Why is the rail gun an interesting weapon?

[mrspeedybob]

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?

 

[jedishrfu]

its doesn't require an explosive charge to shoot things.

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

 

[mrspeedybob]

I know, but I can't imagine explosives being so expensive that they justify this thing as an alternate way to deliver energy. There has to be some physical reason that 64Mj of kinetic energy is sooo much better then 64Mj worth of explosives.

 

[A.T.]

I know, but I can't imagine explosives being so expensive

As if the military would care about saving your tax dollars.

It's not about the money, but storage space and explosion risk of gun powder. Especially on ships, that's why the Navy is the primary driving force here.

 

[nsaspook]

It's mainly for terminal defence of a incoming missile/rocket. In theory it's got a fast reload capacity, none hazardous ammo and 8 mach plus speed to the target. What we have today are counter-measures, radar guided guns or anti-missile missiles for close in or fast moving targets.

 

[d3mm]

Considering RAM has a 90% hit probability I don't understand the benefit of a railgun for close in missile defence.

Also once ships have sufficient electrical power generation, a laser would just be plain better.

I think this is one of these projects that will die off or morph into something very surprising.

I have not posted any links to RAM because if you don't know what it is, you aren't qualified to post an answer.

> Why is the rail gun an interesting weapon

Because humans like to fight each other.

 

[nsaspook]

Laser counter-measures are pretty cheap and light but it's hard to deflect an mach 8 block of Lexan.

 

[Borg]

I have not posted any links to RAM because if you don't know what it is, you aren't qualified to post an answer.

That's not how this forum works.

 

[Crazymechanic]

""""> Why is the rail gun an interesting weapon

Because humans like to fight each other. """"


According to this reasoning we could just as well fight the next war with baseball bats and stones.It would qualify as fighting and they say that "everything new is actually well forgotten old..."

 

[jedishrfu]

""""> Why is the rail gun an interesting weapon

Because humans like to fight each other. """"


According to this reasoning we could just as well fight the next war with baseball bats and stones.It would qualify as fighting and they say that "everything new is actually well forgotten old..."

I think its more fear of what the other guy may have hidden or is secretly developing that is the driving force behind many standoffs and conflicts.

 

[mikeph]

I think the answer might be that, in a nutshell, there are no foreseeable countermeasures to a block of metal traveling at that speed.

I have not posted any links to RAM because if you don't know what it is, you aren't qualified to post an answer.

Possibly the least useful post I've ever seen on this forum.

 

[Nugatory]

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?

The very high muzzle velocity means that the 68 MJ is delivered to the target in a very short time and to a very small area. A 68 MJ kinetic impact does far more damage to a hardened and/or fast-moving target than a chemical explosion, even with a sophisticated shaped charge. A laser is in principle capable of similar effectiveness, but in practice a laser capable of delivering tens of megajoules to a 100 cm² area in a millisecond or less is a fairly daunting engineering proposition.

Generally this advantage does not outweigh the awkwardness of a railgun; it's easier to just use a larger explosive charge. However, there are situations such as missile defense where that's not an option (On a smaller scale, CWIS systems depend on kinetic energy instead of explosives to kill their target).

 

[d3mm]

Laser counter-measures are pretty cheap and light but it's hard to deflect an mach 8 block of Lexan.

I'd like to see how you stop a laser with equivalent energy.

The very high muzzle velocity means that the 68 MJ is delivered to the target in a very short time and to a very small area. A 68 MJ kinetic impact does far more damage to a hardened and/or fast-moving target than a chemical explosion, even with a sophisticated shaped charge. A laser is in principle capable of similar effectiveness, but in practice a laser capable of delivering tens of megajoules to a 100 cm² area in a millisecond or less is a fairly daunting engineering proposition.

Generally this advantage does not outweigh the awkwardness of a railgun; it's easier to just use a larger explosive charge. However, there are situations such as missile defense where that's not an option (On a smaller scale, CWIS systems depend on kinetic energy instead of explosives to kill their target).

I like that post but I will just correct one thing:

(On a smaller scale, CWIS systems depend on kinetic energy instead of explosives to kill their target).

Change this to read : On a smaller scale, gun-based CIWS systems don't have the range to deal with a supersonic SSM. So RAM is good enough to bullseye a target without needing proximity fused detonation, but it does have an explosive warhead, so it's not really a kinetic kill.

 

[etudiant]

Rail guns have the potential of pushing projectiles to much higher speeds than are possible with chemical propellants. That allows for much greater range weapons.
If the projectile is terminally guided, accurate bombardment from a couple of hundred miles away becomes possible. That plus the elimination of the volatile and dangerous propellant (read up on the USS Iowa accident) are the drivers of the US Navy's interest.

