# Understanding the dispersion field

## Prelude

In a recent discussion, the user jmb posted the following answer:

The ship is much much larger than a crew member / combatant; if the hull shielding incorporates some sort of active dispersal (whatever kind of "field" physics makes sense in your world) which spreads the kinetic energy of a small impact across the entire area/volume/mass of the hull material (and possibly an additional mass sink somewhere in the ship) it would take an inordinate amount of energy to even scratch the hull - but a combatant suit with comparable technology could only spread the impact over its own area, very much tipping the balance. Whipple shield 2.0, needs a catchier name.

For some reason, this got stuck in my head, and might even be making its way into my story for NaNoWriMo (depending on the result of the discussion here, and if jmb is okay with me using it).

## Question

Let's imagine some kind of device or field that allows to spread energy over a larger surface. I want to use this for space ship shielding. I imagine that the perfect shield would spread the impact of e.g. a small micro meteorite evenly across the whole surface of a space ship. I can very well see what happens if something small hits the ship - it just bounces off the (still required) armor. Here is some more parameters: The system is always on. The system can handle very very large amounts of energy. Enough that the ship will be destroyed long before the system fails to disperse the energy.

The question has two parts, actually:

1) Are there any concepts or ideas in real life physics that support something like this? It doesn't need to be a perfect explanation, and it doesn't have to be a shield, neither does it need to be applicable to every form of incoming energy (our "shield" could very well consist of several subsystems, one against lasers, one against bullets etc....). I just want something to reduce hand-wavium to an acceptable level.

2) What would actually happen if the system is confronted with a really large energy, let's say by impacting an asteroid at very high speed. It would have enough energy to damage the armor, even after dispersion, but not enough to straight out pulverize the ship. (The "we are taking damage" level of energy). Would it "dent" the armor everywhere, rip off armor plates all over the ship? Or is it a binary system? No damage or total descruction? I really can't imagine what happens in these "levels" of energy. I am thinking something similar to what happens when a submarine dives too deep?

## Sources

• There's sort of a similar behavior with heat (as opposed to damage) being applied to a superfluid, in particular helium. Because the thermal conductivity is so high, you essentially can't evaporate a section of it without the whole thing dissipating the heat evenly. It is still technically possible to evaporate a section, just ridiculously difficult. In this case, incremental change is just heating in the bulk until it fully leaves the superfluid state. – Lacklub Oct 14 '16 at 12:02
• The "Langston field" from the fictional CoDominium universe by Jerry Pournell has many of the attributes you suggest, although there is also a time element, extreme amounts of energy delivered to the field will "burn through" in some places, and there is an ultimate amount of energy the field can absorb before imploding, destroying the generator and the ship with it. – Thucydides Oct 14 '16 at 14:43
• See this answer for some idea. – JDługosz Oct 14 '16 at 20:57

My answer for supermaterials is something that could be used. In fact, this variation was answered under Hard Sci-fi energy shields.

Small bits of matter are held in place using magnetism. Any impact will not crack or destroy a tiny grain, since it doesn’t have much inertia. The grains that were struck will accellerate away from their station. Thanks to the nature of superconductors, the motion will induce currents and this will re-enforce the power bonding it together. In your varient, the energy is shared among all the bonds, preventing the superconductor in any one place from being overloaded. The control system feeds additional power into the bonds to dampen the disruptions and send everything back to its proper position.

If the nodes are the size of large molecules rather than the size of mineral grains or large plates as described in earlier answers, you have yourself a real hard-sf version of a Puppeteer’s General Products hull! With elements being as small as light wavelengths in scale, the optical properties will be controlled by phonons in the bonds. Besides being simply a very still and/or very strong bond (changing on the fly is the secret to the shield), it will also serve as a metamaterial in the optical regime, offering protection against lasers and even “cloaking” effects! Power the same principle in reverse and it can emit coherent laser light with as much power as you feed it.

I don't know of any substance or theory that would distribute kinetic energy. Heat and charge can be distributed at the speed of light (effectively instant for the size of a ship) with superconductors. I'll use "instant" as a shorthand for lightspeed hereafter.

But let's dream. To distribute kinetics, you need a substance that rapidly distributes inertia, angular momentum, etc. in short, you need a trampoline-like surface where the distortion of the trampoline is instantly propagated. It is a lattice of molecules, and you can imagine a ripple wave moving through them. The difference between this and other substances is the instant spread of those ripples.

