back to article US Navy to test fire electric hypercannon

The US Navy will astound the world tomorrow by test-firing a radical new weapon system at an unprecedented power level. The new piece of war-tech on trial is that old sci-fi favourite, an electromagnetic railgun. According to the Office of Naval Research, which is in charge of the project, the electric cannon will deliver over …

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  1. matt

    ooo

    You tube video please!

  2. Paul Murray
    Thumb Down

    Didn't these guys get the memo?

    Didn't these guys get the memo? Warfare ("big war") is dead.

  3. Hate2Register

    You forgot to mention..

    You forget that it's actually a 32 mega-joule device. The 10 mega-joule effort was from General Atomics. Oh and you didn't mention Bae as the supplier..

    I wonder if UK forces will get equiped with similar electric guns, although ours will probably stop the electronics from working, and the vehicles housing them may explode in sparks.

  4. Hate2Register

    @Paul Murray

    I'm not sure warfare ever goes completely out of fashion. You're welcome to hope, though.

  5. Anonymous Coward
    Thumb Up

    @Paul Murray

    That's what they say after every big war, right up until the start of the next one ....

  6. Anonymous Coward
    Boffin

    That Would Be Good

    Hopefully the boffins will sort out the issues and get this one into service. It would eliminate a lot of current headaches for military mariners, especially transport/storage of those pesky propellant cartridges.

    And anything that 'tips the balance' back toward *real* fighting ships, away from aircraft, missiles and over-inflated floating runways, would be very welcome indeed. Now if we could do something similar underwater ......

    "A willing foe and sea room"!

  7. Joel

    (untitled)

    Youtube yet?

  8. dervheid

    Faster then a speeding bullet...

    but not much use if you can only fire off a few rounds before the gun collapses. More time required on the drawing board, methinks.

  9. John Marsh

    Shore Bombardment (?)

    If the projectile is still travelling at Mach 5 when it hits the target, doesn't that mean the projectile has a virtually flat trajectory? If-so, it'll be of limited use in shore-bombardment where targets tend to be in-land, behind buildings, forests, hills, etc.

    You could drop the rail-gun's muzzle-velocity, but you also reduce the impact's kinetic-energy - In this case isn't "old" HE ammunition better?

  10. Anonymous Coward
    Anonymous Coward

    @Hate2register

    We've already got it, we're just waiting for EDS to sort out the fire control systems as the gunners will be identified using biometric ID cards.

  11. Derek Hellam
    Gates Horns

    Just how effective?

    If this "gun" fires projectiles at such high velocities mach7? and the projectiles do not have explosive warheads, then I'd have thought that the damage they could do to other large surface vessels would be minimal. You need to punch an lot of holes in a ship to make it sink, as any U-boat commander knows (Deck gun action). Of course damage to smaller objects like aircraft would be critical. I also question the wisdom of having this as a primary weapons system, reliant upon the same source of energy for propulsion, all controlled by windows for warships.

  12. Pete

    ...back in favour of surface craft - hardly!

    OK it might just be possible to shoot one or two rounds, depending on the recharge rate, at an attacking aircraft with one of these thingys, but they won't be much good against submarines. As the old (submariners) saying goes:

    "there are two types of naval vessel - submarines and targets"

    Oh yes, what happens to all the loose metal on a ship when it fires it's rail gun, will there be more friendly casualties from flying spanners etc. than the enemy will suffer?

  13. Anonymous Coward
    Anonymous Coward

    Ye canna change the laws o physics Jim !

    I wonder how long a barrel is needed to impart mega joules to a pellet via EM attraction alone...

    You need a pellet tight enough so it is accurate but loose enough so it doesn't friction weld to the barrel.....

    We talking smoothbore or rifle here?

    Errrm they do know that the sea "moves a bit" don't they ? Precision ballistics at sea?

    Oh just put it on the pile with the others Lewis.......

    I'll mention it next time I'm at the gun club and we'll all have a good chuckle..

