-Moogatee-Hah! spell, which consumes your enemy's castle in a somewhat makeshift volcano, will cause an intensely bright light followed immediately by the unprotected wielder converting into a lovely cloud of carbon.⁹
• For the purpose of this question, the wand is indestructible. You can't drill through it or cut slots into it, either. The surface has friction similar to any smooth hardwood and does taper from the base to the tip. It's about 1.5cm (5/8") at the base and 0.6cm (1/4") at the tip.

Question Limitations

• You cannot use magic to solve the problem. Using magic to solve a problem that's a consequence of magic would be like trying to put out a fire with a bucket of gasoline.¹⁰ That's why the science-based tag has been applied. No magic!

• If you're thinking, "this is just a heat-sink problem!" you're exactly right! Good luck!

• The wand must be usable in a melee situation. In other words, you can't simply encase the wand in a 2-foot diameter column of iron sitting in a custom-designed cart wherein the wizard sits comfortably on a velvet stool while embracing the rod bar. (a) while that would probably work per my rules, it's not practical in a melee situation and (b) the wand would probably blow a hole in the front of the bar, spewing sub-vapor-point iron all over the place. It would look spectacular — and probably fry the wizard anyway. So, the wizard must carry the wand and can't be more encumbered than a suit of plate mail.

• You may only use 13^th century technology (my sincere apologies to TimBII for not stating this here, I can see where it was easy to overlook).

---

Question: Using 13th century technology, what can I do to protect my erstwhile wizard when he casts a fireball spell with this wand?

Bragging rights to answers that point out how to avoid the cloud of carbon problem — but that's optional.

---

_{¹ Fine! I'm a level 1 wizard... OKAY! I'm some dumb schmuck who found the wand in a gutter! So sue me.}

_{² YES! There are wizards in Grubda! Well there only had to be one! It didn't LOOK that hard! If it means that much to you, ask your own @#*& question! Sheesh, everybody's a critic!}

_{³ That body on the sidewalk had nothing to do with the wand. Yes... I'll swear on my mother's grave! Now let me finish!}

_{⁴ Except you! Now shut up!}

_{⁵ You know she's my sister... right?}

_{⁶ Yes, I skipped! Like a 6-year-old girl! I was excited, alright? What would YOU do if you found a wand? Turn it in to the constabulary!? Are you nuts!?}

_{⁷ Don't say it! You were thinking it! Yes you were! I'm saving up for my first horse, alright?}

_{⁸ And molten metal thinly plating everything in a 3-meter radius. Wapatay! is not for the faint of heart.}

_{⁹ Magic should always have a price, don't you think?}

_{¹⁰ This is obvious, right? Just because it's liquid doesn't mean it'll act like water? Yeah.}

Answer 1

The solution to your magic wand problem is actually a staff and flowing robes... I love when one dumb trope is the right solution to another.

First the Staff:

Much like your chopsticks proposal, you are using a device to hold it away from you. The staff puts distance between your hand and the wand which is important when you dealing with limited insulating materials. While the heat of the wand is enough to cause 3rd degree burns, the head of the staff will heat up a lot at the end but much much less at the handle; so, slip the wand into the end of a staff and it's like holding a pot over a flame.

An ideal staff would probably look a lot like the diagram below. The wand itself would be inserted into a glass or high-cone ceramic since these are the most heat resistant materials available in the middle ages. The wand would be held inside of an oak holder. I know what you are thinking, "that is WOOD, you don't hold hot things with wood!" But there is good reason to use wood here. While materials like glass, ceramic, and steel all have higher melting points than wood, the wand gets very hot very fast. If you encase it in a hard and brittle material like glass or ceramic, the rapid nature of heating it up will cause a phenomenon called heat stress where the material will be encouraged to shatter as the inside becomes hotter than the outside. If this effect is extreme enough, which it sounds like it will be, then your ceramic holder will shatter killing your would be mage with shrapnel instead of heat. Making direct contact with steel, you are much less likely to have your staff explode, but the nature of rapid heating is again against you: A thin inner lining of metal will become molten and the metal around your wand will melt and blast the wand out the front of your staff.

