Why is the rail gun an interesting weapon?

[nsaspook]

So their counter for lasers is "do not get hit". The rest of it deals with things like anti-ship TASERs.

"do not get hit" is a very effective counter for a water balloon and a laser.

There are also 'cloaking' based counters using meta-materials that can shield objects from EM energy.

http://en.wikipedia.org/wiki/Metamaterial_cloaking
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA535595

 

[olivermsun]

When you hit a tank with a sabot (which is a solid, non-explosive round)...

Just to nitpick a little, the "sabot" is actually the part of the round that doesn't fly toward the target. ;)

 

[Drakkith]

Out of curiosity, how?

Do you mean it's hit by fragmentation? Then it might detonate the explosives inside, or at least mess up the guidance system?

What kind of ballistic missile are we talking about here?

 

[mikeph]

Is there a difference?

Basically I'm trying to understand how shooting a missile at this railgun ammunition will even vaguely alter its course towards a target.

 

[mrspeedybob]

Is there a difference?

Basically I'm trying to understand how shooting a missile at this railgun ammunition will even vaguely alter its course towards a target.

There is a possibility that the projectile would transfer enough energy to the missile to cause catastrophic structural failure.

If that is not the case, there is still an aerodynamic effect of having an entrance puncture on one side and an exit puncture on the other.

Besides the mechanical effects, the impact would have a significant probability of damaging some essential system onboard the missile. I'm sure you would agree that a few hundred kg of metal and a few kg of radioactive material landing on downtown New York would be bad, but not nearly as bad as a nuclear detonation.

All this is beside the point that hitting an ICBM with an unguided projectile would be nearly impossible. Even if the projectile is going 5000 mph, hitting a target 500 miles away still requires a travel time of 6 minutes. Atmospheric conditions along the projectiles flight path cannot be precisely known and therefore cannot be precisely accounted for. 6 minutes of uncontrolled flight through unknowable atmospheric conditions would make it unlikely to hit a target that may only be 1 meter across.

Now if this could be turned into a rapid fire system the accuracy problem may be mitigated. 100,000 rounds over a 10 minute period may have a pretty good chance of hitting whatever the target happens to be.

 

[Drakkith]

Is there a difference?

Basically I'm trying to understand how shooting a missile at this railgun ammunition will even vaguely alter its course towards a target.

You mean shoot a railgun at a missile? Missiles aren't like artillery. Hit it with a round and it will most likely explode, disintegrate, stop working and fall out of the sky, etc.

Even if you're talking about the reentry vehicle from an ICBM you'd still do catastrophic damage to it.

 

[mikeph]

No, I mean shoot a missile at a railgun (the projectile). Some others in the thread were talking about the railgun as an anti-missile weapon but that makes no sense to me.

What does make sense is using it as an anti-ship gun, because the ship's defences against missiles will not have much effect on a lump of metal traveling at Mach 8, and it won't even have an exhaust plume to lock on to. That was my original point: I don't see any countermeasures. If it's mounted on a ship, it's mobile, if it's mounted on a coastal battery then it controls a huge area of sea. If it can fire that weight at that speed, you'd be mad to move an aircraft carrier within 200 miles of it.

 

[anorlunda]

Secondary characteristics

A ship with a rail gun does not need to carry any explosives on board. Explosives on board can be the number one hazard when hit by enemy fire.

Also, rail guns can have extremely large range.

Also, very high velocity projectiles can perhaps defeat most terminal defense systems. 7000 mph means only 0.5 seconds to cover the last mile. That leaves very little time for defensive systems to react.

 

[Drakkith]

No, I mean shoot a missile at a railgun (the projectile). Some others in the thread were talking about the railgun as an anti-missile weapon but that makes no sense to me.

No, they mean shoot the missile with the railgun. Hence anti-missile.

What does make sense is using it as an anti-ship gun, because the ship's defences against missiles will not have much effect on a lump of metal traveling at Mach 8, and it won't even have an exhaust plume to lock on to. That was my original point: I don't see any countermeasures. If it's mounted on a ship, it's mobile, if it's mounted on a coastal battery then it controls a huge area of sea. If it can fire that weight at that speed, you'd be mad to move an aircraft carrier within 200 miles of it.

