I have been thinking about this for an unhealthy amount of time, truth be told.

Simply put, a 4-meter, 8-meter, if stretching the limit, tall mecha, made out of carbon-based synthetic muscles, hyper-strong light materials. Examples such as magnesium come to mind.

I'm not a scientist, or an engineer. And I bet a material scientist can think of better materials, much less in a hundred years.

Just for clarity, we're talking advanced, but still hard sci-fi.

What roles would it be useful for? What roles would it be terrible at? Civilian roles, combat roles. Considering environments, such as space and urban situations.

For some reason, I also want to ask if putting thrusters on it would make it go fast, Armored Core style.

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    $\begingroup$ What's the actual question? At present "Can someone explain to me why this a is a terrible idea?" , well the answer would be "Yeah, sure" or "No way". Care to edit your question in a way that offers more scope for useful answers? $\endgroup$ Commented Sep 16, 2019 at 22:39
  • $\begingroup$ Welcome to Worldbuilding.SE GundamFan, glad you found us. We have a tour and help center you might wish to check out. $\endgroup$
    – Cyn
    Commented Sep 16, 2019 at 23:11
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    $\begingroup$ Basically.... Tanks do a better job. Are less prone to break. And are more bang for buck. $\endgroup$
    – Shadowzee
    Commented Sep 16, 2019 at 23:49
  • $\begingroup$ "Why this a is a terrible idea?" Well, it all depends on what you want to do with such a piece of machinery. What do you want to use it for? Will there be an onboard driver, or will it be driven remotely? $\endgroup$
    – AlexP
    Commented Sep 17, 2019 at 2:21
  • $\begingroup$ This is literally what the mechs are made of in Neon Genesis Evangelion; they're artificial but organic constructs. $\endgroup$
    – stix
    Commented Sep 19, 2019 at 17:17

7 Answers 7


Why is it a terrible idea? Because organic things aren't good at fighting. Humans were built with endurance in mind. We're incredibly resilient. If we suffer scratches or nicks, we can heal them up in a few days. Deeper cuts can be healed and replaced with tough scar tissue after a few weeks. Broken bones? No problem - those can be healed as well. Internal bruising, fractures, and sprains? All can be healed up. The point is that we're designed to be able to recover from repeated minor to major injuries over the course of time. As long as nothing gets detached, and the we aren't killed, of course.

That comes at a cost, namely short term, something which humans are remarkably bad at, compared to other animals and things like robots. Steel limbs sound great, but they can't be remade if broken without invasive surgery. Similarly, armor can block blows much better than skin can, but can't regrow from nicks and cuts. And it's weight means shorter operating time. So, short term - having solid but unrepairable defense is better, but humans were built long term in mind.

And combat is short term. Very short term - a one on one fight to the death can take seconds, especially if side A is built for short term victory and side B is built for long term endurance. Humans aren't built to fight life and death situations - they're built to avoid them or use their big human brain and dexterous hands to manipulate the situation and create tools to give them an advantage - tools that give them short term advantages, like weapons, armor, and tools.

In other words, humans aren't built for combat, and anything designed solely based on the human physique is just subpar for combat because the same materials could be used on better designs. That aside, you run into issues like the square-cube law, meaning that building humans to scale for double or triple their own size is almost impossible because it needs materials with a strength that scales exponentially.

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    $\begingroup$ A series of semi organic robotic lions though... $\endgroup$
    – Joe Bloggs
    Commented Sep 17, 2019 at 6:44

Your mecha would be a fine synthetic body for a human mind.

When it comes to motor functions, our brains are used to things being laid out a certain way. You want to walk, you effortlessly trigger the correct muscles in sequence and degree, and off you go. No machine would be laid out the way are bodies are, with muscles hooked here and there along bones. Our bodies are the product of long evolution and many intermediate steps. But they are what we have.

If you had the tech to move a mind into a synthetic body, Avatar-style, it would be nice if the unconscious found everything laid out the way it liked. You could walk away, scratch your bum, do high kicks or whatever else you wanted in your new body, using your mind as the pilot the way you have since you were born. It sounds like your fake muscles mecha is a synthetic giant human body, ready for a human mind to move in.


Expanding on Halfthawed's answer:

Specialization is Powerful

Why isn't a morningstar carved like a human fist, since a fist is good at punching? Because a morningstar hits harder than a fist can.

