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back to article US Navy achieves '100 mile' hypersonic railgun test shot

The US Navy, continuing its quest for a hypervelocity cannon which might restore the big-gun dreadnought to its lost dominion over the seas, has carried out a new and record-breaking railgun test. This latest trial firing pushed muzzle energy to a blistering 33 megajoules (MJ). The muzzle velocity, as in the previous 10 …

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  1. Desk Jockey
    Grenade

    Good god!

    Being hit by one of those things would hurt! Is Lewis proposing to aim a large, several tons worth of railgun in a manner to take out aircraft? I think they had better stick to smaller and faster firing weapons or better still self guiding ones! By the way, lots of aircraft can fire cruise missiles from about 200 miles out, 10 aircraft, say with 2 missiles each? Not good odds for the railgun carrying dreadnought which will be back to using point defence systems.

    Which brings me to range, 200miles on a ship is still not enough. The Chinese strategy for countering US aircraft carriers (well known by everyone) is to fire a lot of short range ballistic missiles. Couple that with the fact that the projectiles will not be explosive (other than just travelling very fast) it makes this technology useless for anything other than taking out other ships. Other ships of which can fire their own cruise missiles or send out helicopters or stay outside of 200 miles and scream for aircraft or submarines to do the job for them.

    A huge railgun firing ship sounds scary, but the weapon is likely to take up the whole ship, won't be hugely effective and so it will need to be defended by other ships, best of all by an aircraft carrier which.... can do everything it can and more! Now a submarine fitted with this system that just requires it to surface, fire and duck back down again would be useful, but seawater and electricity? Hmmm, fried sailors!

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    1. Eric Crippen
      Reply Icon

      hurt???

      I don't think that there would be anything resembling a nervous system, much less a stain, to feel the pain. The shockwave would probably spray you four sheets to the wind (I don't think I got this phrase correct).

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      1. asdf
        Reply Icon
        Joke

        hmm not sure about 4

        but 3 sheets to the wind is what they say about most Scots by about 10pm on the weekends.

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    2. Anonymous Coward
      Reply Icon
      Anonymous Coward

      Hmmm.

      Fried sailors or seamen stains?

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    3. YARR
      Reply Icon
      Thumb Up

      Why surface at all?

      Better still, why not design it so the sub doesn't have to surface to fire the railgun? All that's needed is for the tip of the railgun to break the surface of the water for a second while it fires.

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      1. Vic
        Reply Icon

        Not a great idea...

        > All that's needed is for the tip of the railgun to break the surface of

        > the water for a second while it fires.

        Something similar was tried with the M1. The idea was to surface, bang out a shell or two, then submerge again.

        Trouble is, getting the barrel open at the right time always seemed to be a problem. Most firings of that gun took the end of the barrel off...

        Vic.

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  2. Steve 13
    Grenade

    @Nigel

    I was just wondering about the time taken to cover 200 miles at mach 5. Turns out it's about 3.15 seconds.

    Assuming that it's fired accurately in the first place, I doubt that a 3 second warning, even with automation is sufficient for any naval target to move significantly.

    I'd hazard a guess that even with computerisation it's actually pretty difficult to land your mach 5 slug in a space the size of an aircraft carrier though, so I guess like the gun battles of old, multiple shots would be exchanged (assuming the target is capable of returning fire at 200 miles range).

    As an anti aircraft or missile system, presumably a variant firing many much smaller projectiles would be developed. At closer ranges (ie within a couple of miles) even a high G missile couldn't avoid being hit.

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    1. Steve X
      Reply Icon

      Nope

      Mach 5 (at sea level) is pretty much exactly one mile per second.

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    2. Tim Parker
      Reply Icon

      @Steve 13

      "I was just wondering about the time taken to cover 200 miles at mach 5. Turns out it's about 3.15 seconds."

      Unless i'm musch missteakin - 3.15 seconds at Mach 5 would get you about 17,500 feet at sea level on an average-ish hyper-sonic projectile flinging day. That's about 3 Nautical miles which, though quite a fair distance, is a tad shy of 200 miles (Statute or otherwise)

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    3. Stoneshop
      Reply Icon
      FAIL

      You're way off

      Speed of sound is 340m/s, roughly. Mach 5 is 1700m/s, a bit over a mile per second. Now explain how you can cover 200 miles in 3.15 seconds at that speed.

