US Navy preps railgun for tests The US Navy’s Office of Naval Research is preparing to test a prototype railgun delivered by BAE Systems under a $US21 million contract signed in 2010. The industry prototype – a kind of dream machine for Mythbusters’ fans – is due for tests in coming weeks at a facility in Dahlgren, Virginia. The ONR’s aim is to develop a …
You've got to give it to the US, they learn from their mistakes. 68 years ago this June, some stupid general, in the fashion of Haig, sent thousands of his soon to be dead men onto a beach without any protection because the boffins' mine clearing devices looked (and I quote) "funny."
Even so, he lost a lot less men than General (you'd be a war criminal now with such crass stupidity,) Haig's "You don't need to charge the enemy, cos' we've blown them up, so you should just walk to the edge of the Somme.
Can you imagine D-Day all over again, where nops amis yankees don't lose thousands of men, because of this crass stupidity, and they turn up, a mile offshore with a nuclear reactor powering one of these, and literally turn the Normandy beach front in front of them into a gentle blood and sand covered, landmine free, slope.
I'd really like to seem them get this working (while still an ally, of course.)
A rather simplistic, one-sided view.
If we assume some foreign power has managed to invade and hold Europe, between Russia and the Atlantic coast we must assume they have some neat toys of their own. For example they probably have their own railguns able to fire 100nm.
Now add that in to your view of WW2 and you have the whole US invasion force being killed on the South coast of England as they board the ships to France...
"If we assume some foreign power has managed to invade and hold Europe, between Russia and the Atlantic coast we must assume they have some neat toys of their own."
We don't really need to assume that, the Germans had been working on "neat toys" of their own for quite some time prior to D-Day - the V1 had been under development for almost 2 years by that point (and was pushed into service very soon after D-Day), and von Braun had been working on the ideas that eventually led to the V2 since before the outbreak of war. And although they weren't railguns, the cannons that formed the heart of the V3 projects had the same basic principle in mind - long range bombardment using relatively cheap and practically impossible to detect/intercept projectiles.
It's a question for debate that, had German industry been left to make up its own mind about what weaponry to develop, rather than being pushed and pulled in a variety of incompatible/incomprehensible directions on the whims of certain members of the German High Command, the Germans would have been able to deploy some seriously effective weaponry against the allied forces far sooner and in greater number than they eventually did.
"Routemaster" is the only kind of bus I know the name of, and here's why:-
True story:
A few years ago a colleague was giving me a lift to the station. All of a sudden he exclaimed "F**k me! It's a type 53 Routemaster!", did a "U" turn and headed off in the opposite direction at an insane speed.
I had no idea what a "Routemaster" was at the time, so just sat there spluttering "err, train... Station,..... ARRRRGH Cyclist, OH MY GOD"
I eventually twig that the object of his desire was a bloody bus. The bus pulls into a stop, and Nigel (for that was his name) pulls in in front of it, blocking it in, whips out his camera and proceeds to take pictures of the bloody thing. The bus driver just looked bored, as if this kind of thing was a regular occurrence if you happen to drive a Type 53 Routemaster. I just slid down in my seat and pretended I wasn't there.
Nigel finished his photography, got back in the car, the glazed, insane look, lifting from his eyes. He drove me to the station for me to catch a later train, and we never spoke of his dirty little bus spotter secret agaiin.......
Until.....
A year or so later (this was during the 1st Gulf war) I received a phone call:
caller: Hello, is that Mr Anonymous Coward.
me: Err, yes.
caller: This is sergeant Plod of the MOD Police. Do you know a Mr Nigel Nerd?
me: Err, yes.
caller: Can you tell me anything, err, unusual about him?
me: He's quite fat.
caller: With regard to his hobbies?
me: Oh god. You don't mean busses, do you?
caller: Yes, thank you, we'll release him.
Nigel had been out photographing busses outside the naval base. The MOD Plod didn't like the look of that and pulled him in, not believing his "I'm a bus spotter" plea.
I have often wondered how things would have progressed if I'd said "Errm, well, He's a founder member of the Sadam Hussein fan-club" when asked about his unusual attributes.
So you should divide by the square root of 7.7 = 2.8, so 36mph.