So what makes wood so much better than steel? Specific heat, for starters. Oak has the highest specific heat out of any solid material available in the medieval period. Heating 1kg of steel to its melting point of ~1470°C requires ~670kJ at a specific heat of 462 J/kg.°C. Heating 1kg of oak to its ignition point of ~300°C at a specific heat of 2380 J/kg.°C also requires ~670kJ. This means that the ignition temperature of wood and the melting point of iron both require about the same amount of thermal energy; however, what wood does when it reaches its critical temperature is much more desirable. Wood only burns at 300°C in the presence of oxygen, but if your wand is fitted tightly in the oak then it can not burn until the OUTSIDE reaches 300°C. Instead the part touching the wand will continue to absorb heat until it reaches ~500°C at which point pyrolysis kicks in and the wood begins to anaerobically react by turning into charcoal, but even still wood does not violently explode when superheated, at worst the end of your staff will catch on fire, but the charcoal will expand and remain a solid medium continuing to grasp your wand well past the point that metal, ice, or ceramics would have found some way to melt/explode.

The Oak holster will absorb heat well, but not be good at dissipating it, and it will become brittle once it turns to charcoal. For this, you want to encase your Oak with a steel head, preferably with seamingly decorative spines loops or other patterns to work like heatsinks. Then the head would taper back, thick to thin. The steel closest to the head will get hottest so extra girth will help keep it from melting or warping when it reaches malleable temperatures, but the taper makes sure that less heat can spread back through the shaft. The handle itself should also be wooden; since wood does not propagate heat well, this will further insulate you.

Your Wizardly Robes:

Ever notice how people who live in deserts seem to like to wear over-sized, full body clothing? The reason is because air is a great insulator. By wearing lose fitting wizardly robes your robe will heat up from the blast of heat, but poor contact between this surface and you skin means that it will not transfer that heat too you. Most robes will be made out of wool because it is the most fireproof natural fiber, but asbestos cloth is also an option in your 13th century setting for those wizards willing to trade good health for more powerful spell casting potential.

He could also use a cloak held out in front of his body to shield himself from especially powerful heat blasts. To keep his hand safe while doing this he could drape your cloak over the staff rather than holding the cloak directly.

To fully protect your body, a well to do wizard would also cover his face with a conical hat or hood (because it minimizes heat and maximizes coverage), a scarf, and some manner of goggles (yes, eyeglasses existed in the 13th century so goggles are a distinct possibility).

The Castle Problem:

Your castle volcano problem is a bit ridiculous for which you will need a ridiculous staff (aka pike staff), that will put a great as possible distance between caster and wand. More importantly, you need what basically amounts to a ballistic shelter similar to what Davy Crockett crews often used. That much heat will be explosive, and you will be in the blast radius, but if you are protected by a bunker where you are physically underground, the blast will mostly pass over you. The pike staff will be destroyed, but the caster, ducking under the level of the ground and with a shelter to absorb most of the radiant heat might just survive the blast.

Answer 2

Treat the wand like it came from a blacksmith's forge

While some blacksmiths don't use gloves at the forge, others do. And they generally wear them for very short exposures to heat (a wand going whamo should count).

Leather gloves won't be enough to protect against very high heat (fireball spells) but it will protect you from radiant heat near the wand. You also want a leather apron, some kind of safety glasses, and boots.

About the Leather gloves - Experienced blacksmiths will sometimes recommend no gloves. I strongly recommend a glove on your not-hammer hand. At least just to start. This will prevent burns. Later, as you get more experienced with blacksmithing you can decide what you like.

