"but these have the inevitable downside of spraying thousands of cannon shells all over the surrounding area as they do their work - which is unlikely to win over hearts and minds among the neighbours."

Actually, no. Most area protection system use projectiles designed to self destruct long before they return to earth, for precisely this reason.

(Paris, because she too blows as she goes down....)

What about a Personal Edition of it where I can zap street sales people trying to get 2 minutes of my time to sell me my sympathy on some sort of misery in animals/children/people/wars/fish/birds/babies/the earth by giving my personal details to a random stranger with a coat on trying to make 10% on each person they sign up.

I could say I HEL Ped these people to a better place.

No more "you have a kind face, do you want to help baby squirrels by reducing the amount of paper we use by filling in these paper forms made from the former homes of baby squirrels".... Eat frikkin' death ray nancy boy!

"these have the inevitable downside of spraying thousands of cannon shells all over the surrounding area"

A multi kilowatt beam waving about stands a good chance of ruining your day too.

Rumour has it that the US Navy made room in its Arleigh Burke destroyer design for eventual upgrade to include a laser system or two (for close-in defence), probably replacing the Phalanx currently fitted. Personally, I think that was an incredibly optimistic decision, assuming the rumour is true.

@Paul Williams - you miss the point. The anti-mortar/shell cannon system fires inert projectiles at very high rates of fire - only a very small fraction strike the incoming targets (and there's a lot of those) so there's a very large number (thousands) of spent projectiles sprayed over the area surrounding the place that's being defended. If that place happens to be adjacent to a town or village, it will royally piss of the locals.

I want a friggin truck with a laser cannon on it.....

No fair!

Mines the one with the Lasercannon mounted on the roof and NO traffic worries.....

Sure, I forgot to mention the self-destruct fuses on the cannon rounds this time. But you need a fairly hard, penetrate-y cannon slug to reliably smash up mortar bombs, katyusha rockets etc. They use solid penetrators in the basic naval CIWS, I think. So when the inland version's shells self-destruct, they'll still scatter hard, heavy (thus deadly) frags pretty often. And anyway, most self-destruct fuses have a noticeable dud rate, at least a percent or two. Over time, you'll still be dropping quite a few intact rounds into the local neighbourhood, and you only need to hit one kid ...

Where oh where is the Real Genius popcorn reference?

"and you only need to hit one kid .."

...to win any prize from the bottom shelf?

Would something as simple as chrome plating mortar rounds not defeat a laser defense system?

Why have they stopped doing their airborne version? Because they realise their pilots would point it at the very first chav with a laserpointer shining into their cockpit?

PH because we don't get it.

No, chrome plating will not work.

This has been discussed every time the concept of lasers for defence has been brought up.

Google is your friend.

"Would something as simple as chrome plating mortar rounds not defeat a laser defense system?"

No, I work in engineering and we have a 2.5Kw laser profiler which happily slices and dices mirror finish stainless steel.

Furthermore, high power laser systems are actually self destructive and the beam path mirrors are made of polished copper alloy for easy refurb as they slowly vapourise in use.

A good defence to laser radiation would be a diffusive ceramic coating which would then render the power requirements for destruction totally unfeasible.

As has been discussed every time the concept of defencive lasers has come up:

'Oh yes it will!'

Where's the pantomime / troll icon ?

Lasers will be the perfect weapon WHEN we get into space combat. The recoil of guns- to some extend- missiles just won't allow them to work in a zero G environment. Lasers on the other hand will just be perfect

Missiles and bullets work just dandy in space. Missiles would work fantastically well actually and you don't even need to fire them _from space_. At least three satellites have been shot down with missiles so far. More if the Soviets did it too.

There are also rumors that the Soviets tried firing a 20mm cannon from a space station to see how it'd work.

Meanwhile, getting _electricity_ and venting heat is a bitch in space. Powering a laser is much easier in an oxygen rich atmosphere. Maybe if you have a real nuclear reactor you can power your lasers but again there's no reason to _base_ weapons in space.

It's cheaper to launch a small interceptor rocket than it is to put a massive nuclear reactor laser satellite into orbit.

...Although maybe a nuclear powered satellite with a laser might do hits much cleaner.

Presumably this thing will be tracking other air traffic within range of the cannon to ensure that the beam, if it misses (or burns through) the target, doesn't fry commercial aircraft in the distance, friendly planes and helicopters, people standing on the sides of mountains which happen to be higher than the position of the cannon truck, etc.

Now they are jealous and want their own.

I had to say that.

That is all.

Even a laser would probably need to be accounted for in zero G as there is a reactive effect form a laser. Think of photon sails and I'm sure I have read something about a possible laser propulsion system.

"Furthermore, high power laser systems are actually self destructive and the beam path mirrors are made of polished copper alloy for easy refurb"

So... polish up a good shine on your copper-cased mortar shell? For added fun, have the spinning mortar shell pop off the tip of its nose on the way down, exposing a flat copper mirror that's not quite perpendicular to the flight path. Then the well-targeted shell reflects the multi-kilowatt laser into an ever tightening spiral Beam Of Death(TM) that slags everyone and everything in the compound even before the shell hits?

Remind me not to volunteer for units testing the HEL TD in the field, thank you very much. I'll just grab my polished copper jacket and be off.

And where do install the radiator and multi-kilowatt cooling plant that is attached to the polished copper alloy mirror into a 1 kg mortar shell?

The laser itself it not that big... just imagine the core of an Intel Pentium 4 HT processor.

The actual hardware is not that big - but the radiator on the other hand is fricking humungous!!!

Ergo, that 20 ton truck will have a 200 kg laser, a 5 ton genny and a 5 ton HVAC and a 5 ton fuel tank to run the whole kit...