  14. Peter D'Hoye
    Boffin

    no way

    "They could take out a single vehicle from far out at sea, perhaps"

    From a ship bumping up/down the whole time? No way...

  15. Anonymous Coward
    Black Helicopters

    200 Mile Range

    And once you put them into low-earth-orbit everywhere is within range; game on!

  16. James O'Brien
    Joke

    They might also be good for shooting down fast-moving flying things.

    *snickers* fast-moving flying things.

    CLASSIC!!

  17. Steve
    Flame

    idle speculation

    Surely most of that article is idle speculation.

    Rail gun slugs that steer themselves in flight? Not even in most sci fi, the whole point of the slug is that it's just a lump of metal.

    Even at mach 7 this will be of no use for shooting down planes, unless they are only 50 feet from the barrel. The ballistics computation might be fairly straight forward, but you'd only ever hit a plane that was flying on a steady trajectory.

    Mach 7 is 2.3 Km/s, so for a target that's 15 km distance it will take the slug 6.3 unguided seconds to get there, any course or speed change in that time will cause a miss, and planes can engage ships from much further away than that.

    Rail guns may well replace most of the projectile weapons on a warship, but that won't really alter the fact that air power decides the winner.

  18. heystoopid
    Alien

    Hmm

    Hmmm , what would Gerald Bull a total walking encyclopaedia of everything known about long range artillery tubes and shell flight dynamics from a to z , now say today about this rail gun concept if he were alive and had not been assassinated back in 1990 ?

  19. Simon
    Black Helicopters

    Something similar underwater

    Supercavitating torpedoes and blue laser LIDAR/LADAR?

    At Mach 7 or 8 and 200 miles, this could be a workable ABM system.

    /black helicopter because I want one of those too.

  20. Simon Neill

    I have a better idea

    Ah, but this is just the begining. Once we crack it as a weapon all we need to do is make a bigger one and then we can fire stuff into space. Like new parts for the ISS. Or perhaps we can use it to get rid of all that pesky uranium we have left over.

    Failing that we could build a REALLY big one and get rid of the moon so that no-one can build a "tractor beam" and pull it into the ice caps flooding the earth....

    one coat with extra long sleeves tied behind the back please.

  21. Tony Barnes

    How far/fast??

    So, 200 miles after being fire, the munition has only scrubbed ~600mph (no idea what angle this thing is going at, so altitudes will change speed greatly) from it's 2380mph start point....??

    That seems like a very slippery round to me... maybe someone knows some numbers on normal bullets, that'd be interesting...

  22. Matt

    Not so sure

    More accurate strikes... hmmmmm. Well it'd be an improvement if the yanks correctly identified the continent, let alone a particular vehicle :-)

    I'm not sure about surgical strikes though. Even a those speeds my car would have moved before they got the "shot" arrived and I may have stopped at lights if they try and predict my movement. Might also prove problematic if I'm not in line of sight. Or are you saying they can be guided? In which case they may be prone to jamming and heat problems.

    On the subject of surgical strikes, wouldn't something hitting a car at Mach 5 be likely to pass through and hit other objects or spread pieces of car at high velocity? Obviously if the car was a Toyota pick-up you'd be OK but for normal cars it could be a problem.

    On a more serious note. Isn't one of the problems of modern warfare that the country being attacked feels they can't compete with "cowards" attacking them from afar, so they resort to suicide bombing and so on? Just a thought......

  23. graham crocker

    Clarification Factoid

    At the risk of sounding too much like a train-spotter, it's worth mentioning that 1 megajoule is 1 megawatt for 1 second.

    Once this is clear, the whole article is much easier to understand - For example, the 100 megawatts to provide 64 megajoule is actually a burst of energy lasting roughly half a second.

  24. Louis Cowan

    Re: Shore Bombardment (?)

    John, you're assuming the ship will simply be "afloat". Did you see the article on the chinese wind-farm planting ship with six legs? Imagine those legs being 500m tall...

    Sounding more and more like War of the Worlds, eh? :)

  25. Billy
    Thumb Up

    @That Would Be Good/AC

    Totally off subject, but......

