Weapons for a civilisation-destroying giant robot

Question

An assortment of alien adolescents accompanying adult aliens on an alcubierre-drive ship just happen to have been passing near the Sol system. Having noticed that there is lots of EM radiation coming from the third planet, their ship was stopped so that its scientists could gather data. Firing up their quantum computers, some of the digital transmissions were decrypted. The aforementioned alien adolescents saw one of the decrypted transmissions, which happen to be a broadcast compilation of alien/monster and modern warfare movies, in particular, but not limited to, movies like Godzilla, Super-8 and Cloverfield.

Having entirely missed the point (since they neither read nor speak English) that the movies were intended to be entertainment, the alien adolescents have misinterpreted them as documentaries recording what they see as humanity's barbarity, celebrating warfare, the destruction of hapless lifeforms and the unjust capture and escape of an alien pilot and its ship.

The alien adolescents have resolved to show those arrogant humans what a real giant monster attack is, and to that end, they have designed a giant robot, a snakebot with a circular cross-section 1 Zode-la in diameter (1.19 km), and 2xPi Zode-la in length (7.48km), plus a 1.5 Zode-la (1.79 km) tapering tail (9.27 km long in total) that can mate with the snakebot's similarly-shaped mouth, forming a 4 Zode-la (4.76 km) high torus that can move in a rolling fashion, as well as being able to move in other serpentine methods when not hooped and rolling.

The robot has a maraging steel core and mechanism, with six equally-spaced hydrogen-fusion power-plants along its length for redundancy, any one of which could power the entire bot. The outer 1 Zode-gu (1/8 Zode-la, or 224 metres) is armour, made from overlapping, flexible arrangements of depleted Uranium-Tungsten alloy plates coated with Boron-Carbide.

To build all this, the alien adolescents simply program a 1 Rel-ek (3.84 liter) capacity atmospheric-descent-container full of versatile programmable construction nanites, which will self-replicate until there are enough to build, operate and maintain the snakebot.

Fortunately for the humans, these aren't military nanites, which are chock-full with weapons designs, strategies and rod-logic brains, just one of which could be expected to render Earth ripe for conquest (for whatever value of "conquest" is chosen) all by its lonesome. No, these are just engineering nanites, individually only about as smart as a human, and only with fairly basic programming. Unless given about the same time as a human committee, these nanites won't be coming up with too many innovations.

Hearing their seniors approaching near the end of their design conference, they jettison the incriminating nanite pod. The container lands on Antarctica, and the nanites immediately start building the snakebot. The better part of a decade later, we have 8.3 or so cubic kilometres of snakebot, weighing at least sixty billion metric tons advancing on the cities of the world, with the objective to destroy all human infrastructure.

Question:

The alien adolescents' goal is for their snakebot to flatten all human infrastructure more substantial than a tent, and to generally knock humans back to something approximating the stone-age.

Since the alien adolescents intend to be slightly more sporting than the humans in the "documentaries" seemed to be, the engineering nanites are programmed to build only one snake-bot, and to self-destruct, individually if separated or captured, or collectively, along with the snake-bot if possible if the bot is mission-killed or achieves its objective. On the other hand, they want to protect their snake bot until it completes its mission.

Given the likely capabilities of a species capable of building an alcubierre warp-ship and rod-logic nanites, what offensive and defensive weapons might the alien adolescents (who can be considered to be about as intelligent and well-educated as the users of WB SE) build into the outer armour of their snake-bot designs, considering their goal and that they have seen fairly recent movies containing images of modern human weapons - including atomic weapons - in use, and can speculate on their probable design and function. What use would each of these weapon systems be expected to fulfil?

Since the alien adolescents know nothing about human biochemistry, toxins are off the table, save as an accidental side-effect of a physical weapon system.

Any weapon deployed on board the snakebot must address the matter of resupply in the field, though remember that there will be quite a few nanites hanging around in the bot to act as its brains and self-repair mechanism, that could be repurposed to making ammunition if necessary.