About the boots - This is important because you are going to be dropping hot pieces of steel and you want a solid pair of boots to protect your feet from burns. If you plan on handling heavy pieces of iron and steel then I would go with steel-toed shoes.

So lots of safety gear to start then you can reduce it when you get used to spellcasting.

This site also recommends wolf jaw tongs (not plain jaw/flat). I'd recommend some made special to firmly hold your wand near the base. If blacksmiths can use these to hold on to heavy metal glowing like a miniature sun, and then be able to manipulate the metal on the anvil, you can use them to hold your freaking wand still while you cast.

Remember, the apron and boots and eye coverings (if possible) are for when you are an idiot and drop the hot wand as soon as something blasts out of it.

Okay, so this covers you for basic fireballs. Now, what about the Sheeeaaaaah-Moogatee-Hah! spell?

Okay, this requires some setup. I recommend the following:

• A large barrel made of thick oak plated with metal with a 3-4 inch hole drilled near the top.
• Fill with water such that it will later reach up to the bottom of the hole.
• Get in the barrel with something protective on your head.
• Put on a leather glove.
• Stick your blacksmithing tongs out the hole and grab the wand.
• Make sure that under the wand is a bucket of water or a pile of sand.
• Cast the spell.
• Drop the wand.

Alternatively...fire that sucker from a stone castle window or rampart, the kind archers shoot out of. Have a trusted running retrieve the wand after it drops in the water/sand and is cool enough to pick up with tongs or a gloved hand.

No, it's not melee-worthy like your fireball and other low to high level spells are. But if you want the nuclear option, you need to build a launch point. This completely violates your requirements, but seriously, do soldiers with fire launchers run around with them in combat? No, they use a sturdy base, sometimes one that is somewhat portable. If you fight with a cannon can you carry it in your pocket then pull it out and boom? Nope.

Remember, your question was protection for a fireball spell. And you state: "casting the fireball spell generates enough heat to cause 3rd degree burns on the unprotected hand and wrist." My solution easily protects against that.

Answer 3

Do what every successful business has ever done with hard to crack problems: outsource it.

In order to outsource the problem of hot wands, you will need:

• feathers
• a bow

See a picture below of some witches invoking some explosive fireballs (you know, the kinda that goes boom when it hits something). Notice that they are grasping the wand firmly with the right hand, while grasping the bow with the left hand.

Once the wand flies, the issue has been successfully outsourced to whomever you were aiming your fireball at. Any heating concerns are now SEP's (Someone Else's Problem).

And before you tell me that goes against the melee usage rule: you can use an arrow on a melee fight if you really want to.

Answer 4

I have an answer, but I'm not sure if it breaks the rules or not it goes against the rules on two fronts - drilling holes in the wand (thanks JBH) and violates the 13^th century rules (thanks Nosajimiki). But, I'm going to throw it out there anyway as an apocryphal answer.

First of all, you're completely right; this is a classic heat sink problem. But, you're also wrong; a gun barrel heats up because of convection from the gases in the gun barrel; the barrel itself is metal for strength, and also because you actually want the barrel to get hot so that the next bullet doesn't discharge prematurely because of a massive heat buildup in the rifle. This was the whole point of gatling guns back in the day; give each barrel time to cool down before being used to fire another bullet.

In point of fact, the whole problem you have with your wand in terms of thermodynamics is that it isn't like a gun barrel, which would make better sense. What you really want to do is conduct the heat away quickly so that it an dissipate in the atmosphere rather than cooking your hand. This is also why gun stocks and handles are not made of metal - They're designed out of wood, pearl, composites, etc. to shield your hand from the excess heat buildup.

I'm going to assume that your wand is some form of magical wood or other element that traps the heat to insane levels without spontaneously combusting. That is about the only model which could work the way you describe, although it also means that the biggest issue with your wand isn't that it gets hot, it's that it doesn't cool down fast enough. That said, the solution is twofold; firstly you need to reinvent a 'stock', or wand handle, and then you need to borrow an ammunition concept from science fiction.

