Quote Originally Posted by Tiadoppler View Post
Unlike a living being, a robot does not go into shock when severely damaged. There's the possibility of using genetic algorithms to allow a robot to continue functioning (at decreasing effectiveness) as it is damaged. If you disable one weapons system, or one ammunition feed, or one turret motor, a well programmed combat robot might be able to continue fighting. Anti-material would definitely work. Do you think Armor Piercing Incendiary rounds would stay inside the robot long enough to cook the electronics? I'd be worried that they'd overpenetrate and shoot out the far side without spending enough time inside to transfer their heat.
API would almost certainly stay in (by the time it penetrated the initial armor, went through whatever components are there, and struck the other side, it would have shed way too much velocity to keep going), and it wouldn't take that long to transfer the heat.

Secondly, you're seriously overestimating the durability here. Get a hit on the battery? The battery bursts into flames and cooks the robot (remember a few years ago when one of the Samsung phones was banned from aircraft because the battery was spontaneously combusting? Same principle applies here). Strike an ammo feed? The ammuntion is likely to chain-fires and combust, cooking the robot. Strike a motor? Might just disable it, might cause an arc that cooks the robot.

Looking at your idea in more specific detail:

Quote Originally Posted by Tiadoppler View Post
Think of a robot that's roughly the size of a car tire lying flat on the ground. It's got treads underneath, an articulated sensor "tower" that can be raised over obstructions, an array of cameras and sensors in the shell and an armored carbine-caliber turret on the top of the shell, and is deployed by the hundreds.
There's simply no possible way you can construct this and have it armored against any real firepower, by simple size. If we are looking at it with a near-future technology bias (which is critical, otherwise the weapons used against it would be better as well), a car tire is about the minimum possible size for a turret, depending on what you intend the meaningless phrase "carbine caliber" to denote. So, best case scenario, you have a car-tire turret stacked on top of a car-tire body.

Let us assume that the designers are not stupid, and go for a round turret on top of a square body instead of making both round. This allows for much more efficient use of internal space. For a power supply, let us assume an electric drive. You'll need at least one, probably two Lithium-ion battery packs roughly the size of a car battery to get any kind of endurance. So two battery packs. Some research suggests that an electric motor roughly equivalent to 2 horsepower is also about the size of a car battery. So you get two of those, one to run each track. Now, you need a brain, which will require a CPU, a PLC, some communications equipment, and some relays (the motors will draw too much power to switch directly - a burning PLC taught me that). Since it's going into combat, put this in a 5mm armored box with data ports on the bottom (where fire is least likely to come from). Charitably, you'll wind up with a box about the size of a car battery. The result would be five equal-sized boxes all in a row. Almost forgot - you'll need a sixth box, because all of these components are going to generate a lot of heat and simple ventilation won't cut it. That means you'll need to install a radiator block and run cooling lines. Put that on the back. Once you've run all your wiring, installed the tracks, and run the cooling lines, you've used up pretty much the entire "car tire" worth of space, and put in between 100 and 150 pounds worth of weight. Ignore the body armor for now.

Your turret needs to carry the weapon itself (as I alluded to earlier, "carbine" is a very sloppily defined word that could mean anything from a long-barreled gun firing pistol cartridges, to a P90-style PDW, or simply a short assault rifle - given the need to balance size and firepower, I think a P90-analog is a good pick for your proposed idea), a plentiful supply of ammunition (500 rounds minimum if you want any kind of sustained combat capability), rotating gear, and at least two high-quality cameras for sighting and observation purposes. You'll probably also want another water-cooling system, but that's probably optional here. You won't be able to pack this in as tightly as the hull, because you'll need easy access to resupply ammunition. Before armor, let's call this fifty pounds with the bare minimum framework to hold it together.

Now, let us turn to armor. Assuming a square box, 5mm of hardened steel will weigh about 16 pounds per face. The rounded turret is more complicated, but assume similar weight for napkin calculating. This means that putting 5mm of armor on all sides of both hull and turrent will add about 128 pounds of weight. Alternatively, you could use composites. Each "face" would have about the same surface area of a chestplate, so we can use that as a basis. A chestplate rated to stop a single rifle-caliber AP round (it will stop all lesser rounds, but multiple AP shots will shatter it and allow penetration) weighs 7.5 pounds. Round that up to 8, and you can armor it for about 64 pounds.

So that puts us at 328 pounds for the steel-armored version, and 264 pounds for the composite-armor one. This would be more than adequate protection from intermediate rifle cartridges (such as an M4 or AK), and will even keep out battle-rifle or machine gun fire as long as they don't have AP rounds handy. It would be a wise idea to reduce the rear armor to boost the frontal armor - that could bring you high enough to keep out rifle-caliber AP rounds from the front, at the cost of opening up the rear to just about anything - this is offset by putting the radiator in the rear, which would be very likely to convert a penetration from a hard kill (the thing is destroyed completely) to a repairable mission-kill (radiator destroyed, unit goes into preventive shutdown).

If, however, the machine was penetrated, it would be disabled or destroyed easily. With everything packed so tightly, the bullets would have no place to go except through very valuable and volatile components. With that in mind, I'd suggest that thinking of them as disposable would be ideal, and don't bother increasing the armor further. This is particularly sensible because you can't armor the sensors (which is critical for a remote-operated vehicle, and even more critical for an autonomous one) much.