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    4. Personne
      Reply Icon
      FAIL

      Maths fail

      If you cover 200 miles in a bit more than 3 seconds, you're travelling at almost 200 * (60/3) = 4,000 miles a minute = 240,000 miles an hour, which would make Mach 1 about 48,000 miles an hour, rather than the more commonly quoted figure of 768 mph.

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    5. Tim
      Reply Icon
      Boffin

      Might want to check your sums

      It's over 2 minutes, assuming sea level mach number and constant velocity for the entire flight which it won't be.

      To cover 200 miles in 3.15 seconds you'd need to be travelling at nearly Mach 300. Again, sea level.

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  3. CaptainHook
    Stop

    Trajectory

    Wouldn't a project moving so fast have an extremely flat trajectory, how do you hit anything just below the horizon?

    Or is the projectile going to be guided?

    If so, then you need electronics and actuators which can with stand reliably being accelerated from 0 to 7.5 Mach in the lenght of the rail (based on the video about 10 meters at most). The G-Force would be insane.

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    1. lglethal Silver badge
      Reply Icon
      FAIL

      Someones forgotten their basic physics lessons

      If you launch something with a trajectory on Earth, even at hypersonic speeds, gravity still provides a 9.8m/s^2 downwards acceleration (downwards being towards the centre of the Earth naturally). Hence you will get a standard parabolic arc, as you do with any weapon.

      Bullets fired from a gun follow the same path (only at much slower velocity), so your right that the object will APPEAR to have a very flat trajectory, but will indeed be following a parabola back towards the Earth... It might just take around 100 miles to do it...

      Only problem i see is if your trying to hit something thats behind a mountain...

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      1. Paul RND*1000
        Reply Icon
        Grenade

        Behind a mountain

        Wonder how many of these projectiles it would take to literally move mountains?

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      2. CaptainHook
        Reply Icon
        Flame

        There is still a dead spot

        Imagine an Artillery target, just the other side of a steep hill. The guns can send shells which either hit the hill, or fly too high and the shell ends up miles down range, in either case the target is unaffected.

        The flatter the trajectory, the bigger that dead spot behind that hill that a ballistic flight profile can't hit.

        A railgun has a very flat trajectory because of the speed of the projectile, therefore although it will come back down to earth I don't think it could drop fast enough to hit a target just beyond the horizon, the curve of the earth is acting like the hill in my Artillery example. Either the projectile hits the water before it hits the target or it flys harmlessly overhead and splashes down miles (and miles and miles) down range.

        I suppose you could vary the power output of the railgun so that the velocity of the projectile allows it to drop faster, i.e. less power the closer the target is but that means less energy delivered to the target.

        I suppose that targets just beyond the horizon could be dealt with using missiles but that kind of defeats the point of a railgun battleship to start with since you now have to load the battleship with explosive, large expensive ammo which is what Railguns are meant to avoid.

        I still think the projectiles would need active guidance to be useful, i.e. they aren't just following ballastic flight paths, and that means they need electronics and actuators capable of being acceralated from 0 to 2800m/s in the space of 10 meters.

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        1. Anonymous Coward
          Reply Icon
          FAIL

          @CaptainHook

          "I don't think it could drop fast enough to hit a target just beyond the horizon"

          The Horizon isn't a point at which land suddenly starts to drop away, it's due to the curvature of the earths surface and is relative to the location and altitude of the observer (affected by any intermediate surface deformations like hills and mountains).

          Given that the horizon is relative to the observer, anything just over the horizon will very rapidly be closer than the horizon relative to the projectile once it has left the muzzle (assuming a fairly flat landscape).

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          1. CaptainHook
            Reply Icon

            I know horizon isn't just a sudden drop

            My concern was that the trajectory would be so flat in the early stages of the flight path that the curvature of the earth would be greater than the drop of the projectile resulting in an area which couldn't be hit. However, I've now done some spreadsheet calculations.

            At Mach 7.5, after the first second of flight, assuming a completely flat firing angle, the earths curvature means the surface would be 35 cm lower but the projectile would would have dropped by nearly 10 meters. So this thing wouldn't have a flat enough trajectory to cause a problem.

