We all know a LOT of the soft sci-fi/science fantasy/mecha genre applies heavy doses of handwavium to sudden deceleration and impact injuries. Iron Man would realistically be liquified in his suit should he actually crash land to a dead stop after flying at Mach 1. Exoskeletons in much of military sci-fi allow people to go hurtling through the air, be thrown through walls, fall off buildings, be punched by superhumans/monsters/robots/whatever large enemy.

Realistically, rigid plate armor doesn't really protect one from falling, sudden deceleration, bomb blasts, or other impacts. How would we design a suit for military sci-fi that includes a strength-enhancing exoskeleton as well as a way to protect the wearer from some halfway decent impacts, like falling 15-20 feet, being thrown 20 feet through the air, maybe being hit by a car at whatever speed is somewhat commensurate with those forces?

Think "light/Medium Protection" -- i.e. nothing on the level of Iron Man or other genres. Falling off a skyscraper still kills you; but the giant from Game of Thrones might need to hit you a few times before you stop breathing.

Have fun with this, I think there is not as much as one would expect to find on the net regarding the specifics of making this work.

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    $\begingroup$ science-based almost preclude any answer but "It's not the fall that kills you, it's the landing" $\endgroup$ Commented Mar 25, 2020 at 10:47
  • $\begingroup$ cant you just make the force absorbent armor as inner armor while wearing the plate as outer armor or vice versa ? like gambeson wear inside chainmail or plate or the vice versa with plate armor under surcoat or jupon ? $\endgroup$
    – Li Jun
    Commented Mar 25, 2020 at 10:51
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    $\begingroup$ Motorcycle armor suits may be relevant examples of real life which are designed to protect the wearer as much as possible exactly from things like being thrown 20 feet through the air and falling on asphalt afterwards, possibly after being hit by a car. They don't make you invulnerable to such things, but it's considered much, much better than nothing. $\endgroup$
    – Peteris
    Commented Mar 25, 2020 at 23:02
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    $\begingroup$ You might get some inspiration from the class physics experiment, the egg drop. youtu.be/nsnyl8llfH4 $\endgroup$
    – David Elm
    Commented Mar 26, 2020 at 5:17
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    $\begingroup$ I know of at least one person who has taken an "experimental" approach to answering this question: Troy Hurtubise, the "Bear suit guy": youtube.com/watch?v=1MEUOW7cERI The video is a news segment where he talks about his homemade "bear suit" and demonstrates it by ramming it with a truck. $\endgroup$ Commented Mar 26, 2020 at 16:23

12 Answers 12


There's two issues here. One is to protect your body from being physically squished by the impact of a giant taking a beating on your unfortunate soul. For that, you need armour, and it's not going to be light. A solid, incompressible exoskeleton would prevent the wearer from being compressed. It would look like a harness, though if you don't care about stab or bullet wounds a cage would function as well.

The other issue is sudden acceleration when the kick propels you, or deceleration (which is acceleration from a different point of view) when you hit something solid at great speeds. For measures to protect oneself against those forces, you need only look at jet pilots, who regularly undergo those forces when making tight turns in a plane that goes at the speed of sound.

One thing they do is position their body so that the acceleration comes from the direction the body can best handle. If you're accelerated upwards, blood leaves your brain and you pass out. The best direction is forwards, pressing you into your seat. So in combat, you might want to take care to turn to face away from whatever is going to hit you, though that is problematic because one might want to spend that time moving to dodge the impact instead.

There aren't that many other options; the body is just not designed to take such pounding. The most exotic idea in circulation is liquid breathing. You see, the body is mostly water, which is really hard to compress. When you are going splat, it is the empty pockets in your body, mostly your lungs, which collapse and give way to any organ not supposed to be located there. Goodbye ribcage. But if you were to fill your lungs with some liquid that can carry oxygen as well as air can, then it cannot compress that easily any longer, meaning that you would be able to withstand greater acceleration. That's why this idea is being researched for jet pilots; if you can make tighter manoeuvres without risking your life, you have a strategic advantage. There are similar concerns for astronauts.

So far only rats have breathed liquid and lived; it is theoretical, and scary. But it is not impossible, and a near-future supersoldier might want to use it if they think they are going to face giants.

