Thread:OrkMarine/@comment-5135903-20131015154127

A few days ago you were asking for tips on self-healing, organic armour. Turns out it's mighty tough but I've done my best.

There are a whole host of problems with using organic armour. Compared with artificial substitutes, organic matter isn't particularly strong; it needs to breathe, consume food and... er... excrete waste. Also, organic matter doesn't heal damage very quickly; in many cases large wounds don't heal at all (like if you chop a person's arm off). These are the challenges that an organic armour designer would have to contend with.

Of course, made-to-measure organic armour isn't just going to evolve on some alien planet somewhere; it will have to be genetically engineered. It is likely that it would be made up of some form of colony-based single-celled organism, that is grown in a vat over an artificially contructed extracellular matrix made to fit the wearer.

The armour would exude some sort of rubbery coating which would be rich in carbon nano-tubes. carbon nano-tubes are one of the strongest materials producible today, and it is sometimes said that if we could manufacture them in any significant quantities, they would make the ultimate lightweight armour. The (relatively) long nano-tubes would end up wrapping around each other in a similar way to the polymer chains in a plastic shopping bag, which would provide a strong but flexible barrier.

Genetic engineers may want to genetically adjust the viscosity of this rubbery coating, allowing them to control whether the armour is thick and strong or light and rigid, while the armour is being grown.

This rubbery coating would also contain a polymer such as polyurethane or polyurea, which would eventually be squeezed onto the outside surface of the armour by the denser carbon nano-tubes. This coating spreads the force of impacts rather well. Polyurethane is famous for stopping bullets in their tracks by 'absorbing' them. There was also a test done by the US Navy in which they put two identical trailers (though one was sprayed with polyurethane) next to a 230kg bomb. The trailer with the polyurethane coating was dented, while the second trailer was completely destroyed; now imagine if that impact-spreading was backed up with that super-strong carbon nano-tube armour!

As for healing, since the armour is actually made up of single-celled organisms living in a colony, the only way you could prevent the armour from completely healing is if you destroyed every single cell that it was made up of. As long as the extracellular matrix that it is grown around is maintained, the armour will grow back into the right shape eventually (if the extracellular matrix gets damaged, medics may carry replacement samples to patch up any holes). However, it would take a long time for any damage to be healed over, and the armour would probably have to be placed in a vat of nutrients for it to feed on while it heals.

In the short-term, if something does manage to breach the armour, it is likely that the energy from the impact would cause the area around the breach to momentarily liquefy and spread over the gap. The cells of the armour may also contain special proto-cells (big spherical molecules with more molecules trapped inside). If cells within the armour are damaged, these proto-cells break open, releasing chemicals which cause other chemicals within the cell to 'set'. If the biochemistry of the cell was made up of lots of metal-rich componds, it would set very hard indeed. Think of a cross between a scab and industrial super glue!

One other thing. It would be less messy if the armour sustained itself via phototrophy (which basically involves the direct conversion of sunlight into energy molecules for the organism). However, the armour wouldn't get much energy from that, so to heal serious damage to the armour, you would probably have to place it in some sort of nutrient vat, in which the armour could use a process such as fermentation or respiration to provide the extra energy and organic matter needed for healing.

There. I've finished! Well, I've covered impact-resistance (not so sure how it would fare against lasers, though) and healing, but there are many other adaptations such as heat/cold resistance that I could go into as well!

Alas, I take too long with these things... 