Put more simply, you need to insulate the hand AND absorb the heat out of the wand fast enough so as not to overwhelm the insulative properties of the stock which you use to grip.

Let's deal with the stock first. If it wasn't for their combustible nature, wood or paper would actually make a good option here. But, in this instance, I'm going to suggest a fibrelass handle with a styrofoam core. This would have several benefits;

. You can turn this into a simple collar or tube which your wand slides into
. The styrofoam will grip the wand quite well, meaning less chance of it slipping out in a fight
. Easily replaceable if the styrofoam starts to wear.

Secondly, we need to create something like a thermal clip for your wand. Basically, the idea of a thermal clip in scifi games is that we have all moved to energy weapons, but those weapons can't disperse their heat so they capture it in a disposable thermal clip, which basically stores the heat and can be replaced quickly in battle. In gaming the idea is to keep the idea of ammunition. In your scenario, it's actually a pretty good analogue for the problem you face.

I'm going to suggest that you drill a small hole down the centre line of your wand (hence the idea that it could be outside the rules) and put a small rod of something like Tungsten in it, with a screw thread on the back end. Why tungsten? Because it has the highest melting point but still pretty good thermal conduction properties. Then what you need is a supply of Liquid N₂ bulbs that screw or clip on at the base of the wand.

The idea would be that the tungsten conducts the heat to the bulb, which absorbs the heat and converts the nitrogen back to gas. Once it has done that to all the nitrogen in the bulb, you discard and replace.

Now, I know this isn't a perfect solution; how do you keep your N₂ bulbs cold in the field? How many shots can a nitrogen bulb acting as a thermal clip absorb? Seriously, you want me to insert what in my wand? How is that going to affect the magical properties?

I suggest that you get one of your friends who wants to be a 'level 6' magician to assist you with some field trials (preferably one you don't like very much) but ultimately, the engineering of this is quite simple - you need to dissipate heat quickly while insulating your hand from it until the heat has dissipated.

For that reason, gun barrels getting hot is actually a good thing; it's touching them that's bad. Your wand needs a similar dynamic. Putting a styrofoam / fibreglass grip around it will hopefully protect your hand while the 'thermal clip' sucks as much of the excess heat out as quickly as it can, reducing the load on the insulated grip.

In any case, be very careful during your testing and don't let anyone do this who will be indispensable in your future magical career.

Answer 5

Grab yourself a fishing rod and create a setup like in the following (beautiful) picture:

You would have to learn how to aim properly first, but once you are used to it you can swing your wand around as if you would use a morning star. The only difference: Your wand is in most cases more deadly.

You could also expand on this and make the wand useful over larger distances, when you cast greater magic (e.g. "Sheeeaaaaah-Moogatee-Hah!") by switching or combining the Magic Rod™ with a crossbow and a long enough rope (hopefully cannot burn). With that you can be at a more safe distance while encasing your enemies castle in a makeshift volcano.

Answer 6

Sand/Water Cooling

The Heat dissipation doesn't need to be a function of the wand itself. If the user's hands are themselves insulated, they can use traditional cooling techniques. A wand user can carry classical cooling systems as part of their kit. Since I presume this wand doesn't need ammunition, if you equip them similar to a medieval fusilier they can carry sand cartridges/water pouches instead of ammo

Answer 7

If rules could be slightly bent, as we are talking about discovery from the 15/16th century, but hey - magic is involved, and when there is a need, there is a will to discover, then a solution of "how to hold the wand" exists.

Waterglass (Sodium Silicate, etc.) While certainly sounding like magic, it is not magic at all, and holds a couple of very useful properties:

• Is used for bonding things together
• Fireproofs wood to some extent (not that small of an extent too!)
• Waterproofs wood too (yay for water spells!)

