Raillguns are nice & all but...
why hasn't anyone built a nice coil gun up to the same specs. This is something I have always wanted to do. And it seems simple enough.
The US Navy has handed out a $12m contract to Texan academics to carry out research into electromagnetic hypervelocity railguns. According to the Pentagon contracts feed: The Institute of Advanced Technology at the University of Texas, Austin [will] perform railgun assessment including laboratory testing and scalability …
It's not like the US Navy today has more to do than blow away Somali pirates from time to time or maybe deliver force packages onto goats, women and children through their own air arm for in support of their own infantry arm fighting against random sand denizens.
Yes, a railgun will come in handy ...
Coil guns, or as their sometimes called Gauss Rifles, are harder to build, and less efficient than a rail gun. They both use electromagnetic forces to propel the projectile, but the need to switch magnetic coils on and off at incredibly high rates means a large scale high velocity gauss rifle is essentially impossible. To start with, a electromagnetic coil is naturally resistant to state change, so it's got a delay while it powers up and another delay while it powers down, plus a greater delay if you switch the polarity as that's essentially a power down coupled with a power up. To achieve the kinds of velocities you can with a railgun using a gauss rifle you'd need to switch the coils at essentially the velocity of the projectile. Even assuming you could manage to get the coils to switch fast enough, if you think it's difficult preventing the rails in a railgun from ripping themselves apart, just try to manage the same feat on a whole set of coils (hint, coils tend to deform when you put large pulses of electricity through them).
Now change the scale and adapt a similar concept to replace Vulcan-Phalanx or Goalkeeper?
An electrically powered jumbo nail gun, capable of literally throwing a wall of metal at incoming missiles and any stupid jet jockey or egg beater driver who gets close enough. Wouldn't be too healthy for any small boats who want to get up close and personal either!
Railguns are intrinsically self-destructive. The reason for this is seen in the old, school pastime of flicking a wooden rule on a desk and sliding it in. The reverberations get worse towards the tip and alignment is lost. Gun barrels actually do the same but are much more controllable.
Putting what is effectively a big longbow on a ship is just plain silly due to the sea's motion. Lobbing shells used to make sense before the advent of missiles as they are area effect weapons (big boom.) A near miss would do the job well enough.
Trying to bullseye a target with a tiny ballistic slug (no boom) while the ship is rising and falling on a swell is too impractical.
Imagine how many slug holes you would need to put into a bombardment in order to destroy the target.
Typical negativity Lewis, and quite misplaced as it happens.
Not only are these railguns delightfully green in there use of clean, quiet electricity instead of noisy, loud explosives, if one doesn't slavishly follow the doctrine of approaching one's opponent once battle is joined but adopts a more prudent retrograde course, one can clearly see that the motive force for the vessel while firing is derived handily from the recoil of the weapon itself, leaving the output of the turbines fully available for high-speed munitions deployment.
Railguns nice, if you can get them to work and keep working.
Personally, I prefer mass drivers and orbital bombardment as we can just about do them with our current tech (Given a bit of future tech, I prefer SIN guns, APWs, CTDs or even just the mis-application of a infinite improbability drive, but we've a way to go yet)
@ mark : Gyro gimbals. sea swell on something the size of the nimitz is pretty negligible, as for vertical rise and fall, I believe naval artillery accounts for that on a per-shot timed basis.
@ stevie : if you can move a nimitz-sized vessel (or hell, even a good ole regular battleship) with the recoil from this cannon, I'll give you a cookie. Oh, by the way, its in water, too.
@ mike : yeah, coilguns are an utter breeze to both assemble and understand, right? Only they deform under high load. and you cant cycle the coils fast enough.
the most practical use for something like this that I can think of, considering the guns inherent necessary downtime-for-refit would be a sudden-emergency strike thing, where a reasonable large target needs to come under fire within a very specific time frame, with the option for an abort; i.e. Our OP went wrong, please smash this mountain now. (conventional ship ballistics and even cruise missiles have a massive to-target time compared to hypervelocity projectiles)
frankly im inclined to believe that this is just a step-one in research process, where rail technology could be extended to existing ballistics, essentially accelerating already conventional rounds to ^^velocity, which is what the video looks like : some kind of cut-down rocket/exposion-plus-sled delivery vehiclewith a good pulse tacked on the end.
Very fun stuff to play with.
Just for those who didn't realise yet, when you 'fire' a coil you get an internal (to the coil) electrical recoil-type reaction which wants to come out as soon as you remove the power from the coil.
You can capture that reaction and stuff it back directly into another coil, or into a secondary capacitor bank, etc.
In doing so you can reduce recycle times in the coils and the capacitor banks.
Create a design with two or more coils on the barrel and at least two capacitor banks, and you'll get your rapid fire white-hot metal shower cannon of doom.
Then all that is left is set up such a thing in a dual or quad cannon setup for mass-driver like performance and some proper liquid cooling, and you'll be set for WW3.
It's really not that hard to design and build, just takes a little time and good materials.
"Putting what is effectively a big longbow on a ship is just plain silly due to the sea's motion. Lobbing shells used to make sense before the advent of missiles as they are area effect weapons (big boom.) A near miss would do the job well enough."