            My bad.

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  4. Popup
    Boffin

    Escape velocity

    Mach 7.5 corresponds to about 2.5km/s, which is about 20% of the escape velocity. Methinks NASA ought to be investigating this as a method for launching satellites...

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    1. Sir Runcible Spoon
      Reply Icon

      Sir

      "launching satellites"

      really? how many satellites do you know of that could withstand that kind of G?

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    2. Miek
      Reply Icon

      a tit is required

      25Kms and you can kiss the grass goodbye.

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    3. Anonymous Coward
      Reply Icon
      Flame

      Yep

      Hear hear. The ideal usage would be to use the railgun to give the initial thrust to get the payload moving, then fire rockets to actually get to orbit. From what I can recall, rocket engines are really inefficient at getting something moving from a dead stop, especially since most of what they're lifting is the weight of their propulsion.

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    4. lglethal Silver badge
      Reply Icon
      Boffin

      Sorry theres a fair bit to go....

      In order to get a working mass driver/rail gun orbital launch facility you need to have an ejection velocity of ~20km/s.

      Current studies suggest that ~3km/s is the maximum ejection velocity you can achieve due to power losses and heat (hence why i suspect that the navy are keeping there gun at Mach 7.5 and just upping the payload being launched).

      So whilst i would love this sort of tech to be used at the moment its nowhere near getting us into space. I suppose the best current solution using this tech would be to use the rail gun launch as the first stage in a multistage rocket. However, firing a highly explosive rocket from a highly electric, high heat rail gun seems like it could be a slightly dangerous (explosive/suicidal) operation...

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  5. Anonymous Coward
    Anonymous Coward

    A cloud of deadly Teddy Bears! - your kids wouldnt sleep unless there was a monster under the bed!

    Does anyone else feel that this technology could be far better used by putting objects into orbit?

    And by 'objects' I dont mean warheads! Would be far better than using rockets to get large parts off the ground!

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  6. nigel 15
    Alien

    More impressive than world record breaking...

    ...ballistic weapon is....

    the panning camera shot. which must have been taken by clark kent.

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    1. Jon 63
      Reply Icon
      Thumb Up

      Glad im not the only one...

      ...who noticed this, anyone who has tried any type of sports photography or filming knows tracking targets is very hard work - even when you have foreknowledge and leadin (think sitting oncomong to a car which then turns a corner infront of you) so following this projectile out of a tunnel is mind bogglgingly awesome (and obviously baed on timing math/laser traps and very telescopic lenses!)

      Tracking that projectile at those speeds is a feat of acomplishment as big as getting this thing to fire

      On to the weapon!

      A little math:

      200miles = 321,868.8meters / mach7 = 2 382.03m/s = 2:15 travel time until impact

      (assumptions for constant velocity projectile not final impact velocity)

      If you solve for mass, you get a projectile weighing 11kg(ish), thats one hell of a punch (same assumptions used)

      Interesting point about trajectory and firing over the horizon given this things speed, distances etc if you fired at a 200 miles target your bullet would drop 1,324.35m's (again assumptions made on shape/wind/etc)

      Sadly I've run out of mathtime(and ability) to work out how far "up" from the origional point of firing this would make your projectile reletive to sealevel but its certainly an interesting problem to a firing solution at other seafairing or ground based targets!

      This thing would be fun to play with if it weren't for the rebuild requirements! Wonder if we reach lasers with this type of energy level which would be easier to use. it'd be an interesting game of cat and mouse if you can shoot over the horizon with a railgun, but obviously out of line of sight for a laser? - Rock Paper Railgun, Lasers, Spock anyone?

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    2. Anonymous Coward
      Reply Icon
      Coat

      Bet the cameraman drinks...

      ...Carling Black Label

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  7. Anonymous Coward
    Anonymous Coward

    Interference?

    I wonder whether the electromagnetic radiation produced by switching all that current would interfere with the ship's radar and telecommunications.

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    1. Steve Evans
      Reply Icon

      Re: Interference

      That's the least of their worries, have they not seen the Philadelphia Experiment?!

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  8. Anonymous Bastard
    Thumb Up

    Velocitas Eradico

    Did you notice the logo at the end of the vid?

