It's all go in the world of hypervelocity railguns this week. Following Friday's 33-megajoule test shot carried out at a US Navy laboratory, it has also been announced that a different railgun known as "Blitzer" has recently carried out firings which suggest that it is almost combat ready. The Blitzer comes to us courtesy of …
Smart? At 60000G?
Lewis, did you by any chance start on the Christmas hampers too early by any chance?
Can you tell us the unenlightened in the art of ultramodern killware, exactly what kind of guidance package out there will be able to survive that acceleration and actuate fins or command nozzles after that.
"an you tell us the unenlightened in the art of ultramodern killware, exactly what kind of guidance package out there will be able to survive that acceleration and actuate fins or command nozzles after that."
A previous US navy project was a naval gun launched "smart shell" using GPS guidance. Can't remember if it's gone to deployment or hit some cost snags but the *hardware* was *very* hard indeed. A far cry from radio proximity fuses in WWII for AA shells using metal shelled valves.
Generating the power to swivel the guidance fins *is* tough as the forces are quite substantial. Military stuff tends to use thermal batteries. Special, designed to application and *very* expensive but potentially Kw power levels (for enough time to get the job done).
Errr... Apples and oranges
You can steer stuff with fins at 1-3M. We know how to do that fairly well.
Steering stuff effectively with anything _within_ the earth atmosphere at 5M+ is a completely different ball game. This is especially so if the "stuff" is spinning like crazy at several hundred (if not thousands) RPM to maintain its in-flight stability which it will.
While not outside the realm of the technologically possible, the cost of making the projectile smart in a system like this is likely to negate all the advantages of having a system which can spit out slugs at 5M in the first place.
...for munitions have been in the tens of thousands of g for decades, definitely 10,000g and maybe as much as 20,000g. Electronics can be made to survive this acceleration because as things get smaller and lighter they are inherently resistant to the resultant forces.
...sabot means shoe. Usually wooden
Early sabotage consisted of kicking one's shoe into the gears.
And in English...
,,, the word for wooden shoe was clog. Hence "clogging up the works."
Some back of the shopping receipt calculations say that, to reach Mach 5 at 600000ms-2 (roughly 60000 g), you'd need 24 metres of accelerating - a quick wikipedia-ing claims this is longer than the barrels of the guns on Iowa-class battleships (21m). Considering that the US Navy probably don't want ships the size of battleships anyway, and that modern guns generally seem to be quite short, that's starting to sound like a pretty long gun.
How'd they intend to fit that on a ship?
always about size
Would a telescopic barrel work? I should probably leave the thinking to the smart ones.
In fairness to Lewis, he used the same numbers posted in the GA article..."exceeding 60,000 gee". The picture in the article shows a barrell about 10-12ft (3-4m) long, and shows a shell in flight with fins out, so unless this is a bit of early/late April Fool's on the part of GA...
*Read The effing Link
...mine's the one with the sabot in the pocket.
No reason the railgun acceleration needs to take place in a linear fashion. Think of the LHC with it's ring shaped acceleration.
Perhaps having a tight coil is beyond current tech (magnets will be interfering etc), but that's how i always imagined them to work. That or a single loop that then allows the projectile to exit at a given point (fore/aft turret, emergency sea-ditch tube (what would happen if that was fired directly into water? Presumably not fun times). Again think the LHCs emergency dump sections (gets fired into a giant slab of granite)
Plus.. a gun barrel has to start where the magazine ends (or loading room is situated)
A railgun could have its acceleration below-decks and just have a fixed-arc turret to actually aim the projectile.
This is my pseudo-science take on events, anyone feel free to tear it to shreds :D
put it in a turret that will track fast enough to knock out a variety of threats ranging from (possibly multiple) low flying low visibility missiles/planes to descending MIRV's...
Factor of 10 out there
My back of the envelope calculation gives the distance as 2.4 metres.
distance = (1701.45 m/s)² / (2 * 60000 * 9.8 m/s²) = 2.4 m
where 1701 m/s is Mach 5
The things being fired around the LHC are essentially points; the slugs in a railgun, as with pretty much any gun are essentially linear. I would have thought it would be extremely non-trivial to make a curved railgun that fires straight slugs.
I maybe wrong but:
v^2 = u^2 + 2as (u=0)
s = v^2/2a
why have you include g which would account for the factor of 10?
@AC Factor of 10
Well bugger me, so I am. I declare my original question null and void.
I blame google calculator.
only the sabot needs to be curved, the slug can remain straight.
Err... because acceleration is measured in g so 60000g is 60000 * 9.8m/s/s
There's also centripetal acceleration but there *might* be a way round this.
the particles being fired around the LHC are so small relative to the pipe they're in that from their POV it is a straight pipe.
