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Science Navy Railgun Fires 33-megajoule Shot
Shane McGlaun (Blog) - December 13, 2010 10:02 AM
Print 87 comment(s) - last by Iaiken.. on Dec 21 at 11:31 AM

High-speed camera captures 33-megajoule shot of Navy railgun  (Source: U.S. Navy)
Projectile can travel at least 110nm at many times the speed of sound

Much of the buzz in the defense community tends to focus on the Air Force with major aircraft programs like the F-35 and the ongoing tanker debacle. Other branches of the military are also working in some very interesting projects for new weapon systems.

The Navy announced last week that it hit a milestone with its railgun project. The railgun fires a very fast projectile that is accelerated with electricity rather than gunpowder or explosives. The weapon payload uses kinetic energy to destroy targets rather than a high-explosive warhead.

The Navy milestone hit last week was the world-record 33-megajoul shot from the electromagnetic Railgun aboard the Navy Surface Center Dahlgren Division. A megajoule is a measurement of energy associated with a mass traveling at a certain velocity. A one-ton vehicle moving at 100mph is a single megajoule of energy. 

"Today's railgun test demonstrates the tactical relevance of this technology, which could one day complement traditional surface ship combat systems," said Rear Adm. Nevin Carr, chief of naval research.

The 33-megajole shot is capable of reaching targets at extended ranges with a velocity in the area of mach five. The Navy says that the rail gun has many benefits other than the ability to shoot projectiles over one hundred miles with accuracy. The electromagnetic weapon improves safety on the ship because there are no traditional propellants needed and the projectiles need no high-energy explosive warheads.

"The 33-megajoule shot means the Navy can fire projectiles at least 110 nautical miles, placing Sailors and Marines at a safe standoff distance and out of harm's way, and the high velocities achievable are tactically relevant for air and missile defense," Rear Admiral Carr said. "This demonstration moves us one day closer to getting this advanced capability to sea."

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Tank Upgrades
By Mitch101 on 12/13/2010 10:19:14 AM , Rating: 3
Sounds like Tanks are going to be getting this soon.

Last I heard of this technology I dont believe they shoot explosive rounds but round circular tubes that the velocity alone destroys the target. Potentially on the plus side we dont have unexploded munitions lying around.

For the record land mines scare the heck out of me. I cant imagine living in a country where there are known to be tons of them still around.




RE: Tank Upgrades
By MrTeal on 12/13/2010 10:33:49 AM , Rating: 4
You need to find the person who told you you'll be seeing a multi-megajoule rail gun on a tank any time soon and make sure they're in the seat beside you in Phys 101 next semester. These projects make sense for large warships since many are nuclear powered and have the ability to generate the kind of energy and space you need for these weapons, and even then they won't be in active service soon.


RE: Tank Upgrades
By mcnabney on 12/13/10, Rating: 0
RE: Tank Upgrades
By MrTeal on 12/13/2010 12:44:48 PM , Rating: 4
These rail guns are huge, and the power requirements are more than you would think. You're talking energy, which isn't the same as power. You can't use a battery, other than for storage as you can't draw energy from it quickly enough. You need a capacitor bank, and the energy density of even good capacitors is lower than that of batteries. A big capacitor bank is BIG, even if you get energy density of 0.05MJ/L (very good for a capacitor) to store 50MJ you'd be looking at 1000L (1 cubic meter) even outside of all the packaging and external circuitry you'd need. As far as efficiency, I'm not sure, but a previous 10MJ test used a 9MJ+33MJ capacitor bank.

If you want to assume 33% efficiency, for a 10MJ gun you'd need 33MJ of capacitor storage, maybe a large battery system to provide extra storage, and a generator large enough to power it. The M1A1 can do 10 rounds per minute, even doing 1 round a minute constant with battery enhancement for burst firing would require about half a megawatt of power. All this outside the actual size of the weapon itself.

All this, when the 120mm gun in the Leopard 2 and M1A2 can fire the 8.35kg DM53 kinetic energy projectile at 1750 m/s. That's 25MJ of kinetic energy.


RE: Tank Upgrades
By Solandri on 12/13/2010 1:01:57 PM , Rating: 4
quote:
The M1A1 can do 10 rounds per minute, even doing 1 round a minute constant with battery enhancement for burst firing would require about half a megawatt of power.

Time for my favorite engineering unit conversion:

In fourteen-hundred and ninety-two,
Columbus sailed the ocean blue.
Divide the year of his voyage by two,
and you get the number of Watts in a horsepower.

0.5 MW = 670 hp. The engine in the M1A1 is capable of producing about 1500 hp. I agree that we're not there yet, but I can see these things eventually finding their way into tanks.


RE: Tank Upgrades
By MrTeal on 12/13/2010 1:14:46 PM , Rating: 2
:) I know. The actual power was 0.55MW, so about half a megawatt. That's 737HP, about 740HP. These are all educated guesstimate numbers, so I didn't think the 10% would be a huge issue.