The missile has the advantage of being guided. I don't know exactly what velocity a railgun slug would travel at, but someone mentioned 5,000 mph up above. Even at that speed it would take nearly two minutes to arrive on target. And that doesn't include the drop in velocity as it travels.You would need to have accurate and precise knowledge of the enemies position, their heading, and how fast they are capable of maneuvering in order to score a hit. (Which still isn't guaranteed since the ships can randomly maneuver to avoid the shots) This is much harder than one might imagine, especially from hundreds of miles away in a modern warzone. And your coastal battery isn't mobile, so it's a sitting duck just waiting to be hit.

 

[mikeph]

No, they mean shoot the missile with the railgun. Hence anti-missile.

I can't figure out what you're disagreeing with here.

 

[Drakkith]

I can't figure out what you're disagreeing with here.

You've confused me as well.

 

[Crazymechanic]

Confused or not confused one thing's for sure a unguided projectile no matter how fast isn't capable of destroying a ICBM.
The only way to do that would have to bring the rail gun really close and personal to the ICBM but then it would also be too late to do something about it , and I believe that by shooting it down right over your head or close to the coastline of the US soil it would probably still detonate atleast one of it's warheads and so you still have pretty nasty consequences.

now forgive me if this sounds rude but this whole situation reminds me of the classical "fart in the classroom" When someone makes one there is pretty much nothing you can do about it than open a window close your nose and hope that it will be over faster. :D

Now in the case of an ICBM there is no "open the window" option so...

Also I think the rail gun is being designed for usage on ship in battle with enemy attack ships.
But because of it's size and weight it is basically only either a stationary weapon like on land or one that could be used on a ship , and when on a ship or on land it is practically very inefficient or even useless against fast moving manouverable targets like fighter jets or ICBM or anything other of the kind

 

[Drakkith]

Confused or not confused one thing's for sure a unguided projectile no matter how fast isn't capable of destroying a ICBM.
The only way to do that would have to bring the rail gun really close and personal to the ICBM but then it would also be too late to do something about it , and I believe that by shooting it down right over your head or close to the coastline of the US soil it would probably still detonate atleast one of it's warheads and so you still have pretty nasty consequences.

A hit on the reentry vehicle would be devastating to the warhead inside. The warhead would be extremely unlikely to detonate, but it would probably be blown apart. Nuclear safety standards are extremely tough, and the required safety margin is something like a million to one chance of a nuke going off at any time other than when it is supposed to. And it's not just the safety standards. The actual warhead design requires that the integrity of the warhead remain intact. Otherwise the explosive shockwave that compresses the fuel doesn't work right.

Also I think the rail gun is being designed for usage on ship in battle with enemy attack ships.
But because of it's size and weight it is basically only either a stationary weapon like on land or one that could be used on a ship , and when on a ship or on land it is practically very inefficient or even useless against fast moving manouverable targets like fighter jets or ICBM or anything other of the kind

The power of the projectile is directly related to how fast you can accelerate it before it exits the barrel. For anti-aircraft fire you don't need a big round, so it's much easier to accelerate to the required velocity. I can easily see a smaller version being land portable and used for anti-aircraft or anti-vehicle use. Bigger ones, perhaps for anti-tank use are still feasible. They'd just need a little larger or beefier vehicle. The kicker in all this is the power supply. Many naval vessels use nuclear power plants and don't have to worry nearly as much about concerns such as fuel usage like a land vehicle would.

And I don't understand your belief that it wouldn't make a good weapon vs fast maneuverable targets. Anti-aircraft guns don't need to move that quickly since their targets are in the distance. The aircraft are not simply flying 200 ft off the ground at mach 2 right overhead. The increased velocity of a railgun makes it an ideal weapon for anti-aircraft fire.

 

[Crazymechanic]

Well I was skeptic about the aircraft because I thought that in order to bring down a plane , a fast moving fighter jet you would have to have extremely precise measures of where the aircraft is located because the projectile is non guided as opposed to a missile so you would have to do the Rambo style machine gun shooting rather than just one precise projectile hitting it's target. Not to mention that non guided projectiles are prone to weather like high winds, heavy rain and etc.

Yes I agree i was kinda wrong about the A bombs , they would probably not detonate if torn apart with bullets.As the parameters to obtain critical mass would be changed or destroyed.

 

[Darwin123]

This video is from 2007 but it stated the goal at that time was a 64 mega-joule weapon? I understand the advantages of extended range but it seems like a huge, awkward, and expensive weapon to deliver a relatively small amount of energy. 64 mega-joules is the equivalent of only 14 kg of TNT. Aren't there already much more efficient ways of delivering that amount of destructive energy to a target?