The problem is the side force or centripetal acceleration. Using a = r omega^2 with a circle 10Km in radius I got roughly a 16g side force (when the package is hitting orbital velocity of 7950 m^-1) with a 3g front to back acceleration. Not too serious for electronics or anything less complex than say an insect but bad news for humans. Humans don't seem to do 2 axis accelerations well. BTW an F1 driver at 200mph is roughly 89ms^1 or 1/90 of low earth orbit speed. The possible solution follows.
The ring is approximated by an n sided polygon with straight sides and cylindrical chambers at each chamber. The structure is evacuated to reduce the losses of the payload package pushing all that air ahead of itself.
The wall segments act as linear accelerators giving 3g kicks to the package. As the package free flies between segments (although still under levitation) its yawed about its centre of mass to line up its front end with the next segment for more acceleration. Anything at or near its CM *should* only experience pulses of linear front to back acceleration.
The structure has 2 exits, one aligned to the latitude and one for a polar orbit. Once the package has reached its release velocity it is diverted to an exit tunnel leading to an exit valve while the rest of the system is sealed to preserve vacuum.
*if* it sidesteps the centripetal acceleration then it just becomes a problem if weather a human can survive repeated acceleration pulses without their sense of balance being permanently scrambled. Using 9144ms^-1/30 000 fps and a 3g acceleration gives roughly 3mins 11 secs
At least 2 methods exist to handle the attitude problem. Control moment gyroscopes at each end of the package or push/pull electromagnets at the entry and exit of each straight section can do the job if their big enough. Passive magnets have a pull/weight ratio of c50:1 (better than any known jet engine)
People who've looked at this have talked about "Shutter" valves of metal foils moving on *very* fast carriers. The differential pressure is still only 1 atm.
Note that while the *rough* layout is simple to describe there are multiple *key* trade-offs which would radically affect how much it would cost to build and run it. The obvious ones are the number of sides in the polygon and the angle of the exit tunnels (45deg gives the shortest length to any given exit height but maximum force needed in the diversion system. Shallower angles give lower forces but much longer tunnels (but with longer to seal the main system). More subtle one would be where to apply the yaw forces. If the package is being turned while still partly *in* a straight section it will need clearance between itself and the wall. Less clearance -> more force -> less power needed.
This still leaves you with a substantial object moving at orbital velocity at near ground level. The thermal protection system is *not* trivial.
Mine would have a copy of the last even years February IEEE Trans. Magnetics in. It's the Railgun Issue, packed with all sorts of pulsed power goodness (or alternatively elaborate ways to make yourself the guest of honor at a closed casket funeral).
"but the Blitzer's projectiles are already finned - it would be comparatively easy to make them smart, "
Is the making of smart electronics with the ability to survive the inside magnetic/electric environment easy?
Yeah - High Performance Rah-Rah
1.) S-400 has more payload, longer range, higher terminal speed and is agile.
1.1) S-400 only needs 100g maximum acceleration.
2.) Show me the Vector Thrust Control, Electronics and Sensors Which Can Take 60000g.
3.) I have pleny of time to measure trajectory and launch my ESSM in the exact opposite direction for all long-distance (50km or more) launches.
4.) Mach-8 devices are Very Hot. Infrared Sensors love this. My Stealth Glider is as cold as the atmosphere while slowly (80 m/s) gliding into the carrier and detonating 700kgs TNT.
Can a rail gun be used to
bring down rail gun weapons fired at it?
I'm tempted to build one cos it looks like fun to a loony geek like me so are there any laws against it yet in the uk?
Manufacturing a firearm
The Firearms Act 1968 provides:
57(1) In this Act, the expression "firearm" means a lethal barrelled weapon of any description from which any shot, bullet or other missile can be discharged, and includes -
There are also laws covering airsoft guns, I think you need a liscence to manufacture them so I'd say you are out of luck.
With Risks of being Owned by your own side!
One of the drawback of such levels of EMP discharge on a mobile platform, either on land or sea will be the biological side effects on crew!
(the US Navy already has prior history with messing about with High EMP projects on warships, they didn't go down too well with the crews health)
The big Battle ships of WW2 also required evacuation of all open upper decks when the big guns were being fired or the shockwave would splash the crew over the bulkheads or overboard.
Its in all likelihood that such ships will have to be fully computerised in both navigation and operation, simply due to the long term health risks to anyone onboard.
such platforms would therefore be highly vunerable to cyber attack by hostile forces or BSOD!
and god forbid if it decided that all surrounding fleet ships were designated as hostile!
lets hope they use ADA as the next generation operating system to Windows for Warships.
we welcome the arrival of our Autonomous Dreadnought Overlords
Re: With Risks of being Owned by your own side!
