I love spider tanks, ever since I watched that episode of Ghost in the Shell: Stand Alone Complex, with an experimental spider tank going rogue.

Most of them consist of three main parts:

  • The forebody, which mainly contains the sensors, the ammunition holder of the primary (machine gun) weapon, and the Central processing Unit.
  • The post body contains the power generators, the ammunition holder of the secondary (railgun) weapon.

Regardless of type, all spider tanks possess

  • 3 pairs of legs, which are made out of artificial muscle tissues(more precisely, vanadium dioxide) and have a few traits designed after the world's cutest spider (the combination of a few). These legs are usually protected by reinforced plates and have claws and retractable wheels on them as a way of faster travel, and more effective climbing.


A military spider tank from Ghost in the Shell: Stand Alone Complex (video link in the picture :)

Their armor and weapons are mostly dependent on their size. Larger ones usually have a "stinger railgun", that can be moved around with a high degree of freedom, enabled by the same types of artificial muscle.

Even the heaviest ones are relatively light-weight (because they're mainly built out of carbon allotropes), as all spider tanks are capable of jumping up to 15 meters high, via their powerful legs.

Now, I wonder, whether these tanks have some sort of a "fatal flaw", that I overlooked (we're talking about modern day and near future settings, the 40k one was just there for the lulz)?

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    $\begingroup$ Downvoted as well as VTC'd as unclear what you are asking because there is a lot of fluff distracting from the actual question and even statements saying that the fluff is unnecessary and distracting. $\endgroup$
    – dot_Sp0T
    Commented Apr 8, 2017 at 21:24
  • $\begingroup$ @dot_Sp0T I don't get it. 99,9999 percent f that stuff was about the tanks and their inner working. $\endgroup$ Commented Apr 8, 2017 at 21:28
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    $\begingroup$ We have a Sandbox for Proposed Questions on the Meta Site. You can test questions there by posting them as answers to that Post and then waiting at least 24 hours. People will comment on the general stuff, such as on-topic, grammar, spelling, missing information, ... Maybe you could try using that for your next question. $\endgroup$
    – Secespitus
    Commented Apr 8, 2017 at 21:53
  • $\begingroup$ I think you should ask the question there scifi.stackexchange.com $\endgroup$
    – Vincent
    Commented Apr 9, 2017 at 15:35
  • $\begingroup$ @Vincent These tanks are somewhat different, the wheel idea was from Ghost in the shell, but aside from, that there are significant differences. $\endgroup$ Commented Apr 9, 2017 at 15:41

2 Answers 2


When we talk about reliability, there is a motto:

What is not there cannot get broken

Legs and joint are the key weak point in your concept design, expecially if you want to move around some tons of body and even jump. You are now multiplying this weak point by 6, which gives both an easy target to any enemy wanting to take the tank down and a nightmare to reliability engineers trying to make the thing operate as intended. Sure you can reinforce the hull to withstand anti tank shells, but doing the same on joints which are supposed to move around is another story.

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    $\begingroup$ I prefer: "perfection is attained not when there is nothing more to add, but when there is nothing more to remove". $\endgroup$
    – Harabeck
    Commented Jan 8, 2021 at 22:16

Their legs are vulnerable - they have a large surface area to volume, which means that they won't be able to be heavily armored, as any added mass on the legs would greatly restrict mobility (moving legs -> moving tank, adding weight -> slower legs -> slower robot) - very similar to how cars try to minimize their unsprung wheel weight as much as possible in order to remain fast & efficient. Furthermore they have many exposed joints which are vulnerable to getting gunk / sludge / stuff stuck in them, which would make them unable to move

Speaking of efficiency, jumping is not an efficient maneuver - while I won't doubt your 15m jumping ability, as you can hand-wave an energy source, you will also need to hand-wave it as to why it won't make sense to use that energy source in a more efficient method (i.e. traditional tank, flying robot, whatever)

You mentioned wheels on the legs - All of the above still applies, you need to not only make it possible, but make it somehow better than the alternative (normal wheeled vehicle, or even compared to a tread-drive tank). Strong, light-weight armor? Why not put a plate 2x as thick on a regular tank for more protection?

That said, there is one distinct advantage that the legs give your tanks - that is they can step over large obstacles or cross very difficult terrain. You may want to reference the AT-ATs from star wars and see how their legged tanks could adapt to various terrains.

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    $\begingroup$ When looking for fatal flaws, I would also reference the AT-ATs and AT-STs. They were destroyed by speeders, and teddy bears respectively. Those joints are vulnerable. $\endgroup$ Commented Apr 9, 2017 at 4:44
  • $\begingroup$ I can only repeat myself, diamond has a density that would still be in the light metal category (lower than 5gramms/a cubic centimeter), not to mention carbon nanotubes and graphene, the tanks are supposed to out maneuver regular tanks, and be able to climb walls for height advantage. $\endgroup$ Commented Apr 9, 2017 at 7:44
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    $\begingroup$ Nothing armored enough to withstand the shell of a tank can climb walls. No metal is light enough, diamond isn't light enough. Physics wise not possible. $\endgroup$
    – Mormacil
    Commented Apr 9, 2017 at 11:39
  • $\begingroup$ @Mormacil With lasers, who needs armor? $\endgroup$ Commented Apr 9, 2017 at 12:12
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    $\begingroup$ The moment you switch to lasers and forego armor your opponent switches to ballistic weapons. A tank armed with a regular cannon will also be able to fire significantly longer then one based on lasers unless if has a tiny internal cold fusion reactor. But if that's in the cards particle beams are superior to lasers anyway. And you might as well weaponized an Orion Drive. $\endgroup$
    – Mormacil
    Commented Apr 9, 2017 at 12:41

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