It is the speed, not the explosive power. A rocket with the same explosive power would be moving much more slowly than a projectile launched by a rail gun.

The 64 MJ is carried by the kinetic energy of the projectile, not the chemical energy of the projectile. If a light projectile were carrying 63 MJ of potential energy and 1 MJ of kinetic energy could be traveling very slowly. However, a light projectile launched by a rail gun could have 64 MJ of kinetic energy and 64 MJ of explosive power. The light projectile would be moving much faster.

A rail gun is one example of a kinetic weapon. A kinetic weapon is one where most of the explosive energy is "stored" as kinetic energy.

Kinetic weapons would be the weapons of choice in outer space where there is no atmosphere. An rocket in the atmosphere has to store chemical energy both for explosive power and to counter air resistance. Relatively little chemical energy would be left for explosive power.

There is a historical cycle going way back. Kinetic energy weapons used to be popular in cannon. Cannon balls were kinetic projectiles. Most eighteenth century cannon balls did not carry explosives. They were launched by explosives but their damage was induced by their kinetic energy. This was great for short distances, where air resistance is negligible. Then, the use of explosives in projectiles became more popular as the range of cannon increased. Then, kinetic weapons came back as humans started to go into outer space. Those supersonic uranium projectiles that you heard about in the news is a kinetic weapon.

The distances in outer space cause large delay times in projectiles. The target could see the projectile coming from a large distance using light or radar and move out of the way. Nothing goes faster than light or radar. There will also be a delay for the projectile seeing the target move out of the way. Therefore, the most effective projectile will be the fastest projectile in outer space.

Speed would become far more important than efficiency in outer space. If battles were to occur entirely in outer space, rail guns and lasers would be the weapons of choice. Both are kinetic weapons in the sense that the energy that does the damage is stored entirely as kinetic energy.

These weapons would be much faster than rockets. Lasers would be faster than anything. However, lasers could be countered by reflective surfaces. So that would leave rail guns.

 

[nsaspook]

Well I was skeptic about the aircraft because I thought that in order to bring down a plane , a fast moving fighter jet you would have to have extremely precise measures of where the aircraft is located because the projectile is non guided as opposed to a missile so you would have to do the Rambo style machine gun shooting rather than just one precise projectile hitting it's target. Not to mention that non guided projectiles are prone to weather like high winds, heavy rain and etc.

It's not that hard to aim directly at the anti-ship weapon what's in the terminal guidance mode (seconds before impact) because it can't really move off track by very much and still hit the target. You need a good search radar to find the target and move the gun into a coarse firing cone until the tracking radar narrows down that cone and can lock in a thermal Imager. The high resolution Imager can then track down to a small fraction of a arc for the firing solution.
http://img.photobucket.com/albums/v699/xu-an/phalanx_eo_track.jpg

 

[cjl]

The V2 rocket in WWII was a kinetic weapon.

While I agree with much of the above post, this part is wrong. The V2 had a thousand kilograms of high explosive onboard, and most of the damage it caused was from the detonation, not from the impact.

 

[Darwin123]

While I agree with much of the above post, this part is wrong. The V2 had a thousand kilograms of high explosive onboard, and most of the damage it caused was from the detonation, not from the impact.

My mistake. Sorry. You are right.

 

[Darwin123]

It's not that hard to aim directly at the anti-ship weapon what's in the terminal guidance mode (seconds before impact) because it can't really move off track by very much and still hit the target. You need a good search radar to find the target and move the gun into a coarse firing cone until the tracking radar narrows down that cone and can lock in a thermal Imager. The high resolution Imager can then track down to a small fraction of a arc for the firing solution.
http://img.photobucket.com/albums/v699/xu-an/phalanx_eo_track.jpg

Note that a kinetic weapon can still be a guided weapon. It takes a lot of energy to accelerate a stationary object. It doesn't take much kinetic energy to change the direction of motion.

A rail gun could launch a projectile with high kinetic energy that has long range sensors, a smart guidance system and low energy maneuvering devices. In the atmosphere, the device can use aerodynamics to change direction. Gyroscopes can move a little, the projectile can rotate a small amount, and then the system can hit. Small rockets, ion engines or even lasers can be used in space to change the direction of motion just a little. The projectile doesn't have to have an explosive pay load.

The target may not get advance warning before the kinetic projectile gets there. The kinetic projectile doesn't have a rocket plume. The kinetic projectile can be made very cold, like the cosmic background. The rocket plume may be very hot. The guidance system may use passive sensors. Hence, the kinetic projectile can be nearly undetectable as well as fast. A rocket would be slower and easier to detect than a kinetic weapon.