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    1. Tim
      Reply Icon

      Good spot

      I think that's the motto of my local safety camera partnership.

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  9. Brian Miller 1
    Flame

    Turbo Boost

    Aim all railguns directly behind us.....

    Fire on my command.

    WHOOOOOSHHHHH,

    150 NAUTS SIR!!! She cannae take it captain.

    Just a little more Scotty.

    Tha's as much as I can gi ya cappin.

    Very well, Uhura, see me in my quarters.

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  10. Anonymous Coward
    Anonymous Coward

    Ballistics?

    I'm curious as to how ballistics would affect this type of weapon, for a long range target I would guess that active projectile guidance would work, but what happens when you shoot at a target just far enough away to be below the horizon, but close enough that the ballistic curve is shallow enough (at mach 7) so that it flies over the top. (you wouldn't be able to depress the elevation enough without hitting the surface).

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    1. Gotno iShit Wantno iShit
      Reply Icon
      Boffin

      @Ballistics

      Say you fire a projectile horizontally 10m above sea level. It will accelerate downwards at 9.8m/sec^2 due to gravity. There is a precise speed the projectile can travel in order to remain at exactly 10m above sea level with the curvature of the earth compensating for the fall due to gravity. Lets call this speed X. If the projectile is fired below X it will always end up wet, if it is fired above X you have a blind spot over the horizon. The correct name of speed X is Escape Velocity and as others have said mach 7 is well under that.

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    2. Charles 9
      Reply Icon

      That's assuming you take the low road.

      However, in naval gunnery, the preferred method is to take the high road. Reason being you have a chance at hitting one of the less-armored parts of a ship: the deck. That's why dive bombers packed such a punch during WW2: not only were they delivering bombs from beyond terminal velocity, but they were targeting a pretty vulnerable part of the ship.

      Given assistance from an AWACS, computers should be able to provide a targeting solution that takes a higher arc, allowing them to nail a target even at just beyond the horizon.

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  11. Brian Miller 1
    Pint

    Sattelites? Building materials more like.

    The G's pulled in reaching escape velocity would pertty much rule out a lot of manufactured goods. However sending raw materials into space for assembly after reaching orbit is a good shot. I'm talking rolls of sheet metal, girders/framework. PV panels, Screws and Fixings, etc.

    It means that only sensitive materials would need the expensive launcher based mode of transport.

    Eventually if we get enough machinery up there they could start pulling in NEO's for material and processing them up there. No more energy would be required to reach escape velocity, and space ventures might actually become an energy SOURCE rather than a SINK.

    Heres to dreams...

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    1. Baskitcaise
      Reply Icon
      Thumb Up

      B&Q home delivery?

      "However sending raw materials into space for assembly after reaching orbit is a good shot. I'm talking rolls of sheet metal, girders/framework. PV panels, Screws and Fixings, etc."

      So if there is a malfunction and the power is not enough for orbit at least the houses that will be demolished by the stuff coming back will have the tools and supplies needed to repair the damage.

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    2. annodomini2
      Reply Icon
      FAIL

      NOPE

      The materials would vaporise due to air heating, because of the velocities involved.

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  12. M7S

    Flyboys won't lose their superiority for long, if at all.

    Once they get "orbital", then they're still higher up in the gravity well.

    Or that X-37B could start to seed the skies with lots of things pointing downwards in readiness. One shot railguns perhaps. Treat as mines with range.

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  13. Liam 8

    NASA

    NASA are already looking at this as a space launch system but it would probably never see the light of day. The reason why this can both only use inert slugs and it is less than ideal for satellites is that the acceleration is not entirely conducive to sensitive electronics. A human would be reduced to warm jelly, electronics would be turned to scrap.

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  14. Daedalus
    FAIL

    Yawn...

    33 MJ is about the energy of a few litres of petrol. Or a few kg of solid rocket fuel. A missile launched from the ship could have the same range and better guidance. It's not as if these slugs will be any old piece of iron. They'll be expensive specialized ammunition. This is a system in search of a purpose.

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    1. Anonymous Coward
      Reply Icon
      Black Helicopters

      Actually, we've got the purpose,

      just not the rail gun. This is only a first generation gun and we'll need another 7 generations before we've got the weapon we want.

