Reflective paint is surprisingly ineffective. In order to work at all, it needs to be tuned to the frequency of the attacking laser, and not get dirty, or scratched up, or otherwise gain significant imperfection in the finish, which is rather difficult to achieve when firing out a cannon and flying through the air.
Even if those conditions are met, however, mirrors still make for surprisingly bad defense against weaponized lasers, simply because no mirror is 100% efficient. The 0.1-ish% of a well focused, high-powered weapons laser that doesn't get reflected by a ridiculously high quality mirror on initial contact will still damage and deform the mirror, thus allowing more and more of the laser's power to be deposited in the target with increasing dwell time.
Laser weapons avoid destroying their own optics by, first, using optics tuned exactly to the specific frequencies the weapon is designed to fire, and second, by using relatively large focusing mirrors / lenses which keep the power/area on the weapon optics below dangerous levels. Even so, real laser weapons have ridiculous cooling requirements to keep from destroying themselves with waste heat, which keeps their efficiency rather low.
There are other countermeasures that can be used against lasers, to be sure; mirrors just ain't one of them.
You took "reflective" too literally. I just meant more reflective to IR than dark green paint that most military stuff gets painted with. I never meant a mirror surface. Just the IR equivalent of white paint.
White paint (or IR-colored paint, in this case) is worse than a mirror surface; it starts out at a disadvantage already. By assuming a mirror surface, I'm giving you the benefit of the doubt- anything else would be even more useless.
Are you saying that picking a coating with low absorption in the part of the spectrum that the laser is in doesn't matter?
I'm not sure I agree with you, since it makes other strategies (such as rolling the projectile in flight or using ablative materials) more effective if the projectile is slower to absorb energy from the laser.
The whole name of the game is to collect as little energy as possible, disperse it as evenly as possible (in non-important areas), and avoid deep penetration.
It doesn't magically stop the laser to paint it the right color, but choosing the right paint is an important part to penetrating laser based defenses.
For a sufficiently powerful laser weapon, yes, low absorption doesn't matter.
If the attacker is just trying to heat up the bulk of the target until it melts, or is otherwise disabled, then a low-absorption coating would indeed slow them down. Such weapons have been proposed, but they're not especially effective anyway, and that's not how modern experimental military lasers are designed to work.
Weapons lasers are designed to focus as much power as possible into as small an area as possible in order to cause physical damage at the point of impact- blasting a hole in the thing, setting it on fire, etc. Heating the bulk of the target is a mere side-effect.
In that regime, anything less than 100% reflectivity is essentially pointless. Sure, it'll delay penetration, but not by any significant amount. Within a very tiny fraction of a second, the part of the laser energy that you do absorb in the target spot will be enough to destroy the reflective coating, and bring the full beam energy to bear. Unless your projectiles are expected to have flight times measured in milliseconds, the delay provided by a special low-absorption coating is utterly useless.
If you can prevent the enemy from dwelling on a particular spot, then things look much better. If you can screw up their targeting quickly enough, maybe you can actually prevent damage to the reflective coating after all. Even if you can't, maybe you can keep the laser occupied with constantly eating through fresh areas of reflective armor, never absorbing the beam's full power. But at that point, it's not the low-absorption coating that's saving you- it's your ability to screw up their targeting.
Again, I don't think reflective coatings are a lone solution, but I do think that they enhance other tactics, and as such, are a key aspect of defense in depth. However, those contributions are key to those other systems working at all.
For example, the typical bullet rotates at ~200,000RPM. This is about 3,000 revolutions a second, or about 300 microseconds a revolution. Figuring a larger projectile could only rotate about a tenth of the rate, we get about 3 milliseconds per rotation on a shell.
At 3 seconds per revolution, I suspect that we're inside of the timing windows that talking about the efficiency of energy absorption and dissipation in the coating that the laser is striking is relevant, and we can begin to talk about the laser energy being dissipated over more than a single fixed point.
However, I suspect that such tactics (as high velocity spinning) can only mitigate the effects of the lasers and not stop them in isolation. It needs to be tied together with a coherent plan to dissipate the energy that areas do absorb and scatter the beam's focus using ablated coating.
In terms of energy absorption rates, energy dissipation rates, and ablative properties, picking the right coating for your mortars trying to pierce laser defenses is essential.
tl;dr: It's a synergy thing, since the low-absorption coating reduces the demands on screwing up their targeting, and screwing up their targeting reduces the demand on a protective coating.