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    $\begingroup$ Small point about g-forces and positioning: duration matters. Orienting your body to help survive a ten second 5 g manoeuvre is probably not helpful if trying to survive a 0.1 second 10 g manoeuvre. $\endgroup$
    – Joe Bloggs
    Commented Mar 25, 2020 at 11:10
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    $\begingroup$ It’s not the fall that kills you, it’s the sudden stop at the end. If you can spread the deceleration over some distance/time it’s much more survivable. That’s how bouldering mats make falls from 4.5m of height more or less harmless. $\endgroup$
    – Michael
    Commented Mar 25, 2020 at 19:51
  • $\begingroup$ @Michael how big of a crumple zone are we talking about here, though? And one that rebuilds itself, even? And you'll need two - one for the punch, one for the ground. $\endgroup$ Commented Mar 26, 2020 at 4:02
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    $\begingroup$ On the other hand, small rocket engines on the Armor could sense an impact and start accelerating you beforehand and also burn in the other direction to slow you down before crashing into the wall. - I think this is how Iron Mans durability is explained in many cases. $\endgroup$
    – Falco
    Commented Mar 26, 2020 at 16:23
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    $\begingroup$ Very, very much like the liquid breathing: I've though about this problem myself a lot in the past and only ever came up with things to reduce the forces. Very intelligent way to completely sidestep that problem! I could still see at high enough velocities you having problems with varying densities in the body, but this does almost entirely sidestep that. Great answer. $\endgroup$ Commented Mar 27, 2020 at 10:17

How would we design a suit for military sci-fi that includes a strength-enhancing exoskeleton as well as a way to protect the wearer from some halfway decent impacts, like falling 15-20 feet, being thrown 20 feet through the air, maybe being hit by a car at whatever speed is somewhat commensurate with those forces?

When you're thinking of an exoskeleton, what you're really designing is a vehicle.

We can certainly design vehicles to take impact damage for us - that's what crumple zones do. It might be possible to design a "suit" to provide provide protection in that sense. This requires that the "suit" is flexible in terms of having structure designed to deform on impact. It the deformation of crumple zones that absorbs energy and reduces deceleration forces on the occupant.

Such a skeleton suit would need a core that does not deform and an external part that deforms to absorb the energy of impact. This allows the core to decelerate relatively slowly while it remains unchanged.

Note that the energy of impact depends on the square of the velocity. Double velocity and you quadruple the energy you need to absorb.

Another way of looking at this is that the force of impact depends on the inverse square of the time to stop. The slower the impact (for the core safety cage) the better. The purpose of the external "absorbance cage" is to deform and slow that impact down for the safety cage.

Being hit by a car is not necessarily lethal. When you see a speed limit in an urban area set at e.g. 30 km/hr it has been chosen because below that speed survival is significantly more likely than above that speed.

Being thrown 20 feet is not the problem. It's exactly how you were propelled in the first place (that could involve dangerous forces itself) and exactly how you land. If I throw you by your head you're in trouble either way, as I could be breaking your neck. If you land and whack your head into the ground (with or without a helmet) you could end up with a concussion or worse.

You want the vehicle occupant to have support for their neck and spine to reduce the danger of neck and spinal damage. Look at F1 drivers and you'll see they have a brace they wear on their necks and shoulders that performs this function. In cars the co-called head-rest is actually there to support your head and neck in a collision and stop them being thrown back violently.

Likewise the purpose of harnesses (like safety belts) is to reduce movement and prevent you from being thrown against objects (including other people if you're in the back seat !). Airbags and other safety systems are there to reduce the effects of impact (both the initial impact and "rebound" effects).

You would most likely separate the functions of strength from the functions of safety. Again it's in your interest for the occupant to be protected from sudden application of forces by the strength part of the gadget (as for every force there is an equal and opposite reaction), so you don't want the "strength" part preventing the "safety" part from doing it's job.

You might be able to use complex sensors to detect problem acceleration or deceleration on the safety cage and activate the "deform" mode of the suit by turning off systems that make the strength part rigid. The occupant can withstand relatively high loads for very, very short times so this should not compromise safety significantly - hey, it's the military - some risk is acceptable for certain sceanarios.

So it's possible in theory to make such an exoskeleton.


Starship Troopers (Heinlein). The powered armour contains rockets in the feet to cushion falls. Add a load of those that can rotate to face towards your direction of motion, and then fire at just the right time to stop you safely. Job done.


Thinking about a full suit, I would begin by combining crumple-zone capability in the outer skin, with just-in-time impact cushioning in the inner skin.


I'm sure we are all familiar with this kind of toy: enter image description here

When squished, the soft bits "ooze" out of the netting. Now, consider this toy as a metaphor for the construction of our exo.


