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US Navy ready to deploy laser for first time (apnews.com)
74 points by Varcht 1393 days ago | hide | past | web | favorite | 75 comments

This seems misleading:

> Both costs pennies on the dollar compared with missiles and smart bombs

A laser weapon is not an over-the-horizon weapon, so its spear of effect is quite a bit smaller than a "missile and smart bomb." It might be able to displace a Mark 45 gun or the Phalanx CIWS point defence system, but neither of which are missiles or smart bombs, and both fire relatively inexpensive (but heavy) ammunition.

It could not replace weapon systems like the Harpoon, Tomahawk, or Trident.

You could, in theory, get rid of SAMs and replace them with this laser system. But you better be damn confident in the laser system's ability to automatically target and destroy incoming projectiles as the laser has to wait a lot longer to fire than a SAM system does just due to line of sight (which is damn scary if the attackers are in supersonic aircraft, as it is reasonable to expect them to be).

Now you might say: "It is computer controlled! It will be like Robocop!"

But if you look at the Phalanx CIWS which is also computer controlled, it is damn terrible at targeting pretty much anything unless it is someone approaching in a trawler going 8 knots (and maybe even then you might miss a few times).

Yes, this is strictly a point-defense augmentation.

The challenge of Phalanx CIWS is not targeting, it is that you have to (1) predict bullet trajectory in a complex environment that continuously deviates from the "in a vacuum" trajectory and (2) predict the trajectory of the target while the bullet is on its way to the target. In the case of the original Phalanx gun, they compensated for the intrinsic difficulty of this with a high rate of fire.

However, today the CIWS guns are being replaced with small missiles, which solves the problem of hitting the target. Terminal guidance against hypersonic targets was a solved problem twenty years ago; a computer can react much quicker than materials science allows a real object to alter its trajectory in a material way.

The obvious problem with using small missiles for CIWS is that they are relatively expensive and more difficult to store and handle. This is where a laser CIWS system becomes a nice augmentation to both gun and missile CIWS. Tracking targets in real-time with high-precision is a problem solved many years ago so the real challenge is getting sufficient power on target in a practical laser package, which they apparently have figured out.

>A laser weapon is not an over-the-horizon weapon

I'd imagine the long term plan is to roll both lasers and rail guns. The combo seems ideal. Cheat laser shots to swat missiles and drones out of the surroundings whilst bombarding everything further away with the railgun. I bet with a bit of clever tech you can pull off some insane over-the-horizon railgun shots.

>Phalanx CIWS which is also computer controlled, it is damn terrible at targeting pretty much anything

Laser having +- zero flight time should solve most of that.

> I bet with a bit of clever tech you can pull off some insane over-the-horizon railgun shots.

The projectiles would only have the force of gravity/terminal velocity behind them unless they have been able to create an explosive railgun projectile (that doesn't explode on the launchpad due to the extremely high temperatures and other shock railguns apply to their projectiles).

> Laser having +- zero flight time should solve most of that.

I think "most of that" is a little overly optimistic. Target tracking is a complex problem, particularly in a war-like scenario where the target might very well be supersonic and in less than ideal weather conditions.

Anti-ship missiles can and are designed to travel below radar range, so trying to get a good sense of depth against a blue sea and white/blue horizon is far from trivial even for a computer.

The laser still might be the "least bad" defensive weapon against anti-ship missiles, but the whole thing is far from full-proof. We haven't really seen a full on naval conflict between two modern navies, so we kind of forget just how amazing most of the weapons are these days.

>I think "most of that" is a little overly optimistic. Target tracking is a complex problem

I disagree. The current complexity of target tracking comes mostly from that fact that you need to work out firstly where the thing is, secondly where its heading (in 3 dimensions & in real time) and third how fast. Having a +- zero flight time means you only need to do the first step. You can always rinse & repeat if its a laser pulse.

Essentially its the difference between hitting a moving car with a tennis ball and hitting a stationary car with a tennis ball. Thats why I think it would solve "most of that".

Obviously if the laser isn't a pulse(s) then you're back to square one.

That assumes that aiming the laser is instantaneous, too. I have no idea if that is the case or not.

>That assumes that aiming the laser is instantaneous, too.

I was simplifying quite a bit & making assumptions yes. Another slightly sketchy assumption is that the laser fires instantly...chances are there is some kind of power up delay.

