Comment by nickpinkston | Hacker News Reader

Comment by nickpinkston | Hacker News Reader

I'm really interested to see how the arms race changes with laser / directed energy weapons. I don't see ablative armor [1] discussed very much, even though it seems like an obvious / hard to defeat countermeasure. The idea being that the target is covered with a material that turns to gas when hit by a laser - such as the ceramic tiles used on re-entering spacecraft - the idea of being the tile insulates the target from the heat damage and the smoke released by the laser hitting it both carries the laser's heat away and scatters the laser's light.

You can imagine using fancy smoke generators (similar size/weight as the smoke grenade of today) that block all forms of light [2] further pushing smoke out of the surface for a larger protective bubble of scattering - perhaps activated when the ablative armor starts vaporizing and/or even being expelled through the armor's porous surface.

Remember that missiles, jet drones, etc. may only take seconds to close the distance to engage your laser system, so you only need this protection to last that long. Also, energy weapons point both ways, and are very well painted targets - analogous to the "anti-radiation missiles" [3] that home-in on radar emissions to guide them to destroy enemy radars.

In the ship example, a sticky smoke chemical targeted near the laser defense systems could blind or scatter them pretty effectively for hours before they could be cleared to make the systems combat operational again.

Anyway - just some ideas from a non-professional military nerd.

[1] https://en.wikipedia.org/wiki/Ablative_armor

[2] https://en.wikipedia.org/wiki/Smoke_screen (Ctrl+F for"VIRSS")

[3] https://en.wikipedia.org/wiki/Anti-radiation_missile

Ablative armor won’t help much. It creates enormous engineering challenges for endoatmospheric hypersonic missiles at energy levels orders of magnitude lower than what a laser will deliver. The amount of ablative armor required to slow these lasers would be infeasible on a practical weapon. Similarly, smoke wouldn’t even be a speed bump, since it would be instantly turned into plasma like the rest of the atmosphere. The base challenge on the receiving end is that it is very, very difficult to divert enough energy when the power levels are that high to limit damage. Based on the description of these laser, they are explicitly designed to defeat dielectric mirrors[0], which is the only vaguely plausible material that might survive a simple laser at these power levels.

The original design target for the military lasers the US has been developing and refining for the last 40+ years is that they could deliver sufficient power on target such that no ordinary molecular material could withstand them as a matter of physics. That is a non-trivial objective but it looks like they’re starting to design practical systems that can approximately achieve that over some range.

[0] https://en.wikipedia.org/wiki/Dielectric_mirror

>instantly turned into plasma

Is plasma itself not reflective enough?

To the contrary, AFAIK plasma is very absorbing, very "black", despite its bright thermal radiation. It will heat up, an transfer the heat to anything next to it.

It will of course diffuse the energy a little bit.

The plasma being warm is perfectly fine from the point of the weapon, as the weapon is moving and the plasma is not.

Usually you need your weapon to move much faster than the target. A rocket, like s Javelin or an NLAW, apparently moves fast enough to hit s tank or an APC. You don't necessarily need much-much faster, but it's important to pack a punch.

But against a rocket you need a weapon that's much faster than a rocket. A laser (or a maser) reaches a rocket in negligible time, and may be very fast to retarget.

A rocket can't have ablative armor on the side, it will be blown away instantly. Landing space capsules have an ablative cover on the bottom. Also, landing capsules only decelerate, so they can afford to carry much more mass for evaporation than a rocket that needs to accelerate and maneuver.

The best a rocket can do us to become highly shiny. It's not as easy though to be shiny in a wider spectrum, from optical to deep IR or even sub-millimeter. I can imagine a multi-color ray gun :)

So I think ray guns are going to be more widespread as anti-missile defense systems, to intercept incoming rockets, warheads, and even shells. At least one actually exists (in Israel), and works.

> So I think ray guns are going to be more widespread as anti-missile defense systems

The issue as highlighted by the situation in UA is that the highest-tech weapons cannot be deployed to the front lines where they are needed, as they might fall into the enemy's hands and be reverse engineered.

I am much more interested in hacked low-tech solutions. For example, walls of anti-air racing drone style quadcopters which can seek out an Iranian drone and just ram it. I am a little surprised that we have not seen these yet.