Since this is [science-based], we aren't having any hand-wavium weapons here. If you couldn't say, or find out, how it works if asked, you don't get to include it in your answer, since the alien adolescents' schooling won't have covered it yet. That includes any futuristic technology required to make an alcubierre ship work.

EDIT

In response to a comment by Gianluca, I recalculated the mass of this thing. My original calculation was that it weighed around 600 million tons. This has proved to be wrong, it actually weighs in at around 60.2 billion tons, assuming that it has 50% internal voids and that 5% of its armour is Boron-Carbide plating on top of Tungsten-Uranium plates/scales.

Answer 1

This question is a bit weird. Although the aliens are clearly inspired by Earth monster movies, it seems to me that they would be more likely to base their monster on some pre existing creature from their own biome. They already understand the Ravenous Bugblatter Beast of Traal and its various modes of destruction from watching National Xenographic specials as children, but where will they learn about snakes?

For that matter, if they were big fans of National Xenographic and did catch the Planet Earth Christmas Special (widely considered to be the worst show ever, and never rebroadcast), the segment on the snake would either show a constrictor, so they would believe the appropriate measure for their snake would be to swallow and digest cities (that hinged jaw on a 9km long snake is a masterpiece of engineering), or that the snake should inject venom into its prey. Since the fangs on a beast that size would be as big as office towers, it is a bit unclear as to what, exactly, they would be injecting venom into (or what would need venom glands the size of city reservoirs to poison).

Given their research seems to be a bit hasty and incomplete, I will give them a pass here and say they logged onto Galactopedia and learned about the spitting cobra.

Their huge mechanical snake can rear up and strike, and eject either a cloud or a stream of some powerful acid (Galactopedia was not clear on the nature of cobra venom, so they made the next best guess). Given the size of the creature it can certainly have venom glands that would put a water tower to shame, and a fusion powered internal ecology could synthesize common acids relatively quickly, so the huge cobra would not run out of "venom" to spew. With the size and power available, the acidic "venom" could be shot out to several kilometres, taking out incoming bombs and missiles. The launching aircraft, unlike the movies, would be relatively safe. Some glide bombs can be launched from over 100km from the target, and missiles have similar ranges (remember that the next time the intrepid movie hero goes to "eyeball range" to release a weapon).

The major weakness is the snake will have a lot of inertia, so swinging the head rapidly around to engage multiple targets coming from different angles will be difficult. This suggests the best strategy is to simply overwhelm the creature with a squadron of "Strike Eagles" or SU-34 "Fullback" bombers coming at all angles and releasing dozens of bombs or other armour penetrating ordinance at the same time.

Otherwise nuke it from orbit. Its the only way to be sure.

Answer 2

The first thing the military in the various films do is shoot at the creature with small arms fire. Your monster is quite obviously immune to that kind of damage, and will ignore it, just like the monsters in the films. The next step is larger weapons - tanks, small air-to-ground missiles, and ground-based explosives. Those are unlikely to do much more than mar the finish of your monster, but at least it will notice. The response is the usual mounted weapons:

• Teeth. Nothing screams monster movie like a tank getting bit in half then thrown into an airplane.

The national guard dealt with, the monster next goes up against the full forces of the army, taking long-range missiles to the face (always to the face). These are bigger than the previous missiles, and may cause it to at least halt its attack; the response is, usually, widespread destruction that causes the government to halt its actions, even though they seemed to be working, and instead retreat. This weapons has to be flashy, over-powered, and useless outside a minimum range. Fire breath, laser-beam-eyes, and sonic shockwaves are all possible; however, I suggest:

• Heatwaves. The creature heats internally, turning red-hot and melting and/or burning any nearby objects. I can imagine a lead scientist working with the military explaining (in dubbed English) how hot skin makes the monster invincible, and to stop shooting at it.