So, it's going to have to be spherical, I think, so that it starts off evenly distributed. Any impact on any side results in a contraction of the entire sphere. If you compress it beyond the strain point of its lattice then it shatters, but the bigger the sphere, the harder that is to do.

It's a solid sphere. The only way in or out is Star Trek-esque transporter. Or you have to be able to turn off its superconductivity, cut a hole in it, then patch it and make it superconductive again. Maybe some sort of magnetic switch -- rotate all the molecules to the left and they hook together and become conductive. Rotate right and it unlocks. It needs to be something that can be turned on/off at the same time across the whole sphere or the sphere would collapse. YMMV.

I have no idea how you propel this thing. It's a solid sphere and if you push against it, it contracts instead of moving. That's probably the biggest problem. You're going to have to have an "inertial dampener" (see Star Trek again) so that every point on the sphere gets the propulsion force at the same time. When you detect an incoming meteor, kill any acceleration from the engines, turn off the dampeners, let it hit, then turn stuff back on.

That is possible, at some extend, not absolute or perfect. And in case when it is possible I would not relay only on that use of this system, I mean on use of it in that particular way only.

## Case 1, solid shell

One way to move things, have kinetic energy and stay in one place is to rotate object.

Interaction between that system, let say cylinder for simplicity, and kinetic projectile will depend on speed of projectile and how fast is that cylinder rotating. Result will be less bouncing off, but rather like grinder wheel. Basically you use stored kinetic energy to destroy projectile faster then it fly in, and you sum impulse vectors for shell and projectile.

In this process part of shell is destroyed, in case speed of projectile is same order to speed of shell, as result we will have second volume inside cylinder protected from projectile. With sped ratio 1:1, in simple case, we can expect this volume to be a circle inscribed in to a square which inscribed in the circle.

As far as my drawing skillzz allow me to show it.

Idea is simple, but there are problems - strength of that cylinder, bigger it is, faster is surface velocity. Forces which try to destroy this construction, is centrifugal forces, and it is proportional $a=\frac{v_{surface}^2}{r}$, bigger radius less tearing force. So it is kinda your situation, where it is less efficient for smaller objects.

## Case2, redistribution of force over surface

• we like to have complex forms

Same principle works with flat surfaces as example rotating disc and such discs can form some shape, by approximation that shape with these discs, by overlaying them on each other etc. Plane of rotation is not important(rotating cylinder or rotating disk is almost same thing)

Now handwavium - imagine tiny strands, miniature version of launch loop, and you weave them as usual fabric. Those strands have 2 important parts - carcass which resists centrifugal forces, and active part which destroys projectile when carcass is destroyed. When carcass is not destroyed force is redistributed according how those strands are weaved, with velocity of that active part. Velocity should be significant, it have to be faster then sound wave in usual materials, with is pretty high speed, for water it is 1.5 km/s as example, so rotor speed have to be really 10's of km/s, to be better then usual materials in therms of redistributing force.

If strands are circles, you can create spherical mesh from them, kinda like this http://demonstrations.wolfram.com/FifteenGreatCirclesOnASphere/ it will have weaker points and stronger points, as single layer, but combine lot of such layers, you can create tick spherical shell with even redistributed resistance. (Link is mostly for illustration that there have not necessary to be 2 poles where where all circles intersect, each circle will intersect with each other circles(if they have same radius) but intersection do not have to be in one point, as it is with meridians and poles)

Same thing you may cover some shape with such circles over its surface. More complex weaving is possible, which totally inscribe given shape, actually any polygonal model we use in 3d, nodes are where force to rotate active element have to be applied, and it should possibly(not necessary) be closed loop created from path's between vertexes.

## Handwavium

Overall idea is simple, and not far from what is used in active protection systems on tanks and such, and physics of it totally described by Newton mechanics.

So main handwavium is concentrated in - how to make such strands possible in first place, and what to do in case of their partial destruction, which we actually expect, and to answer question will they do more harm then good.

There are candidates for such strands - carbon nanotubes. Some ideas about that are described in this answer in part of it called Note about Venus scrap, snake elephant. Actually this situation is just another use case for same system used in that answer.