Even if you siphoned off half the power from the turbine to power the generator, you still need that generator. Really, I can see them being used at some point in the future, but not in the next 50 years.


RE: Tank Upgrades
By mindless1 on 12/16/2010 4:04:59 AM , Rating: 2
Correct me if I am wrong, but wouldn't it be a mass problem not a generator problem, that due to the (relatively) low mass of the tank isn't it impossible for it to project at 33MJ without being pushed backwards such that the actual impact force is offset by this amount of propulsion in the opposite direction?


RE: Tank Upgrades
By Keeir on 12/16/2010 3:02:27 PM , Rating: 2
What? That makes no sense.

If we consider this simple a conservation of momemtum problem (energy is coming from the application of electrical force), a typical M1 tank would have an end velocity of ~.2 m/s to give 33 MJ of energy to a 1 kg projectile. M1 tanks are already capable of firing amunition with 10s of MJ of energy at muzzle


RE: Tank Upgrades
By jive on 12/14/2010 1:13:37 AM , Rating: 2
you are missing the point here. The main benefit of rail guns is that they are point and shoot and never miss. The theoretical maximum is closer to speed of light than speed of sound. Rail guns would make excellent AA defense weapons and put the battle ships back on the map. They are the next best thing before lasers actually make it to weapon systems. Neither is suitable for bomber or artillery replacements and not particularly useful attack weapons due to the low rate of fire.


RE: Tank Upgrades
By mooty on 12/14/2010 8:38:24 AM , Rating: 3
Firing a projectile at any appreciable fraction of light speed in Earth's atmosphere is totally out of the question. Even mach5 is a big achievement.

1 mach in air is very roughly 300mps (metre per sec)
light travels roughly 300 000 000mps.

While 5 machs is a very respectable speed, it's really not worth mentioning compared to the speed of light.


RE: Tank Upgrades
By Bruneauinfo on 12/14/2010 12:46:27 PM , Rating: 3
still, his point is valid as projectiles flying any faster - in the case of antiaircraft weapons - would essentially add no appreciable benefits to accuracy. A TI-85 adds no benefit over a free basic calculator when all you're doing is 3rd grade addition and subtraction problems.


RE: Tank Upgrades
By Iaiken on 12/21/2010 11:31:23 AM , Rating: 2
An additional problem that you haven't really considered.

The earth is round, you are limited to certain velocities in order for the projectile to curve in such a manner that they can hit a target beyond the horizon.


RE: Tank Upgrades
By MrTeal on 12/13/2010 12:52:58 PM , Rating: 4
http://www.dtic.mil/ndia/2008psa_peo/elliotday2.pd...

Check out page 10 of this PDF, the image at top left is the 33MJ capacitor bank used in a Navy test shot, and the top right is the gun itself.


RE: Tank Upgrades
By abscode on 12/14/2010 10:34:10 AM , Rating: 2
Cool. Thanks for the link!


RE: Tank Upgrades
By AnnihilatorX on 12/14/2010 9:48:46 AM , Rating: 2
Railgun technology requires superconductors for the electro-magnets to get any reasonable efficiency at all.

Superconductors still reqruie chunky cooling systems unless we discover room temperature superconductors.


RE: Tank Upgrades
By Mitch101 on 12/13/2010 11:59:36 AM , Rating: 2
Lego Railgun Tank v.2
http://canonfodder000.deviantart.com/art/Lego-Rail...

The military has a projected date of 2015 for a rail gun tank. More likely not at the level a warship would need.


RE: Tank Upgrades
By fic2 on 12/13/2010 12:20:11 PM , Rating: 4
Like most military/gov't projects I think they flipped a couple of numbers. Probably closer to 2051 than 2015.

But then again once you have a Lego model a working prototype is just around the corner.


RE: Tank Upgrades
By MrTeal on 12/13/2010 12:46:44 PM , Rating: 2
Got a link to the 2015 projection for a tank made of something other than lego?


RE: Tank Upgrades
By Mitch101 on 12/13/2010 1:11:17 PM , Rating: 1
Railgun Pulsed Power Program

Army Electric Gun Program

Pulsed AC Rotating Machines

Research into pulsed alternators at UT-CEM can be traced back to the late 1970’s with the invention of the compulsator (compensated pulsed alternator), a new type of low impedance electrical machine designed for very high power operation. Although it was conceived at UT-CEM to power laser flash lamps for fusion research at Lawrence Livermore National Laboratories (LLNL), the compulsator concept has been successfully applied to electric launchers for the U.S. Army and NASA, and high frequency microwave sources. Iron-core prototypes built for LLNL in the early 1980’s proved the operating principles of the concept. This involves the use of a compensating shield or winding in the alternator to lower its internal impedance to a very low value, while simultaneously tailoring the very large (multi-mega amp) current pulse to suit the required loads.

