In science fiction and real life, robot designs vary quite extensively, and rightly so as each design is meant to tackle a different task. A more common design is based on the human form: four limbed, bipedal, head on top etc.

But what would be the best design for an all purpose robot designed to replace military infantry? Humans are able to accomplish a wide array of tasks and yet I feel a robot designed to look human is quite limited. Should it even have limbs? How many? Should it have legs? Wheels? Both? How big should it be? Is human size too big? Too small?

I would like it to be a single structure, so no nanobots that can form bigger bots. Consider the budget to be incredibly vast, so don't worry too much about what it costs.

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    $\begingroup$ There is no objective "optimal" unless at know what tasks will it have to perform. Without this defined everyone will answer with his ideas of robot job in mind. And of course idea of universal robot is not economical. If I need an astro droid, I won't pay for it to be able to cook or perform veterinarian surgery. Why anyone would? $\endgroup$
    – Mołot
    Dec 20, 2016 at 9:27
  • $\begingroup$ Ah, good point on your comparison, I'll try to edit the question to be less general. $\endgroup$ Dec 20, 2016 at 9:28
  • $\begingroup$ And sorry for poor language in previous comment. I was in a hurry and can't edit it now. $\endgroup$
    – Mołot
    Dec 20, 2016 at 9:36
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    $\begingroup$ Isn't this a duplicate of Robotic Replacement for Infantry now? $\endgroup$
    – Mołot
    Dec 20, 2016 at 9:38
  • 1
    $\begingroup$ Thanks for the advice, a bit too late to really dig deep and fix the question, I will do it tomorrow. $\endgroup$ Dec 20, 2016 at 9:43

9 Answers 9


I think it would not be one frame. Just as you don't have only one model of tank, and one model of ships, you would have a array of different robots optimized for a specific role/terrain.


  • Need to deal with civilians, and you don't want to make them afraid? You don't need a lot of firepower, but have something they can relate to, so a humanoid form.
  • Need to rush buildings and just make them go boom? A cat like or toy car suicide bomber like Goliath tracked mine.
  • Secure a area already under control (road barrage)? Some sort of mini tanks with appropriate weaponry should be perfect.

For a military combat robot, I'd prefer a dog or cat style design.

4 legs for speed and manoeuvrability and a low centre of mass. Main weapon on the side, left and right, to cover the complete 360° area around and above the robot.

Main sensors in the head, containing IR and optical sensors, ears are supersonic radar, similar to bats. A tail as an electronic whip for close combat and a smoke grenade launcher in the butt, to cover emergency evasive manoeuvers.

The military transport would be similar, just bigger, horse sized, and without weapons, but a big storage in the armoured belly, big enough to hold a grown human in embryo position.

I would not recommend bipeds, because the high up centre of mass and the unstable position when only one leg is on the ground.

  • $\begingroup$ Personally, I'd hazard a guess that with good inertial sensors, a single leg working much like a pogo-stick could be a good design. $\endgroup$
    – nigel222
    Dec 20, 2016 at 13:43
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    $\begingroup$ No, you could easily throw it over, as soon as the centre of mass is outside the body radius. When you push it, it cannot counteract like it would do with 2 or more legs. Although a pogo stick robot would be a great distraction for enemy forces :o) $\endgroup$ Dec 20, 2016 at 14:07
  • $\begingroup$ So, the problem is not about sensing the g-force, but to counteract. $\endgroup$ Dec 20, 2016 at 14:08
  • $\begingroup$ With a pogo stick you are airborne most of the time and can redirect the stick to absorb/recycle the impact energy and determine the trajectory of the next bounce. Freed from the limitations of human anatomy I think a pogo-stock robot could "always" land stick down, using tricks similar to those a cat uses to "always" land feet-down. $\endgroup$
    – nigel222
    Dec 20, 2016 at 14:25
  • $\begingroup$ @nigel222 A cat only "always" lands feet down when the fall is far enough to give it time to recover from any situation, there are certainly times when this is not the case. $\endgroup$
    – James T
    Dec 20, 2016 at 15:22

There is NOT an optimal shape, ESPECIALLY for military use.