I'd assume that even with a laser they'd do most of the targeting work with a radar, in which case it's pretty easy to distinguish the target from the background. Just look at the Doppler shifts of the returns and don't worry about anything that isn't moving with respect to the radar. Missiles might indeed hide below the horizon on their approach, but that makes them just as invisible to visual ship-based detection as it does to radar.

Anti-ship missiles are designed specifically to make for small radar cross-sections and to fly below radar range.

Yes, but "below radar range" in this context means below the horizon, which even from the top of a ship is only 15 km away or so. At mach 4 a Sunburn can cover that distance pretty quickly. I'm sure the low radar visibility make a big difference when hiding from AWACs on the approach, but since radar returns scale with the fourth power of distance I don't see how a missile could possibly have such a low cross section as to be invisible at as close a range as 15 km.

> The projectiles would only have the force of gravity/terminal velocity

Horizontal velocity will, presumably, be reduced by drag. But it won't be zero for a long, long ways over the horizon.

Not sure I follow.

You point the projectile too low and it just hits the ocean (due to the curvature of the earth), you point it higher than the horizon then the projectile will continue to travel upwards indefinitely until it runs out of energy and then will fall back to earth with the force of gravity.

The only way what you're saying works is on a flat planet or against a target within your horizon.

It will still be travelling sideways when it hits the target, and unless your target is a long, long way off it'll be travelling sideways with significant speed.

Railgun projectiles, like cannon shells, travel on a parabolic curve - not a half-circle.

Cannon shells cannot be fired over the horizon either. Firing over the horizon will convert the projectile's forward momentum into height, it will reach whatever its apex is, run out of momentum and then fall due to gravity. The angle is just too steep.

The only way to make this an effective weapon is to fill it with explosives (since then you've just created a mortar). But firing explosives from a railgun has its own issues.

Most weapons which depend on a steep parabolic curve to hit their targets also have explosives in them, like artillery, mortars, ICBMs, etc. You can use a less steep curve to deliver blunt force to a target (catapult, cannon, gun, etc) but these weapons have a finite range as the earth is curved, therefore you'd have to tilt them too far back to overcome that, which will cause all that lovely forward force you're depending on to do damage going up into the sky as it flies higher and higher.

You seem to be saying that in order to fire a projectile farther, one needs to make launch angle closer to vertical. But that is not the case, unless the distances get very large you always achieve the longest distance by firing at a 45 degree angle, so half the velocity is in the horizontal direction. Making it more vertical than that will make the range shorter.

For extremely large distances (probably not relevant for naval railguns), the curvature of the earth becomes significant. But the correction goes in the other direction, it is optimal to fire at an angle more horizontal than 45 degrees. In the limiting case, the optimal angle for an ICBM is 22 degrees [1], and they will re-enter the atmosphere more horizontal than veritical [2].

[1] http://www.fas.org/rlg/garwin-aps.htm [2] http://www.fas.org/nuke/guide/usa/icbm/Slide92.JPG

Rather, in order to hit further away targets you need to initially fire at more than 45 degree. A higher trajectory gets you into thinner sections of the atmosphere more quickly so you lose horizontal velocity to air resistance less quickly. Air resistance doesn't seem too big a problem to us in our day to day lives, but increases as the square of velocity so at the speeds that artillery shells travel it will tend to start out as a much stronger force than gravity.

What ICBMs (and space_bound rockets) do is to travel vertically initially to get out of the thickest part of the atmosphere before starting to put on rotational velocity. You'll notice the article you linked specifies a reentry angle of 22 degrees, not a launch angle of that. A missile has an advantage over artillery in that it can apply thrust over time, and wait to start accumulating horizontal velocity until it has gained some height.

EDIT: A better way to explain things. When a bullet leaves the barrel of an artillery piece the forces on it are dominated by air resistance. As it travels it's kinetic energy decays exponentially with distance due to air resistance, and eventually it's traveling slowly enough that gravity becomes an equal source of acceleration as it settles into terminal velocity.

> You seem to be saying that in order to fire a projectile farther, one needs to make launch angle closer to vertical.

I didn't say anything even close to that. Not even ballpark.

I said that if you fire at a high angle you won't have much kinetic energy when the projectile finds its target. This topic is about firing non-self-propelled projectiles (cannon balls, railgun pellets, etc) from a ship or some other platform near sea level, several people are claiming that you can fire at a high enough angle to escape the horizon while still maintaining enough forward momentum to do significant damage, I am saying that at those angles the forward momentum is largely consumed as height.