      Well, that and a few other odds and ends that aren't really worth mentioning.

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    2. annodomini2
      Reply Icon
      FAIL

      ah but...

      If you have a ship that is nuclear powered, which I think is the main aim of this thing.

      Then you only have to store ammunition, which contain no explosives and are much smaller, so you can store much more of them in a given volume and they don't need special handling requirements or protection.

      Also if it was so simple where are the hypersonic missles?

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  15. call me scruffy
    Thumb Up

    Bombardment

    The crucial issue here is bombarment.

    There isn't much you can do about an inert supersonic balistic projectile once it's in flight. One of these could shell whitehall from 200 miles away, and the best you could do would be to evacuate.

    CIWS works by disrupting a projectile that would otherwise explode on impact, and which might just fall to pieces once intercepted. Anti Ballistic Missiles work by nackering the guidance systems of incoming warheads, or just vapourising the warhead, so that it doesn't detonate. Neither of these countermeasure techniques will work against a simple solid lump of depleted uranium.

    Say you want to take out a runway on the Falkland islands, one of these could do that before most navies could even tell that you were there. And even if ships don't go for station keeping, one of these could take out an entire harboured fleet in a few minutes.

    As for generating power... we could take a leaf out of the German U boat book, and mount one of these on a nuclear sub. Surface, Shell, Submerge in ten minutes?

    (Now I've got an idea about a 4.5 incher fitted into a trident launch tube;-)

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    1. Anonymous Coward
      Reply Icon
      FAIL

      @call me scruffy: Oh Really ?

      I'll launch either a S-400 with a 100kg Uranium warhead or a Mad Cowboy Navy Rocket (SM-3) with 50kg Uranium at it. Let's see what your 17kgs of Mach-8 Uranium will do.

      I'll leave the verification of the 17kgs to you. And the performance of the S-400, probably the most powerful supersonic tactical missile in existence.

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      1. Charles 9
        Reply Icon

        That's a lot of missiles you're firing.

        In terms of the maths, the delivery system in this case (the missile) is the more-expensive consumable in your equation. And for a multi-shot bombardment, that's going to add up the war costs. OTOH, once you have the railgun in place, the projectiles aren't exactly much more expensive than your warheads (at worst, you'll probably be using up some relatively-cheap sabots). Given enough juice, you could launch a bunch of them for much less cost than using a bunch of missiles. Not only that, the projectiles could be made quicker since they're simpler.

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        1. Anonymous Coward
          Reply Icon
          FAIL

          @Charles 9

          Your Electric Dreadnought will be hit by my widly-and-randomly-up-and-down-left-right jumping S-400 after firing three rounds. Game Over.

          The S-400 I can launch from a submarine, a stealthy fast attack boat or a slightly reworked A340 with a decent ELINT package and a search radar. I just peek over the horizon at 600kms distance, acquire your Dreadnought, go down to 3kms height, close in to 300kms distance and launch the S-400. When it hits, it is at Mach 12.

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      2. SkippyBing
        Reply Icon

        Hypersonic Interception

        Is extraordinarily difficult*, assuming the rail gun becomes suitably weaponised, it should be relatively easy to saturate your defences with multiple rounds in a short period of time. I'm also not sure why you're using inert uranium warheads on weapons systems that aren't designed for them. SM-3 and I believe S-400 aren't designed to necessarily hit the incoming target, just get close enough for the explosion of the warhead to rip it to shreds.

        *The difficulty increases by an order of magnitude for every Mach number you go up.

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  16. Anonymous Coward
    Pirate

    title goes here

    ".. recharge it for another shot in a little over a second and a half, though this rate of firing would leave little juice left for propulsion"

    cba to do the sums, but wouldn't the recoil keep the matelots chugging away quite nicely? Perhaps not a good idea to fire uphill or sideways though ...

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  17. Neil Stansbury

    Not a launch vehicle

    This can't be used as satellite launch vehicle, this is still a gun - the G forces exerted on the projectile over such a short barrel distance are enormous, and would easily crunch delicate satellite bits.

    Now... constrain the projectile in a donut shaped barrel, taking multiple cycles to bring it up to launch speed before ejecting it, then you might have something useful for flinging stuff other than HE shells....

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