Laser defense is fundametally short range, so it's best use case is probably behind the front lines, to defend your air force bases and keep the air power active. Also to defend ships. Critical infrastructure such as fuel depots, power stations. Anything up to a few kilometers. This also means your lasers are connected to power lines.

The best idea is to keep your rear echelons free from missile and drone harrassment, so you can focus your attention on the offensive.

Drone swarms are an interesting idea as well.

> Drone swarms are an interesting idea as well.

I am curious if the US defense industry is up to the task of delivering such systems at a cost level which can be implemented in places like UA.

Otherwise the most significant systems may be developed by other sources. This honestly scares me a bit, as given the alternatives, I am a fan of the predictability of Pax Americana.

mmmm. ah dunno bout that. I'll take pax Europa a lot quicker.

I'm OK with that as well! Should be even better.

The only problem is that this project is about 40 years behind in budget and political will in most European countries. It's a travesty which is being paid for in Ukrainian blood as we speak.

A Switchblade-300 is $6k. Phoenix Ghost is a few hundred dollars. Both easily within range of Ukraine.

> For example, walls of anti-air racing drone style quadcopters which can seek out an Iranian drone and just ram it. I am a little surprised that we have not seen these yet.

Quadcopters can’t carry much, are slow and can easily be stopped by a marksman with a rifle or a fixed SCG. They are a lot more useful for recon than as offensive weapons. Plus drones are a lot more nimble and can fly at height where a quadcopter becomes useless.

I'm sorry, but this is wrong on nearly every count.

A moving quad is really hard to hit by gun, see the yearly DARPA challenges. A racing style quad is way more nimble than any winged aircraft I have ever flown or seen. A quad tasked with knocking out an Iranian winged style drone just needs to foul the propulsion, no need to carry anything aside from some trailing weed trimmer cord or durable plastic sheet. The only practical limit on quad max altitude is the FAA/DJI control limitation which is easily bypassed on my quad. Also, all the cruise missiles style winged drones fly relatively low.

The only real challenge is getting in the flight path of said Iranian drone.

I really hope someone is working on this as we have been told that we can take out freaking airliners with cheap drones, on accident, for a long time now.

> A moving quad is really hard to hit by gun

A properly trained human with a military rifle can hit a quad easily. A FCS controlling a military gun does mince meat of them.

> A racing style quad is way more nimble than any winged aircraft I have every flown or seen.

That has zero carrying capacity.

Even then, you clearly haven’t flown or seen much if you are impressed by the manoeuvrability of a quad.

A fixed wing drone will just toy with it. Quads, even racing quads, are unbelievably slow. That’s inherent to their design.

> The only practical limit on quad max altitude is the FAA/DJI control limitation which are easily bypassed on my quad.

You are confused about what kind of altitude we are talking about here.

> The only real challenge is getting in the flight path of said Iranian drone.

The only real challenge to going to the Moon is jumping high enough.

There is a reason quads are not used offensively and it’s not because no one thought about it.

Frankly, quads are used offensively, and there is a ton of videos from Ukraine showing quads dropping small bombs onto valuable targets.

But this is usually not a frontline operation. Quads penetrate to the rear where ammo warehouses are, or find small groups preparing an ambush, etc. They are typically not used against moving targets, or heavily armored targets.

With all their shortcomings, quad copters have two advantages: they are much less optically prominent, and they can hover over a target, allowing the operator to hit it exactly at an opportune moment.

> > A moving quad is really hard to hit by gun

> A properly trained human with a military rifle can hit a quad easily. A FCS controlling a military gun does mince meat of them.

I honestly have no idea where you started on this. I was talking about defensive use of quads to foul the propulsion system of another aircraft.

> There is a reason quads are not used offensively and it’s not because no one thought about it.

Again, I am talking about AA, (Anti-Aircraft) weapons to take out incoming cruise missiles or Iranian drones. This is a DEFENSIVE tool.

However, you have to work pretty hard to avoid the fact that there are hundreds of videos of drones being used offensively in UA. Additionally, welcome to 2023 [0].

>You are confused about what kind of altitude we are talking about here.