But the figures don't add up, 32MJ with a one ton (1016Kg) projectile would be 561mph, and a Routemaster 202 mph (OK, until you consider the G-forces when it stops at the bus stop!)
A one tone projectile at 100 mph would be 2MJ, so they are loosing 94% of the energy to... Well, I guess they won't need central heating.
I, for one, welcome our Routemaster-throwing overlords.
Using E = 1/2 * m * v^2, and rearranging for v = sqrt (2E / m), a 1 ton car would be doing 594mph, and a London routemaster (using dogged's mass) would do 224mph.
Also, dogged's maths is off - multiplying mass by 7.7x reduces speed by 2.77x, for the same energy.
One you are assuming that all of the energy goes into the projectile, I seriously doubt that.
Also dogged seems to be equating the projectiles momentum and you are equating KE. Now in this instance I am trying to work out who is right but I do know when a gun goes off momentum is conserved but KE isnt.
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We've been given values for mass and velocity from which we can easily calculate momentum (p = mv), in that we're given 1 imperial ton and 100 mph for m and v respectively.
Now, when you scale up the mass to a London bus (7.7 tons) that momentum should remain equal thus p = mv = 100 * 1 = 7.7*12.99.
The megaJoules measurement is irrelevant since at no point are we supplied acceleration and cannot infer it from the given values. One Joule is equal to the energy expended in applying a force of one newton through a distance of one metre. We could convert miles per hour to meters per second but that won't help us calculate a force (m*a).
It makes perfect sense, because the Kinetic Energy can be calculated using E = ½mv²; the acceleration and distance fall out. (For constant acceleration, take E = Fd and substitute in F=ma to get E = mad. Now use s = ut + ½at² with an initial velocity of 0, to get d = ½at²; and substitute in to produce E = ½maat² = ½m(at)². Finally substitute in v = u + at, again starting from rest—i.e. v = at—to get E = ½mv². ∎)
By contrast, the final momentum will depend on the length of time the force is applied (F = ma and v = at so F = mv/t; i.e. Ft = p) or, equivalently, the distance over which it is applied.
Forces are the means by which Energy is transferred around a system. So the gun will take a fixed amount of energy, "turn it into a force"*, and apply it to the projectile. The heavier the projectile, the lower the acceleration that force will produce, and so the slower it will end up travelling. But an ideal system will transfer all its energy to the projectile.
Momentum, by contrast, is stolen from the Earth's rotation, and there can be as little or as much as necessary. It can only be from the forces and times (back to F=ma), or via Energy. We don't know the forces and times, so the kinetic energy is the only way to do it.
And despite knowing all that, my initial reaction was to scale it linearly, too. :oops:
* An electromagnetic force is a bunch of virtual photons transferring energy and momentum from one particle to another. Kinda.
That's 6 to 10 rounds a minute for a naval battleship sized gun. The smaller anti-missile guns will produce a lot less waste heat, be a lot smaller and thus take a lot less power to fire and recharge. You can expect the anti-missile versions to fire a couple of rounds per second.
Still not very high compared to currently CIWS solutions, but then railguns can be considerably more accurate so they won't have to spray 50 rounds at an inbound missile and hope one will hit.
1. 6-10 RPM will be for artillery-style use... the sorts of things that cruise missiles might be used for these days.
2. This particular device is unlikely to be used for missile or aircraft defense, but if it were it would like as not be used in a lower velocity or lightweight projectile mode.
Read Reg warporn articles passim for talk about the other naval railgun project going on.
That sort of warship displaced a good 40000t and needed to be enormous to support those sorts of guns and the huge amount of infrastructure they required. The guns weight about 100t each without any ammunition, needed huge crews and threw their projectiles about 20 nautical miles at best and managed perhaps 2 rounds per minute at best.
This means that the low-end range goal for this prototype railgun, 50 nautical miles range at only 4 rounds per minute, would utterly outclass those old cannons and be capable of being mounted on a much smaller and more manoeverable vessel.
Whilst you're there, have a quick think about the relative safety merits of a ship carring hundreds of tonnes of explosive propellant, vs one carrying a load of spare gun barrels and a crate of little metal rods.