 

[nsaspook]

A rail gun could launch a projectile with high kinetic energy that has long range sensors, a smart guidance system and low energy maneuvering devices. In the atmosphere, the device can use aerodynamics to change direction. Gyroscopes can move a little, the projectile can rotate a small amount, and then the system can hit. Small rockets, ion engines or even lasers can be used in space to change the direction of motion just a little. The projectile doesn't have to have an explosive pay load.

Adding all the fancy gizmos mainly defeats the concept of a complex gun but simple inert projectile.

My positive viewpoint on the utility of rail-guns is mainly about close-in protection where the highest possible speed to the target allows you to fire at the target several times in case of a miss and to engage multiple close targets with one gun.

Russian navy CIWS firing at surface target.
It's pretty effective on a dead in the water pirate ship but those bullets seem really slow when compared to a incoming missile.

 

[cjl]

They don't need to be fast compared to the missile - they just need to be able to predict its flight path well enough to hit it. Given the (lack of) maneuverability of most anti ship missiles, that's not actually as hard of a problem as it may initially seem. In fact, most anti-missile systems (especially anti-ballistic missile systems) are traveling slower than the missile they intercept at the time of interception - it's almost more of a case of them getting in the way and letting the missile fly into them than anything else.

 

[nsaspook]

They don't need to be fast compared to the missile - they just need to be able to predict its flight path well enough to hit it. Given the (lack of) maneuverability of most anti ship missiles, that's not actually as hard of a problem as it may initially seem.

For a one on one engagement this is true but it's been standard doctrine by the FUSSR and other Navies to defeat systems with several cheap missiles near points of single gun coverage. So we could increase the number of CIWS systems or make each system faster and increase the lethality of a single hit. Pushing out the engagement range makes this 'easier' as a counter countermeasure.

The Soviet saturation strategy was one of the reasons for bringing back the old battleships during the 1980s. They were designed to take hits from other 16" inch guns so the protection from the armour belts made them almost bullet proof to the current day Soviet anti-ship missiles.

http://en.wikipedia.org/wiki/Saturation_attack

I installed and certified some of the data processing systems on several of the battleships being upgraded back then. There is no modern (non-nuke) missile counter for 2 foot thick steel.

The most notable difference between modern warships and the Iowa Class battleships is the huge amount of armor protection the Iowas employ. Modern warships are hardly armored at all, instead relying on their ability to stop incoming threats before they can hit the ship. Newer warships have only a few inches of armor plating and in an effort to save weight, have even used aluminum in their superstructures. In contrast, the Iowas were built at a time before missiles and since you could not shoot down or destroy an incoming projectile, the ships were built to withstand the tremendous force of impact produced by naval gunfire.

http://www.kbismarck.org/forum/viewtopic.php?t=2925

 

[d3mm]

Just to nitpick a little, the "sabot" is actually the part of the round that doesn't fly toward the target. ;)

You're right - that part is called the penetrator or "long rod". However a US crew calls it "sabot" when loading as in "target (whatever) - load sabot - fire". Not being a tanker I don't know the exact commands but that word is used for sure.

You mean shoot a railgun at a missile? Missiles aren't like artillery. Hit it with a round and it will most likely explode, disintegrate, stop working and fall out of the sky, etc. Even if you're talking about the reentry vehicle from an ICBM you'd still do catastrophic damage to it.

Counter-missiles often require two hits to disable something like a Scud ballistic missile. Read your Gulf War(s) history. The second shot was often needed because the missile's warhead was a solid, heavy object that often survived a single hit.

No, I mean shoot a missile at a railgun (the projectile). Some others in the thread were talking about the railgun as an anti-missile weapon but that makes no sense to me. What does make sense is using it as an anti-ship gun, because the ship's defences against missiles will not have much effect on a lump of metal traveling at Mach 8, and it won't even have an exhaust plume to lock on to. That was my original point: I don't see any countermeasures. If it's mounted on a ship, it's mobile, if it's mounted on a coastal battery then it controls a huge area of sea. If it can fire that weight at that speed, you'd be mad to move an aircraft carrier within 200 miles of it.