Iron-Core Compulsator

In the mid-1980’s, the first compulsator built for the U.S. Army electric gun program was successfully demonstrated. Named the "Iron-Core Compulsator" (ICC), the device is a 6-pole, rotating field machine which stores 40 MJ of kinetic energy at 4,800 rpm, and can repetitively deliver ten 1 MJ, 2 ms pulses. The ICC generates an open circuit voltage of 2 kV and operates at a peak current of 1 MA, resulting in a peak power rating of 2 GW. After fulfilling its stated contract goals by firing a burst of railgun shots at 10 Hz, the ICC has become a reliable CEM laboratory power supply for testing other components including high power switching for newer compulsators, and advanced railgun barrels.

Small Caliber

After seeing the proof of principle demonstration by the ICC, the U.S. Army then pursued the development of more compact, lighter weight pulsed power generators beginning in 1988. UT-CEM proposed and was contracted to build two single phase, self-excited, air-core compulsators. The air-core nature of the new machine concepts allowed required use of very high strength composites for construction of the rotor, which enabled it to be spun much faster - both storing more energy and making it much lighter. The first of these machines was built during the Small Caliber Rapid-Fire Railgun Program. The compulsator for this system is a 2-pole, rotating armature topology. While rated at half the power of the ICC, the small caliber compulsator weighed only 8% as much - so the power density was improved by a factor of six. The new machine demonstrated the viability of the SEAC concept and developed several new components; including the high speed composite rotor, the SCR based output switch and field rectifier.

9 MJ Range Gun

On a larger scale, the U.S. Army desired the capability to fire a large bore railgun at a test range and demonstrate the pulsed power supply at full scale. UT-CEM therefore began working on the 9 MJ range gun in 1988. Designed to launch 2 to 4 kg packages at velocities up to 4 km/s, the range gun system uses a much larger version of the small caliber compulsator as the pulsed power supply. Design features of this machine include 230 MJ stored energy, 6 kV and 3 MA peak output ratings, and 9 shot repetitive fire capability. Unfortunately, funding constraints combined with revised electric gun program focus has meant that the machine was shelved at 95% complete level.

Cannon Caliber Electromagnetic Launcher

The early 1990’s brought continued interest from the U.S. Army, but also from the Marine Corps. The Cannon Caliber Electromagnetic Gun System (CCEMG) is a joint project which seeks to demonstrate an EM gun system designed from a system/mission prospective. Presently undergoing lab testing, the CCEMG uses a second generation single-phase air-core compulsator which represents a factor of 3 increase in energy (3.5 J/g multi-shot) and power density (to 1,500 kW/kg) over the range gun system. The machine powers a rectangular bore railgun to accelerate 185 g launch packages to muzzle velocities far exceeding the conventional state of the art for this caliber. Rated at 4 kV and 850 kA, the compulsator stores 40 MJ and can deliver 15 shots without recharging the rotor.

Focused Technology Program

Presently, the U.S. Army is funding the Focused Technology Program to develop the next generation of compact compulsator power supplies, which will be consistent with their concept of the Future Main Battle Tank (FMBT) to be fielded by 2015 . The FTP machine concept represents a fundamental departure from the previous air-core compulsators by evolving to a rotating field topology and a multi-phase operating modes. These changes, combined with light weight composite stator structures will result in great increases in specific performance over the CCEMG machine, and will ultimately allow integration of the system into a tank vehicle chassis. The compulsator will be a part of the all-electric tank which includes electric vehicle drive and suspension, and electric armaments. In this concept, the flywheel energy can be used as a flywheel battery to provide power for vehicle acceleration and regenerative braking, and will also produce electrical power for the electromagnetic armaments.


RE: Tank Upgrades
By MrTeal on 12/13/2010 1:31:40 PM , Rating: 2
Other than perhaps a lighter 60-ton M1A3, the current Army plan is keep the Abrams in service until 2050. There is no FMBT currently under testing, and the FCS program was canceled.


RE: Tank Upgrades
By drank12quartsstrohsbeer on 12/13/2010 4:44:46 PM , Rating: 3
iirc this document was written in the mid 90s


RE: Tank Upgrades
By melgross on 12/13/2010 2:12:53 PM , Rating: 2
A tank wouldn't need this amount of power. A smaller gun would suffice. Even if it were 25% less, that would be significant. And if we do see this in tanks, it will likely be a new design that was done for this purpose. I'm pretty sure the Abrams isn't the last tank design we'll have. In fact, I'm pretty sure they've got newer designs they've been working on for years.

A tank that was designed around this gun would look very different.


RE: Tank Upgrades
By Chernobyl68 on 12/13/2010 7:51:34 PM , Rating: 2
the only nuclear warships the US Navy has are carriers and submarines, currently. They've been looking at magnetic catapults, but they aren't really a candidate for railguns.