Finally, we come to the last chapter of the monster movie: the military's deus ex machina weapon. This is a nuke, another monster, a really big sword, the common cold - something that could easily destroy the monster, but hasn't been used before for... reasons. Of course, the teenage aliens don't want their monster destroyed, so they pack as many real weapons into as possible to combat this weapon. I would suggest:

• an anti-missile gun, to bring down any large-scale nukes before they go off.
• a high-powered rail gun, for long-range base-destroying.
• defensive skin-shedding (the nanites can make another layer), to repair damage.
• body-slam enhancing rockets, also useful for a quick retreat.
• legs and/or wings (surprise! It's actually a mecha-lizard/wyvern/dragon!).
• a large victory sign that reads "Hi mom!" (or, alternately, something slightly rude).

Of course, the aliens may have overestimated the size of their snake. This snake-monster is huge. It's big enough to level most cities by sliding straight through, and its skin is tough enough to withstand anything but a direct nuke - even then, that would only make a hole, not destroy it utterly.

Earth military wouldn't even bother to send tanks at it; as soon as it shows up and starts smashing stuff, they'll try to nuke it to a cinder. Not those little nukes, either; anti-missile guns will wipe out anything that comes near enough. They'll use the big ones, the well-that's-it-for-this-planet ones. It won't be pretty. We can only hope the parents catch on and stop it before it actually destroys the world...

Answer 3

building off of the previous replies: how about a grid of point-defense laser batteries covering the entire outer skin, with support from advanced targeting systems? They would have to be able to retract inside when the portion they cover rolls to touch the ground or something, but otherwise would make the snake (even more) indestructible, as it is already immune to bullets and light explosives and is now able to shoot down any number of missiles or bombs that come its way. This assumes that the fusion reactors are each able to cope with the demand of thousands of fairly powerful energy weapons individually, as specified, but solves the problems of ammo by not needing any. Although really, if they wanted to follow kaiju tropes, the only additions would be some kind of breath weapon (plasma, acid, etc) and a natural meelee weapon.

Answer 4

If they've watched the sort of films you're talking about then the only possible answer is that they make it breathe fire. It would probably glow and make a strange sound first (cos that's what happens in films) then open its mouth and fire would spew out.

Beyond that if they want it to complete its mission then small arms are no threat. It would need radiation detectors to detect nuclear land mines and some sort of medium range interceptor missiles that can be used both to take out the land mines and any incoming nukes.

Beyond that it's fine. It will rampage around as a virtually unstoppable self-repairing killing machine.

P.S. Note that something like this forming would most likely get noticed, even in Antarctica. That thing is big.

Answer 5

None of your material can withstand a direct hit with a nuclear weapon.

Uranium has a melting point about 1100° Celsius
Tungsten is about 3400° Celsius
Boron-Carbide is about 5000° Celsius (the highest you use)

A nuke develop temperatures in the million degrees scale, so a direct hit will vaporize them.

The problem here is that the snake is really big... or not ? A nuke with a 2 megaton yield produce a fireball with a radius of about 1.27 Km

The biggest nuke (as reported) the USA deployed is the W53 (Titan II) with a 9 Megaton yield, which produce a fireball with a radius of about 2.33 Km

Given that your snake has a diameter of about 1.2 Km, a somewhat direct hit with a 2 megaton nuke can cut it in half and probably is sufficient to disable it.

A W53 nuke that hit the snake in the middle probably destroy it, taking into consideration the direct and indirect damages.

Update
I seems that I have misinterpreted the question and interpreted it as how it is possible to destroy the snake.

But given the limitations of the question, (science-based tag and explicit exclusion of futuristic technology) I think there is nothing that the snake can have that can save it from a direct hit from a nuclear weapon since we have no idea how to build something that withstand such conditions.

But to answer the question, the best defense that the snake can have is to intercept all the things (by air, land and, eventually, sea) that come closer than few kilometers from it. I would tend to exclude lasers, since once you enter a city they are useless, and opt for a electric railgun with a high rate of fire.

