Previous questions here:

Creating a scientifically semi-valid super-soldier, part 1: Skeleton

Creating a scientifically semi-valid super-soldier, part 2: nervous system

Creating a scientifically semi-valid super-soldier, part 3: Physical shock resistance

Creating a scientifically semi-valid super-soldier, part 4: respiratory system

Creating a scientifically semi-valid super-soldier, part 5: Heart and circulatory system

Creating a scientifically semi-valid super-soldier, part 6: Radiation protection

Creating a scientifically semi-valid super-soldier, part 7: Hearing

Creating a scientifically semi-valid super-soldier, part 8: Communication

So you've build your super-soldier. He's faster, he's stronger, he's got enough super-dense fat to go for days! You want to test out your new soldiers and have a few regular soldiers as control group next to them. But within 5 minutes all your super-soldiers are on the ground, overheated and unconscious if not worse. The extreme metabolism that must be plaguing just about every super-soldier ever conceived killed them.

You could hook them up to a suit with a constant airco, but it's far more efficient if the super-soldier's body build, maintained and repaired his own temperature control. You don't want battle damage to hit an airco and cause your soldier to become useless on the spot!

After some deliberation there are a range of requirements for this temperature control:

  • Reduce temperature in hot environments and when exerting themselves.
  • Maintaining a minimum temperature in cold environments, such as a snowstorm.
  • Having ways to radiate heat when in space.
  • The soldier is expected to be wearing armor, both fully covering and partially covering depending on the environment they are in. This armor is expected not to influence the temperature a lot as the material will breathe for sweating purposes and won't have heat-conductive materials touching the skin.
  • The temperature control needs to keep working as best as possible after the armor is damaged. and the soldier might experience shrapnel in his body or other injuries. This is mainly important for when a space-suit gets holes in them.
  • These are super-humans, while "standard" human temperature control is excellent for releasing heat compared to the rest of the animal kingdom, it is insufficient for an engineered creature. Also it's an engineered creature, you can create something better than the mere randomness of evolution offers!
  • Again, it needs to be a biological solution, or so biological that a body can build, repair and maintain it.
  • As a bonus, the ability to manage a thermal signature and (temporarily) become hard to see/invisible to thermal sensors.

3 Answers 3


Implanted liquid oxygen tank.

How to get rid of heat? Conduction, convection, radiation or the jettison of relatively hot matter.

You have insulated your soldier with armor / This armor is expected not to influence the temperature a lot as the material will breathe for sweating purposes and won't have heat-conductive materials touching the skin/ and so greatly limited the ability of the body to get rid of heat.

The supersoldier could heat up some dispensible matter (water?) and jettison it. Exactly how and when this water gets heated in the body is not clear. The human body plan offers a few possibility for jettisoning hot water which might poses difficulties for the writer of young adult fiction, but it is doable.

But there is a better way - counteract the heat. If you can't get rid of your heat, you need to bring some cold which you can let out little by little on demand. Your supersoldier has an implanted tank of cold. Specifically a tank of pressurized oxygen within its body.

When a gas under pressure is allowed to decompress, it absorbs heat.
In your shop, after you compress the gas and heat it up you let it cool off in your shop, using radiators or what have you. Then you fill your soldier's tank with cool compressed gas. The amount of heat which can be absorbed depends on the pressure of the compressed gas - as much energy as you put into the gas to compress it (heating it up) then can be dumped into the gas when it is released from pressure (and cools down).

Liquid oxygen can be considered maximally pressurized gas - a way to store an immense amount of compressed gas in a very small space. The high tech futuristic superstrong onboard LOX tank will be filled up before the supersoldiers go on a mission. When it gets hot, the LOX tank will outgas very tiny and rapidly absorbed bubbles into the bloodstream. These bubbles come out very cold and so counteract the heat they encounter in the blood. As a bonus the extra oxygen released to dissolved in the blood can help the supersoldier meet its (apparently very high) metabolic needs.

There is a downside to having a tank of liquid oxygen inside your body. If hit in the right way, the tank could explode. Liquid oxygen rapidly supports combustion and so after exploding everything in the vicinity will burn merrily. It is dangerous, being a smoking hot supersoldier.

I am aware that one can calculate the heat absorbed by a given volume of liquid oxygen under pressure turning to gas. The calculation is beyond me (hangs head). I welcome anyone capable of it to edit this question to add this calculation or post it in a comment.

  • 1
    $\begingroup$ Similar to Gustavo's answer I like the idea, but having a tank and requireing specialized equipment to refill is kind of against the "needs to be build, maintained and repaired by the body". Perhaps you could also alter the bit about letting oxygen loose in the bloodstream to having lung-like area's near the bloodstream where this happens to prevent air-embolisms from happening. $\endgroup$
    – Demigan
    Jul 17, 2018 at 7:51
  • $\begingroup$ Supercold ice will absorb more heat per volume (especially when melting), and won't explode when shot at. And once it's hot, you can sweat it for extra cooling. (As the armor breathe, it will also work in space.) $\endgroup$
    – Eth
    Apr 2, 2019 at 15:28
  • $\begingroup$ @Eth - the potential for the gas to absorb heat is maintained by keeping it under pressure, where it can stay indefinitely. How do you maintain the potential for your super cold ice to absorb heat? $\endgroup$
    – Willk
    Apr 2, 2019 at 15:45
  • $\begingroup$ Good insulation will keep the ice cold for days or even weeks. If the soldier needs longer autonomy, a small heat pump should not be too big an addition to its gear - I doubt adding a biological heat pump is worth it, but is also an option. Insulation may take up more volume than a pressure tank, but this is balanced by the better volume heat capacity of water, and by the lower density of both. $\endgroup$
    – Eth
    Apr 2, 2019 at 16:27

When you press and hold a spray bottle for several seconds, you can feel decreasing temperature. Instead of relaying on mere sweat glands, adding an organ to create abundant mist can quickly lower your temperature.