RE: Tank Upgrades
By wordsworm on 12/17/2010 7:31:08 AM , Rating: 2
Seems simple enough: build a nuclear powered tank and outfit it with a rail gun.


RE: Tank Upgrades
By Connoisseur on 12/13/2010 10:39:49 AM , Rating: 2
I think this will probably be relegated to warships for quite some time until they:
a) can create a compact high-density energy source to constantly charge the capacitors for this beast
b) increase the efficiency significantly so they can compact the coils. I seem to recall a few articles indicating that railguns are extremely inefficient.


RE: Tank Upgrades
By Schrag4 on 12/13/2010 11:49:21 AM , Rating: 2
I don't think efficiency has anything to do with why these aren't on tanks (which are relatively small). Rather, a long rail is needed to spread out the acceleration over a longer period of time. The shorter the rail, the more the thing just acts like an explosive accelerating the projectile very quickly. Railguns aren't magic, they still do the equal/opposite reaction thing just like all other weapons that accelerate projectiles. Maybe you could put a shorter rail on a tank that's a lot less capable. (Or else maybe you don't mind that your tank goes tumbling backwards violently whenever it fires if it had a shorter rail that still transfered the same amount of energy).

I agree, though, about your energy source point a).


RE: Tank Upgrades
By Solandri on 12/13/2010 1:23:24 PM , Rating: 4
quote:
I don't think efficiency has anything to do with why these aren't on tanks (which are relatively small). Rather, a long rail is needed to spread out the acceleration over a longer period of time. The shorter the rail, the more the thing just acts like an explosive accelerating the projectile very quickly.

Not that long. The length of this one is about 10m. I can easily see scaling that down to ~3m for a tank turret.
http://www.navweaps.com/Weapons/WNUS_Rail_Gun.htm

quote:
Railguns aren't magic, they still do the equal/opposite reaction thing just like all other weapons that accelerate projectiles

Compared to chemically fired rounds, yes they are magic. Chemical propellant operates by generating high pressure between the back of the gun bore and the round. The high pressure pushes the round forward. But here's the catch - as the round moves forward down the barrel, the volume of space between the round and the back of the firing chamber increases, rapidly decreasing the pressure. So the round only gets maximum acceleration when first fired. After that, acceleration is constantly decreasing. (Some of Bull's cannons mitigated this problem by injecting high pressure gas further down the barrel after the round had passed.)

A railgun doesn't suffer from this. It can continue to apply full acceleration energy to the round right up until it leaves the rail.


RE: Tank Upgrades
By xthetenth on 12/13/10, Rating: 0
RE: Tank Upgrades
By Smartless on 12/13/10, Rating: 0
RE: Tank Upgrades
By Jaybus on 12/14/2010 9:16:51 AM , Rating: 2
Ridiculous. Of course you can hit a target over the horizon. Mach 5 is no where near orbital velocity. This works no differently than any other gun.


RE: Tank Upgrades
By menace on 12/13/2010 2:18:18 PM , Rating: 2
quote:
I can easily see scaling that down to ~3m for a tank turret.


Scaling down from 10m to 3m would reduce the muzzle velocity by 70% and power by 90%. Woefully inadequate compared to today's tank guns. To compensate you would have to increase acceleration by 3 times which requires 10 times more power transferred to the projectile over the 3m length as you used for the 10m barrel for the gun to achieve the same muzzle velocity. So power density of the field would have to increase about 33 times and the amount of capacitance needed increase ten times and also have to be able to expel the full charge three times faster. Not so easy you see?


RE: Tank Upgrades
By Solandri on 12/13/2010 2:59:59 PM , Rating: 2
The whole point of the project is to put these things on ships and tanks. If you flip through the PDF someone else posted, you'll see that there's collaboration on this with the Army for use in tanks. I agree we're not going to see this particular research railgun on a tank (or a ship for that matter). I was referring to whatever railgun this research eventually produces.

And wouldn't the energy transferred be reduced by 70% with a corresponding 90% reduction in muzzle velocity?


RE: Tank Upgrades
By Solandri on 12/13/2010 3:28:28 PM , Rating: 2
Bleh, did the square instead of a square root. 45% reduction in muzzle velocity.


RE: Tank Upgrades
By 91TTZ on 12/13/2010 3:51:33 PM , Rating: 2
quote:
Compared to chemically fired rounds, yes they are magic. Chemical propellant operates by generating high pressure between the back of the gun bore and the round. The high pressure pushes the round forward. But here's the catch - as the round moves forward down the barrel, the volume of space between the round and the back of the firing chamber increases, rapidly decreasing the pressure. So the round only gets maximum acceleration when first fired. After that, acceleration is constantly decreasing. (Some of Bull's cannons mitigated this problem by injecting high pressure gas further down the barrel after the round had passed.) A railgun doesn't suffer from this. It can continue to apply full acceleration energy to the round right up until it leaves the rail.