"One of the drawback of such levels of EMP discharge on a mobile platform, either on land or sea will be the biological side effects on crew!"
"(the US Navy already has prior history with messing about with High EMP projects on warships, they didn't go down too well with the crews health)"
Which projects were those?
"The big Battle ships of WW2 also required evacuation of all open upper decks when the big guns were being fired or the shockwave would splash the crew over the bulkheads or overboard."
That's because their projectiles were propelled by rapidly expanding gas.
"Which projects were those?"
Yes, the one that's just been degaussed, please...
which even Wikipedia lists as " widely regarded as a hoax" - oh look, what are those pretty black helicopters doing outside? Aaaaargh.....
It surely is tactically relevant ...
in the battle to transfer wealth from taxpayers to arms company CEOs
Somalia Pirate Repellant
If they were to fit one of these babies onto a tanker? One shot from this should take care of any pirate ship. And at a 200 mile range, it would also be a good patrol weapon!
Can't be done
...for the same reason that a tanker isn't allowed to carry more conventional weapons. Once you arm a ship it isn't a merchantman any more, and many ports will not accept armed ships.
smart railgun dart? unlikely
Great technology and article, I have been following this for a few years now. Just a point about this sentance
"but the Blitzer's projectiles are already finned - it would be comparatively easy to make them smart, though the railgun would need to be aimed reasonably accurately to begin with."
I see two problems with this. Firstly the acceleration is extremely high (60,000g from your article), much more so than conventional projectiles and even more so than missiles. A typical gyroscope (lets take for example the analog devices ADXRS453) is only rated up to 2000g powered or unpowered, so the act of launching the projectile is likely to destroy the controlling electronics, optics/radar/GPS etc.
Secondly as its electromagnetically launched, the transient fields generated from this will be HUGE and will induce some high voltages onto any conductor (circuit boards, chips etc) within the dart. As an electronics engineer, I can tell you that designing electronics and shielding to deal with that is not a simple task, you could spend a long time just finding out if its possible.
So in summary, Whilst it may be possible (with a hell of a lot of work), I would certainly not call it comparatively easy to make the finned projectiles smart. I felt the need to write this in case any misguided project managers at general atomics takes your article to heart and decides to give the local sparkies a hard time!
pedantic electronics geek
Note: no electrons were harmed during the creation of this educational missive, they were merely inconvenienced for a short period of time
"I see two problems with this. Firstly the acceleration is extremely high (60,000g from your article), much more so than conventional projectiles and even more so than missiles. A typical gyroscope (lets take for example the analog devices ADXRS453) is only rated up to 2000g powered or unpowered,"
In the late 70's/early 80s there was a brief report in Practical Wireless (still in business AFAIK) about this artillery launched battlefield surveillance camera.
Some years later I'm looking at solid state gyroscopes and receive a spec sheet from IIRC GEC at Loughton. They were supplying an unusual "Wineglass" resonator design and listed one of their design wins as "Professional grade camera mount." However they also listed it as having been tested to 40 000g. I suspect it was developed for the gun camera project. Impossible. No. Expensive. Probably.
IMHO another S&M fiasco from the Generally Evil Corp. Tried to sell it at near mil spec prices then wondered why almost no one wanted it. So look out for it on Ebay for a fiver.
"Secondly as its electromagnetically launched, the transient fields generated from this will be HUGE and will induce some high voltages onto any conductor (circuit boards, chips etc) within the dart. "
IIRC rail gun electronics tends to use lots of hardware "floating" at high potential using things like solar cells and opto isolators to stop the electronics from being zapped.
My guess would have been a high conductivity shell to ground the currents outside the electronics pack but also a magnetic shield of mu-metal to keept the field out (I'm not current. I seem to recall reports about amorphous metal films that can do a better job).
The joker would be every sensor line into the package is a possible induced current path. How to keep the system safe during launch then enable data flow into the package.
Not really "leap-ahead"...
...its just evolution.
Stealth fighter was possibly only leap ahead as no one had much idea about it. But still realistically someone was going to try it.
Still very cool though.
It is a leap ahead
The rail gun PR teams have been struggling to find something positive to publish about rail guns for a long time. Being able to spin a semi-credible line is indeed a leap ahead.
"Blitzer's projectiles are already finned - it would be comparatively easy to make them smart..."
How would one go about protecting "smart" innards of a projectile from the brief EMP caused while firing any rail gun?