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"A London routemaster weighs 7 tons 14cwt unladen according ot the internets, which means to match the force of a 1ton object moving at 100mph, it would have to move at 100/7.7mph or in real money, 12.99 miles per hour (2 decimal places)."
We're talking about kinetic energy here, not force. A 1 ton car travelling at 100mph has a kinetic energy of about 1.1 Megajoules, not 32 Mj (correct me if I'm wrong). A 7.7 ton bus would have to be travelling at around 36mph to have the same energy. (E = 0.5mV^2)
32Mj would require speeds of 561.55 and 202.37 mph respectively (2dp) i.e. bloody fast!
At a range of 100 miles, and travelling at 5600 mph, it's going to take more than a minute for the projectile to reach it's target (and that's assuming it doesn't slow down along the way, which it will). A minute is plenty of time for the target ship to change course to avoid the incoming projectile... all they need to do detect the launch and plot the trajectory (OK so that will be tricky but give it some R&D and it's probably do-able).
Unless... we combine giant-rail-gun technology with steerable-projectile technology, then there's no escape!
At a sailing/steaming/turbine speed of 30 knots, the ship would travel 0.5 nautical mile in a minute. The turning rate of large warships is not too impressive, but let's pretend that it can be instantaneous.
Ergo, the target could be anywhere in a circle of radius ca. 0.5 nautical mile. That's what the shooter has to aim for, and that's part of the reason the old fashioned battleship guns frequently have multiple barrels, to be able to fire barrages. I've heard that navies that have nuclear weapons are loathe to forsake them, because they have a large destruction radius, and, after all, you don't make permanent holes in the water.
From the point of view of the target, the trick is to use, e.g., radar, to find the projectile (the horizon is 50 miles away, so you won't see the projectile until it is already half way to you), predict its path, and avoid the patch of ocean where it will hit. Not an easy task, especially if the projectile is a slender 10 kg tungsten rod.
Actually around 40 seconds (assuming that the round doesn't slow down as you pointed out so call it a minute) ... Large Ships don't necessarily maneuver that well, the firing ship will fire a barrage most likely (over the horizon so you aren't going to know there incoming rounds) so it's not as silly as it sounds.
Cheers
Most modern warships have relatively thin hulls. Such a slim projectile needs to hit something with substantial mass to impart a good proportion of its energy otherwise it will just go through like a rifle bullet through paper. There might be local damage but it could easily be insignificant to a ship-sized object.
Its also an unguided shell equivalent so it need to follow a ballistic curve and allow for the curvature of the earth. This is likely to increase errors in aiming.
For close quarter defence there might be a different picture.
I calculate the 1 ton kinetic energy as ~1.5MJ so there is a large mismatch somewhere
(Imperial AND SI units - urrgh!!)
if you make it into a sieve it will sink but it seems rather far fetched to assume that it will be hit a sufficient number of times BELOW the waterline. If its a small vessel then game over and if the projectile hits something heavy or critical that it can vaporise/ be vaporised by then ditto.
100000 tons takes a lot of sinking with small holes.
Indeed, not ship to ship, but ship to ground.
As mentioned, it's a replacement/alternative to using cruise missiles, so will most likely be being fired against things like anti-air and radar emplacements, hardened structures, airfields, army bases, comms towers etc.
In essence, neuter your enemy from 50 to 200 miles away, before they can hit back, and before sending the rest of your forces in to mop up.
We could drill through 1 Ceres. That's a railgun near 1000 km long in near 0 g.
There's plenty of water and such to make into air and traditional rocket fuel. You can store up hydrox and use it for burst power too. Being in the asteroid belt it's probably a rich mine of iron ores on the surface as well.
Round figure the 1000 km railgun launcher. From 1 Ceres' orbit solar system escape velocity is 30 km/s or so and its orbital velocity is 17, so 13 more km/s is needed as long as you're headed the right way. It's a bit more than Earth escape velocity in near-0g. This is just a hair short of 10 g's over the length of 1000 km, in 154 seconds. That's well into human survivable territory which is well over 17 g. Augment the launch boost with some solar sail fluffed by both the sun and/or some high-intensity lasers and we're well away even without complex stuff like gravity slingshots or onboard thrusters. For an unmanned probe you can do well over 100x that acceleration.