The bullets fired by regular guns also continue to accelerate up to the point where they leave the barrel. When you load bullets for a particular gun, you choose a certain type of gunpowder for the application. They make pistol powder burn faster than rifle powder for that very reason.


RE: Tank Upgrades
By Schrag4 on 12/14/2010 9:24:21 AM , Rating: 2
This. The shorter the barrel, the higher the acceleration over a shorter period of time (for the same muzzle velocity). Perhaps a railgun would allow for more evenly spreading out the force over the time that the projectile is being accelerated, but in the end, for every action there's an equal and opposite reaction. Again, there's no magic here. I stick by my point that muzzle velocity will have to drop significantly to put this thing on shorter rail, and to attach it to a "lighter" vehicle.

Maybe the way they intend to use it on tanks is to significantly reduce the size of the projectiles. If you get a "bullet" moving fast enough, it doesn't have to be very big at all to pass through a tank, neutralizing the crew inside. So the warship hurls huge projectiles that can travel vast distances and level buildings and the tanks spit out tiny projectiles so fast they pass through any armor. I'd buy that.


RE: Tank Upgrades
By kingius on 12/20/2010 10:16:57 AM , Rating: 2
As if we need any of this stuff, we're very good at killing each other as it is. What a massive waste of intellect.


RE: Tank Upgrades
By JediJeb on 12/13/2010 5:10:19 PM , Rating: 2
Need to read the part in the article about how right now these have a tendency to melt the rails when trying to hit such high velocities. If you shorten the rail, you will also increase the temperatures which are produced by the greater acceleration needed to gain the same speeds in the shorter distance. I can't imagine needing to replace the rails after a shot or two in a tank, that would not be very efficient.

It also says that without huge capacitor stacks on a warship the warship generator would not be able to fire more than a round or two per minute, the power available in a tank format would make firing even slower, also not good for a ground battle situation.


RE: Tank Upgrades
By xthetenth on 12/13/2010 1:48:28 PM , Rating: 2
quote:
Last I heard of this technology I dont believe they shoot explosive rounds but round circular tubes that the velocity alone destroys the target. Potentially on the plus side we dont have unexploded munitions lying around.


You do know the standard AT round is HVAPFSDS, or in layman, a high velocity fin stabilized dart that uses kinetic energy alone to destroy the target? Any tank with a smoothbore is basically designed only for kinetic energy round, HE rounds need volume and that doesn't fit with fin stabilization which generally needs a sabot to work properly.


RE: Tank Upgrades
By Fritzr on 12/19/2010 8:47:27 PM , Rating: 2
Tank rounds are spin stabilized. The "dart" rounds already use a sabot that is discarded in flight.


RE: Tank Upgrades
By Aloonatic on 12/14/2010 6:26:44 AM , Rating: 2
How useful would this sort of weapon be on a tank? Assuming that you could power it, as discussed in the multitude of comments above.

Would the range of the weapon, tank to tank, be limited to line of site and the curvature of the Earth, as the projectiles travel at such high speeds as to make them behave in the same sort of way as a laser?

Do current tanks have a range that relies on a parabolic type trajectory, where the shell is "lobbed" and as such can actually hit targets on the ground further away than a rail gun projectile could.


RE: Tank Upgrades
By Schrag4 on 12/14/2010 9:11:24 AM , Rating: 2
quote:
Do current tanks have a range that relies on a parabolic type trajectory, where the shell is "lobbed" and as such can actually hit targets on the ground further away than a rail gun projectile could.


I would think if you needed to "lob" the projectile over some sort of terrain, you could simply reduce the power of the railgun to achieve the same, slower muzzle velocity. I would imagine an onboard computer could pretty easily calculate the angle and power that would deliver the most energy to the target.


RE: Tank Upgrades
By Aloonatic on 12/14/2010 11:13:06 AM , Rating: 2
quote:
...you could simply reduce the power of the railgun to achieve the same, slower muzzle velocity
Wouldn't that entirely defeat the object of a rail gun, which are about delivering energy to the target through a ludicrously fast projectile?

I wasn't really talking about over some sort of terrain either. My English was perhaps a little, how you say, inelegant.

Basically, doesn't the parabolic trajectory of conventional cannons allows artillery and tanks to fire "over" the horizon? Wouldn't a rail gun fire, quite literally, over the horizon, and on and on and on?

Wouldn't a rail gun just be wasted on a tank any way?


RE: Tank Upgrades
By Aloonatic on 12/14/2010 11:30:22 AM , Rating: 2
By the way, I get what you mean about reducing the speed of the projectile as an option, whilst firing at silly high "conventional" rail gun speeds when a line of sight is available. However, you will need to use some sort of explosive round to have any affect on the target at the lower speed, which I'm not sure is the plan.


RE: Tank Upgrades
By Fritzr on 12/19/2010 8:53:44 PM , Rating: 2
Tanks are armored artillery. Within the limits of their gun travel and range, they can fire over hills or over the horizon at targets that are out of line of sight.