Answer 6

For the most part, a giant metal snake is a pretty formidable weapon i itself. If one came rolling through the average residential area, the effects would at the very least be comparable to a violent tornado. However, considering that Earth has land 149 million km^2 of land, and even if only half of it is inhabited with major human structures, that is still a lot of ground for a 9km snake to cover. Basically, people will notice quickly. Even though the snake might fair well (depleted Uranium-Tungsten sounds pretty indestructible, especially if the snake moves fast), no doubt extra defenses would be put up to protect from this snake. Therefore, for the most part, it will need offensive weapons. One such weapon could be fire. It doesn't necessarily have to breathe fire, but rather just make some sparks, perhaps with live wires powered by its power plants. This will have the added bonus of having some defensive use, as well as wrecking essential buildings without necessarily setting them on fire. A large enough voltage applied to, say, a human power plant, or some center of communications (internet, phone) will definitely shut it down at least long enough for the snake to destroy the rest of the surrounding area.

Additionally, it could take advantage of its environment. If it happens to be by a coastal city, for example, it could go into the water (presumably it can swim- how else would it get off Antarctica?), and cause enough tidal waves (perhaps with the help of extensible fins pressed against its body) just by smacking the water hard enough. Even if this might not exactly cause what people would expect from tidal waves, enough buildings would be devastated to allow the snake to burn the rest, and roll around on what's left. This could last maybe a few hours, allowing it to hit maybe 7, 8 modern cities daily (assuming it doesn't "sleep").

Suburban and rural areas, being made of mainly plaster, wood, and the occasional grassy field, would not stand against the snakebot even if it didn't have any weapons. This leaves non-coastal cities, where, again, even if the snake had no weapons, it would still likely destroy everything quickly. Your snake is BIG. The tallest building in the world, at 828m, is not as tall as the diameter of its cross section. The average skyscraper is not even half its radius. Honestly, more of a problem is what can humans possibly do to avoid the giant snakebot of doom, because at the moment I can't think of anything. Sending out the snake unarmed is probably enough to destroy mankind in a matter of years, as the only thing that could conceivably harm it is nuclear bombs, for which fleeing and a strong exterior (you got that) are the only defense.

Congratulations. You've doomed all of mankind to inevitable destruction by giant alien snake robot.

Answer 7

Many comments are concerned with the snakebot's vulnerability to nuclear attack, but I believe the concern is overblown. The snakebot would protect itself from nukes the same way the world's major powers do: airspace sovereignty and a missile defense system. Except the snakebot has a major engineering advantage, as I'll explain shortly.

The snake's most important weapons system is that described by @Duncan Urquhart:

a grid of point-defense laser batteries covering the entire outer skin, with support from advanced targeting systems

This grid could effectively enforce a no-fly-zone of at least 100km radius. Google "horizon calculator" for details. The bot is a great platform for multiple heavy lasers (have you seen how big those things are?). I would also add hypersonic rail guns for use in bad weather, and high-power long-distance radar.

The Engineering Advantage

The alien designers don't have to concern themselves with collateral damage. Designing a system that can literally shoot at anything that moves, whether it's on the ground, in the sky, or in space orbit overhead, is much easier than designing a typical human weapons system that has energy, space, and cooling constraints and has to fit on a ship, be stocked with ammo, and have a certain level of safety features.

The targeting subsystem may not even require special coding for nuclear ICBMs: a generic "vaporize anything coming in my direction" module probably would do the job.

The system naturally would shoot out any orbiting satellites as soon as they come over the horizon. Humans will have only a few hours to react before most low-orbiting satellites and all geostationary satellites on the same side of the planet are taken out. This is not nearly enough time for any kind of massive coordinated attack. And without satellites, the world's military are essentially stuck to WW2 tactics.

Pre-GPS ICBMs are not precise enough for a direct hit on a skinny target like the snakebot, even if it was stationary. Even if you shoot a barrage of ICBMs, the bot's targeting system can prioritize the ones flying directly at it, and still avoid a direct hit. Humans will run out of ICBMs fairly quickly. Cruise missiles are slow, easy targets.