Sky Captain wrote:A land based railgun still would be useful even if it has less ROF than comparable standard artillery piece because of much greater range.
Against a weak opponent that is very true, but a weak enemy won't require large numbers of rounds fired either, which undermines the wider economic rational of railguns compared to tactical missile systems, where the launcher costs little. And honestly while any missile is expensive, GMLRS is about 110,000 dollars a shot, for a 100km range 200lb warhead missile.
Against a peer or near peer enemy low ROF has several problems
1) effect on target per round fired is less, because the targets will move or take cover once engaged and pure KE projectiles will already have fairly low effectiveness (unless you get the impact velocity to about 3km/s or higher, which is far beyond present goals)
2) enemy counterfire becomes an ever greater threat with time taken per fire mission, particularly given typical proposals for EM gun projectiles are purely ballistic to keep down cost. No railgun is on the table that it will outrange existing 8x8 truck mobile missiles. Gun systems involving multiple vehicles will have little or no tactical mobility and limited armor, making them very vulnerable if located. And since the gun itself is expensive, not the ammo, they are worth firing just about anything back at.
3) C-RAM defense systems already exist capable of engaging artillery shells, if not ones with exceptionally high performance. Still this is combat proven technology, while EM guns remain around a decade from plausible service, a lot of time for C-RAM to improve, and indeed it rapidly is improving with what I think are worthy of being called 'second generation' systems already hitting live fire testing. A low rate of fire artillery weapon might thus have its entire existence negated by enemy defenses. Even if the enemy defense can only stop the first couple rounds this will feed back to point 1, the enemy can get out of the way in the time he's bought himself, while waiting for his counterfire weapons to destroy the offending EM gun. One might end up with a situation in which both sides EM guns are doing nothing but shooting down each other shells and accomplishing no other purpose!
Cruise and aeroballistic weapons are much harder targets, but of course also more expensive shot for shot. But if the target is high value that doesn't matter in economic terms.
A battery of few railguns could provide artillery support over much larger area that otherwise would require more numerous conventional guns to cover.
That is true in all scenarios, but against a serious enemy its likely to only be a logistical advantage, fuel and ammo supplied to guns further behind the front and not at all reduce the number of weapons needed. We've already fully developed 155mm rounds for conventional guns and without using wings that can go 70km. That's not a joke on range, you need a pretty powerful railgun to shoot further then that with a useful payload.
Especially if range is so good they can partially replace expensive missiles or airstrikes to perform same mission. If huge volume of fire is needed than it is hard to beat rocket artillery, but in case like need to occasionally take out a building where some insurgents hide railgun may be more cost effective solution.
It might be, but you've got this issue where you need to fire enough rounds to justify the cost of the very expensive EM gun and power supply, but not so many that you are in such a big war the enemy will just stand a high probability of destroying your semi static weapon. Certainly this niche does exist, but it tends to mean that even if EM guns became highly refined technology they are unlikely to replace all existing tube artillery and certainly not barrage rocket and artillery missile systems. Nor will they replace a lot of direct fire weapons without some radical changes in technology.
Purple wrote:The problem with that is accuracy. Once you get to a certain range conventional artillery just isn't that accurate. Wind, environmental conditions and stuff like that really mess up your flight path in ways that no amount of muzzle velocity will fix. That's why all the weapons that fire beyond conventional artillery range tend to be area weapons or guided. And for both of those a rocket is just plain superior. The far smoother acceleration curve means that your sensitive electronics don't get kicked in the genitals sometime fierce like they would if you fired them from a super high velocity cannon.
The higher velocity a weapon the less the wind and weather will affect it proportional to the range assuming unguided rounds. EM guns specifically should also have more consistent muzzle velocities then powder guns, aiding accuracy with unguided rounds. This velocity issue is a reason why sabot firing tank guns have useful accuracy, even though they are only fin stabilized and disturbed by the sabot falling off. Simply they go so fast the wind doesn't have time to do anything until they are several kilometers away. Nothing fancy about it.
Probably if your going to shoot a ballistic anything more then about 50-60km, very roughly, you need guidance to get good effects even with cluster bomb equipped warheads . Firing to greater ranges will fall into the harassment and interdiction category of fire. However a static target could still be very vulnerable much further away simple because volume of fire is a thing. That's a problem with big elaborate land based railguns. Shoot and scoot probably isn't possible.
I don't think anyone in the industry is taking unguided EM rounds serious for artillery roles at this point though, and frankly we are not far away from an era of 100% guided munitions above 120mm in caliber anyway. We could do it right now if we wanted. Even without GPS such rounds are much more accurate then unguided fire. Careful adjustment by a forward observer can reduce this disadvantage by a wide margin, but its very time consuming and the time rises with range because the shells end up taking several minutes to fly the distance. And many targets have no observer to use, just locational data from say ELINT or counterfire radar.