All they need are accurate targeting coordinate to aim the gun with.

The most common usage is line of sight, but for all but point blank shots, the shell rises on the way to target, then drops. When range, trajectory and velocity are all set correctly, the shell passes through the target as it follows it's normal trajectory.

To fire over a hill, you aim high and fire with a relatively low velocity ... similar to pitching at a batter vs throwing a ball over a house to a catcher on the other side.


Nautical Mile
By chaos7 on 12/13/2010 10:09:51 AM , Rating: 5
quote:
...can travel at least 110nm at many times the speed of sound


nm = Nanometer
M, NM, Nm or nmi = Nautical Mile




RE: Nautical Mile
By borismkv on 12/13/2010 11:18:09 AM , Rating: 4
Thank you. I was trying to figure out why it was a big deal that it could fire a projectile 110 nanometers.


RE: Nautical Mile
By rcc on 12/14/2010 1:13:41 PM , Rating: 2
Cuz it was going soooo fast the projectile broke up after 100 nm??


RE: Nautical Mile
By WoWCow on 12/13/2010 11:22:40 AM , Rating: 2
Yeah, now I'm left wondering when or if this technology can be used to create a gun to send/shoot something fast enough across the galaxy in a reasonable amount of time (like a mass relay station!).

Course; we also need to figure it out a way to stop the object in question after it is shot...

Damn mass effect 3 announcement got me all excited >_<.


RE: Nautical Mile
By Akrovah on 12/13/2010 11:30:40 AM , Rating: 3
quote:
Damn mass effect 3 announcement got me all excited


Oh I'm with you on that.

Though I don't think this tech would be good for a ship. With accelaration like that any crew on board would be a nice gooey paste, making the whole slowing down issue kind of moot.


RE: Nautical Mile
By Solandri on 12/13/2010 12:56:34 PM , Rating: 2
quote:
Yeah, now I'm left wondering when or if this technology can be used to create a gun to send/shoot something fast enough across the galaxy in a reasonable amount of time (like a mass relay station!).

Doubtful. It might work as a launch vehicle (for cargo) - it's a toss-up whether railguns or gas guns will turn out to be more practical for that application. As a launch vehicle, you're not launching your fuel with the payload, which can mean a 95%-99% weight savings, which is just huge. (A gas gun works by using a light gas like hydrogen whose compressed and heated molecular velocity, and hence the highest speed it can accelerate something, is greater than escape velocity.)

For use in space travel, they just don't generate enough velocity. This gun can currently fire a payload at 3000-5000 mph. Escape velocity from Earth is 11.2 km/s, or 25,000 mph. Due to kinetic energy being the square of velocity, it costs you a lot more energy to increase payload velocity from 24,000 to 25,000 mph than to increase it from 4000 to 5000 mph. You are better off carrying your fuel with you and using a rocket or railgun to fire the fuel backwards, using the momentum balance to increase your velocity further. (In kinetic energy terms, it costs less energy to fire your propellant backwards than your spacecraft forward because your propellant, even though it's fired backwards relative to your spacecraft, is still moving in the same direction as your spacecraft from the reference frame of where you'd be launching the spacecraft - the Earth.)

As it turns out, a "railgun" for firing propellant at high velocities out the back of your spacecraft has already been invented. It's called an ion thruster, and can fire xenon atoms at about 28 km/sec, or 60,000 mph.


I made this!
By GreenEnvt on 12/13/2010 11:34:29 AM , Rating: 3
Well not this specific one, but I did build a rail gun in High school about 12 years ago. It shot a steel ball bearing a few feet.
I had hoped it would go further, but the prof was quite impressed it worked at all. Apparently a few other people tried to make one over the years but it never did much.

I made the magnets myself, coiling wire around some iron spikes. Control method was pretty simple, V-shaped rail with one side being solid, the other having cuts in it to control when each magnet fired. No fancy computer control, but it worked. I'd love to rebuild that one day.




RE: I made this!
By Helbore on 12/13/2010 12:51:15 PM , Rating: 2
You should have told the government. They might have thrown billions of dollars at you to build it on a bigger scale!


RE: I made this!
By jive on 12/14/2010 1:02:13 AM , Rating: 3
Sound to me you were building a coil gun. The difference between coil gun and rail gun is that coil gun uses magnetic energy to accelerate the projectile where rail gun use the electric field. Coil gun is what people often think when talking about rail guns. The reason I think you were building coil gun is that rail guns usually turn their projectiles into plasma.

The aerodynamic shape of the projectile is not a big concern because it's going to be flow formed by the drag into a shape of drop anyway. This is also cause of the rail meltdowns.


RE: I made this!
By GreenEnvt on 12/14/2010 2:25:45 PM , Rating: 2
Indeed you are correct, never knew the difference.


nm
By gibb3h on 12/13/2010 10:09:42 AM , Rating: 4
am I the only one who read 110nm and thought "110 nano metres, thats not exactly impressive"




RE: nm
By chaos7 on 12/13/2010 10:10:44 AM , Rating: 2
No you are not, my comment 9 seconds after yours confirms it.