Combine it with some thin collector and your suit can transform the heat in electricity.

Edit: Elephant ears radiate heat passively, we do the same with our feet. Depending on the needs of the mission, deploy an Assault for burst of action or an Endurance geared soldier. Make the change in the Bio-lab and your All Rounder soldiers can switch from Scuba to Scouts, always optimized for the mission parameters.

  • 1
    $\begingroup$ Using this: sciencing.com/canned-air-cold-5157676.html it would seem that this method would be excellent for short-term losing heat, with enough heat absorbtion to cause frostbite in a can you don't have to compress it as much as a regular can, which is good as creating 40bar in your body seems hard even for an engineered body. For a continuous cooling it seems not a good option, as compressing air/nitrogen to liquid is probably going to generate a lot of heat and nullify the advantage. Got any more info perhaps? $\endgroup$
    – Demigan
    Jul 17, 2018 at 7:45
  • $\begingroup$ You can use it as shock troopers. High performance in violent assaults. Then have other soldiers for sustained engagements. That's the concept of combined arms, we have paratroopers, infantry, etc. Different setup for different tasks. The All-Rounder troop's cooling will be worse than specialized Space Marine when considering Space warfare. Now drop a Space Marine on Sahara for extended missions, and efficiency is king. Your mission parameters dictate your logistics. $\endgroup$
    – Gustavo
    Jul 17, 2018 at 22:06
  • $\begingroup$ So you engineer some shocktroops that are Sahara resistant, and you also engineer some combat troops that can fight all day in thr Sahara hear. Or during winter, the possible night-time freezes that are alternated by the hot hot days. Your idea is perfect for shocktroops but do you have an idea for the combat troops? $\endgroup$
    – Demigan
    Jul 18, 2018 at 6:21
  • $\begingroup$ You can; radiate the excess like desert foxes with high surface ears, generate less lowering you metabolism or shield yourself with air gaps as africans do. $\endgroup$
    – Gustavo
    Jul 18, 2018 at 22:52

Peltier cooling: Thermoelectric Effect

Thermoelectric cooler

From the first question of this series, it appears that your soldier will have an exoskeleton for defense purposes. Plus, it will have some sort of skin over this exoskeleton, to provide a human-like appearance.

Let's modify the exoskeleton a bit. Your exoskeleton is made up of plates. Both the external side (the side with skin), and the internal side(the side facing the muscles) of the plates will be made of layers of graphene, interspersed with a ceramic for stiffness. Graphene has excellent thermal permittivity, as well as being electrically conductive. The ceramic serves to electrically insulate the arrangement. The middle can be made of two special organic polymers arranged in pairs (as "pillars") right between the two layers. The polymers have different electrical conductivities, and also serve as a sort of "glue" for the inner and outer layers of the plates.

Now, if Mr. Peltier was right, then all you need to do is apply a electric potential to the sides, and voila! The inner side of your exoskeleton can be made upto 60 degrees cooler than the outer side! (Although a temperature difference of 20 degrees celsius from the ambient would be a more practical estimate. Still significant!) And since your soldier's exoskeleton is covered with human skin, this means that the side that has to dissipate all the heat has a very effective mechanism of heat dispersal right on its doorstep, namely sweating. (Something that is a unique human evolution, and a very effective heat dispersal technique, given the thermal capacity of water.)

Note This does mean that your soldier's skin will have to be genetically modified to withstand higher temperatures though, but since there are multiple natural examples of species surviving near literal lava vents, that shouldn't be a problem. As for where you'll get the electric potential from, electrocytes (from electric organs) should help you out quite nicely. Also, if our soldier doesn't want to waste precious energy on cooling himself quickly, then the arrangement is thin enough (3-4 mm in thickness) and thermally conductive enough to act passively as a Heat Sink, with good old sweating acting as the heat dispersal mechanism again.

Let me know what you think!

  • $\begingroup$ It's a good idea for getting the heat to the edge of your body, although as mentioned in the question I have my doubts that sweating alone will be able to handle this heat. Your picture shows a flat disk (so do most examples on the wiki), that limits the range. Is it possible to have this effect over longer distances, say the center of your body to the edge? And how much space would it take? Could you perhaps use hollow tubes around bloodvessles and connect them to plates near the skin to ferry heat from inside to the skin? The purpose here is to improve your question to be as good as possible $\endgroup$
    – Demigan
    Mar 15, 2021 at 10:11

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