As far as electronic sensitivity goes, as long as the electronics can survive the launch acceleration at all (you will find this more technically labeled as 'setback' acceleration, setback referring to the actual movement the pieces undergo as they get compressed from the initial motion) then they aren't going to give all that much of a damn about how fast the round actually travels in an artillery role. The time of flight will be measured in minutes, so the guidance system has plenty of time to figure out what to do and listen to GPS signals as it begins to fall back down to the earth. GPS weapon accuracy will not be much affected by velocity or range with a well engineered system. Honestly its technology that has gotten kind of easy.
The real difference between an artillery shell with GPS and a missile will be the missile can be a lot better against enemy jamming, provided it was engineered with a high level of GPS jamming resistance, which most existing systems were not. This is basically a size issue more so then just cost though, the missile has more room for a bigger antenna. On way we do GPS anti jam is using a phased array antenna. That way the computer has multiple points of reference with a known time delay to judge the difference in directions from. So it can start to tell the real signal is coming from one way and the jammer signal from another.
If the GPS jammer is in orbit or high altitude above the battlfield this ceases to work!
Guided missiles for say, SAM purposes are a lot more sensitive an accelerations in fact, because they might make a whole series of sudden violent turns completely changing the weapons course, turning it around ect..... A guided ballistic artillery shell undergoes more violent acceleration, but only once, and then it just needs minor corrections the rest of the way. That actually makes the guidance problem very easy, and is what led to programs like the GPS Competent Fuse (XM1156 Precision Guidance Kit).
Pelranius wrote:
BAE and Lockheed Martin have developed guided railgun ammunition (using things like laser gyros for inertial guidance, IIRC).
Interestingly enough all developmental test flights to date have been conducted out of a conventional cannon. If we can count a 5.2in 100caliber smoothbore at Wallops island as conventional. Fires full caliber shells at something like 5,200fps. Such a weapon could easily be fielded for combat, but it just doesn't have any real appeal.
We could have staggeringly better land artillery if we wanted with combustion tech, it's just not good enough to make it worthwhile compared to missile weapons. I even found a citation from the 1970s that we could now make 16in gun barrels stronger then the originals for half the weight, and as one piece rotary forgings, with the rifling cut directly into the tube. The cost different would be enormous to say the least compared to WW2 era barrels with a half dozen pieces. But the problem then, and really still now, is achieving enough volume and density of fire to justify building such implements of war.
Pelranius wrote:For what it's worth, the USN wants the BAE Hyper Velocity Projectile to be GPS guided (though might just be easier to input a cold atom clock (sp)).
The problem is an atomic clock based shell will lose accuracy with time of flight, and time of flight for the really long range 200-300km kind of railguns people want, with 30MJ kind of muzzle energies, are considerable. Also if GPS is lost completely, which is not implausible, then you have a new problem which is the location of the GUN. The awesome thing about GPS weapons is they don't care where they were fired from. As long as its physically possible to reach the target, they will. But if you use INS guidance, even augmented with an atomic clock, your gun locating error compounds your target locating error. And that gets bad fast and is a major reason why artillery used too and largely still does need huge amounts of ammo to engage targets. This will affect non EM artillery too, but then that's where a rocket or missile with a big warhead can help make up for the inaccuracy by exploding more!
The accuracy with INS won't be useless, but the shells themselves are not going to be very effective. A lot of Em\M gun proposals involve pure KE shells with shrapnel payloads (this includes all the BAE work), but to say the least the effectiveness of this sort of round is unproven, and the balance of evidence says they'll be kind of crappy. Meanwhile making long range EM rounds with explosive fillers will 1) require fairly large shells and 2) reduces the appeal of having the guns, in terms of having totally inert or nearly so ammunition. So its kind of a tough situation.
But that's how the technological arms race works. No one technology exists in a vacuum, and typically a technology that allows one thing also allows countermeasures. Prime example, the miniaturization tech allowing us to make all these guided shells at a sane cost is also letting us build very small interceptor missiles to shoot them down with. And that's all probably my real point. Don't fawn over any one technology in a vacuum. The point isn't to build weapons, unless perhaps you are Hitler and even that fool wasn't totally a fool on this, the point is to create an effect on a target for a purpose, and to stop the enemy from doing the same. Most information on weapons these days is released by corporate marketing divisions whom have no need or desire to elaborate on this, but the militarily services making the end decisions on money have a very strong one, but they also tend to prefer not to make 100% of the logic and thinking public for security reasons.
"This cult of special forces is as sensible as to form a Royal Corps of Tree Climbers and say that no soldier who does not wear its green hat with a bunch of oak leaves stuck in it should be expected to climb a tree"
— Field Marshal William Slim 1956