That's not the way military things are designed: think about general purpose airplanes, boats and submarines. Those projects are often too full of compromises and they're sub-optimal in every scenario. For each intended use (or, at best, for a family of uses) you need a specific design.

Few things to consider (but there are many more):

  • Bipeds and quadrupeds aren't the best for equilibrium (tripods are far better because for three points there is always one plane). Best is a vague concept, they may be flexible and provide a great maneuverability paying the cost of increased amount of energy (and complexity) used to keep balance. However quadrupeds may be better to carry heavier stuff. Consider that:
    • Mass distribution (just for example think about crossing an iced lake) is important; more legs and better you distribute weight.
    • Quadrupeds are more stable than bipeds and, distributing mass, you may need smaller, less expensive, infrastructure.
  • Simpler design is easier to produce in case of war and it's cheaper (again it's very important for volume production in constrained resources scenarios).
  • World is designed for bipeds (human beings) and if your soldiers need to interact with such environment then two legs are better (also with a comparable size).
  • We already have a huge amount of existing weapons, to redesign them to fit those robots isn't viable (at least at very beginning). It's much better if they can handle what already exists.
  • Sometimes wheels, skates, etc are better than legs. Again it's about intended use. Do you easily walk above snow? What's the maximum speed for a reliable device with high complex moving mechanical parts (like legs)? For military components reliability is the master.
  • If your soldiers will need to interact with human beings (for example for pace keeping missions) then an humanoid shape (but not too much humanoid) is more appreciated, regardless their effectiveness in combat.
  • According to combat environment you will need completely different shielding and it may then impose completely different choices.
  • Different missions impose different soldiers. Infiltration? Smaller and fast (probably with less shielding). Frontal impact? High shielding and speed is less critical. Quick response? Faster and with huge impact, probably leaving thick shield out...
  • Technical limitations will impose their own rules. Do you want a fast, highly armored tripod which can combat for one week inside enemies' country? You probably don't have the battery to power such soldiers...
  • $\begingroup$ Bipeds and quadrupeds aren't the best for equilibrium Not quite - bipeds are inherently unstable (but can be balanced, and this can provide mobility/maneuverablitly - think of Eurofighter; designed to be unstable (so much so that it is beyond human capability to control) so that it maneuvers well). Quadruped (or any platform with four points of contact) may not be stable (they do tend to rock on a uneven surface) but they require more displacement to fall over than three legs. This is why stools and tables often have 3 legs, but the majority of cars etc are based around a square chassis. $\endgroup$
    – Baldrickk
    Dec 20, 2016 at 16:02
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    $\begingroup$ @Baldrickk I agree with you, the true point should be the amount of energy used to keep equilibrium. Updated to reflect this, thanks! $\endgroup$ Dec 20, 2016 at 16:04

This may not be the answer you are looking for, but I'm convinced it will not look any like a human. An ideal military robot is bacteria-like. Very small, very deadly and present in very big numbers. It probably also should be able to propel itself, so it could move much faster than usual bacteria.

In practice it may be very hard to design something so small, that can move very fast. So in the end, it may be much bigger but still will remain similar. Imagine a small balls, almost not noticeable, but that can move very fast and kill in seconds. Maybe something like an AI-powered bullet or rocket?

If we assume we are not so much technically advanced, it will still be small, just bigger. The drones, that carry a firearm is a good example. Other option is something like a small spider that can jump very far and fast. I do not remember the movie name, but there was one (probably more than one) that showed one of such things.

All of this if we assume a real warfare - combat. If we are peacekeeping, surely something humanoid will work better, but I guess this is closer to police task, rather than military.

  • $\begingroup$ RE Spider robots: Are you perhaps thinking of the Retinal Scanners in Minority Report? $\endgroup$ Dec 20, 2016 at 14:00
  • $\begingroup$ @ObsidianPhoenix It looks very similar to what I remember, so this film is probably what I was talking about. Unfortunately, I just remember a single frame from it, so unless I review it completely (which I probably should do), I cannot confirm - but it looks very alike. $\endgroup$
    – Archeg
    Dec 20, 2016 at 15:31


I'm anthropomorphising of course, but a humanoid shape is pretty optimal (since we evolved over millions of years into our currently optimal shape and size).