And the rest of the time you can be a logistics hub for the human mining settlements on the asteroid belt.
It's limited to stuff on the solar system plane though for the 10+g launch, give or take a few degrees. To go close to north or south requires some freaky calculations, or using Jupiter or Saturn to both both boost your velocity and change your direction - and you're going to need some onboard traditional rockets to pull that off. A shame Alpha Centauri is almost due north. The space geeks can figure that out.
We can head for the stars now with available technologies if we want it badly enough and can find some patient volunteers. Or we can send much faster unmanned probes. Or both. It would be interesting if Dawn mission got to Ceres and found it full of odd tunnels.
http://en.wikipedia.org/wiki/G-force
http://www.wolframalpha.com/input/?i=solve+acceleration+to+13000+m%2Fs+in+1000+km
http://www.ajdesigner.com/constantacceleration/cavelocityt.php (13000, 0, 85)
Interesting post. However, a couple of things I should point out:
1) Alpha Centauri is due south, not north. It's one of the pointers to the Southern Cross, and as such it's within 30 degrees of the south celestial pole. (It's circumpolar from where I live in Adelaide, Australia)
2) Mounting a bloody great fuck-off railgun launcher through the guts of Ceres and launching multi-hundred-ton spacecraft from it at multiples of earth gravities will, by virtue of Newton's 3rd Law, undoubtedly do wonderful and interesting things to the orbit of said asteroid. If you orient the launch vectors appropriately, you could even start it on a collision course with Earth, which, considering Ceres is comparable in size to Texas, would go a long way towards doing the Universe the favour of removing the human race from it! ;)
I'm pretty surprised this hasn't been touted as a "green gun" or a "zero emission sabot slinger." I'm more curious about which senator invested in which stock(s) prior to the funding of this lead-sled than if it will actually work, which I doubt. Not that it won't ever fire really fast, over-sized pellets, but I seriously doubt it will ever be effectively weaponized. Then again, if man was intended to fly, God would have given him wings. Penguin, because God gave them wings, and they still can't fly.
Hang on ... You mean that BAE is actually producing something of value, and the American Navy is interested?
Oh right, the article was not written by Lewis....... ratfox Posted Thursday 9th February 2012 05:05 GMT
Err.... hang on a cotton-pickin' moment there, ratfox. BAE Systems has blagged $21million to try and produce something of interest to the US Navy’s Office of Naval Research and prepared to test for the destroying of things of value. And that is something altogether completely different.
As others have written, the trajectory can be observed and a counter-missile be launched for each projectile.
Also, launching something at excessive G-rates necessitate the projectile to be a stupid lump of material, as valves and other complex stuff won't survive the violent launch. So, no way for evasive maneuvers.
Missiles are still superior to this "exciting" technology, as they can accelerate at "moderate" G-rates of about 1000 m/s^2, and still reach several machs in very short time. They can include any complex tecchnology such as computers, radars, valves and steering surfaces.
These dumb projectiles can be downed using ESSM, now a standard weapon for all modern navies. (that definition does not include the British navy, though)
I'm not sure that's true, as there's not going to be any explosive charges in the projectile, and it's probably got enough kinetic force behind it to plow through any explosion. Additionally as it's a solid slug of metal it's going to have a much smaller profile than standard missiles.
Also unless I'm completely uninformed, there isn't currently a defence against solid slugs except not being there. Another point would be that the ship that has this gun will be able to have a lot more ammunition than the opposing ship will have missiles due to the fact that it's smaller...
So just explain to me how a Sea Sparrow missile can "down" a lump of hypersonic lump of tungsten (or whatever they are slinging out)? Short of vapourising it or knocking it off course, it will just keep going, energy intact.
One of the main drivers for this technology is logistics. Instead of having a magazine full off stuff that blows up, you just have an inert pile of projectiles, and a source of electricity. For a nuclear powered ship, that is already availabile in abundance. There lots of logistical issues associated with propellant, that aren't there for diesel.