    Isn't "A willing foe and sea room" for Fridays? I thought Thursdays was "A bloody war or a sickly season", though it's been a while, so I could be wrong.

    Yours Aye!

  26. Rusty Warrior
    Thumb Up

    I've got this mole

    What would Jasper do with one of these instead of a shotgun and a torch? Perhaps a bloody big hole where Birmingham used to be?

    I have to have one of these if only to get rid of the damn neighbours cats who keep crapping in the flower beds!

  27. Paul
    Coat

    "A long shot, in other words"

    Coat, door, now...

    Also, @ Pete

    "Oh yes, what happens to all the loose metal on a ship when it fires it's rail gun, will there be more friendly casualties from flying spanners etc. than the enemy will suffer?" Most of the stuff on ships is not made of ferous materials. It tends to rust dontcya know. (I know some things are, but not spanners etc).

  28. Anonymous Coward
    Black Helicopters

    @Hate2Register

    re a British rail gun.

    a couple of yrs ago, I did some work on a computer system related to a Dera/Q-TipEx/dstl project.

    computer's user/owner had just returned from a field trip to a test site somewhere in the UK, and described the test firing of something which sounded remarkably like a rail-gun (the person in question was doing other research, but got invited to see this demo - said, there was a lot of Brass and suits there, both UK and foreign )

    suppose you can treat it as a FOAF story, of sorts.

    Besides, a British Rail gun? (cue obligatory jokes about speed of projectiles, arriving late on target, failure to fire due to leaves on line etc etc..)

    Black Helicopter because.. I'm sure the Whirlypig that was hovering outside my window t'other night was black.

  29. This post has been deleted by its author

  30. Vladimir Plouzhnikov

    Mark_T

    "You need a pellet tight enough so it is accurate but loose enough so it doesn't friction weld to the barrel.....

    We talking smoothbore or rifle here?"

    Oh, c'mon - surely there is no barrel - it's called a railgun for a reason.

    "Errrm they do know that the sea "moves a bit" don't they ? Precision ballistics at sea?"

    Since the time of the HMS Dreadnought ship batteries fired sunchronised with the ship roll. And nowadays the girostabilised platforms are not unheard of either.

    And about the shore bombardment: the Mach5 projectile will deliver the necessary shock and awe with its sonic boom. Joke.

  31. David Mayne
    Paris Hilton

    @ Graham Crocker

    Yeah, but to get the slug to move from a dead stop to mach7 (2.3 Km/s as is pointed out above) in half a second you'd need a barrel 575m long.... (if I can remember my old mechanics lessons....)

    I should imagine you'd need to get that down to more like 10 or 15 m as a maximum, and that's going to be a very very short pulse.... Not so easy

    Why Paris? Why not :-D

  32. Oscar

    Re: Ye canna change the laws o physics Jim

    I thought the whole point of a rail gun was that the projectile is suspended in the EM field and as such never actually touches the edge of the barrel (which is just a set of electric coils). So not sure where the bore of the barrel comes into it ...

  33. kempsy
    Thumb Up

    Gun accuracy at sea

    With regard to the gun supposedly bobbing up and down while at sea I can't see that being too much of a problem.

    Firstly big ships are reasonably stable in all but the roughest weather, although I agree there will still be some movement.

    Secondly, if BAE are making it they could just mount it on a gyroscopically stablised platform, much like the one used for the main gun on the Challenger 2 tank.

    If they resolve the issues of the barrel's longevity and the rate of fire I suspect it will be quite an effective weapon. Certainly I would not like to think of a hail of Mach 5 rounds heading towards me!

  34. Anonymous Coward
    Anonymous Coward

    just imagine

    Just imagine trying to convince the common man in 1944 that there was a bomb that could vapourise vast chunks of a city.

    Imagine if you will trying to convince a man with his musket that one day his bullets would be self contained with their own proppellant.

    Imagine trying to convince a Halberdeer that he was soon to be made redundent by a man with a musket.

    Imagine trying to tell a guy in the 1950's that we'd have super computers, mono trains and hydrogen bombs.

