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Comment by WJW | Hacker News Reader

Note: this is only for charged particles such as happen in solar flares, and only in space. Your personal shield against bullets and the like is still impossible, sadly.

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Well this may work for future phasers, and ceramic/steel plates work well for bullets.

Emit the shield from the plate armor and you'll get protection from both.

Bonus points for chainmail or kevlar suits for knives / shots on non-vital areas.

Extra bonus points for gelatin to avoid broken ribs / stopping power from bullets.

Basically a spartan suit...

Oh and a (shielded) micro nuclear reactor for power!

Now how to solve the heating problem...

Nano Black Hole to sink all that extra heat.

A small blackhole is basically just a very compact nuclear bomb.

Not one you could carry. One with an initial mass of 606,000 metric tons would have an initial power output of 160 petawatts, most of which was so high energy you'd have to worry about proton-antiproton creation on every atom those photons interact with, and it would still have a 3.5-year lifespan.

The lower the mass, the worse it gets.

https://benwheatley.github.io/blog/2022/05/14-17.06.59.html

Perfect, self destruct in case of extreme emergencies / prevent tech from being captured.

If you are going that far you might as well think about sending a surrogate [1] instead. :)

[1]: See https://en.wikipedia.org/wiki/Surrogates

Porque no los dos?

You can jam the remote control for "surrogates".

You could do local AI to workaround that, but then ya'know... skynet...

Also distance may be a problem, especially if we're talking space warfare.

And surrogates would probably look more like the robot dogs or air/ship drones we currently have though, with some human-like ones sprinkled in.

Put a remote control operator in a spartan suit to pilot drones nearby!

One of the benefits of using "human like" surrogates is the compatibility of hardware. Lets say its a spartan type design, if a human needed to be on the front lines for that space warfare to manage things then taking the hardware from a surrogate make all the other things in war easier (fabrication, supply, support, etc...).

A few tons of superconductors work very well against bullets.

Who's making a 600 T magnet that weighs only a few tons?

https://physics.stackexchange.com/questions/115011/how-much-...

You don't need 600 T, just a few tons of superconductor should be enough to stop most bullets. No need run any charge through them, just place them so that most of it is between you and the bullet.

lol this is true.

The 6 order of magnitude resonant eddy current induction looks like the more interesting solution. I could see this being done with a giant beamforming array that would be more practical than a giant steady state magnet. It would be pretty cool to melt a supersonic projectile midflight with eddy currents.

In sci-fi, shields seem to basically evaporate bullets. A shield that melts bullets could be a very cool sci-fi visual; the ship would still need some conventional armor (you still have molten metal flying at you), but it would splat against the armor. Plus it would provide a nice visual for a fresh fleet vs the battle-splattered one that’s seen combat.

From small arms. A heavy machine gun can cut through an engine block and still kill you.

> just place them so that most of it is between you and the bullet.

Easier said than done

I think at that point you probably have to worry about the effect such a strong magnet will have on the brain and nervous system, so probably not the best fit for personal protection.

I’m no rocket scientist, but I feel that statement holds true for bullets too

The bullets are the problem they are trying to use the shield to solve. If the shield also kills the user, that sort of renders the whole thing moot, right?

Not to agree with the actual idea that the magnet is necessarily dangerous, haven’t looked that up…

> If the shield also kills the user, that sort of renders the whole thing moot, right?

Depends, are you the mook hiding behind the shield, or the contractor making and selling a million shield units?

I think you actually have to worry about your soldier not having any metal objects on him because I don’t know what use he’s going to be naked

"He was turned to steel In a great magnetic field"

That’s for stopping the bullet. All I need from a personal bullet shield is to deflect it enough to miss me.

A few tons of steel is cheaper and also works very well against bullets

Not really. Bullet would just orient itself to minimize eddy currents. People would start using thin disc shape bullets that would slide through the magnetic field without much trouble after orienting themselves in the best direction.

https://youtu.be/g0amdIcZt5I?t=735

"Just fire discs" well that's easier said than done, and there's probably a tons of reasons nobody uses discs. One of them is already that we have no experience building or using disc-shaped bullets, especially compared to the trove of experience for... bullet-shaped bullets. So that's not a solution as much as it's an indication that this defense mechanism wouldn't be perfect given an adversary with enough time and will. That being said, nothing is ever perfect, and "arms race" are named this way for this exact reason.

