# How would height be affected in an exoskeleton-based humanoid?

I've been curious about writing about a very durable exoskeleton humanoid species, but I have wondered about how the extra weight of a thick exoskeleton would affect their height.

I do not see them as 'prawn like' insect-like creatures (like from District 9). Instead, the prehistoric armored fish would be a closer relative for the general make up of their thickly armored exoskeleton while retaining bipedal mobility.

The main idea is their exoskeleton is some sort of ultra-dense variation of our bone material, thickness tbd, maybe 5-10mm, and effective armor against any bladed weapon and many pistol and submachine gun rounds.

Side Question: The skeleton a human male weighing 200 lbs is supposed to be about 15% of that body weight, or 30 lbs...your skin is supposed to weigh another 15% or so, so another 30 lbs, that would leave 140lbs of guts for a 200 lb endoskeleton male. Anyone have any good guesses of what an 8mm thick complete human exoskeleton would weigh on top of the 140 lbs of guts?

Thanks!

• and effective armor against [..] many pistol and submachine gun rounds. Sorry, but no, that won't happen. Keratin is not tough enough to stop a gram of lead moving at 1200 feet per second. – Draco18s no longer trusts SE Jun 21 '18 at 1:25
• @Draco18s low caliber rounds especially from a pistol often dont have the capacity to penetrate a human skull (on average, not on specific spots like the orbitals). Bone is one of the hardest and simultaneously flexible materials in nature. The rounded shapes of the human body also make deflecftion likely. A bone-like material as exoskeleton would be very useful against small-caliber bullets and even if it doesnt stop the bullet it wilk make many lethal shots surviveable. The bigger problem is that an exoskeleton humanoid would weigh so much it can barely move and have trouble losing heat – Demigan Jun 21 '18 at 12:20
• the real problem is how they grow, exoskeletons usually means molting. – John Jun 21 '18 at 14:36
• @Demigan The human skull is also 6.5 mm (quarter inch) thick, which is way thicker than a believable exoskeleton. Yes, your question says 5-10mm, but think about wearing a quarter inch thick layer of stiff plastic all over your body. – Draco18s no longer trusts SE Jun 21 '18 at 15:42
• @Draco18s you claimed it wouldnt be adequate for bulletprotection. No one is going to deny that an exoskeleton humanoid is going to have a ton of problems unless its quite literally engineered with specific materials. – Demigan Jun 21 '18 at 15:51

I would say use a mineralized protein fiber matrix in a Bouligand pattern similar to that of crustaceans with particularly hard claws. It wouldn't necessarily have to look like crab shell to benefit from it's structure and engineering. It likely wouldn't deflect bullets though, so much as be ablative. It wouldn't let the first one or two shots through any one plate and would fracture and chip to dissipate the kinetic energy. This would still generate enormous amounts of pain and could still potentially damage internal organs but wold not likely lead to fatalities unless the same plate was hit consecutively.

Then you could have the person molt periodically to replace cracked plates for new ones.

That said, the Mineralization of the shell would weigh heavily on the frame of the person. This structure is extremely hard but it would also make it dense and therefore heavy. The outer surface would be much denser than the inner surface as the inner surface should be more concerned with kinetic and thermal dissipation. It would have a greater density of pores and may even have capillaries to help dissipate heat. You could make more of the shell with the mineralized proteins but the more you do the denser the shell and the heavier the person will be and heat and kinetic dissipation become an issue.

• Thank you and everyone else who weighed in, very helpful! – LightYears Jun 28 '18 at 15:43

You can have the exoskeleton in form of a honeycomb structure. In this, the Keratin will be joined together in a hexagonal maze, with lots of air space between them.

This will reduce the overall weight of the armor to a great deal and still would be able to deflect the bullets to some extent.

Naturally, the space in this honeycomb will be empty, so the creatures can have a good average height. On the other hand, they can be really smart and when an adult decides to become a warrior he will bath in some kind of fluid(natural/chemical) that will fill up these cavities with gel-like material to increase the bullet resistance.

Easy, if you are saying they somehow have a "super dense" bone structure on the outside just give them super dense muscular tissue