Millennia of combat refined weapon designs away from human-oriented designs, because humans are versatile. Versatility is good, but something specialized for its task will outperform the versatile option every time. If you've got a power source sufficient to drive a mech, it will be able to drive a tank much more efficiently, and have power to spare. If you have materials that are strong enough to build an eight-metre mech, you can layer more armour onto an APC instead.

I should also point out that a magnesium alloy is a terrible idea for a combat vehicle, because fire is generally a hazard in combat.

Now, that said...

Building a mech would be useful for the same reason that building the Tsar Bomba was: to demonstrate that you can. "Look at how good our military science is," boasts the country fielding combat mechs to occupied territory. "Look at how many resources we can waste on this!"

So you touched on the real reason one would build one of these things in your question - it would be scary. It would be a demonstration of how advanced the technology of an occupying force is, and might help cow the populace. But if two countries are at equivalent technological levels, and one fields mechs while the other fields tanks and drones, the latter's going to be the winner.


Well it depends on the role you plan to use the unit in. As is I would keep mecha around 15ft (4.572 meters) tall for a large one on average,max of 20ft (6.096 meters) if pushing it and keep them between 8-15ft (2.4384-4.572 meters) tall ideally.

Use them for built up urban warfare where tanks are non-viable,rapid response forces, military police service (very intimidating and well armed for security),are highly modular ideally to fit a wide variety of roles,can be used more instinctively due to similar body plan and if using a neural link can be even more effective.

Don't expect them to fight tanks. Not in a head on confrontation,it'll be like an IFV (Infantry Fighting Vehicle) or APC (Armoured Personnel Carrier) trying to duke it out with one. Sure you may have more heavy armaments than an IFV depending or be more maneuverable in three dimensions;but the tank will have thicker armour,heavier armaments and more ammo for those armaments.

Mecha will be more prone to mechanical failure due to the amount of moving parts; especially in the joints and will suffer from wear over time due to the stresses from the artificial muscle. This is to be expected however. When a tank is tracked it can't move without repairs. A mecha can crawl with one leg or drag itself along with none. However the fall will be harmful to the occupant.

There are pros and cons,this argument has run for a long time for tanks versus mecha. I always solve it by just not using mecha as tanks. They are closer to a ground based helicopter gunship,lots of guns,very maneuverable,hit hard,but can't take the big hits very well. This can be alleviated to a degree with better armour and sloping;but it will always be an issue.

Honestly,I'd say it's not a matter of if it's a terrible idea so much as how the idea is presented. I hope this answer was helpful to you.


Don't scale up, scale down

The problem with giant mechs is that they are basically just expensive tanks with lots of weak points and wasted mass, but mini-mechs would offer a wide range of advantages. By mini-mech, I am referring to a military purposed android in the 1-1.5 meter tall range. In this case, your mechs are not designed to compete with tanks, helicopters, and artillery. They are made to compete with infantry, field technicians, etc.


  • Robotic parts can generally be made stronger than human muscles meaning a child sized android could carry just as much armor, supplies, and firepower as a full grown man.
  • Bipedal anatomy and small size means it could infiltrate any location enemy personnel can hide. They can enter buildings, climb stairs and ladders, crawl through caves, operate a mouse and keyboard, etc.
  • Small size means a smaller hitbox. They will be harder to shoot than a full sized man or larger mech.
  • Mechanical sensors and computer driven processing means better vision, hearing, precision, and response time than a human soldier. Even if it does not physically move any faster than its human counterpart, its electrical circuits could detect and process an entire combat strategy in the time it takes the chemical circuits of the human brain to recognize a threat; which they can do from distances that human senses just don't work. This means that they will almost always have the initiative advantage.
  • Uploadable skills. A human must be trained. An AI must be trained too, but once trained it can be duplicated to other androids. This means that if your Field Medic gets shot, you can simply upload the field medic plugin to one of your combat mechs and you have new doctor.
  • Simpler support requirements. Sending troops in the fields means sending food, water, cloths, medical supplies, shelter, etc, etc, etc. Androids only need a source of power, their combat gear, and maybe some spare parts. They can also be turned off and put in crates instead of housed and feed. So in the space you can house and supply a single soldier, you could pack several androids.
  • Hostile environments. Robots can survive where people can not. This means they can keep fighting in the vacuum of space or battle fields that are contaminated with radiation/bio weapons, or places too hot or cold for people.
  • More expendable. The biggest enemy of war is a disillusioned populius. When the news comes back saying that 1000 soldiers died in a battle, the widows, orphans, and parents of those casualties suddenly want to end the war at any cost. But when news comes back saying that 1000 androids were destroyed in battle, a few people might get upset about the economic implications of replacing those losses, but the general population won't demand sweeping changes because of it.