I wonder how many explosive compounds are stable at 60,000g? Many high explosives work by transmission of the explosive shockwave from a trigger - 60,000g would likely do the trick too in many if not all cases - and for other compounds, I wonder how much friction heat is generated by their inevitable compression under acceleration?
I think the first generation of these things are going to have to be hi-tec cannonballs - just very fast passive projectiles rather than proper shells, let alone smart ones...
Probably just pass straight through relatively thin skinned ships. Might be nasty but not terminal.
Title..title, I think I have heard of titles
When the depleted uranium / other heavy heavy stuff projectile is going at mach 5-7 You don't need explosives, kinetic energy does the job.
That's the idea
it just hits things really fast and relies on that to **** them over. Explosives would be overkill, plus it massively eases the onboard storage problem as you don't need to worry about accidentally setting them off.
"Kinetic energy does the job."
Particularly if the engine, fuel tank, magazine etc itself happens to absorb a small part of it ( The sea on the far side of the rapidly disintegrating object absorbing the balance).
If you read stories of naval battles in WW2 it seemed fairly common for shells for example to go right through say a destroyer without going off or causing too much damage. When they did hit something or go off is when you read about all hands lost, etc.
"I wonder how many explosive compounds are stable at 60,000g? "
Pretty much everyone that launches in an artillery shell capable of air bursting.
The granules are *solid* and tightly packed together in a single lump. As long as they are already resting on a solid base and *everything* accelerates together there is no problem.
OTOH a small weight positioned above the explosive on a strong string which would snap if the load it carried increased by 60000 times *would* detonate most (if not all) known explosives by impact.
re: Shells going through
I was thinking about that, it might be better to just miss the ship and put all the energy into the water next to it, like a heavyweight torpedo that goes off under the ship rather than on impact. This creates a big bubble, various things I just about understand happen* in terms of it attaching itself to the ship et voila two bits of ship. Not 100% sure how that would work out in terms of the explosion being next to the ship rather than underneath but I think it might be a better idea than just punching lots of holes in it.
*Like what it says here
Bit of Peter F Hamilton
Much like the orbital bombardment by kinetic harpoons that happens in the Nights Dawn Trilogy really. The speed of the weapon causes the devastation as the energy has to go somewhere on impact.
I am sure it would be terminal for sombody...
"Probably just pass straight through relatively thin skinned ships. Might be nasty but not terminal."
I don't know about you, but having a 'cannon ball' punch threw one side of my cabin and out the other anywhere in the Mach numbers is gona cause me issue, from the pressure wave upto the fragments of my own hull.
I do get your point however, that something akin to a holo-point would be more effective as it would make bigger holes as it tubles around.
I wonder what a depleted uranium shell punching through the skin of a ship into its nuclear power-plant would do? - nothing good I reckon
Sheesh even the navies of the world
are getting into this twilight/vampire craze. ;)
I wonder if they settled on the generic "Vampire" rather than each radar/scanner operator (whatever they are called) calling out the name of their favourite bloodsucker whenever they detect an incoming missile.
NATO's been calling inbound ASMs 'vampires' for more than 25 years. Way back in 1986 Tom Clancy managed to know that, when he wrote _Red Storm Rising_.
Hint: the standard radar displays use stylized symbols to display various objects. Inbound ASMs are carets, ^s... upsidedown Vs. V for vampire. And inbounds also show up in red.
True. Greg Bear also uses this terminology in the first pages of Eon, written in 1985.
They are testing this thing in land based facilities. Now, I would love to know how one of these would behave as a ship based weapon, because in the sea there are things like waves and constant vibration, plus the ship's movement. Moving the barrel while you are accelerating ammo through it at 60.000 gee doesn't sound as such a great idea -torque, momentum an all that. My bet is that, on a ship and under real battle conditions, one of these railguns will be able -with luck- to shoot once or twice. And then it will explode.
"IMPORTANT ADVICE - READ FIRST: Before using the Blitzer, stop at a dry dock, sink the lower half of the ship in fast concrete and wait for a few hours" :D
Yeah, I know, they're scientists and experts and all that crap. On the other hand most companies I know wouldn't say no to a little bit of money from a government, whatever the circumstances.
Are affected by all the wave stuff as well, that's why they have gyro-stabilising systems which keep the barrel pointing the right way while the ship moves around it. Anti-vibration mounts are already common, as are active anti-vibration systems.
A bigger question
Have they been able to make these rail guns sustain a reasonable rate of fire? Last I looked the rail guns were only good for a few shots before needing a significant maintenance job.
No point in having a deep magazine if you have to switch out rails etc after a few shots.
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