The projectile will travel away and up, and then after it reaches its apex where it has consumed a lot of its forward momentum to elevate itself it will fall back to earth only at the speed gravity carries it at (minus wind resistance).

So while, yes, you can likely hit a ship or other target beyond the horizon, you cannot do so with more kinetic force than the projectile's weight being carried down by gravity (which is typically not very much relative to the kind of speeds we're talking about when initially fired).

I think you have an inaccurate understanding of how projectile motion works.

First, there is no particular angle that you need to fire to "escape the horizon". The horizon is not a well-defined distance (it depends on how high how above sea-level you are), and in any case you never need to fire at a steeper angle than 45 degrees.

Second, momentum is not "used up" to elevate a projectile. If you ignore air resistance, a cannon shell will hit the ground with exactly the same speed as it was launched (no matter what angle it was launched at). For example, if you fire it straight up, then the kinetic energy of the projectile when it lands (again, disregarding air resistance) is exactly the height it reached times the force of gravity. And that is exactly the speed it had when it was initially fired (which is how it could reach that height).

> First, there is no particular angle that you need to fire to "escape the horizon".

You cannot make up fictional quotes then chastise me for my lack of understanding based on those quotes. I'm not even going to respond to that.

> Second, momentum is not "used up" to elevate a projectile.

That is where you're mistaken. The higher the angle that the projectile is launched at the more energy that gets transferred into elevation.

So when firing straight forward you transfer almost no energy from forward momentum into height, which is why when you stand straight, stick out your arm, and fire at a target down range you have to adjust for gravity.

As you point the "gun" further and further upwards the "bullet" will travel higher and higher but start to hit the ground at no more than its terminal velocity. This is because energy is going towards height from forward speed until forward speed is near zero.

> If you ignore air resistance, a cannon shell will hit the ground with exactly the same speed as it was launched (no matter what angle it was launched at).

Then where does the energy come from in order to gain their altitude? If we take what you just said literally, then a mortar is an impossible kind of weapon, since you have no way of making the projectile travel upwards, only forwards.

The problem with that is that you just contradicted your own post. Earlier you said that 45 degrees was the optimal angle for distance, correct? So you acknowledge that at different degree elevations projectiles travel different distances, would this also be correct? Therefore if we combine these two points together: that different degrees cause projectiles to travel different distances, and that that travel requires energy, you must acknowledge that that energy has to come from the projectile's forward momentum.

If you acknowledge that forward momentum is converted into height at higher degree elevations (as you did earlier, see 45 degree point) you must also acknowledge that energy is being eaten for this additional height.

> For example, if you fire it straight up, then the kinetic energy of the projectile when it lands (again, disregarding air resistance) is exactly the height it reached times the force of gravity.

That is incorrect. If you fire a projectile straight up it doesn't come down "times the force of gravity." In fact things cannot exceed their terminal velocity which is 1x gravities unless they're being artificially accelerated (e.g. firing a rocket straight down can go beyond 1x gravities, but a falling brick cannot exceed 1x gravities).

The image you posted in the sister comment made me see what's going on. You are arguing according to the Aristotelian theory of projectile motion, while the other commenters assume the Galilean theory. See e.g. this link: http://www.met.reading.ac.uk/pplato2/h-flap/phys2_2.html#sec... .

(In the presence of strong air resistance, the Aristotelian theory is not a bad approximation. If there is air resistance, a falling object will indeed gradually slow down to a terminal velocity, like you write in your last paragraph.)

I'll try to explain it with simplified physics. Let's assume for a moment that the projectile is fired 50 ft off the surface at a speed of mach 8, or about 9k fps. If we assume no resistance vertical or horizontal at a 50ft drop the projectile is travelling downward at 55 fps by the time it hits the ground. As you can see, the horizontal velocity is still orders of magnitude greater than the vertical velocity. As you start to deal with curvature of the earth your drop distance will increase, but not enough to overcome the 9k fps in horizontal velocity any time soon. The horizon is 3 miles off, or 16k ft. Less than 2 seconds of travel time for our projectile. Of course, there's always going to be resistance, so at some distance the horizontal velocity line will cross paths with the vertical terminal velocity, but I doubt that happens at any practical firing distances.

You seem to have forgotten the actual problem scope.

Nobody is claiming that railguns (or cannons) don't work. The issue is that to fire a projectile over the horizon the projectile's angle has to be increased.

