This theory blog is a continuation of this previous blog about the Time Limit. So it may be helpful to read that one first.
So, as I seem to have enough time to waste thinking these things over, and the time to write these blogs...why not? (Oh who am I kidding, I write these things to stay sane...sigh)
Now I'm going to give my thoughts on Ultra Armor, the skin of Ultras and see how realistic or if there is a realistic equivalent and/or explanation for the durability of Ultras. Let us begin!
What is Ultra Armor
If you really have to ask this question...get out, just get out, I don't know why you're here, but look go read 'this' and get back to me.
Now, for those of you still here...I still feel the need to explain what Ultra Armor is...well what's made off and such. We know one thing if nothing else...Ultra Armor is made of Specium. Now this may seem weird since you know...Specium is used for death rays and high tech warheads. It really doesn't like something that should be making up the skin of an organism. Please remember that this being in question has a light based/dependent biology which may or may not involve cellular nuclear fusion.
We also know that the densest amount of Specium on the body is the face, hence the mask like faces, and possibly the Protectors as well. For Ultras from M78 (though truth be told it seems like all other Ultras are beginning to operate on the same principles) the silver parts of the body are the most protective and absorb the most sunlight. Which leads us into our next point. Ultra Armor is Photovoltaic.
Solar Absorption and Markings
If you don't know what that word means (Photovoltaic), don't worry...actually you should but aside the point. It basically means, that something, usually solar panels...hence why you should know what that word means, (Hey, my country is classified as 'Third World' what's your excuse?). It means something takes Photons and uses them to generate an electrical charge.
Plants use Photosynthesis which uses sunlight to power a process which combines the minerals they absorb through their roots and the water they drink, into food for the plant to survive on. This process involves a Photovoltaic substance Chlorophyll the stuff that makes plants green, but no Ultras aren't plant. Instead, I believe this charge goes into Cellular Fusion process I mentioned in the last theory blog. Sunlight is absorbed, converted into a charge, and said charge keeps the Specium centered fusion process going.
Now to Markings, there are three main tribes or ethnicities for Ultras, the Red Tribe, think Seven and Taro, Ultras who are mostly red, the Silver Tribe, which covers the Original Ultraman, Jack, Zoffy, Ace, 80 and Mebius, these are Ultras who are at least fifty or more percent silver (from what I can assume) but also red. Then you have the Blue Tribe, who are mostly blue and then some silver.
Now where do these markings come from...that should be simple, the Inner Light, the internal energy, which also carries their energy signature/genetics. After all, these groups are called 'tribes' which heavily implies their color is genetic in nature. Then you have Zero, who has the bloodline of the Red and Blue Tribes. The Inner Light decides which parts of the skin are densest after the face, causing the silver markings. These parts are the most protective because they are the thickest and thus more light and heat from fire and lasers. Everything else, is interacting more readily with the internal energy causing the coloration of what would otherwise be silver.
So How Does Their Resistance Work
This should be rather obvious by now, their resistance...is absorption. All Ultras are universally resistant to fire, heat and lasers because their skin actively converts those things into an electric charge. As for why it hurts, why wouldn't fire hurt Ultras if it's hot enough? Or lasers or fireballs? These things should still trip nerve endings, or the Ultra equivalent. Though in the end I'm grabbing at straws since Ultras have literally dove into the sun to recharge...so what's some halitosis going to do? Meh.
Chances are, it may have something to do with the atmosphere and not just them absorbing heat. Maybe in space their ability to feel pain and such is deadened which is why they seem more durable there. That or their skin is specifically meant for sunlight and absorbing heat and such is a bonus.
The mechanism of Ultra Armor and the internal composition of Ultras, also explains why they are so resistant to ionizing radiation such as Gamma Rays. (Sorry G-Fans...actually no G-fan'boys', cause I know G-Fans have respect for other properties) After all, Ultras have been hit by Atomic Heat Rays before, and Ultraman survived a nuke point blank in space. In fact, the fact that radiation didn't cover half of the Earth, means that Ultraman had to have done something like absorb it all to stop that.
Attacks such as lasers, fire and general heat are not actually hurting Ultras, well they are causing pain but not physically causing damage, or the damage is so minuscule to the Ultra Armor/skin, enough to cause pain, but not be visible, while the rest of the energy is absorbed into the body.
Electricity is also a confusing bit. Is it tripping nerve endings, or interfering with the internal fusion reaction? Ultraman was literally immune to that stuff, so maybe the former.
In the end Ultra Armor is also very durable as modern ordinance is generally ineffective as well, so it takes some superhuman strength to cause injury.
In short Ultras are some durable creatures.