First, the exterior (and overlapping) plates would be extremely rigid, such that impacts are spread across a wider area. These would be Mandalorian armour style plates, but many more of them. They would not be smooth, but rather knobbly, with plenty of curves, to aid in deflection of projectiles.

Behind the plates would be a strong but flexible continuous interlocking mesh, perhaps something like this: enter image description here Not in discrete pieces, like the picture, but rather continuous across the entire suit. Flexible enough to permit movement of limbs, but strong enough to retain its shape during compression. Notably, the mesh is thicker and stronger towards the outside, getting thinner and more flexible the closer to the skin we get (or perhaps the other way around - a few crash-tests will help determine which). I envisage a 3D-printed mesh for this purpose: not only would it then be possible to make the suit exactly fit the wearer, but this also allows the interlocking, which would not be possible to build with conventional manufacturing.

The mesh layer has membrane coatings on both the inside and outside. A bit like a wetsuit, only considerably more resistant to rupture than neoprene, with the outer membrane much stronger than the inner one. The interlocking mesh is bonded to the membrane (both inner and outer). It is important to note that the inner membrane must be a smooth fit against the skin, across the entire body. There must be no gaps. This should not be difficult since the suit will be a perfect fit for the wearer.

In between the membranes, is the "squishy" layer. This is a thick viscous fluid that surrounds the mesh and occupies all the space between the inner and outer membranes.

How It Works

When there's an impact, the armour-plating serves to distribute it over a wider area, thus diminishing the actual PSI of force acting on the body.

But as the armour plate moves against the outer membrane, the mesh bends and flexes with the impact, spreading the force out even further (due to its interlocking nature) and transferring it into the fluid.

The fluid (which is incompressible) perturbs the inner membrane only slightly, and over an even wider area in turn, ensuring that the actual impact that reaches the body is a small fraction of the force it began with. To illustrate, a "Superman punch" in the chest might be felt as increased pressure across the whole front of the torso... but would not be enough to do any significant internal damage.

Optional Extras

The mesh could be made up of nano-poles that generate tiny amounts of electricity when the poles are compressed. And the fluid could be electrically responsive, turning thicker in the areas where current is applied. The result is that the fluid thickens automatically and instantly in the areas where the poles are compressed due to impact.

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    $\begingroup$ Brilliant! Came here to suggest liquid layer surrounding an inner suit, supported by breakaway struts, but your mesh is much better. Also, consider transferring some energy into one-time projectiles, even liquid ones - a suit spraying water out of a bunch of valves would be a great visual to describe. And unrelated: you could use a mechanism like seat-belts, which can be drawn out slowly, but lock if pulled quickly, to keep the wearer from ragdolling - perhaps tiny wheels with hinged weights, that spin when the joints of the suit bend, locking via centripetal force when it bends too quickly. $\endgroup$ Commented Mar 26, 2020 at 6:17

Falling over short-ish distances is detectable by the zero-g and the exoskeleton may have time to quickly extend some telescopic shock absorbers in preparation for the landing - feeling of guts, a fall of 5-7m won't require excessive distances to bring the max acceleration at landing in a survivable range, after all the velocity of impact falling from 7m (23feet) is 11.71 m/s or just 42.17 km/h.

Protection against being hit by a car - large impact surface - may be possible by a set "surrounding awareness sensors"+"defensive AI" embedded into exoskeleton, to deploy the same shock absorbers and intercept the hit. It would be harder to intercept a hit - of the same energy - of a baseball bat or the tip of a spear/bullet, though.

Some back-of-napkin calculation: decelerating from 12m/s to full stop without passing the limit of a survivable 8g, requires a deceleration time of 153ms achievable over a deceleration distance of 0.92m. So, using shock absorbers of about 1.2m should do.

The total energy a 120kg (80kg the human, 40kg exoskeleton) falling from 7m is 8232J. Not very impressive to dissipate even for today's mechanics. There may be a problem stopping some projectile at this energy level, it's almost equivalent of being shot with two shots of a 12-gauge shotgun at point blank range.

What else?? Ah, the friction necessary to hold your ground while the shock absorber dissipates a blow worth of 8232J... So, assuming a constant friction shock absorber, dissipating 8232J over 0.9m means a friction force of 9146N = 932kgf.
Standing on a flat ground, unless the exoskeleton takes care to keep you in place (I don't know, deploys a prop on the opposite side of the blow or starts a rocket there), you will take off 'cause there's no way the friction between you and the ground can be close to 1tonne-f. And if the exoskeleton compensates just to keep you in place, it better be tough, a crushing force of 1tonne isn't something to sneeze at.