 

[Kevin2341]

I'm going to use a lot of layman's terms and very non-sciency ways of explaining things. So forgive my being a novice, but I have explored this weapon quite a bit, and I'll share what I know:

Electric energy is released from a bank of capacitors (rather discharged) with a VERY short period of time. Ideally, that time would be extremely close to zero. This energy is delivered to a set of rails, the current is flowing opposite directions between those two rails. From this, I believe it is the biot-savarte law (possibly a different EM law, it's been a while), that the current generates an electromagnetic field. Between the two rails, because one current is running north and the other south, it creates opposite electromagnetic fields that have a "corkscrew" effect. Simply put, it's like the projectile is getting both pulled and pushed, and with the amount of energy flowing through the rails, the pushing and pulling is enough to propel the object to speeds of 3000 meters per second

Now, imagine a projectile hurtling through the air at those speeds, if it only weighs a couple grams, that is still a tremendous amount of energy.

You claimed that the energy deliverance is 68Mj's. Sounds about right. Imagine a projectile that weighs a few grams with kinetic energy equal to 68Mjs.

To me, that makes sense why this is an effective weapon. A projectile hurtling through the air at those speeds could easily rip a hole through a tank. And from what I've read about the matter, is that as that projectile ripped a hole through that tank, not only does it destroy the tank, but supposedly a pressure is created within the hull that as the projectile leaves, so does everything else inside that wasn't bolted down.

It's a precision weapon. Bombs are area of effect weapons. A railgun could probably be aimed several miles away and hit a target right between the eyes through a foot of concrete. That's just a personal speculation however.

 

[d3mm]

I think the answer might be that, in a nutshell, there are no foreseeable countermeasures to a block of metal traveling at that speed.

Ballistic missiles can be hit, and they come in much faster. Mach 20?

It's all about warning time, but electronic systems get better, and you can use a drone to get it out before they shoot.

 

[Crazymechanic]

@Kevin2341 Pretty much right there about the tremendous speeds and energies but no I believe if a bullet of that size and speed hit a tank the tank wouldn't go flying in air it would stay there just the armor would be penetrated probably (haven't calculated , just assuming)
and while going through it would still have enough energy left to kill someone inside , that is if the bullet wouldn't be too damaged and fused with metal parts and scrap from the initial impact.


Also trying to stop a ICBM with a railgun even a huge and powerful one is still a pretty tough mission to achieve.Not because the rail gun's projectile wouldn't have enough speed rather because the ICBM is traveling so fast and the rail guns shot has to be very very accurate otherwise all that kinetic energy is wasted, remember an ICBM is kinda big but not that big so for a projectile from many hundreds of miles away it's still a point like object that kas to be tracked down to precision now attacking a ship would be much easier as a ship is something so much bigger and thousands of times slower.

 

[nsaspook]

I'd like to see how you stop a laser with equivalent energy.

http://www.afit.edu/en/de/heeleeosproducts.cfm
http://www.asdl.gatech.edu/GC-2011-CDEW.html

 

[Drakkith]

Also trying to stop a ICBM with a railgun even a huge and powerful one is still a pretty tough mission to achieve.Not because the rail gun's projectile wouldn't have enough speed rather because the ICBM is traveling so fast and the rail guns shot has to be very very accurate otherwise all that kinetic energy is wasted, remember an ICBM is kinda big but not that big so for a projectile from many hundreds of miles away it's still a point like object that kas to be tracked down to precision now attacking a ship would be much easier as a ship is something so much bigger and thousands of times slower.

The re-entry vehicle (Multiple Independently Targetable Warhead Reentry Vehicle) that the warhead sits inside of is about the size of a person, so they are EXTREMELY difficult to hit. The rocket that propels the warhead into space is much larger and easier to hit, but you'd need to be able to hit it while it's still over its launch nation, requiring weapons that are already fairly close.

See a few MIRV's here: http://en.wikipedia.org/wiki/File:W87_MIRV.jpg

 

[Crazymechanic]

That's right Drakkith , also if you want to hit the rocket itself while at enemy lines the closest you can come is at international territory borders so basically the rail gun's projectile would have to travel atleast some 300 to 500 miles and for a physical object now matter how fast it is ejected to travel that far and still be precise and energetic is a total NO GO.Also once the MIRV warhead is close enough and splits up into it's multiple bombs now it means you have to shoot down not 1 target but 7 to 10 targets on average.And they still travel fast and are even smaller than before.
Now add the fact that both Russia and the US have multiple ICBM's in the order of couple hundred for each country , imagine what it takes to take them all down if atleast half of them are being fired from each country.
Not to mention the fact that in nuclear weapons you can pretty much throw out the accuracy because you have the yield , and even if the bomb doesn't hit it's target that close the target is pretty much dead anyway also even one nuclear explosion in the middle of a crowded city would be a national tragedy for any country.
So by all this I think that a rail gun would be feasible for all kinds of enemy transport that is big and moves rather slow, like ships.
As for ICBM and fast moving things I think there needs to be something of a laser , some weapon that can attack enemy vehicles or missiles with a force that is carried by a massless force carrier like photon.Now EM pulse bomb and laser is the case.
A physical projectile no matter how fast it gos is still a physical projectile, let's not forget the huge banks of capacitors and wires and equipment needed.