Fire... well just because !

The laser doesn't melt the projectile - it just tracks it for long enough to cook the HE inside. Then it jumps rapidly to the next target.

So the system works well as long as you send dull, absorbent, HE projectiles over. On a clear day. With no smoke or rain. All from the same direction.

However, we have to be very careful that our opponents do not start their attack with a few polished, rotating, solid projectiles. Cos if they do, our laser will keep tracking them in an effort to blow them up, but they won't pop, and it won't be able to switch rapidly to the other bombs which are also coming in.

Or perhaps the first few projectiles could be smoke rounds? When the laser blows those up it will handily blind itself along the trajectory that the HE is coming in...

I hear tell that a lot of laser labs are lined with resin-bonded plywood? Apparently when a stray beam hits this, it starts to smoulder, and the local smoke disrupts the beam enough to stop further damage? Sounds like a good low-tech countermeasure. Isn't Operational Research wonderful...?

I'm not up on current solid-state laser diodes, but a shufti (google IS your friend) shows that 10W is considered "HIGH POWER". I can imagine a variable parabolic emitter with 10.000 of these, producing a beam of 100KW.

Given a system that can focus on and track a target the size and composition of a light mortar shell (cheap steel, 60mm diametre, optimal absorption), how long would it take such a system to heat such target to the point of detonation? I have no knowledge of explosives, but I assume it would take require a temperature greater than 232C (Fahrenheit 451 :-)) to detonate.

Is this time greater or less than the time-to-target of the mortar shell?

Extra credit for computing the delta-t from focussing on the target to the time of detonation.

'It's cheaper to launch a small interceptor rocket than it is to put a massive nuclear reactor laser satellite into orbit.'

Very true, but it's a lot less cool.

Come on, 'massive nuclear reactor laser satellite'? Who DOESN'T want one of those?

The problem is that they are shiny because they reflect visible light. This isn't a star wars blaster, the beam won't be in the visible range of light and polishing metal doesn't make it nearly as reflective to IR as to light.

Firing plywood mortars just isn't going to work, the smoker might make sense, but only if the laser actually causes a proper detonation, which is unlikely I'd have thought...

For that matter, smokers don't go bang and a cloud of smoke appears, they go fizz for quite some time and smoke appears over that period. So unless you can land one close to the laser it's not going to help you get additional rounds in.

Solid rounds would still work though. Keep firing those until you get a hit on the laser platform, then switch to your HE. Or maybe (my newly copyright) low fragmentation rounds. Laser hits it on the incoming trajectory, gives a little pop and there are now 20 fairly large incoming bits of scrapnel on and around that trajectory.

I've had a play with AutoCad to work out the geometry. At 500m to hold a beam spot within 5mm of desired position requires an accuracy of 0.00057 degrees or 2.1 seconds of arc. This to be achieved tracking a target doing up to perhaps mach 2 by a projector fitted to a truck. 500m at mach 2 takes roughly 0.66 seconds.

The talk of reflectivity is very misleading. What a human sees as shiny or transparent with his mark 1 eyeball is not necessarily true for the light wavelengths used by lasers.

An Ultra-Violet. laser doesn't see all shiny metals as very reflective. However even optical glass is pretty much opaque to it.

Alright, you win. I wish I had a badass nuclear powered space cruiser with lasers.

"even optical glass is pretty much opaque to it." Which would make it a bloody awful defence- it'd be absorbing all that UV light, heat up and crack.

The problem here is they're thinking about it as a single beam. They'd be better off with a number of slightly less impressively-sized lasers. Like a truck-back-full of 10W diodes, all firing up fibres. These fibres would then be aimed so that the emergent laser light was concentrated on a single spot (i.e. on the shell, which the on-board sensors would track in all 3 dimensions) using a bucketload of servos or some other type of actuator.

This would have the benefit of saving anyone stood in front of them (troops fixing it in the event of firing) or behind them (big buildings, planes). Also means you'd need a bloody huge projectile to make a significant dent in the power of it as so many elements were actually doing the firing. A 10W laser is only a couple of cm x a couple of cm x a couple of cm, and a truck is a couple of meters each direction. So 1000 elements wouldn't be horrendously hard, and 10000 wouldn't seem impossible. Even with the other equipment (radar, cooling, etc).

Assume that Boeing have access to more powerful semiconductor lasers than you or I, and suddenly it all becomes very possible. And the lack of any high-power light anywhere except the focus point means you've not got any problems of melting mirrors or lenses.

Another advantage would be that due to the low mass actually being shifted per fibre-end, you'd be able to target it far more quickly and efficiently than you could with a massive monolithic laser. You could concievably even scan CRT-style over the area the enemy shells are passing through, illuminating them and focussing for a few seconds on anything that's reflective.

Plus with power and targetting like that you could probably create 3D holograms like this (http://blog.intuitymedialab.eu/2008/04/30/three-dimensional-images-in-the-air/) with a decent resolution. Just imagine being some random islamic terrorist in Iraq seeing some ethereal image of Allah, God or an Angel appearing in the sky. Or seeing "good guy"/"western" troops being preceeded by glowing galloping horses who tear through the terrorists' friends. You'd probably need more elements to manage a decent resolution, refresh rate and power rating, but this is Boeing working for the US military- it's not like they'll have a lack of trucks or funds!

That, and you could put on a helluva light show at the end of the night...

>>>...These fibres would then be aimed so that the emergent laser light was concentrated on a single spot...

"That blast came from the Death Star! That thing's operational!"

I want it on a shark ;)

Mines the one with a gold member sticking out of the pocket