If your goal is to retain human control over them (more mech, less android), then treat them like drones. The best case scenario would probably be a remote human operator who defines mission parameters, designates targets, and monitors their progress, while the on-board computers worry about the intricacies of motor control, targerting, reactionary actions, and skill execution. In this capacity, it would be the androids fighting the war, and humans would be the unseen "officers" coordinating them behind the scenes.


A mecha like that would have civilian purposes in less developed regions. Say a machine that cuts wood needs a lot of space and maneuvering to get to where it wants on rough and uneven area's, while a Mecha can be used intuitively by the operator. Climbing, crouching, ducking the Mecha can do it, and the operator can then use the hands of the Mecha in the same way humans do as an omni-tool.

For combat the Mecha's arent likely to be able to stand up to tanks in direct engagements. But in indirect engagements they will reign. Think of urban environments where tanks are at a disadvantage, or fighting through forrests where heavy equipment normally is mostly useful on the road but too bulky for the forest itself. But as mountain warfare brigades they would be best. In mountains infantry is king, as any vehicle has to use the limited roads available where they are vulnerable, easily identified for artillery attacks and easily stopped or destroyed through mines and demolitions. But a Mecha could avoid the roads, it would be a perfect infantry support tool to bring supplies and firepower over terrain that tanks and other combat vehicles cannot cross. For weapons you can look to solutions we have on combat helicopters where the recoil cant be allowed to destabilize the craft or push it off-course too much.

Mecha's could also be used in trench warfare. A tank in a defensive position needs to drive up to fire, then down again. A Mecha could be crouched, then pop up to fire and crouch again to relocate.

I would suggest using spider-Mecha's though. 2 legs is far too risky, especially since these vehicles have a higher chance of failure. Using a setup similar to combat vehicles like the Striker where with 4 of its 8 wheels intact it is still able to get to safety a Mecha could function better across various terrain and be able to deal with damage or failure of its limbs better. Legs are also easier to armor than wheels and tracks on top of the fact that their discontinuous nature makes them harder targets. "Just shoot the vulnerable legs" is often a way people hope to end Mecha discussions but in real warfare anyone shooting at the legs other than the hipjoints would be court-martialled for endangering his group and not firing at the main body where you can damage both the legs and other vital parts..

For material, hope that Graphene becomes a thing to surround your mehanics in.


Mechas are pure sci Fi. When it comes to artificial biology though your on the right track. I've been trying to see if limpet teeth contract from heat like fishing line and spider silk would. Haven't gotten there yet. Limpet teeth would make excellent bones though. For artificial muscle use electrothermally operated fishing line that is grown with synthetic life or microbots. It has super low efficiency, but a body wide lung for coolant can regenerate around half the heat for reactivation to be around 40% efficient. In comparison naturally occurring muscles are about 20% to 25% efficient.

So an artificial humanoid the size of the Mecha in question can be made and grown and self repaired using either synthetic life or microbots, but using them for war is silly. It would just be for mind uploading to have genuine giants without dealing with the square cube law. The square cube law still exists of course but the strength to weight ratio and efficiency makes it irrelevant at the sizes you mentioned relative to human bones and muscles at the same size.

Since the fishing line is 100 times stronger then human muscles for the same size, someone with muscle size able to bench 200 pounds would now bench 20,000 pounds. Scaled up to your Mecha with big muscles and your well past Luke cage territory. Not as tough though. No such thing as bullet proof,just bullet resistant.

While a single tank would be better then a single Mecha, being able to grow or 3d print the mechas en masse then insert copied minds though not the original as Cannon fodder could be rather effective.

Limpet teeth is goethite nanofibers in a protein matrix. Goethite is an iron compound. They are 7 times stronger then bones.

I'm unsure of the efficiency of spidersilk as a thermally activated artificial muscle. Limpet teeth are stronger and if they were to contract from heat they would be better but I'm still unsure.

Pound for pound the fishing line artificial muscles have a better power to weight ratio then jet engines and tanks tends to be powered by turbo jets. So you'd have the speed advantage, the terrain adaptability advantage but the height would be a con as would overall toughness. A big gun mounted on shoulder would work, but a tanks low center of gravity and large mass would make their guns bigger and adder without falling over.

Put too much weight on your Mecha and they will sink into the soil. Put them on a flat road and they lose the speed advantage over just about anything with wheels.

Hope this helps.


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