See also:

Early experiments showed that untrained humans were able to tolerate a range of accelerations depending on the time of exposure. This ranged from as much as 20 g0 for less than 10 seconds, to 10 g0 for 1 minute, and 6 g0 for 10 minutes for both eyeballs in and out

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    $\begingroup$ Go-go-gadget springs!! $\endgroup$
    – Joe Bloggs
    Commented Mar 25, 2020 at 18:37
  • $\begingroup$ @JoeBloggs or hydraulic dampers $\endgroup$ Commented Mar 25, 2020 at 18:52
  • $\begingroup$ A fall of 5m is easily survivable with bouldering mats which are just 20cm thick or so. Especially when you have an exoskeleton which protects you from broken ankles or wrists. $\endgroup$
    – Michael
    Commented Mar 25, 2020 at 19:53
  • $\begingroup$ @Michael I chose 8g as the upper limit, which is well inside the 'survivable' territory. If accepting higher limits, the shock-absorbers can be shorter. an exoskeleton which protects you from broken ankles or wrists. mind you, it doesn't help if your ankles are protected if your internal organs rupture or get bruised on the nearest bone (e.g. brain gets concussed) $\endgroup$ Commented Mar 25, 2020 at 22:35
  • $\begingroup$ @AdrianColomitchi: Yes for deadly injuries a broken ankle won’t matter (or could even be beneficial). But wrist, ankle, knee and shoulder injuries are very common in bouldering and could be avoided with an exoskeleton (won’t make the mats or other shock absorbers obsolete though). $\endgroup$
    – Michael
    Commented Mar 26, 2020 at 8:00

Airbag Suits

You may be interested to know that such a thing is already in development by various companies for motorcycle riders. Granted, it is more of a one time use thing, but it does protect against impact and being thrown through the air.

In your case, the exosuit would likely need some kind of sensors to detect impact so the airbags are deployed in time. Here's an example and a link below.

enter image description here



Your suit pre-empts and reacts to impacts for you

Cover the suit in sensors, and thrusters. When it sees an impact coming from a specific direction, it starts to accelerate you in the same direction. When the impact is over, it starts to decelerate you to avoid a 'landing' impact.

This would fulfil your desire of making it able to resist some punches from a giant, until your sensors/thrusters are too damaged, or you get trapped between the giants punch and, e.g., the ground.

But as long as you don't allow thrusters with enough power to make you fly, it couldn't sufficiently mitigate the fall from a skyscraper.

This would also have all sorts of fascinating side effects to the combat - like using this mechanism in an opponent to force the suit wearer, e.g., underneath a falling building, and trying to find attacks/angles that the suits fail to detect, penetrating the armour, or sandwiching them with enough force to crush it...

You could also add computer systems that make the suit smart enough to try to dodge - i.e., there's a giants fist incoming, the suit can reduce the impact by accelerating away from it, or the suit can push to the side, and avoid it.

edit: This answer may require a higher tech level than what we have, but so does a viable exoskeleton of any kind.


You know what they say: one man's handwavium is another man's science & engineering.

Anyway, let's have fun with it! Here's what I would suggest:

Each "plate" of our exoskeleton can use a combination of MEMS (micro-electromechanical system) technologies to transform the kinetic energy of the acceleration/deceleration event into different forms of energy (which we can use or shunt elsewhere).

Our combination of MEMS could consist of the following (from bigger to smaller):

  1. Each bulk "plate" is actually a series of plates, with carefully placed electromagnets on each plate. The electromagnets on each plate can generate a field such that particular plates repel/attract. In this way, the plates may act as a sort of dynamically driven magnetic spring.

  2. A Non-Newtonian fluid-reinforced piezoelectric crumple mesh & thermoelectric regenerator (in between the series of plates): it would work a lot like a viscous coupling unit (https://en.wikipedia.org/wiki/Viscous_coupling_unit), but with the addition of piezoelectric cells which convert the mechanical forces of the sheer thickened fluid into electricity. The thermoelectric cells take the heat produced during the process and converts it into electrical current; while also cooling the device.

  3. Vortex Tube + Pyroelectric Crystal system: Along with the liquid fluid between the plates, there could also be gaseous fluids. As particular plates contract, the gases could be micro-channelled to a vortex tube (https://en.wikipedia.org/wiki/Vortex_tube). The resulting heat could be used to quickly charge pyroelectric crystals, which produce a large voltage (i.e 600 V) under thermal stress.