First, even in sea-to-sea combat, such a projectile would be fired from over the horizon, meaning barring an aerial radar, the projectile isn't going to be detectable until it's already partway to you, cutting the reaction time. Second, most military naval vessels (especially large ones) can't turn quickly and take time to accelerate and decelerate, making it more difficult to perform evasive maneuvers. Basically, for evasive maneuvers to be effective most of the time, you have to already be performing them when word of the incoming projectile reaches you. Otherwise, the attacker is likely to simply fire a leading spread to account for the limited types of actions
As for intercepting the thing, no way. You're talking about a sizable lump of solid tungsten. FTR, tungsten is about as dense a solid metal as you can get without going into that bug-a-boo: depleted uranium. So you're talking a lot of mass traveling at high velocity (remember what the article said: mach 7.5). That means a tremendous amount of momentum, which physics dictates is going to be a bear to deflect. And since it's a solid slug, it's going to be a pretty difficult thing to hit. Explosive forces won't impart enough force to deflect it well, and even an ESSM isn't dense enough to work on direct contact: if this thing can penetrate a ship, what's to stop the projectile simply punching THROUGH the missile? And a Phalanx, while capable of spewying out a lot of lead, lacks the range to intercept it early enough for the deflection to have any meaning. So you're pretty much down to intercepting it with another massive kinetic projectile. Ask yourself: when was the last time you recall anyone managing to shoot one bullet with one other bullet?
I agree that one would have to actually test an ESSM interception of one of the mentioned e-slugs. According to wikipedia (http://de.wikipedia.org/wiki/RIM-162_Evolved_Sea_Sparrow_Missile), ESSM missiles weigh 270 kgs, so when they impact the much less heavy e-slug, this should end in a ball of metallic vapour and maybe some minor high-speed fragments.
Regarding the "you can't hit a bullet with a bullet", modern electronics and thrust vectoring have proven otherwise. SM-3 shot down a satellite (which moves faster than most bullets) and the russians claim their systems can do the same or more.
Also, modern russian sea-skimming ASMs fly at speeds of mach 2 or more for several decades now. Intercepting these missiles is more difficult than intercepting a bullet, because they can now maneuver at high g rates. ESSM has been specifically designed to do that and the operating principle is much better suited to achieve its goals than dumb systems like gatling guns.
ESSM won't have the slightest problem to intercept the e-slug, as the trajectory is very predictable. Modern anti-ship missles are a much more dangerous threat than the e-slug. All I can think of is that the software has not been tested against the high speed of e-slugs, but that will eventually be done.
it's only more predictable if you know where it was launched from. You then have to consider that the 10KG projectile has a volume (if it's tungsten) of 519.5cc, that's less than 1 litre (or will fit in a 10*10*10cm cube. Traveling at 5709MPH, and 24 miles from visual range, that's 15.13 seconds reaction time.
The ESSM will be traveling at around 3044MPH and to cover the same distance that would be 28.38 (assuming it was already at max speed). Simple maths says that they will meet each other after 9.8 seconds, at which point the ESSM will have travelled 8.35 miles. More research says that the response time for ESSM is around 6 seconds, which leaves the projectile at around 2.8 miles from it's target at point of contact. And this is assuming that they've picked it up at the maximum 24 mile range for the horizon on earth. If it takes them more than 3 seconds to detect a projectile that is smaller than your average sea gull, and due to aero dynamics will have substantially less radar profile than the gull, the ESSM won't have time to be launched before the ship has been hit.
Just as aside, the time it would take a missile traveling at mach 2.5 to travel the same distance would be around 45 seconds, so that 6 second response time wouldn't matter that much.
It's not getting to the target that's the problem. It's what to do WHEN YOU GET THERE that's the problem. Missiles and slugs work very differently.
Intercepting a missile is possible because its primary action is chemical. It works with an explosive warhead. Defeat that and it'll just be a hunk of metal that isn't even designed to work on inertia. All you're trying to do in a missile interception is cause it to stop or detonate early.
A slug, on the other hand, is pure kinetics: inertia. If a ton of solid tungsten traveling at Mach 7.5 were to kiss an ESSM head-on, the inertia of the slug would more than likely cause it to penetrate the not-as-dense shell of the missile. It'd be like trying to deflect a cannonball with a bullet: it's not going to do much. IOW, a massive ballistic projectile is inherently missle-resistant due to its sheer mass. That's why tanks on the ground love sabot rounds and kinetic penetrators and why insurgents have taken lessons on bodging explosively-formed penetrators: because it's just very hard to beat PHYSICS.