Even HE naval shell are not effective in nearmisses (unless its a very close nearmiss, when some hull panels may be weakened). HE rounds were used to destroy the target's external fittings, optics and personnel and to start fires. They were never used as area weapons. Ever since the end of the 19th century, with the advent of ironclads and armoured ships, the main anti-ship projectile was armour-piercing. I think you will accept that these are ONLY effective when hitting directly.
To compensate for the roll of the ship is a trivial matter. Nowadays all naval guns are giro-stabilised (not counting small caliber manually operated guns and machine-guns). But even in WW1 time the ship guns were fired electically under director fire and used simple circuits that would only fire the guns when the ship is on level keel. So when the officer in charge or firing a salvo squeezed the trigger, the system will wait until the ship rights itself between two rolls and only then fire the guns.
By far the greater problem was to actually determine in which direction and at what angle to shoot as that involved calculating and predicting positions of 3 moving objects (the target, the projectile and your own vessel) at different moments in time. All sorts of complex mechanical computers (plot tables) were used with differing degree of success + optical stereo telescopes (directors) + observation of the fall of shot (as the feedback to correct plotting errors).
The problem with lobbing smart ammunition out of a railgun is the massive EMF pulse of the firing would brick the smart bits in the missile faster than an Apple iBone update. A simple olde stylee explosive shell would work as long as it was a plain mechanical fuse and the shell design was strong enough to resist the stress of launching without tearing itself to bits. Projecting a slipstreamed lump of a single ferrous material such as steel would be fine, as long as the surface was supersmooth enough not to start melting under air friction, which would seriously screw with accuracy.
The next problem I see is the curvature of the Earth. If you pop off a shell at hypersonic speeds then you have to be careful about elevation or the projectile could rise high enough above the horizon to pass into the stratosphere, and then it could skip along the top of the stratosphere like a pebble bouncing on the surface of a lake, until it had expended enough energy to fall back through again. The problem is that bouncing is very dependent on the conditions of the local stratosphere, making it hard to predict when the shell would re-enter. You would really need a smart shell with some form of steering to complete such a task, probably guided by GPS, only GPS won't work through EMF shielding.
And then we get to the simplest problem of all - the greater the range of the shot, the greater the potential error. Every calculation and mechanical system uses little carry bits or approximations, depends on estimations due to such factors as atmospheric density variations due to local temperature, or just wind patterns between the launch point and the target. Is the barrel elevated to EXACTLY 10.23 degrees or is it actually at 10.24 degrees? Same goes for traverse. The longer the range the larger the problem of all those little variations, which makes the likelyhood of shots over several hundreds of miles unlikley unless you're aiming with an area affect weapon like a nuke shell, or you manage to produce an incredibly shielded smart shell that can somehow still pick up weak GPS signals for guidance. So it is much more likely the hypervelocity shots will be to reasonably normal ranges of the old battleship guns or modern artillery, only with the much faster flight time meaning the enemy has SFA chance of evading or intercepting your shot.
Of course, if what you're actualy building is something to launch objects through the stratosphere into space then you don't really care about accuracy too much, you just need a large amount of sheilding you can jettison once you escape the atmosphere. Then your satellite kill-bot or minispysat can switch on and settle into whatever orbit you require.
When any weapon story comes up all the armchair experts come out and fill the comments section with noise.
Let's leave the naval analysis to Lewis shall we? Even if it wasn't his speciality at least he has some knowledge.
Also, please refrain from making noise unless you are a mechanical engineer or have won prizes with your ballistics expertise.
Vlad, I had to laugh that you think you can sink a ship with a/p rounds. Even more so that you think the shooters know what bit of the target they will hit.
As I recall, the Germans developed a canon in WWII that achieved amazingly high muzzel velocities. Saddam Hussein built one, designed to hit Israel and capable of putting a slug into low Earth orbit (as I recall- could be wrong).
These guns involved a shed load of plumbing and were extremely ungainly, but could easily be fitted to a ship, and wouldn't rely on any dodgy new technology.
So Lewis is the only person in the world who could possibly make a reasoned comment on anything Military?
From memory, about half of the male population of the UK has been, at some time, a member of either the regular armed forces, the TA, or carried out National Service.
Rather fewer have degrees in relevant engineering disciplines, but that doesn't mean we don't exist.
I have edited literally several Wiki pages, so therefore count myself as a Published Author on every subject under the sun. In what way, precisely does Lewis out-rank me?
Quick note about aforementioned armour belts. The reason they are referred to as 'torpedo belts' is because, shockingly enough, they were designed primarily with torpedoes in mind, as it is extremely difficult to hit an opposing vessel at or below the waterline with a ballistic projectile, and because self propelled underwater munitions were the usual method of sending the foe under the waves. AP rounds would have the benefit of piercing the casements and decks, and if luck was with you, exploding the primary magazine, which is just as effective as sinking the vessel outright, and more spectacular to behold.
I'm not too taken with the railgun idea. There is just some intrinsic awesomeness in the roar of 16in diameter rifles.
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