So how could it be used? A metal wand could be embedded, using waterglass as the glue, in a random wooden branch branch from of an ancient tree, cut by the elves precisly for magical staffs. It would also be treated with waterglass to prevent sparks, flames or heat from making it catch on fire.

This leaves us with the question of protecting the wielder of such a staff, and here comes the waterglass again! With thick leather armor, enough thermal insulation should be provided, and as to prevent accidental macarena dance caused by a burning - cloth can also be treated with waterglass to ensure some fireproofness (though I am not sure if leather can be treated).

Protecting the head and legs in a metal helmet and boots (but keep leather insulation between skin and metal!) could prove useful if you aim the fireball a bit too close.

Only the problem of protecting the eyesight persists, as Aviators won't come out until 1939, and simple smoke stained glasses are simply not cool enough.

Answer 8

As somebody doing thermal engineering:

• Add heat capacity to the wand (attach it to something heavy)
• Use water cooling/forced convection
• Use evaporative cooling/evaporate water
• Use the heat to melt salt or metal
• Use heat spreaders/pipes to get it quickly to an external head exchanger
• Use isolation (e.g. glass foams)
• Precool the heat capacity
• Make the wand black, so that it radiates
• Make heat conduction anisotropic
• Use a dewar/ keep it in Vacuum (the it will get hot, but not the surroundings)

So my solution would look like

• So probably a backpack with an external heat exchanger/cooling system (+Batteries?)
• Flexible pipes for a cooling circuit going to a special glove which a cooled semi-sphere (to protect the wearer) around the following:
• a wand
• one layer of heat spreader/pipe, a few cm radius of salt to melt
• in the molten salt storage i would integrate a heat exchanger to the pipes coming from the backpack

But obviously for a more detailed caclulation we need

• Peak. thermal power of wand (Mega or Giga W?)
• peak power duration
• Avg. thermal power of wand (up to 100kW should be ok)
• Max. temperature in wand core
• material of wand

Answer 9

Freeze it

Before using the wand, freeze it. In a combat situation, this will involve frequent wand switches. Take a tub of ice with you. Store all your wands in the ice, so they are nice and cold. Put on a good pair of gloves. Reach into the tub and grab a wand. Aim and shout the appropriate spell. Immediately drop the wand back into the ice. If your hand is overheated, stick it in the ice. Repeat with the next wand when your hand starts getting cold.

In the thirteenth century your source for ice would be the top of a mountain. Take a hay covered wagon up the mountain to where it gets cold. Make a hole in the center of the hay. Put ice in the hole. Lots of ice. Cover it up with hay from the sides. By the time you get to the bottom of the mountain, you'll have less ice.

Stuff the wands in the ice at any time, even while still at the top of the mountain. You want them to get as cold as possible so that you can maximize the safe power of the spell.

Answer 10

By your rules, I am not sure if all the flames must directly come out from the wand in one step immediately on casting the spell. But if that is not a requirement, the process of producing a big fireball could be:

• Eject enough flammable substance from wand at high enough speed (which should knock the user back as well because of conservation of momentum). This could be gaseous propane, which is heavier than air and would stay close to the ground while moving towards the target. Also colorless and odorless if you want this step to be discreet.
• Ignite the flammable substance from farther away with a low level small fire spell (which should only heat up the wand a little)

The key is to create the fireball when the user is far enough away. More skilled wizards might use more exotic flammable substance mixtures giving better, safer results

I'm assuming only using fire spell heats up the wand. Your analogy of magic rifle is confusing since in the real world the barrel heats up because of the exothermic reaction of gunpowder which is required to suddenly expand gases behind the bullet and propel it at high speed. Unless the magic wand is using gunpowder or something similar for any kind of magic delivery mechanism, it should not heat up for any other kind of spell (like the flammable substance spell). If it is, the design could be the same as a rifle or you have to tell us more about how magic transforms to fire, if/how it needs any propelling at high speed, etc. Or maybe you meant that "summoning" magic to do anything heats up the wand?