> thin disc shape bullets

Very powerful fans blowing in the direction of the flat side

Rings then.

Probably would be more efficient to vaporize a bullet with a directed energy weapon than to stop it with a magnet.

That's true even without power at room temperature. :P

not against silver bullets :-)

A strong magnetic field would affect all (eletrically conducting) bullets, they need not be ferromagnetic. This would work better on silver bullets than steel, actually (because of better conductivity).

(This is obviously not practical)

or more practically, titanium bullets.

the lead in them may be a problem though.

fortunately software engineers know there is no silver bullet

Plasma could affect bullets and fragments (for example from mines). Just like current dynamic armor, which is just boxes with explosive material, and it's explosion deflect cumulative stream and fragments.

Imagine something like multiple-nozzle rocket engine.

Sure, existing proof of concept realizations are ugly, but with time they will become better.

Everything in space is about distance - want to stop an asteroid walloping the Earth? Nudge it when it is a few million [time or distance] unit away, and it will miss the earth. You could imagine a future spacecraft might have a leading arrowtip also with a field, many miles in front of it to deflect dust and so on.

A ship moving at a double-digit percentage of light speed, with an ablative pilot craft ahead of it.

Moving at significant proportions of c makes a very brief light show of pretty much any ablative solid, unfortunately.

It's worth doing the maths on, for instance, how much ice at 4K you would need to dissipate the energy released by running into a 5g pebble at 0.2c. It's... not a small volume.

Your comment made me try this out on wolfram alpha. Kinetic energy of 1 gram with velocity of 0.1 C is 452.78 gigajoules. Energy of the Hiroshima bomb is 6.3x10^13 joules. It would take 139.14 grams of matter at a velocity of 0.1 C to have the kinetic energy equivalent to the energy released by the bomb. So wow, yes, stopping even a small amount of stuff at those speeds is no joke.

The physics of kinetic weaponry is stupidly simple, and so kinetic defense is also stupidly simple: E = (mv^2)/2

Kinetic "energy shields" (as commonly depicted) are basically impossible, if not literally impossible. You're much better off either dodging or intercepting.

Currently impossible.

We have no idea what technology will exist in say, 300 years.

In physics of the impossible (in 2008, I know a lot of our opinions of the author have shifted) Michio Kaku makes a pretty good case that force fields are the least likely phenomenon to exist.

There’s just not a field that hangs out in space and forms a repulsive boundary to matter as its interaction, besides matter.

The EM field kinda, but no one means big magnets when they think of a practical force field (if so, “QED,” they already exist) :p

3M's mysterious 1980 repulsion field? [1]

[1] https://www.reddit.com/r/ElectroBOOM/comments/9jig1l/can_you...

Nice! I couldn’t remember the details, but I was thinking of this too as the “maybe.”

I’m very skeptical of that story though. You’d think the strength of the electric field would have to be gigavolts/meter.

I just said gigavolts because of Doc Brown :p

I just know it would be more than a van degraff generator or a tesla coil. Lightning is in the 10k’s V/m.

I’m an electrical engineer (ok, ok, 3.5/4 of one. I had already graduated in CS, and quit early for a job).

I can’t imagine a static electric field with these properties.

The dielectric breakdown voltage of pretty much everything, especially air, would be relatively very small compared to that field, to generate a physical force at that distance.

Neodymium magnets can do that at millimeters apart, nothing really does at a few meters.

And why weren’t opposite or neutrally charged things sucked into it?

Sounds like a really sciency-sounding legend. Maybe there was a small effect and a story grew.

—

I just realized that the HN link is like 10 hours of everything I just said in the comments (but higher effort, I guess they went all 4-7 years, lol).

Haha, anyway. Add me to the skeptics. Life is usually boring :/

Shear-thickening gas? Is that anything?

And solar flare based weapons systems.

Gonna save this post for some arbitrary point in the future to pull out as a point against ‘impossible’. Might have to gift it to my descendants to make sure it’s available for long enough… /s

My disappointment is immeasurable and my day is ruined.

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