    I think in all instances they'd think you were start raving mad.

    @Steve, I didn't see anything about projectiles steering themselves, the reference to steering is more about the projectilles flying in a predictable course.

  35. Anonymous Coward
    Flame

    @AC

    "That's what they say after every big war, right up until the start of the next one ...."

    That's probably WHY there's a next one. If mililtary spending was upheld at about current levels after WWI there is good chance that WWII would not have happened.

  36. Anonymous Coward
    Anonymous Coward

    Clearly being developed for other uses

    I don't think it's meant for the Navy to be honest, although I like the idea of using a jack-up barge style ship to mount it on, giving it a stable platform but I imagine those things take quite a while to get in a suitable position and to actually lower the legs, and currently, models only have a leg reach of 48mtrs down meaning they'd probably have to be relatively close to the shore, rendering any sea-based advantage useless as it would be something of a sitting duck whilst it's like that.

    Instead, I think it could be being developed for space (low-orbit?) use in major risk situations where you'd only need a handful of shots to do the job (maybe shooting down enemy ICBMs etc, I'm sure you guys can think up other space bound applications), it has a minimum range of 200mls, space would offer a pretty damn steady and safe operational platform, and it could be positioned above anywhere in the world in relatively little time, plus it would solve the problem of trees getting in the way etc.

    So, what do we think?

  37. Anonymous Coward
    Boffin

    That Would Be Good .... Again

    @Billy

    Yeah, but "A bloody war and a sickly season" was always my least favourite.

    Also:

    Stabilization of weapons on naval vessels is quite advanced - they're pretty accurate, actually, as are the control systems used to guide them. Don't you folk remember all those WWII movies where naval guns where hand cranked yet still reasonably accurate in the hands of trained gunners? Technology has come a long way since then.

    Although the article doesn't expand on the point, I think the idea behind the rail gun, at least for long range shots, involves a GPS-guided projectile with steering fins. The material that gets zapped by 100MW would just be the propellant, with some sort of "wadding" between the propellant and projectile. this could actually be more gentle than the "big bang" used in conventional propellants. For short range AA fire, there'd be no need for a separate projectile if a slightly different type of fusable 'shot' were used. Of course, I may not know what I'm talking about, so I'll grab my coat just in case.

  38. Anonymous Coward
    Happy

    Got Railgun Envy? Build Your Own!

    Full description and parts list at http://www.powerlabs.org/railgun2.htm

  39. Matt Bryant Silver badge
    Pirate

    Weight, spikes and fire control?

    With all the work that's needed to make the things last a few shots, let alone the power needed to drive it, won't we have practical naval laser cannon first? And forget the spanners, what happens to all that sensitive electronic kit onboard when you start pumping out sharp EM spikes with each shot?

    200km or 500m, there is still the same old problem of finding the target and then aiming at it before it can clobber you, so with the current generation of radar and fire-control systems I'd say aircraft still have a fair chance with long-range sea-skimming missiles. Longterm, the only real defence against over-the-horizon sea-skimming missiles is to be able to spot and track them earlier, and that would probably need some form of automated sattelite system that can look down and detect incoming aircraft or missiles by IR, and either aim the ship's weapons remotely or feed the data into the ship's fire control system to allow very quick engagement. In theory, such a system could even detect railgun rounds at mach7 (bet they get hot!) and provide sufficient warning for the target ship to launch counter-fire.

    Gotta go with the skull 'n' crossies..... ;)

  40. Nick Drew

    'surgical strikes'

    "They could take out a single vehicle from far out at sea, perhaps, rather than pulverising a whole area like present-day cruise missiles"

    yeah, in much the same way that a plane currently could take out a single [enemy] vehicle from pretty close up, but generally tends to hit a hospital a few miles away instead.

    As for 'pulverising a whole area' - yes, if you take 'area' to mean '3 countries or so' [ref: the American cruise missiles that hit Syria when supposed to be targetting Iraq...]