I think that demonstration was to show that the laser system can be useful against very cheap home-made mortars and rockets. The military would rather use a laser that costs tens or hundreds of dollars per shot to defend against mortars that cost perhaps several hundred dollars, rather than the current conventional methods that cost tens of thousands of dollars per shot.
The military would rather use a laser that costs tens or hundreds of dollars per shot... than the current conventional methods that cost tens of thousands of dollars per shot.
Wait, I thought we were talking about the USA military? When have their weapons systems ever gotten cheaper? The only time they buy something cheap is when there is no more expensive option that does the same thing available (e.g. drones). If the only consideration is cost/shot, lasers will never be deployed. The point of TFA is that the new systems do things that haven't been done before, like stopping a mortar round in flight.
The reflective coating one in particular was explicitly covered in the article. The rest mostly add weight for dubious benefit; I'm guessing increasing laser power will win that arms race decisively. And it doesn't seem like you have to cook off the explosives to beat the mortar round, since they mention that some don't explode when they're destroyed.
yes but most of the mortars this will be facing will be diy ones or at best ww2 era 80 or 120 mm fired by insurgent's who wont have these exotic rounds.
Among other things, our murder rate is higher than that of most other western nations. Assuming murder rate is a good proxy for other "valid" crimes (it's hard to hide a body), we would expect to have 5x the incarceration rate of the UK or France.
The murder rate is that high because of easy access to weapons that make murdering people relatively easy. Shooting someone is a lot easier than knifing someone, point-and-click.
That's far from clear - even the rate of non-shooting murders is vastly higher than most of the western world (only ~1/2 our murders are done with firearms).
Along the same lines of reasoning as yours, approximately 1/2 our murders are committed by black Americans, and the proportion of people who are black are well correlated with murders. So one could equally well say that the murder rate is high because of the presence of black people. Would you endorse this conclusion? If not, why not?
(Let me emphasize I'm not endorsing the conclusion I derive here - I simply plan to repeat whatever argument jaquesm has against the above conclusion back at him w.r.t. guns.)
IF this was true, we would see a correlation between gun ownership (or access) and murder rates. If anything, the correlation is slightly negative, both in the US and globally.
Where you DO see the correlation is inequality. In US states, using data from wikipedia, I find a 70% correlation between gini coefficients and homicide rates. The same is true globally.
There is a correlation between gun access and homicide rates. "Across developed countries, where guns are more available, there are more homicides. These results often hold even when the United States is excluded."
The study, which just appeared in Volume 30, Number 2 of the Harvard Journal of Law & Public Policy (pp. 649-694), set out to answer the question in its title: “Would Banning Firearms Reduce Murder and Suicide? A Review of International and Some Domestic Evidence.”
The findings of two criminologists – Prof. Don Kates and Prof. Gary Mauser – in their exhaustive study of American and European gun laws and violence rates, are telling:
Nations with stringent anti-gun laws generally have substantially higher murder rates than those that do not. The study found that the nine European nations with the lowest rates of gun ownership (5,000 or fewer guns per 100,000 population) have a combined murder rate three times higher than that of the nine nations with the highest rates of gun ownership (at least 15,000 guns per 100,000 population).
For example, Norway has the highest rate of gun ownership in Western Europe, yet possesses the lowest murder rate. In contrast, Holland’s murder rate is nearly the worst, despite having the lowest gun ownership rate in Western Europe. Sweden and Denmark are two more examples of nations with high murder rates but few guns.
Per the official numbers, Sweden has the highest rate of rape in the world.
Without knowing exactly what they considered homicide and what they considered a firearm related homicide, these numbers are meaningless. Only a few years ago the CDC released a large study where they choose to define a female forcing a male to penetrate as not being rape, thus resulting in very different statistics about rape than had the definitions been the more common 'non-consensual sex' or such.
This is especially true when you look at murders and count out suicides. The effect that gun ownership has on murder rates is a separate topic from the effect it has on suicide rates, but many stats conflict the numbers, enough so that I've begun to doubt it being accidental in all cases.
Switzerland often gets bandied about in these discussions, because people see gun ownership rates and ignore the subtleties. All adult males are required to own and keep a rifle at home (with some minor exceptions). There is no "gun culture" here, people in general are very unenthusiastic and see it as a burden.
In the last 20 years they have stopped giving ammunition to keep with your military rifle, exactly because they started having problems with shootings. Switzerland is the worst possible "example" of gun ownership reducing violent crime.
I read this story a few months ago, it had a few more details then.
They tried giving them iron cookware, but they didn't like the weight. They then tried putting a random piece of iron in with their cooking, but not many kept up with doing it. That's where the idea to shape the iron like a lucky fish came from, and it seems to be working.