This becomes more efficient when robots collaborate on tasks as well.

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    $\begingroup$ Well, it's pretty optimal for tasks we've designed for our shape. $\endgroup$
    – Faerindel
    Dec 20, 2016 at 9:36
  • $\begingroup$ There's nothing "optimal" about us; it's just that certain other apes with a slightly different phenotype died more often in a particular environment than ones like us. But look at how often human women die from childbirth compared to other apes (in the absence of advanced medicine), or the design of our shoulder joints, or wisdom teeth. And think of the organisms that have remained essentially unchanged for hundreds of millions of years.... $\endgroup$ Dec 20, 2016 at 13:54
  • $\begingroup$ @MaliceVidrine - Robots don't reproduce in the same way that we do, and difficulty in birth is a compromise for our design and not a design fault as such. Yes, there's organisms and animals that have remained unchanged, but for a combination of mobility and tool use, I can't think of any better form than the higher primates. $\endgroup$
    – user10945
    Dec 20, 2016 at 14:00
  • $\begingroup$ The specific examples were just to point out the messiness of our evolution, not specific problems robots would have. Considering we don't have to design robots after any previous base species, we can do so much better than anthropomorphic. $\endgroup$ Dec 20, 2016 at 14:09

While @Pete is right, he failed to provide a reason, which i would like to provide.

There are many good generalist shapes. To be precise, every living thing on our planet (and elsewhere, should there be any) has a really good generlalist shape.

But there is only one shape that can benefit fully from the environment shaped by humans, and that is the humanoid form, precisely for that reason: Everything around us is optimized for our form. Shelves and cupboards are where a humanoid can reach them easily. Any machinery you find is built for humans to operate.
And this is especially though in warfare: Every weapon is designed so a human can easily distinguish the right end from the wrong end, and use the trigger, reloading mechanisms and whatnot. So, if you want a generalist combat robot, give it a humanoid form, so he can ride in tanks and aircraft, use weapons that the opposing side spontaneously decided they won't need any more, and reach any places that humans can.

Feel free to add fancy extras, but make sure that the general features are kept humanoid.


In order for our bots to be as efficient as possible and be usable in as many different environments as possible, we're probably not going to see any humanoid bots. The sole exception to that would be if we needed some sort of psychological edge, in which case, mounting our bots in child-mannequin bodies would be ideal.

Nightmare fuel not withstanding, first of all we need to look at mobility. The ideal combatant is one who can be deployed in a short time, in any terrain and through a wide variety of means. So we'll want them to be reasonably small and light. This helps both with transport and because they're small, they'll be harder to hit. In terms of surface area versus volume, we're going to want them to be as close to a sphere as possible, giving us a maximal volume to hide important components while providing a minimal surface that we need to slap armor on. Unfortunately, spheres are annoying to deal with and tend to roll around a lot so we'll probably see something closer to a dodecagon (which co-incidentally, also looks an awful lot like the angular shapes we see on radar-confusing vehicles)

Allright, so we're looking at bots that are probably somewhere between a football and a beachball in size. I think that in terms of weaponry and mobility, we should be following the example of the A-10 Warthog. That is: half of our bot is firepower, the other half is dedicated to getting it someplace where it can deploy said firepower. I'm thinking a number of small ion thrusters, set in different locations in the chassis.
As for weaponry, since we're dealing with warbots in the future, we're probably building them either with high-end coil or rail rifles, with the whole of the bot built off a miniature reactor or big-ass battery.
Speaking of weaponry, some of our bots are probably going to be intended for short-term engagements and should be equipped with a battery of dumb-fire rockets for harder targets.


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It's simple:

The soldier of the future

The best soldier is that which you can't fight. Soldier of the future would either use the best camo available(which, in some distant future, might mean high % of invisibility), or simply won't be a single soldier(swarm of nanobots, some disease, or any other modern invention).


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