  41. Richard Gadsden
    Thumb Down

    Not in space

    There isn't a load of recoil on a railgun if you're on a reasonably stable platform, like a tank or a ship, but that's because the energy is supplied continuously during the acceleration at a steady rate. In space, it's the same amount of delta-V, which is still more than enough to knock your satellite out of orbit.

    Not a good idea.

  42. Anonymous Coward
    IT Angle

    I wonder

    ... how much more we're going to have to antagonize Iran before we have a suitable target for this device.

  43. Anonymous Coward
    Anonymous Coward

    rail erosion

    from what i remember, the power requirements for these are so high, that every shot you fire vapourises part of the rails from electrical arcing. One shot from a railgun isn't that impressive, any university physics student could cobble one together in their spare time.

    The problem is firing several shots in a row without having to rebuild the gun, which is quite a handy feature for a weapon of war.

  44. Dave
    Paris Hilton

    many comments missing the point...

    don't worry about ship motion

    don't put the ship on stilts

    don't steer the flippin' slug

    map the wind speeds and directions between 'here' and 'there' up to 20 or 30 kilofeet

    do lots of sums v quickly in a machine called a compooper (or summink like that)

    shoot the slug on a high paraboloid trajectory with the initial aiming angles compooped to account for all the variables

    PH avatar - 'cos she could have told you this!

  45. Ross

    @Richard Gadsen

    [There isn't a load of recoil on a railgun if you're on a reasonably stable platform]

    There isn't any recoil regardless of platform. Recoil is a result of the gases expanding pushing the projectile forward but also pushing the rather heavier gun backwards.

    In a rail gun the "recoil" force is applied perpendicular to the direction of travel of the projectile, which explains why rail guns tend to bend/explode horizontally a lot :o)

    Until they find some materials that are very conductive, extremely heat resistant and non-magnetic proper rail guns aren't going to appear anytime soon. If they want to use high velocity non-HE rounds for precision strikes they'd be better off filling a satellite full of large ceramic "bullets" and dropping them from space ICBM style. The kinetic energy they would deliver would dwarf a few kilograms of copper shifting at mach 5. It also has the advantage that it's all old school tech - no need to invent anything.

  46. Anonymous Coward
    Thumb Up

    So Cool

    We need this, we should build this, duno why exactly but we should. Erm perhaps we could then civilianise the tech for some sort of space launchy thing for non squishy cargo or make mass drivers for passing stuff around the solar system like some cosmic game of catch. Good way of getting stuff to the moon and back when you have set up the infrastructure. Just dont stand in front of the earth when your catching, be a bummer if you missed.

    We should also make em smaller as well, fit them to tanks, the tankies would love the idea of driving around sat next to a few tonnes of propelant and warheads. Man portable ones would also be cool but then we would get the phrase "I'm Out!" replied by "Of What Ammo or Batteries?" Infantry bunnies may or may not be happy depending on the weight saving.

    I demand Future Weapons and other Military Pr0n show me you tube video!

  47. Steve Charlton
    Joke

    Or how about...

    I think they should produce a Railway Gun* instead! Imagine it. An engine, 10 coaches and a guards van all screaming through the air. It would be a sight to see.

    * - from Usenet, long ago.

  48. JeffyPooh Silver badge

    To sink a ship...

    Don't you need to punch at least one hole BELOW the waterline?

  49. Chronos Silver badge
    Coat

    Velocitas eradico?

    Methinks someone in the upper echelons has been reading far too much J. K. Rowling. You can just picture them in weps in the classic spellcasting pose...

    "Um, sir, nothing's happening!"

    "You gotta believe, soldier!"

    I know, I'm going.

  50. Anonymous Coward
    Anonymous Coward

    Ballistics lesson

    For those ballistics experts who think railguns don't have moving, touching parts.. http://en.wikipedia.org/wiki/Railgun - Apologies for using wiki.

    A railgun pellet IS the barrel albeit twin bore. It slides on one or two rails. So we have a pellet looking like a mini rocket ship with two holes in the bottom. They damage the rails as they leave.