The combined voltage & charge produced by the 2nd & 3rd stages drive the spring action of the plates in the first stage. The suit is constructed such that most of the momentum is transferred into the frame of the suit. The associated kinetic energy is absorbed by the plates of the suit. All of the processes described above are physical processes, so the shields can be regenerated (without the addition of more mass).

It's worth noting that this combination of technologies could be made as/include a pyroelectric fusion device (https://en.wikipedia.org/wiki/Pyroelectric_fusion). Basically, the gas in between the plates would serve as the fusion fuel. The plates (or some portion of them) would be made from graphite, such that the neutrons produced in the reaction would be absorbed by that graphite, and produce heat (the Wigner Effect). The heated graphite could further drive the pyroelectric crystals, or the thermoelectric module.

In this way, the plates would serve as both a power source and a shield. Since power tends to be the biggest practical barrier for such suits, multipurpose functionality might be very welcome.


Borrow from Neal Stephenson's Smart Wheels in Snow Crash. https://en.wikipedia.org/wiki/Snow_Crash#Smartwheels

Cover a suit in sensors and plating supported by telescoping arms. When the suit senses an incoming object (such as a giant fist) the plates could extend and intercept the object and begin absorbing its force earlier than it normally would; the same way an airbag or a car's crumple zone spreads an impact's force over time.

Should the user find themselves falling from a height, the suit could do the same thing, reaching out and spreading the users impact with the ground over time, the way a foam mat or air bag would when people do falls in stunt work.


The pilots of the suit are encased in an acceleration pod that controls the exosuit via a neural interface. The egg like pod contains a form fitted aerogel cushion that is pumped with an oxygenated fluid until it is the same density as the pilot. The oxygenated fluid is also pumped to the pilots lungs replacing the air. This allows the pod to mitigate the effects of pressure waves by minimizing the amount pressure waves reflect when they transition from a higher/lower density medium and to mitigate the effects of high acceleration by reducing the compress-ability of the lungs. The aerogel cushion also serves to spread impacts across the entire surface area of the pilot reducing localized peak compression.

The pod is suspended in an active controlled impact harness that is tied to the frame of the exosuit. The harness has computer controlled tie points allowing the pod and the tension of the ties to be adjusted to lower the intensity of an impact by increasing the duration of the impact. For example pulling the pod as far as possible in the harness cavity from the estimated impact point and lowering the tension of the tie wires allowing the pod to decelerate the entire length of the harness cavity over say a second instead of all at once in a millisecond.

The pod also serves as a ejection seat/escape pod in emergencies.

The real downside of a pilot pod system is that a exosuit using a neural interface driven pod system will replace vs enhance the strength of the pilot and of course is considerably more expensive than just strapping a pilot in a strength enhancing exoskeleton suit. The benefit, however, is your pilots and their suits will last a lot longer if a proximity explosion that can't even penetrate the suits armor can knock out your pilot.


Oragami Armour

No joke.

Oragami has the potential to be used for Force Absorption, and with a suitable metamaterial and the right structure, scale and density would be useful in minimizing impact forces on the wearer.


Oragami Ballistic Barrier

USAF Darpa Patent

Oragami / DNA Based Nanotech

3D printed Dynamic Oragami Metamaterials

3D printed Nano-Oragami Lattices

Oragami Metamaterial


I am going to have some fun with this.

I think you want a compact, portable, high-performance kinetic energy converter & projector. Any projectile launched at the wearer bears a huge amount of kinetic energy. Upon making contact with the armour rather than converting the kinetic energy into strain energy, the converter quickly drains the energy from the approaching mass. This sets the projectile's velocity to zero without traditional deceleration. This only works in close proximity, though. A larger shell, heavy club, vehicle or building will still exert force on the armour.

This is where the projector comes into play: The absorbed energy can be stored in a kinetic capacitor, ready to be transferred into the body of the wearer. A heavy impact will still send the wearer flying. However, with a all of his mass being brought to speed in equal degree, his body will not take damage. Upon impact with the next wall, foe or the ground, the same mechanisms kick in but the other way around.

The system has its limits so it does not make the wearer invincible. The circuits are prone to overheating, especially if overused in prolonged combat. Completely ineffective against all types of beam-attacks.

The kinetic energy converter is produced by the same company which provides the inertial dampener's to the Star Trek Federation. I always guessed Tony Stark had some kind of prototype in his suits. Judging by his comment I suspect John O worked for them, but cannot tell the specifics due to an NDA.


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