The problem with a direct fire gun is that you need to first find the target, and secondly close into range. You might think you know where a carrier is, but let's say it shoots down anything approaching within the 200 miles given (those F-18s are onboard for a reason). How then do you know where to shoot the gun? So you send a self-guiding railgun slug to a map co-ordinate and hope it can find the carrier by itself. In effect your railgun is now a ballistic missile. As the guidance system is electronic there are several electronic means to counter it, such as jamming.

Confused or not confused one thing's for sure a unguided projectile no matter how fast isn't capable of destroying a ICBM. now forgive me if this sounds rude but this whole situation reminds me of the classical "fart in the classroom" When someone makes one there is pretty much nothing you can do about it than open a window close your nose and hope that it will be over faster. :D Now in the case of an ICBM there is no "open the window" option so...

The missile has to come at you. Its speed lowers your warning and reaction time but doesn't stop you intercepting it: missiles cannot dodge at ballistic speeds. You know its flight path.

My positive viewpoint on the utility of rail-guns is mainly about close-in protection where the highest possible speed to the target allows you to fire at the target several times in case of a miss and to engage multiple close targets with one gun.

I kind of agree, but if you have 4 guys with an RPG and bomb in a speed boat, a machinegun works just as well. If they shoot a mortar or an older missile like Exocet, existing CIWS guns can deal with that. If they shoot something heavy, agile and supersonic, RAM can deal with that. This obviously applies to current technology, of course. I fully understand the need to plan for future threats.

For a one on one engagement this is true but it's been standard doctrine by the FUSSR and other Navies to defeat systems with several cheap missiles near points of single gun coverage.
The Soviet saturation strategy was one of the reasons for bringing back the old battleships during the 1980s.

I don't see saturation attack working against a US carrier. No-one has that kind of firepower anymore. If a carrier goes down it, it will be sabotage, a submarine, a ballistic missile, a mine or a surprise attack from suicide speedboats, or perhaps someone hacks and takes over a drone.

I installed and certified some of the data processing systems on several of the battleships being upgraded back then. There is no modern (non-nuke) missile counter for 2 foot thick steel.

Even if you believe it unsinkable, the sensors and missile launchers wouldn't survive, then what use is it outside of 20 miles? I agree that conventional SSMs wouldn't penetrate a 16" armor belt (I cannot remember the thickness of it, but 2 feet sounds too much - the belt does not run full lenght, is probably about 8" near the bow and stern and 14-18" midships) by explosive force alone but it's not exactly hard to build a missile warhead that would: A shoulder-carried RPG can penetrate that.

If you count up the tonnage of iron bombs (regular dumb bombs) that was needed in world war 2 to sink or disable a battleship you find it's less than what an F-18 can carry. The reason battleships were so "hard" to sink in WW2 was the fact that the planes and submarines of the era were terrible.

 

[d3mm]

"do not get hit" is a very effective counter for a water balloon and a laser.

There are also 'cloaking' based counters using meta-materials that can shield objects from EM energy.

http://en.wikipedia.org/wiki/Metamaterial_cloaking
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA535595

So, railgun vs laser! :-)

Why would a water balloon would stop a high power laser? What equations do we use to determine this? A laser can penetrate many meters into water. Just how big is this balloon?

If you can deploy a balloon rapidly enough to intercept a laser (which means you pre-empted firing) you can also deploy a object to intercept the path of a projectile and you do not need to absorb the kinetic energy of the projectile. You only need to knock it off course or cause it to break up.

Metamaterials indeed show promise for invisbility but that's going to work against both systems.

I can't really see any advantage of a railgun if you have visual range. It's possible you can fire the railgun indirectly from several hundred miles but then you basically have a ballistic missile and the flight time and targeting requirement allows for additional defenses.

 

[Drakkith]

Counter-missiles often require two hits to disable something like a Scud ballistic missile. Read your Gulf War(s) history. The second shot was often needed because the missile's warhead was a solid, heavy object that often survived a single hit.

A. That's not part of "history". That's part of weapons knowledge.
B. I wasn't talking specifically about ballistic missiles, but about missiles in general.
C. That's interesting.

The missile has to come at you. Its speed lowers your warning and reaction time but doesn't stop you intercepting it: missiles cannot dodge at ballistic speeds. You know its flight path.

He's talking about ICBM's. The missile itself never gets near its target, only the small reentry vehicle that holds the warhead. And it is small, just a bit larger than a person. Currently there is only two anti-ICBM system in the world. The Russian A35 ABM, which uses another nuke to destroy the target nukes, and the U.S. Ground-Based Midcourse Defense (GMD), which uses a kinetic projectile (a high speed missile) to hit an ICBM. (I assume before it launches its warheads)

Neither of these target the individual warheads after separation. Once that happens you're pretty much toast. Your only chance is to be within range of the missile soon after launch.