    So basically a railgun is a bow "firing" high-speed arrows. It will recoil as Newton's third still applies. A small mass given a large acceleration will recoil like a large mass given a small acceleration.

    No, another one for Scotty's "cool but impractical" file.

  51. Anonymous Coward
    Anonymous Coward

    @@AC

    Most Nations didn't increase their military post WW1, which is why when Hitler turned up with his tanks, bombers and submarines there was such an awful mess.

  52. Hate2Register

    @Anonymouse Coward

    If you think about it the barrel problems are like those faced by machine guns in WW1 (wot with overheating, bending etc). Most boffins seem to like either a superconducting barrel, or a supercooled one.

    I'd like my railgun to have both. And rotating cyclic barrels. A gatling railgun. That's for me. Thaty way average wear-per-shot is reduced.

    They should pay me for doing their job, really.

  53. Anonymous Coward
    Anonymous Coward

    @graham crocker

    yes half a second at mach 7 is howmany KM? that is a long barrel...

  54. Mike

    Good defense against anti-ship missiles

    Imagine you're trying to shoot something heading toward your capital ship at extremely high speeds. That missile has a nuclear warhead and is flying as close to the sea as it can.

    Acquiring it is not so hard -- provided you've got eyes high enough in the sky. But you have a very short time to hit it once its on the horizon.

    So, the missile is acquired from the eyes in the sky. The ship pauses for a second to charge the capacitors for the rail gun. A firing solution is plotted, the gun is aimed. The missile comes over the horizon, and immediately the railgun is fired.

    Seems like that might actually work.

  55. Graham Bartlett

    @Sinking ships and downing planes

    Jeff, to sink a ship you *do* need a hole below the waterline. But you don't have to hit it there. Drop a shell, bomb or missile on the topside of a ship, and the hole will go all the way down.

    Re Steve's plane-shooting, steerable fins on the slug literally isn't rocket science - the slug would *mostly* be a lump of metal, just with a small control module to tweak the fins. With only 6.3s for their electronics to detect it and them to take evasive action, there's a chance a pilot wouldn't even have time to react. And even if they did take evasive action, the control module would be perfectly capable of watching where they're going and guiding the slug onto it, since the slug would be approaching at ten times their speed.

  56. Anonymous Coward
    Flame

    I dont care!

    Right listen here naysayers!

    I don't care about recoil despite the fact that its on a ship and its less of an issue, i don't care that the barrel length thing and i really don't care about heating.

    I demand military pork be spent on this, if you have to beat up some nerd "law of physics" types until they change their dam laws then so be it.

    This is too cool not to spend money on and i couldn't care if it doesn't work that well, just you remember where blutack came from!

    Set Hypervelocity slugs to......erm....dismember?

    They got em or TV, must be possible!

  57. jimbarter
    Thumb Up

    The Mk 1

    they already tested it...

    <a href="http://www.youtube.com/watch?v=y54aLcC3G74">http://www.youtube.com/watch?v=y54aLcC3G74</a>

    ...and I want one.

  58. Mike Moyle Silver badge

    A couple of thoughts...

    1 - Instead of a "slug" shot, could a canister containing a number of flechettes be fired? Hypersonic shot-shells in a cone formation actually sound feasible against airborne targets, as well as against vessels and battle-area targets.

    2 - "Velocitas Eradico"... "Speed Kills"?

  59. Rick Brasche
    Go

    niiice

    armor piercing HV weapon that not only doesn't need DU to punch a hole thru anything manmade, but also works better with lighter, less toxic materials. Better for the environment, no toxic propellants..it's "Green"! for example, Barros of Powerlabs uses aluminum slugs for his test systems.

    Accuracy problems? The USS Missouri could repeatedly lob 1 ton shells from sea to shore with GPS confirmed accuracy within yards. Better and much cheaper than cruise missiles. Plus, it's real hard to shoot down an artillery shell. Not as hard to hit it, but to destroy something designed to survive the hostile launch environment of a cannon? Lots more work.

