Context: The world has been in a world war lasting centuries. Casualty rates are through the roof and can’t be lowered. The warring countries' solution was to make human factories by incubating fertilised sex cells from the most competent soldiers.

Edit: For context, before this the technological focus was on building drones, then countermeasures have developed and rendered advanced field tech useless. The tech focus was therefore shifted to biology and genetics. An artificially-inseminated zygote, incubated for 6 months, produces a body roughly equivalent to that of a 12 year old.

The inspiration for all this: https://www.newscientist.com/article/2128851-artificial-womb-helps-premature-lamb-fetuses-grow-for-4-weeks/

“Ain’t no one got time to be pregnant in war!”


  • Ideally I want all factories in the region in total to be producing 60,000 bodies daily.
  • I want the factories physically small enough to avoid getting easily detected.
  • I want them in large enough numbers (and decentralized) that losing 3 or so factories wouldn’t be a huge loss.
  • Technologically a tiny bit beyond our current level. Machine-operated, extremely efficient.
  • Incubation to the final product takes 6 months.


  • How large should the facility be?
  • How many should there be?
  • what’s its capacity?

The finished products are shipped to training centers for indoctrination, war and survival skills.

I’ve tried to use data from the cow farms in the US to estimate, but I realized the living requirements of the flesh bags are significantly different, so that went nowhere. But, they in total slaughter abt 10,500 cows/day, all in abt 1,300,000 farms with an average capacity of 165 cows/farm.

I’ve been stuck in this problem for a long while, thanks in advance for your answer!

  • 1
    $\begingroup$ Welcome to worldbuilding. Are you aware than humans have 9 months pregnancies? Also, small enough and decentralized are not synonyms. Finally, we simply don't know if a human being, developing in an artificial womb, would be an healthy human at all. $\endgroup$ – L.Dutch - Reinstate Monica Sep 6 '18 at 6:56
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    $\begingroup$ Men are not potatoes. $\endgroup$ – Jasper Sep 6 '18 at 6:58
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    $\begingroup$ @Jasper You don't know that for sure. $\endgroup$ – Clay Deitas Sep 6 '18 at 6:59
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    $\begingroup$ If it's war then thrse factories will be targeted and attacked. Period. Spreading out means of production is not intended to make the factory an unlikely target, it is intended to reduce the loss the enemy can inflict with a single attack run. $\endgroup$ – dot_Sp0T Sep 6 '18 at 7:18
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    $\begingroup$ "Casualty rates are off the roof and can't be lowered" - with technology of today plus some years, the actual fighting should be done by drones. You could build hundreds of drones in a year for less than it will cost to create, raise and train a single human to fighting readiness over 18(ish) years. If the drones are doing the fighting and the casualty rates are still high then you are better off making people the traditional way - expectant mothers will do their best to move away from danger when threatened, but flight may not be an option for a factory. $\endgroup$ – KerrAvon2055 Sep 6 '18 at 8:16

You want 60000 pieces/day, and each machine delivers 2 pieces/year. Therefore you need at least

$n_{machine}=60000 \times 365 / 2 = 1095000$

up and running at any moment.

Assuming that your machines have an availability of 99%, it means that at any moment in time 10950 will be down for maintenance. To cover this lost production you actually need then about 1100000 machines.

To minimize impact of any attack on the facility, you want to spread it so that a local attack would not take down a large part of your production. If for acceptable loss you take the same 1% given by the machine availability, you end up with the constrain of not having more than 11000 machines in the same local area. This gives you a total of 100 factories, each having 11000 machines.

Considering that a human body occupies about 100 $dm^3$, or 0.1 $m^3$, and assuming that the machine will at least double that volume, with a base surface of 0.05 $m^2$ and an height of 2 m you would need at least 550 $m^2$ just for the machines. Adding the necessary facilities would at least require the surface requirement to quadruple, so about 2000 $m^2$ per factory.

Since you mention that these factories where previously used for building drones, it is reasonable to assume they were already well protected, maybe built underground. How sparse you build them it really depends on the attack capabilities of your enemy. Assuming they have access to Tsar Bomb equivalent technologies, I would say that an earthquake proof, underground bunker spaced 50 km from the closest factory could reasonably ensure your production against underground explosions of large nuclear bombs.

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  • $\begingroup$ This was exactly what I needed! I never thought to do the calculations based on each machine, thanks so much for everything! $\endgroup$ – TAG. Perez Sep 8 '18 at 0:10
  • $\begingroup$ @TAG.Perez, don't forget that you can accept the answer which better solved your problem $\endgroup$ – L.Dutch - Reinstate Monica Sep 8 '18 at 3:37

Some basic math:

You will produce 60,000 people/day You will have 6 months worth of people in the factory.

6 months is about 180 days. That is 10,800,000 people in all of the factories at any given time.

Split that up into, say, 20 factories. That's 540,000 people one factory at any given time

Your factory will be big enough to hold 540,000 12yr olds and any life support equipment and food they will need.

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  • $\begingroup$ You forgot that, as per OP, the production must not be impacted greatly by a single attack. Your plan will result in a whole 5% loss just at the destruction of a single factory. $\endgroup$ – Bewilderer Sep 6 '18 at 16:34
  • $\begingroup$ @Bewilderer I was using 20 as an example to break up the >10 million people into manageable amounts. More factories could be used, and the factories would be well protected. If the factory is very difficult to destroy, 5% isn't really that much compared to the resources the enemy would need to destroy one. $\endgroup$ – John Locke Sep 6 '18 at 17:03

Each factory is the size of one growing body. It is provisioned by its host, an adult human.

baby backpack

Like this, but with an external umbilical cord. And creepy.

Human fetuses grow because their mothers provide nutrients to them via the umbilical cord. In your synthetic robowombs, each adult human carries a growing human body in a portable tank. The growing body gets nutrients from its host, who must eat and drink (and breathe) enough for both. Wastes are expelled via the kidneys and liver of the host.

It is a time tested method, upgraded by technology.
Benefit 1: males participate.
Benefit 2: a given growing body does not need to stay with the same host. The growing body might start with a small person when it is small and be serially switched up as it enlarges, finishing its growth on the back of a large male who is physically more capable of hauling around and supplying a child sized body.
Benefit 3: Backpack is a much more physiologic way to haul a load than inside the pelvis and abdomen. You could have tumplines too.

This is maximally decentralized. Your person factories are as protected as your people are. You can grow as many bodies as you have incubator packs and population to carry them. When your fresh 12 year olds emerge, they will be fitted with incubator packs of their own.

"Everyone got time to make babies in war."

  • it occurs to me that like the passenger depicted above, the growing body in the backpack could be awake - not totally awake like this baby but not inert like a fetus. It could be capable of some interactions and maybe even some actions.

  • it also occurs to me that this system lends itself to narrative. Imagine the hero, mortally wounded. The heroine takes her pack off and his and takes out the growing bodies, unplugging their cords. The dripping little kid bodies look stupidly around. She plugs her cord into the hero and crams him into her pack, grits her teeth as she gets to her feet and makes off with him on her back. After a few steps she yells at the new bodies and they toddle along after her.

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