P.S. @Drakkith I have been in some of the former USSR nuclear missile bases while the missiles themselves are not there and the most of equipment is either taken away for safety or stolen for precious metals you can still have the feeling of it and see the sizes.And yes a 1-4 Megaton warhead sitting on top of a 60's missile is not at all that big.the hole in the silos rolling top for the mounting of the bomb is actually something like 1,5m across.
There was also a old book I found in the -3sub level underground in one of the pathways , it was about nuclear missile maintenance and other interesting things written in russian but back then I somehow left it there , now I'm regretting that :D:D

 

[Drakkith]

P.S. @Drakkith I have been in some of the former USSR nuclear missile bases while the missiles themselves are not there and the most of equipment is either taken away for safety or stolen for precious metals you can still have the feeling of it and see the sizes.And yes a 1-4 Megaton warhead sitting on top of a 60's missile is not at all that big.the hole in the silos rolling top for the mounting of the bomb is actually something like 1,5m across.
There was also a old book I found in the -3sub level underground in one of the pathways , it was about nuclear missile maintenance and other interesting things written in russian but back then I somehow left it there , now I'm regretting that :D:D

I worked on nuclear and conventional cruise missiles for 10 years.
Not that it makes me an expert on ICBM's. Just thought I'd share.

 

[Nugatory]

Change this to read : On a smaller scale, gun-based CIWS systems don't have the range to deal with a supersonic SSM. So RAM is good enough to bullseye a target without needing proximity fused detonation, but it does have an explosive warhead, so it's not really a kinetic kill.

Fair enough - I was thinking of the naval version of the Vulcan which does use solid slugs.

 

[Crazymechanic]

@Drakkith , what exactly you did while working on those missiles? Somekind a technician or so ?

To make matters more interesting I can say that one of the sites located some 130km away from me is the R12-dvina a nuclear missile with medium range , about 2000km max built somewhere in the late 50's working around the start of the 60's , the same missile that was deployed to Cuba which started the missile crisis.Only in Cuba they put the surface ones which are lunched from reinforced concrete slabs.The ones we had here were intended for europe and were all silo based systems.The rocket was some 35m high so that made the sile about 40m deep with all the systems and pads on which it was sitting.
About 10 to 12 story building underground basically.Built in 1964.it was closed in the 1980's as these missiles were absolute and aged also not having the desired range and control system , as the fuel was liquid with an oxydizer kept in separate tanks underground.Well the oxydizer is very dangerous and flammable also it can leak and produce vapor which is very hazardous to inhale.

 

[nsaspook]

That's right Drakkith , also if you want to hit the rocket itself while at enemy lines the closest you can come is at international territory borders so basically the rail gun's projectile would have to travel atleast some 300 to 500 miles and for a physical object now matter how fast it is ejected to travel that far and still be precise and energetic is a total NO GO.

I don't think anyone seriously thinks about ABM defence and rail-guns. There have been plans and space allocated on ships (mainly for amphibious force ships defence from small boats) for decades for either DEW weapons or a rail-gun like device but so far nothing comes close to the effectiveness of a wall of lead from a bullet.

 

[Drakkith]

@Drakkith , what exactly you did while working on those missiles? Somekind a technician or so ?

I did maintenance. What a car mechanic does for a car, I did for our missiles. Removing and replacing engines, navigation sets, fueling/defueling, testing, etc.

 

[fivetide]

It also makes a really good pulse drive; you hyper accelerate plasma down a series of ever increasing speed magnets out of the rear of a space ship. Would kick the hell out of Orion..

 

[Crazymechanic]

@fivetide maybe I miss something but how is that relevant to what we talked here ?

 

[mikeph]

Ballistic missiles can be hit, and they come in much faster. Mach 20?

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?

With the rail gun, there is no explosive or guidance, and a few bits metal aren't going to change it's momentum greatly. Its heat signature is probably totally different as well. The only way I can see it being stopped is with a large transverse impulse to deflect it off target, and I'm ignorant of anything that can do this right now.

 

[d3mm]

Fair enough - I was thinking of the naval version of the Vulcan which does use solid slugs.

You refer to Phalanx CIWS. That's exactly the system I was thinking of when I said they were unable to counter large supersonic missiles. Klub is the reason why they had to develop RAM.

Out of curiosity, how?

re: Hitting ballistic missiles. They shoot it with counter-missiles. Against something like a scud you shoot two because the warhead is heavy and might continue.

http://www.afit.edu/en/de/heeleeosproducts.cfm
http://www.asdl.gatech.edu/GC-2011-CDEW.html

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

 

[d3mm]

@Kevin2341 Pretty much right there about the tremendous speeds and energies but no I believe if a bullet of that size and speed hit a tank the tank wouldn't go flying in air it would stay there just the armor would be penetrated probably (haven't calculated , just assuming)
and while going through it would still have enough energy left to kill someone inside , that is if the bullet wouldn't be too damaged and fused with metal parts and scrap from the initial impact.

When you hit a tank with a sabot (which is a solid, non-explosive round) the turret blows off because of the pressure inside the hull. It is not a bullet going through a truck and maybe hitting 1 thing. It is an explosion.

 

[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.