    What dingbats say there's no recoil? It may have a different "profile" as the device is pulsed, but if you watch test vids of even small kilowatt jobs then you'll see there's significant "kick". One of the first challenges the Navy's test team has is to develop a sufficient mounting system-this test cannon breaks it's mountings even more than it destroys barrels.

    And for the amount of energy this thing delivers to target..if you put a megajoule in, and only lose a few kph to wind resistance, that means you get almost a megajoule out. Put in 30 or so, expect at minimum half that to make it to target.

    What's the conversion for megajoules to tons TNT? Or in calories heat? Kinetic to thermal energy should be pretty easy to calculate.

    Next up, hollowpoint hypervelocity KE rounds...sounds like a football thing.."HHYKE"!

    "We don't think we're God, we just borrowed his "Smite!" button."

  60. Dave Jones Silver badge
    Thumb Down

    It's not much to write home about, actually

    1 kg of TNT is equivalent to about 4.2 megajoules of energy. Thus this shot is up in the 3 to 4 kg TNT range, which is about the same as a large artillery shell.

    Star Wars it isn't.

  61. Nile Heffernan

    How does this compare with TNT?

    A ton of TNT releases 4.184 megajoules.

    So a 32-MJ launch is nominally 7.65 tons of TNT and it's all 'warhead' if the projectile breaks up on impact and imparts all the energy to the target instead of leaving a neat hole through it.

    The technical challenges of manufacturing a railgun are formiddable, but it's well worth remembering that all weapons technologies - including aircraft and cannon - begin with cranky and unreliable devices that stretch the existing materials technology just a little *too* far before gradual improvements make them reliable and effective.

  62. Joe Zeff

    Shore bombardment

    Having a flat trajectory isn't a problem; you just elevate the barrel. I know, because I was on the Gun Line in Tonkin Gulf back in '72 doing indirect fire to the backside of various mountains. In one case, to the backside of the second mountain back. It's not rocket science, people, it's ballistics, a well-known, mature section of physics. And, I can assure you that the ship's motion isn't a problem either because the mount would be gyrostabilized just like gun mounts have been for decades.

  63. Mother Hubbard

    Space version was conceived too

    For those of you having the revolutionary and unique idea to put this thing into orbit (and there's some Newtonian physics that you guys are ignoring when you think of explosive projectiles in space), that was a Regan-era Star Wars brain-child version of this already - aka "Rods from Gods";

    HOW DO THE RODS WORK? The system would likely be comprised of tandem satellites, one serving as a communications platform, the other carrying an indeterminate number of tungsten rods, each up to 20 feet in length and 1 foot in diameter. These rods, which could be dropped on a target with as little as 15 minutes notice, would enter the Earth's atmosphere at a speed of 36,000 feet per second--about as fast as a meteor. Upon impact, the rod would be capable of producing all the effects of an earth-penetrating nuclear weapon, without any of the radioactive fallout. This type of weapon relies on kinetic energy, rather than high-explosives, to generate destructive force (as do smart spears, another weapon system which would rely on tungsten rods, though not space-based).

    http://www.globalsecurity.org/org/news/2005/050608-gods-rods.htm

  64. Dave Jones Silver badge
    Boffin

    A thousand off

    Sorry, beg to disagree. I tonne is about 4.2 Gigajoules, or 4200 megajoules. 1 megatonne is about 4.2 Terajoules. For comparison, ordinary everyday bullets have energies in the kilojoule range.

    This rail gun is basically an electric artillery piece. It's actually less efficient than a conventional cannon, but on the other hand you can accumulate energy over a long period and let it go in a fraction of a second. A cannon, being a heat engine, wastes at least 60% of the input energy. If you generate your electricity from a heat engine, you lose more due to conversion.

    The real attraction of rail guns is for very long accelerators for shooting to orbit, or at least to sub-orbital speed so you don't need as much rocket. But those won't fit on ships.

  65. MacroRodent Silver badge
    Boffin

    Paging Mr Newton...