Answer to question how to prevent harm and and what to do in case of partial destruction situation is pretty complex one and highly depend on practical solution, how you form/weave those strands, and is actually part of development and improvement particular implementations - like armor suits and ships. Each one may have exactly same technology as base (those strands, as processors we have today) but how to combine those bits in useful working system is another story, as today some software is better, some not so good, and not in all situations (use cases). Simple software may be better choice for simple task , then complex soft - as example - it is faster, easier to use, do not have things we do not need.

But good thing you can rearrange that solution, in one you need, it is just matter of knowledge. Kinda programmable matter but I do not like definition, and examples are not matching. It is more smart fabric.

## Problems for your use case.

Based on your previous question - The problem: If somebody fires a (kinetic) gun on a spaceship, the bullet is likely to penetrate the hull and cause a host of problems. - the problem with my solution, there is no such problem. If ship is build with that technology, and it is, if that technology exists. Set of problems they are facing is very much different from those problems which are usually considered as problems. Potentially you can blast nuclear bomb inside that thing, and instead perfect shiny sphere it may look like that after the blast:

But if there is not enough energy to evaporate 100% of that ship, it will work, and will get back to norm, pretty soon, just will be a bit smaller.

• I tried to investigate how much bombs it actually needs for 30km diameter ship, I can't recall exact numbers atm, but when they are blasted on surface of ship, it can function pretty long, it needs 10000's of Mega-tonnes blasts to significantly 10's percents alter that construction, with zero defense actions from that ship(Giga-tonnes blasts are significant for that construction). With defense actions, it will be way much harder to affect that ship. True weaknesses of that system are not known at the moment.

Making bouncing shell will be also not optimal solution, it may and probably will be part of more complex solutions, and serve not only that goal, but as energy storage, as part of keeping momentum for different actions this ship may do (anime style tentacles as example), to move living volumes inside ship volume to protect them from impact, to project vibrissae style shell for detecting kinetic projectiles at significant distances and lot of other stuff.

What is good about them for conventional SciFy is that close combat is probably valid option for such types of ships.

What is bad for your situation, boarding such ship, with forces of smaller ship will be extremely difficult - bigger ship should have spoiled variant of weaving, smaller ship should be not significantly smaller and proportionally more advanced in weaving and algorithms used then bigger one. And it will be not people vs people fight, but more algorithms vs algorithms. Same way as hacking outdated system with well known problems, or zero day vulnerability.

Isolating boarding attacker will be more like mouse click to create living volume around penetration zone, and restore it during the time boarding crew try to destroy it. Eventually you can shoot this compartment back in to space, let them board space after they destroy that living room, if they have too much energy and you have problems to contain them.

Ability to form or move let say thermonuclear engine, to make trust in direction away from boarding ship and in the same time roast them with engine plume, makes boarding idea not very much exciting.

### Strategies

For big ship there is simple strategy, destroy everything which is smaller then it.

For small ship there is simple strategy - outrun and fly away.

Smaller ships are faster(if bigger ship carry more cargo percentage wise, if not they are pretty equal), bigger ships are more durable(if they have bigger energy source and more active mass).

Most promising direction of attack between small and big ship is hacking opposite ship. You do not necessary should hack entire ship at once or as whole, you may hack one percent of it, and it will be your booty. Examples of that lead more in microbiology and biology - infections, resistance etc. So potentially super smart people can sneak trough defense - there are reasons why it is a stretch(for small ship), but it is a long story, but if you handwave super smart technology to break trough it will be valid. And then you can have battles between people.

P.S. grammar, spelling, Syntaxis edits are welcome.

• What does a bird’s nest have to do with it? – JDługosz Oct 15 '16 at 1:06
• @JDługosz: If I'm understanding properly, the bird is analogous to a nuke, the green nest is the undamaged ship, and the brown nest is the burned-to-a-crisp ship after the bird-nuke exploded. – MichaelS Oct 15 '16 at 2:28
• @JDługosz semi chaotic structure which still for some reason works. When comparing it to ball, which structure is simply and regular, and have simple logic - bird nest looks like blown-up. – MolbOrg Oct 15 '16 at 3:33
• @MichaelS valid point of view actually, picture just caught my eye when I searched for illustration "sphere made from rings". They both represent irregular structures after blast. But yes, second one looks like kinda from bigger blast))) But first nest is indeed actually build on principles I suggest, as I see it now, after paying more attention to details of that picture. So your impression is good. – MolbOrg Oct 15 '16 at 3:45