This poses one of two issues:

- You fire the projectile SO fast you overshoot the target

- You fire the projectile to hit a target just over the horizon but to do so it no longer contains enough energy to do measurable damage to the target.

Try a diagram and see if that helps:


I'm going to assume that the designers have considered this, and that even though it's over-the-horizon the projectiles will still have significant momentum when they hit.

I assume rather than rail-guns, we will simply park laser batteries in NEO calibrated or perhaps just powerful enough to punch through the intervening atmosphere and water vapor to strike their targets.

Of course I am just a sci-fi enthusiast in this regard, so take this comment for what it's worth...

(I am not at all excited about the weaponization of space, but unfortunately feel it is inevitable given "politicians")

That would probably violate the Outer Space Treaty.

Could it be possible to reflect the laser with a mirror? If so, maybe the navy could use UAVs with mirrors to guide the laser for over-the-horizon shots.

When a high power (megawatts) laser hits a surface, even a mirrored surface, the effect is more like a hammer than a reflection. This was studied extensively during the SDI program. Chrome plating missiles is, in the long term, ineffective; the beam transfers energy kinetically like a bullet, not through heating effects.

That said, it might work for now against kilowatt lasers.

Edit: an interesting and non-theoretical example of catastrophic optical damage is the "fiber fuse" effect: a spot of light burns its way along the length of a strand at about 1m/sec (destroying it as it goes). See this video (the narration is in Japanese):


That is such a crazy concept it just might work. The logistics of it are mind boggling, but other than mirror-heat I cannot see too many huge issues with it right off the bat (aside from logistics).

> The logistics of it are mind boggling

Could you elaborate? I don't think it would be just as simple as putting a big mirror on a Predator drone, but then I can't see it being that much more complicated.

With a laser operating on about 30 kilowatts of electricity - and possibly three times that in the future - the cost amounts to a few dollars per shot, Thompson said.

The important part. Power is plentiful on a ship. No need to pay for and carry ammunition. The cost for a single rocket or cannon volley is usually in the thousands of dollars.

Indeed, and although the US Navy has plenty of power already, I'm interested to know how the polywell prototype fusor that they've been sponsoring is coming along.


I'm having trouble finding any more documents than are listed in that article, but I did find more grants for development https://www.fpds.gov/ezsearch/search.do?desc=Y&sortBy=SIGNED... so it's probably still going strong. It would be nice if someone could update their website with something more recent than 2006. http://www.emc2fusion.org/

I reckon it's going quite well for Polywell...

It's classified. No need to take it seriously as real science without real peer review.

A tomahawk is around $569,000 per unit! http://www.navy.mil/navydata/fact_display.asp?cid=2200&tid=1...

I can't decide which I'm more excited about, railguns or lasers.

Do the Navy's railgun prototypes take a special type of ammunition or are they just launching precision machined blanks of common metal?

It's not common metal. The design of the slug is much of the work in creating a railgun because the electromagnetic push comes from generating back-currents within the slug itself. It has to be good at being pushed, then good at flying, all without melting.

Another very serious design problem with high power railguns is making a gun where firing it doesn't destroy the rails after five shots.

They were looking at GPS guided projectiles http://www.wired.com/dangerroom/2012/08/guided-supersonic-bu...

I am excited about future weapons, but I lament the existence of the military industrial complex and the military innovations that goes with them.

Do you also lament the creation of things like the fore-runner of the Internet that was created by the military industrial complex? Or the countless other advancements we use every day that were driven by military R&D? Or are you just completely and totally unaware of the significant contributions that military R&D has made to civilian lives?

The option isn't military or no military, it is military or spend the money on something else. There are plenty of other ways the same money could have been spent which resulted in similar civilian improvements.

According to the internet the slugs are mostly aluminum and/or copper. I'm sure it's more complex than that, but that's the ELI5 answer I guess.

According to a quick internet search, $25,000 a round.

That sounds insanely expensive but cruise missiles are half a million dollars each, not sure what an LRAP costs or what 'traditional' artillery shells used on ships cost.

I guess half of that is amortized R&D costs, and then some more cost padding so that various people in the military supply chain can have their cut.

Also, I'd assume no one is mass producing these rounds yet, so they're all small scale production which greatly increases the unit price. Once the military puts in the first order for a few million rounds the price will go down a lot.