    "In a rail gun the "recoil" force is applied perpendicular to the direction of travel of the projectile, which explains why rail guns tend to bend/explode horizontally a lot :o)"

    Any kind of gun which shoots a projectile in one direction will always have recoil in the opposite direction, unless it also shoots a compensating amount of mass*acceleration in the opposite direction (like bazookas do). Isaac Newton says so: F = m*a

  66. alex

    Video clip of this railgun

    theres a vid of it in action on liveleak.

    http://www.liveleak.com/view?i=86a_1201817945

  67. Anonymous Coward
    Thumb Up

    @ Dave Jones....and the perfect scenario

    ...would be to to blast errant spy sats into more "burn up" friendly chunks!

    http://www.theregister.co.uk/2008/01/30/stateside_spy_sat_splat/

    ...but can they build it by next week?

  68. Ian Johnston
    Boffin

    Contact!

    Two rails. Slug between them and touching both. Sodding enormous current pulse up one rail, through the slug, down the other.

    Current in rails => big magnetic field/flux between them.

    Current in slug x (that's a vector cross product, folks) magnetic flux => big force on slug

  69. Anonymous Coward
    Pirate

    Double edged sword

    If BAE are selling this, then be prepared for dictators, military juntas, terrorists and so forth to be sporting these - all over the world.

    Especially if it eventually becomes cheap to make (if not cheap to power, although I'm sure that countries without access to their own oil but which have other energy resources will get around this somehow).

  70. Rodger Young

    A few little-known facts on railguns

    1) "I wonder how long a barrel is needed to impart mega joules to a pellet via EM attraction alone... "

    Los Alamos National Laboratories has a railgun tube small enough to fit inside/on the gun turret on an M109 SP artillery piece. Power provided by unholy large capacity capacitors charged by onboard electric generator.

    2) "You need a pellet tight enough so it is accurate but loose enough so it doesn't friction weld to the barrel..... "

    Railgun rounds actually resemble a shotgun or tank sabot round, with a plastic outer surface specifically to prevent undue abrasion from/welding to all-metallic rounds;

    3) "We talking smoothbore or rifle here?"

    Angular momentum can be supplied to the round by the same electromotive force that propels the round out of the tube. 'Rifling? We don' need no steenkin' rifling!"

    4) "Errrm they do know that the sea "moves a bit" don't they ? Precision ballistics at sea?"

    Never seemed to bother the sixteen-inchers on the Iowa-class battleships. And until they were pulled out of mothballs for the Middle East War Games in the 1980s, those sixteen-inchers were aimed not electronically, but by ballistic calculators which applied analog computing methods (i.e., "clockwork mechanism") to work out firing solutions, along with gun-laying radar.

    Scuttlebutt was that BUORD tried fitting Radio Shack Model 100 computers (those book-sized things with the three by eight-inch LCD display right next to the keyboard - and a real keyboard, at that!) to replace the old clockwork ballistic computers, but that they couldn't take the shock of repeated firings of the big guns.

    Solution - find surviving WWII and Korean War vets who were trained to fix the clockwork computers on the sixteens, hire them as "tech reps" and get the old gear working until someone could build a small computer tough enough to handle sixteen-inch gun recoil.

    By comparison, the shock to the surroundings during a naval railgun firing ought to be minimal. The sixteen-inch shells weighed about the same as the Japanese compact car of your choice, and it took bags, and bags, and bags of powder to send them on their way.

    Speaking out of near-total ignorance about the specifics, the delay between shots as the power circuits on a railgun re-charge might not be much longer than the delay while a sixteen-inch gun's breech is swabbed out (to prevent a turret explosion if hot material from the last shot touches the powder for the next shot), reloaded, re-aimed, etc.

    It wouldn't surprise me, either, if the rounds for the new naval railguns included a tiny little GPS chip, a tiny little computer to store the target coords, a tiny little radar to acquire and track the target, and pop-out steering vanes like the Copperhead SP artillery round, so that while Captain Ivan is trying frantically to escape his doom, the railgun round is tracking his every move. Just enough time to pipe "Sweepers, man your brooms!"

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