I don't see saturation attack working against a US carrier. No-one has that kind of firepower anymore. If a carrier goes down it, it will be sabotage, a submarine, a ballistic missile, a mine or a surprise attack from suicide speedboats, or perhaps someone hacks and takes over a drone.

China? Korea? Russia? Missiles aren't that expensive for a modern military.

 

[nsaspook]

Even if you believe it unsinkable, the sensors and missile launchers wouldn't survive, then what use is it outside of 20 miles? I agree that conventional SSMs wouldn't penetrate a 16" armour belt (I cannot remember the thickness of it, but 2 feet sounds too much - the belt does not run full lenght, is probably about 8" near the bow and stern and 14-18" midships) by explosive force alone but it's not exactly hard to build a missile warhead that would: A shoulder-carried RPG can penetrate that.

Because we don't protect the ships with steel anymore protecting them with advanced technology like DEW or rail-guns is necessary to keep up.The BB-62 class ships main use during it's last war was for big gun shore bombardment and cruise missile attacks. You can data link to a UAV or another ship with working sensors for the guns and any (vertical launching system) VLS missiles would still be able to be used.

Keeping the engineering spaces intact is the top priority. The USS Stark topside sensors/missiles survived but suffered massive engineering casualties because the warhead is designed to direct the blast after penetration.
Stark missile damage: http://www.navsource.org/archives/07/images/31/073128.jpg
CIWS nor SuperRBOC was used in defence of the missile attack because of the "cold war' era ROE.

There is no way a RPG class weapon can 'defeat' battleship armor if defeat means more than a pin-prick. We could 'penetrate' the thick walls with a special drill when installing wiring during the recommissioning.
They have a bomb deck to initiate the bomb, and armor deck to contain and reflect the blast, and a splinter deck to trap and collect any spalling or penetrating shrapnel. The BB-62 class could take an aerial hit from a 2000lb bomb and keep firing it's main weapon.
About the only period anti-modern missile that could stop one cold was the nuke option on this. (It was designed to take out our carriers, very nasty saturation attack mode)
http://en.wikipedia.org/wiki/P-700_Granit

 

[Aero51]

It is the method of delivery. The energy per unit volume of a rail gun projectile can be much higher than an explosion (in the later phases).

 

[A.T.]

Why would a water balloon would stop a high power laser? What equations do we use to determine this? A laser can penetrate many meters into water. Just how big is this balloon?

What about rain, fog, smoke etc. Doesn't that significantly reduce the effective range of laser weapons?

 

[mathmathica]

Recoil or not to recoil

I'm not up to date, but...
One advantage might be recoil. So called recoiless guns aren't, the bigger the charge, the bigger the kick; a rail gun is much closer, higher projectile velocities, negligible recoil.
No storage of solid propellant, just draw power from your reactor.
Containing explosions requires big heavy guns, a rail gun should be much lighter.
How stealth can you be with explosions going off on your deck?

 

[nsaspook]

So, railgun vs laser! :-)

Why would a water balloon would stop a high power laser? What equations do we use to determine this? A laser can penetrate many meters into water. Just how big is this balloon?

If you can deploy a balloon rapidly enough to intercept a laser (which means you pre-empted firing) you can also deploy a object to intercept the path of a projectile and you do not need to absorb the kinetic energy of the projectile. You only need to knock it off course or cause it to break up.

Metamaterials indeed show promise for invisbility but that's going to work against both systems.

I didn't mean using the balloon as a defence weapon, I meant dodging one but barge balloons were used during WW2 as an aerial defence.
http://upload.wikimedia.org/wikiped..._balloons_over_London_during_World_War_II.jpg

Water vapor effects on FEL weapons. Maybe a dense fog could be used as a counter.

In this article we discussed and analyzed the key physical processes that affect the propagation of high-energy lasers in a maritime environment. These processes include thermal blooming, turbulence, and molecular/aerosol absorption and scattering. Aerosol scattering and absorption as well as water vapor absorption can be a major limitation for HEL propagation in a maritime environment.

http://www.nrl.navy.mil/research/nrl-review/2004/featured-research/sprangle/

The possibility of Meta-materials on a missile is for shielding from a HEL by bending the energy around the warhead without reflection or dissipation. Wide spectrum "invisibility" is unnecessary.