RE: nm
By fic2 on 12/13/2010 12:25:07 PM , Rating: 3
The article author is the only one that didn't think nano meters.


Comparison to battleship rounds
By 91TTZ on 12/13/2010 2:00:25 PM , Rating: 3
This new railgun fires rounds with an energy of 33 megajoules. It sounds like a lot, but it's not really that much for a weapon of that size. For comparison purposes:

The USS Monitor from the Civil War had a gun with 6 Megajoules.
The Iowa class battleships from WWII fired with an energy of 350 Megajoules. The British had a battleship gun in 1915 that was 410 Megajoules.

So in other words, this isn't really going to give you any new capability that we didn't have over 100 years ago.




RE: Comparison to battleship rounds
By Master Kenobi (blog) on 12/13/2010 7:47:36 PM , Rating: 2
Well in the area of cost/damage analysis this could allow you to wreck a smaller target with better accuracy and minimal collateral damage all while saving the tax payers money. Hey now that's an idea.


RE: Comparison to battleship rounds
By 91TTZ on 12/14/2010 12:32:52 PM , Rating: 2
quote:
Well in the area of cost/damage analysis this could allow you to wreck a smaller target with better accuracy and minimal collateral damage all while saving the tax payers money. Hey now that's an idea.


1. There's no reason that a conventional artillery gun can't be accurate. I'm willing to bet that you could make an artillery shell more accurate than a railgun projectile since you could make a guided artillery shell. So far, there are no guided railgun projectiles.

2. With a solid armor piercing shell instead of a high explosive shell, you wouldn't have a lot of collateral damage. You'd be dealing with kinetic energy from the shell.

3. I'm willing to bet that the cost of designing, building, and operating a railgun is much, much higher than purchasing steel and gunpowder.

Basically, at this point the rail gun is not practical. It's shown possibility but missiles and shells can do the job more effectively.


RE: Comparison to battleship rounds
By DougF on 12/14/2010 3:33:05 PM , Rating: 2
Except the point the Navy is making about railguns is the ability to deliver the weapon over hundreds of miles at high velocity for the cost of a bullet (comparatively). We have weapons that can travel hundreds of miles (cruise missiles, aircraft; but expensive), and we have weapons that can deliver quickly (artillery; but limited range). A railgun combines the best of both worlds. Since bombs and missiles with their (relatively) low speed need explosives to ensure a probability of kill, a solid shot will reduce overpressures and fragmentation issues with containing collateral damage.

As for steel and gunpowder doing this cheaper, I'm not sure that that's feasible, considering Bull's supergun and others like it haven't been exactly winning awards, mostly because the size alone of the systems makes it impractical for anything other than a fixed launch site. The costs associated with having to tear down/build up such a system everytime you needed to significantly change direction, or build a turntable system large enough to hold it would be large indeed.


Since we complained about the nm stuff
By kontorotsui on 12/13/2010 11:36:59 AM , Rating: 1
Why does the article author bothers to use the International System unit Joule (Kg*m^2/s^2) when the rest is written with meaningless miles?

Don't show off your megajoules. If you stick with miles, then you can measure the energy shot by the railgun with (pounds * feet^2 / s^2) and your unscientific performance is now complete.

Make it better, use moon revolutions instead of seconds, so the unmetric total is even much more higher and more impressive.




RE: Since we complained about the nm stuff
By Solandri on 12/13/2010 1:33:04 PM , Rating: 3
Maritime navigation uses nautical miles because a nautical mile is equal to one minute of latitude, or one minute of longitude at the equator (1/60th of a degree). It's somewhat arbitrary, but it makes it a helluva lot easier to eyeball distances on a chart which is labeled in degrees latitude/longitude.


By xthetenth on 12/13/2010 2:03:28 PM , Rating: 2
That and he's reporting Navy news, and the Navy uses those units for that very reason, so any comparable figures you'll find are almost certainly in knots as well. Much better to leave it in nmi like the rest of the comparable weapons systems so you can compare it more easily.


By joex444 on 12/13/2010 6:40:20 PM , Rating: 1
I totally agree. Either go with all SI units, or all Imperial units.

For those playing at home, the unit of energy in imperial units is called a ft-lb force (lb plays the double role of force and mass). Though the hp*hr is probably better. In this case, this thing is a 12.2 hp*hr railgun. Ah, that's sounding impressive enough guys, can't we convert to Joules?


We will need these
By Pessimism on 12/13/2010 11:29:37 AM , Rating: 2
When the malevolent aliens invade!




RE: We will need these
By corduroygt on 12/13/2010 11:48:44 AM , Rating: 4
Yes, these will defend us from the malevolent alien robots. However they unfortunately won't be able defend us from poor sequels to movies about malevolent alien robots.