They sound impressive your numbers but let's look at them at little more closely.
A 1 tonne Mach 7.5 projectile had a kinetic energy of ~3e9 J - that's 3000 MJ - that's rather out of the range of current discussion esp. if the launch efficiency is as low as the data in the article suggests.
It is hard to beat Physics
Regarding the "high speed tungsten will cut through missile" argument, I don't think that the same physics as with "low speed" bullets apply. At speeds of mach 5, even a piece of styrofoam hitting a human will be deadly. So my guess is that the mass of the ESSM missile hitting the tungsten (or whatever they use) e-slug will vaporise both the slug and the missile.
Now to the "can't detect e-slug" argument: It does not really matter if you see the slug being launched or not; what matters is that you will see it several seconds before it will come close to you. Even a small part of the trajectory will be sufficient for software to calculate the rest of the trajectory. Also, the ESSM missile will track the slug and correct for any errors of the calculation. I assume it is sufficient to have 10 seconds of warning time to launch an ESSM. That would be 15km or more distance. Your Radar and IR sensors must be capable of doing that.
Sectional density and Ballistic coefficients come in to play. The sectional density of the projectile will be extremely high. There probably isn't enough density in the missile to vaporize the projectile. A missile has a very low sectional density and is not designed to hit the target head on. That is very difficult to do.
The missile works by getting close enough to detonate and send a clod of shrapnel into the target. When dealing with other missiles or aircraft, this is more then enough to cause them to stop working. With a projectile like this, the best you'll do is alter its course.
Sure, an object at a speed of Mach 5 is dangerous, but how dangerous is it against ANOTHER object ALSO going at Mach 5...only much denser? It's like a Mini Cooper vs. a lorry, both at the same speed. It's gonna be messy for the missile.
As for the warhead, the projectile will not have a lot of cross section for an explosive force to apply, and it'll have all of the projectile's inertia to fight (and given its mass, there will be a LOT of it).
While I was browsing the net looking for more info I came across this quote
"Ellis told FoxNews.com that the big guns on the deck of a warship are measured by their muzzle energy in megajoules. A single megajoule is roughly equivalent to a 1-ton car traveling at 100 mph. Multiple that by 33 and you get a picture of what would happen when such a weapon hits a target." here - http://www.foxnews.com/scitech/2010/12/10/navy-railgun-shoots-bullets-electromagnet/
Could this be what's meant by the following?
(equivalent, the ONR says, to a one-imperial-ton vehicle travelling at 100 mph, or a London bus going bloody fast).
My laptop battery has an energy density of just over one half a megajoule per kilogram and it's not exactly military spec. So maybe 250 shots per kg assuming no losses. (Yes, there will be losses but on the other side battery tech is still improving rapidly) I don't exactly think a 1kg power pack would be a problem for Arnie. On the other hand I do have this image of a young Stallone with dozens of little phone batteries tucked into his bandolera.
Come on chaps, a few LBGBF's* coming at you is not something to miss, well actually it is, since it would hurt!
As in: it wasn't that she was fat, but once she got dancing she was a few LBGBF's and anyone who got in her way...well.
*London bus going bloody fast
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Once you actually get it into the air, it's going to have a LOT of inertia. IOW, it's going to take a lot of physics to make it alter its course. Plus, if it's shaped like your average kinetic penetrator (long and pencil-shaped), then there won't be a whole lot of drag on it, either.
Given that you can only realy fire metal and nothing fancy as anything with electronics would be at the mercy of alot of induced EM via the launch I can see why the Birtish don't have one - probably waiting to build there's from CERN parts once its decomisioned.
I also wonder what kind of high voltage capacitors they will use and how many as for all the will in the world I'm kinda against overloading nuclear reactors with a sudden heavy drain of power - dont want that steam turbine burning out I guess.
Also wondering how much kick this will have, can you face it behind you can up your top speed with pulsed firing.
Either way I look forward to the nighttime test fireings from it, should make from some pretty puictures :).
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