There are dozens of videos of Iranian drones flying at altitudes where UA soldiers are shooting at them with rifles. It looks like the altitudes are sub 1000m, easily. Any quadcopter can hit an altitude of 1000m with a simple checkbox unchecked. The range is no problem, the air density is no problem. You good sir or madame, are the one who is confused on this topic, or at least thread. If I was previously unclear, I hope to have addressed that in this comment.

[0] https://www.youtube.com/watch?v=4McPHBQ9pNw

> I honestly have no idea where you started on this. I was talking about defensive use of quads to foul the propulsion system of another aircraft.

You were replying to one of my comment explaining that drones are not good for offensive action because they are vulnerable.

Also there is no point in trying to foul a propulsion system. That’s extremely unlikely to happen and there are simpler way to disable an aircraft (like just having it collide with something).

> There are dozens of videos of Iranian drones flying at altitudes where UA soldiers are shooting at them with rifles. It looks like the altitudes are sub 1000m, easily.

Low flying aircrafts which can be shot at are easy to disable with traditional canons. That’s cheap and effective. Why do you want to use quadcopters for that? That never was the point.

> A rocket, like s Javelin or an NLAW, apparently moves fast enough to hit s tank or an APC. You don't necessarily need much-much faster, but it's important to pack a punch.

that's also what I thought but it doesn't seem to work that way. For the NLAW at least, all the missile does it to position the explosive charge above the tank. The missile doesn't hit the tank from the side, so the kinetic energy isn't contributing to the destruction.

So from a logical point of view, I assume you could position the same warhead with a slow moving consumer drone and get the same result.

https://www.economist.com/media-assets/image/20220122_WOC909...

Top attack is primarily a way to exploit the fact that most tanks are weakly armored on top. The speed (not KE, per se) trade off make sense because it makes a kill more likely by positioning the warhead for better penetration.

That doesn't make sense for aircraft - even slow drones which are still a lot faster than tanks and move in 3 dimensions. Faster weapons means less time for the target to escape, which is always better even when guided missiles.

A slow-moving helicopter drone may be not fast enough because a tank can make 50 km/h, much like the drone. Even a standing tank is usually attacked froma distance of 500-700m, not much closer (except in an urban environment). While the drone is flying towards a tank, the tank may have enough time to detect it and shoot it down.

You ideally need something an order of magnitude faster.

Unlike a rocket, a drone can loiter, stay high enough above to be less detectable. The most successful anti-armor drone so far, the Bayraktar, is a large winged drone that shoots fast rockets downwards.

> Usually you need your weapon to move much faster than the target.

That’s an extremely wrong take.

The corner stone of missile defence is that the missile already has enough kinetic energy to destroy itself. The way anti-missile system works is by creating a cloud of obstacles close enough to the approaching missile that it can’t avoid some. That can be done with another missile exploding close by, a very large burst of bullets for a CIWS system or even a shell if you are trying to stop something slower.

That’s why efficient laser systems are so hard to actually make. They can’t use the kinetic energy of their target.

You need an anti-rocket munition to move faster than the rocket so that the rocket does not hit its target while the anti-rocket munition is on the way. It's not about the speed of impact.

Also, for an offensive weapon, the munition should move fast enough to reach a moving target. It should reach the target quickly enough to make evasive maneuvering harder, and to not be destroyed by protective fire en route.

That's apparently dead wrong. Patriot anti-missile system would just position the ordnance in the way of an incoming rocket. They would collide and explode in the air.

It seems like the range downside due to diffraction and atmospheric dispersion of most lasers rules them out way before ablative armor becomes relevant. I could imagine close-in missle defense being some kind of exception, but if you can only cover a small area, then the 'high upfront cost, low cost per shot' tradeof stops being a good tradeof.

As for anti radiation missles. The 'directed' part of a directed energy weapon should make that much harder. Besides, a laser like this probably isn't firing constantly, whilst a radar station is emmiting constantly.

Smoke screens are obviously not going to be useful as defenses for things like missiles, since the smoke immediately slows down when it collides with the air while the missile/projectile continues on at high speed.

(It might be useful in space, where you'd be creating something like a comet's halo, which separates from the body on a much longer timescale.)

Ablative armor is generally too heavy and bulky to be practical for use on aircraft or missiles. And it can't really work in combination with low-observable (stealth) airframe coatings.

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