What about...
By Motoman on 12/13/2010 11:31:06 AM , Rating: 2
...the size of the weapon itself? In my head I'm imagining a ship with one weapon that spans the entire length of the ship, basically turning it into a floating howitzer...




RE: What about...
By NicodemusMM on 12/13/2010 12:15:53 PM , Rating: 2
That description brings to mind the MAC (Mass Accelerator Cannon) of human ships in the Halo lore. Basically a massive railgun (or 3) mounted down the spine of the ships. It would be an interesting design... just make sure your target can't outrun your rate of turn.


RE: What about...
By kraeper on 12/13/2010 12:18:02 PM , Rating: 2
You say that like it's a bad thing. Remember the A-10? :D

(Also, stolen from below, other than missing scale, you can watch it here: http://www.youtube.com/watch?v=6BfU-wMwL2U )


Projectile
By ekv on 12/13/2010 2:24:22 PM , Rating: 2
Anybody wonder about the projectile used? The (simply marvelous) hi-speed video of the shot shows a relatively square object, with tail strakes. [Which is what actually got ME to thinking about Mass Effect].

Now, you'd think, if I were shooting something at Mach 8 I'd make it somewhat aerodynamic. At the very least, the projectile would have a lifting-body design. No?

Unless perhaps they're trying to simulate a heavier payload?




RE: Projectile
By foolsgambit11 on 12/13/2010 5:38:04 PM , Rating: 2
I have no idea what I'm talking about here, but a couple of ideas may be that the shape is so that it responds to the magnetic field in the railgun most efficiently, or maybe it's so that the projectile will create the most damage, rather than simply piercing its target.


RE: Projectile
By Chernobyl68 on 12/13/2010 8:02:42 PM , Rating: 2
probably the shape of the "rail" in the lab environment.


Railguns
By Spivonious on 12/13/2010 10:23:26 AM , Rating: 4
You have been erased.




SG-1
By kenthaman on 12/13/2010 10:27:44 AM , Rating: 4
Is it just me or does that photo look similar to the burst from the event horizon when the gate is activated in SG-1? LOL




edit please
By Chernobyl68 on 12/13/2010 7:49:52 PM , Rating: 2
Wow, where to start. You misspelled Megajoule twice, each time a different way

Megajoul
Megejole

a 1 ton (2000 lbs) car travelling at 100 mph has (close, but not quite ) 0.906 Megajoules of Kinetic energy.

nm = nanometers, nmi = nautical miles (or NM, etc..)




RE: edit please
By Shadowself on 12/14/2010 6:27:38 AM , Rating: 2
Not quite a megajoule was my initial gut reaction. A quick, back of the envelope calculation confirmed your number (approximately 0.906476 MJ).

Now if the author had completed the units missmatch and gone with a "metric ton" of approximately 2,204.6 U.S. pounds then he'd have had 0.999 MJ wich is close enough for most people to call a megajoule.


So when do the batteries run out ?
By Silver2k7 on 12/14/2010 2:48:19 AM , Rating: 2
"The electromagnetic weapon improves safety on the ship because there are no traditional propellants needed and the projectiles need no high-energy explosive warheads."

So how many shots can be fired before the battery is out, or will the ship have somekind of nuclear reactor to power this thing ? :)




RE: So when do the batteries run out ?
By jive on 12/14/2010 3:07:53 AM , Rating: 2
quote:
So how many shots can be fired before the battery is out, or will the ship have somekind of nuclear reactor to power this thing ? :)


to put it short, yes it will have.


I wonder...
By corduroygt on 12/13/2010 10:20:58 AM , Rating: 2
How many megajoules of energy were required to fire that shot, or how efficient was it? It's usually pretty efficient to convert electricity into kinetic energy with motors and such...




Can't Capacitors Explode Too...
By ralith on 12/13/2010 10:57:03 AM , Rating: 2
quote:
The electromagnetic weapon improves safety on the ship because there are no traditional propellants needed and the projectiles need no high-energy explosive warheads

From what I've experienced capacitor have quite a bit of potential to explode too.




Video of the shot
By FaceMaster on 12/13/2010 11:57:54 AM , Rating: 2
Note to self...
By mmcdonalataocdotgov on 12/13/2010 12:37:51 PM , Rating: 2
Move all military installations at least 100 NM inland...




Impressive, but...
By silverblue on 12/13/2010 1:13:28 PM , Rating: 2
...how does the curvature of the earth factor into this?




Is it...
By drunkenmastermind on 12/13/2010 11:47:32 PM , Rating: 2
megajoul or megajoule? check your spelling numb nuts.




thanks
By mfed3 on 12/13/10, Rating: -1
"If you look at the last five years, if you look at what major innovations have occurred in computing technology, every single one of them came from AMD. Not a single innovation came from Intel." -- AMD CEO Hector Ruiz in 2007

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