That's just nature making the best it can of a historical accident.
If you were designing the eye from scratch, you'd have the nerves coming out the back like in squid. Then if you wanted something that concentrates the red and green wavelengths, you could put something else in front of the light sensing cells.
You'd end up exactly where you are now, except you'd not have a huge blind spot, and wouldn't have to spend as much brain power compensating for it.
The blind spot is not huge. It's easily compensated for, and it appears the mammalian eye has other attributes that make it work well. We just don't have enough data to understand whether mammalian eyes embedded a major problem that had to be compensated for, or if this design has attributes that make it desirable.
They can't both be optimal. The probability that both are exactly equally good is so remote as to be ignorable.
Successful does not imply "no flaws." It's interesting to see this argument brought up in the context of biology. It's frequently applied to software, for example it shows up in basically every discussion of PHP.
They could both be optimal for their respective uses. Humans don't spend a lot of time on the seafloor, and cephalopods don't spend a lot of time in the open air. Certainly there are other tradeoffs to be made as well.
It's 7.5° high and 5.5° wide. If you don't consider that huge, then that's up to you. But for me, that counts as huge, especially since it's fairly near the middle of vision. That's over half the width of my hand at arms length.
So... this makes a difference in your daily life as a nomad hunter or software engineer how? None at all. You just don't perceive it unless you go out of your way to.
There's a massive difference between the two. The Welsh, Scottish and Northern Irish (plus islanders and whatnot) tend to get pretty peeved when you refer to them as English.
I accept that people outside the UK might not care, but I don't think that's necessarily the case. There's also a significant difference between making the mistake in casual conversation and on a formal document.
There's not a massive difference. These are people who speak (for the most part) the same language, have (for the most part) the same religion (Christianity), live a few miles from each others, listen to the same music, watch the same tv shows and read similar books at home and school. Sorry, but for outsiders, you are the same people and for the most part, they'd be right to think so. People are not that different, especially people who have so much in common as the inhabitants of the UK, get over yourself, you're not that special.
I'm sure you don't know and care that southern Peruvians from Arequipa like to be called Arequipaños and wouldn't like being mistaken with Northern Peruvian from the Jungle etc. Thing is they're the same to any outsider.
Calling all Americans Yankees is exactly like calling all Britons English. It's not a slur unless used as one (Yankees are, roughly, people from New England/northeast U.S.) but many people will take offense when incorrectly labelled so - even if "no one cares". You could imagine a Breton's reaction to being called a Parisian to be roughly similar. Or a self-professed Catalonian being described as Castilian. Or an American asking about best place to get currywurst or bangers and mash in Paris, I mean all these places are pretty similar anyway, y'all listen to Eurovision, sorry if that offends you...
It's not offensive. Of course it's not. It's just blatantly incorrect. Your taking a group of 4 countries + some islands and referring to them by one of the 4 countries names. It'll confuse people. They now have to think: when he says 'England' does he actually mean England - which would be the obvious meaning - or is he one of those people that has no understanding of geography and is actually referring to a group of several countries? If you refuse to use the correct terminology, even when you are very obviously wrong, you're just confusing people unnecessarily.
This distinction has traditionally never been very important in Germany, so people didn't habitually make the distinction.
That's exactly the point: you have no idea about usage and connotations in German, but still consider yourself an expert who should have the power to prescribe a foreign language.
As an aside: we're also lumping together (dancing) balls and (foot)balls. And lots of other things.
This is the first Germany has been brought up in the conversation. At no point was I discussing use in languages other than English and at no point did I argue that. It seems you argument has fallen apart and you have resorted to changing it.
The political country I have citizenship in has a name, it's written on my passport - it is not "England".
Maybe you can see the problem if I explain it in this way: you can become British (meaning "UK-ish"), but you cannot become English.
Not only is it technically wrong, but it also contributes to perpetuating the dominance of England over the other parts of the UK.
I try to clear midconceptions/misunderstands of other countries when I know better, I would invite you to do the same now you know more :)
Hopefully I can soothe some your resentment of my accusation too - I have been learning about Germany and the forms it existed in before the unification of the states in 1871 - the culture goes back a lot further than this, I am currently learning German and planning an extended tour by bicycle (when I have learnt enough) so I can get more deeply into this topic.
Because for Swiss people like you, Welsh people like us don't like doing business with Bavarians who call us English. Maybe if you weren't Austrian, you'd understand.
Reflective paint, ablative coatings, internal vacuum layer, heat insulation, thermally insensitive explosive and detonators, etc.