"Rail guns, ..., fire a projectile at six or seven times the speed of sound - enough velocity to cause severe damage."

I'd imagine so!

It will be interesting to see what counter measures can be deployed against the lasers. Mirrors, heat shields?

On the naval side I'd imagine just pumping a ton of sea water mist into the air should work. And if a laser hits it then...it just turns to steam...which also blocks the laser.

Simply don't move into direct line of sight of an American ship and fire over-the-horizon weapons at it? Or torpedos. Or supersonic aircraft firing supersonic anti-ship weapons (e.g. the Indian BrahMos).

Lasers, unlike SAMs, have a very limited spear of effect.

> spear of effect

Don't you mean sphere of effect?

Yeah, a mere 300 to 600 km range.


Yep. Depends on where the laser is fired from, and it depends on the target. Lasers can absolutely fire 300 to 600 km.

That's not much help if you're in a ship, where a) you'll be close to sea level and b) incoming missiles etc. will be flying low to avoid radar, rather than high up in the air where they can be convenient targets.

Lasers can fire all the way to the moon, and it might be a great idea to put military ones on top of mountains one day, depending on the weather, but if we're talking about lasers on ships...the USS Nimitz (the largest aircraft carrier class) has a height of about 36m above the waterline, so the distance to the horizon is something like 20km or ~13 miles.

The article and my post are about deploying lasers to ships. You're talking about aircraft.

Ships are limited to the horizon.

The Retroreflector (link: http://en.wikipedia.org/wiki/Retroreflector) would reflect the laser back. However, I guess that laser with 30 kilowatt power would melt a cheap mirror.

I guess smoke/mist, active surface cooling and ablative armour.

Gas and smoke probably.

Sounds reasonable, sort of a micro chaff. I'm thinking too, this will accelerate hyper-maneuverable unmanned offensive drone development.

High powered lasers 15 to 30 years from now won't be powerful enough to burn through gas and smoke nearly instantly? Wouldn't the laser just destroy the smoke particulate?

The goal is refraction not obsorbtion. A 100cm x 100cm lasor needs ~10,000 times the energy to penetrate 6 inch steel plate as a 1cm x 1cm beam.

Rotation is another one.


> For the Navy, it's not so much about the whiz-bang technology as it is about the economics of such armaments. Both costs pennies on the dollar compared with missiles and smart bombs, and the weapons can be fired continuously, unlike missiles and bombs, which eventually run out.

Why is no one mentioning what seems an obvious side effect of this class of weapon -- all the people who will be blinded by it once it goes into service? If this system goes into service and sees actual battlefield service, the opposing army will be quickly divided into two groups -- those wearing protective goggles, and those who can no longer make out their hands.

My conspiracy theory (isn't there always one of those?) is that laser weapons are a sneaky plot by the Braille publishing industry to spring back from their present near-irrelevance.

Weapons that are designed to blind have been illegal for a long time. And these types of lasers are so powerful that if one hit you in the face, you'd probably lose more than just your eyesight.

Yes, but as the range increases, the chance of death declines, but the chance of blinding continues out to a much greater range. If there's really an international law against weapons that blind, it's about the be seriously violated.

There's laws against weapons designed to blind, but weapons that occasionally blind as an accidental side effect, are legal.

I mean, bullets and shrapnel can and has blinded people, yet bullets and bombs remain legal.

It's amazing all the cool defenses we get with all the money we pour into the military. I heard terrorists are in the process of killing billions of people by making them age until they die -- we ought to divert some defenses toward this huge and imminent threat. Also I think there might be some terrorists in the Alpha Centauri system. We need an intergalactic defense system just in case.

> The Navy plans to deploy its first laser on a ship later this year

I seem to recall the Navy deployed lasers intended to blind enemy pilots in the mid 80s.

Postscript The UK Royal Navy deployed laser dazzlers in 1982, in the Falklands - http://www.gizmag.com/falklands-laser/28574/

Some video of a prototype shooting down a drone here, although it's not very exciting to look at because it's not a movie.


Wow, the shark must be under a lot of pressure.

It will be interesting to see how they handle the friendly in cone of firing problem

I know this is completely off topic, reddit-ish, and I will get downvoted into the oblivion, but...

Frau: Fire the laSER!

At the NYC Resistor hackspace, one is required to yell "Fire the laser!" before starting up the laser cutter. https://secure.flickr.com/photos/65613494@N00/2932584280

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