# Navy Railgun Tests Leading to Ship Superweapon by 2020



## El Mahdi (Feb 29, 2012)

*New Navy Railgun Tests Leading to Ship Superweapon by 2020* (with video)

The first weapon-scale prototype of a futuristic Navy railgun began undergoing firing tests last week, the next big step toward putting the electromagnetic superweapon on U.S. warships by 2020. The Navy envisions using railguns to destroy enemy ships, defend against enemy missiles, or bombard land targets in support of Marines hitting the beaches.

Newly released video shows the prototype railgun using an electric-powered launcher rather than gunpowder to fire a huge hypersonic bullet in a cloud of flame and smoke. The Office of Naval Research hopes its new test phase — scheduled to last until 2017 — leads to a Navy weapon capable of hurling 40-pound projectiles at speeds of 4,500 mph to 5,600 mph over 50 to 100 miles (7,240 to 9,010 kilometers per hour over 80 to 161 kilometers).

New Navy Railgun Tests Leading to Ship Superweapon by 2020 - Yahoo! News

Hell Yeah!


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## Janx (Feb 29, 2012)

El Mahdi said:


> * using an electric-powered launcher rather than gunpowder to fire a huge hypersonic bullet in a cloud of flame and smoke. *



*

How can there be a cloud of flame and smoke when the delivery mechanism is a series of electromagnets sliding a block of metal out of a tube?*


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## El Mahdi (Feb 29, 2012)

I'm not sure either.  Maybe we have some experts here at ENWorld who could answer that...  Maybe [MENTION=177]Umbran[/MENTION]


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## Umbran (Feb 29, 2012)

I expect one, possible two effects there.

1) A railgun operates by passing a large current from one rail, through the projectile, and into the other rail.  So, you have two sliding contacts with a whole lot of current, in open air.  As the current jumps across a contact, it is probably ionizing the air (and maybe some of the metal of the contact points as well) - so, it is like having two tiny lightning bolts in the barrel, creating plasma.

2) Less likely:  In addition, you have a projectile in a confined space, accelerating from zero to Mach 5+ in nothing flat.  I wouldn't be surprised if there were some friction heating in there.

(And, some fast reading up, and it seems my plasma-guess is the correct one)


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## jonesy (Feb 29, 2012)

That new video footage looks very much like the old one from 2008:

OhGizmo!  Archive  Navy Test Fires 10 Megajoule Railgun (Holy Cow)


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## Dannyalcatraz (Feb 29, 2012)

Yay for blowin' stuff up _*REAL*_ good!

(Or is that "_*RAIL*_ good"?)


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## Umbran (Feb 29, 2012)

jonesy said:


> That new video footage looks very much like the old one from 2008:




Well, it would.  It is the same base technology, after all.


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## Thunderfoot (Mar 1, 2012)

While this looks all well and good, I have a couple problems, namely is the acceleration capable of penetrating armor plated steel ship hulls?  If so, then this becomes a great weapon in close support of ships as the magazine can be removed an secondary explosions caused by direct hits could be a thing of the past.

If I'm reading the technology right, basically this is a very high powered catapult, meaning it's fire and forget, straight line trajectory so anti-aircraft and missile defense uses are neigh unto impossible as there would be no way to "direct" the round or have it home like radar, sonor, laser, video and fly by wire munitions.  

As a ship to shore weapon, this thing would be devastating against soft (people) and semi soft (light vehicles, minimal armor and light wooden buildings) targets, but my concern is loss of velocity over extended distance.  (Obviously they aren't going to release that data until they field it. )  Conventional weapons have given way to ship to shore missiles, so unless they could ensure minimal collateral damage, I don't see this being implemented, by 2020 or any other time.  

Naval bombardment in support of a landing hasn't been a Navy tactic for many years, in part because we don't do conventional landings anymore.  (though there are three tactical landing craft undergoing sea trials.) but their primary function is helicopter operations for troops and then logistical landings to disgorge vehicles, and materiel.   

The military has had to contend with collateral damage reports over the last 40 years, in WWII carpet bombing and strategic bombing while effective also destroyed buildings and killed non-combatants.  Something that if happened in a modern assault would be met with a media firestorm.  Which isn't a bad thing, it's really cool when you can fire a missile from 25 miles away, fly in through a window and land on a bad guy's desk taking out the building which is oddly located next door to a school, a religious center and an emergency response center all of which didn't feel anything other than a slight tremor and a loud boom.


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## jonesy (Mar 1, 2012)

Maybe they could try and build something similar to the A-10, built around a later smaller more advanced version of this. That would make a terrifying anti-armor plane.


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## Dannyalcatraz (Mar 1, 2012)

Part of what makes rail guns fun is that the higher the velocity you can achieve:

1) the less massive a round you need to do X amount of damage

2) the less you need to lead a target, meaning accuracy increases


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## Starman (Mar 1, 2012)

Now if they can just figure out the power issue.


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## Kzach (Mar 1, 2012)

So, math whizzes, the article says that one 'megajoule' of kinetic energy is the rough equivalent of a one-ton car travelling at 100mph. So does that mean a 33mj rail-gun is the equivalent of a 33-ton car travelling at 3,300mph or a 33-ton car travelling at 100mph?

If it's just 100mph, then that's not exactly impressive. As devastating as such a crash would be, I wouldn't want to spend billions of dollars equipping the equivalent of it. But if it's 33x3,300mph... whoa.


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## Dannyalcatraz (Mar 1, 2012)

I'm no math whiz...but here's a video of a couple hundred tons at 100mph for perspective.


[ame=http://www.youtube.com/watch?v=zJflu7z4QyI&feature=youtube_gdata_player]Spectacular 100mph Train Crash Test - YouTube[/ame]


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## Kzach (Mar 1, 2012)

Dannyalcatraz said:


> I'm no math whiz...but here's a video of a couple hundred tons at 100mph for perspective.




Like I said: unimpressive.


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## Dannyalcatraz (Mar 1, 2012)

Kzach said:


> Like I said: unimpressive.





Now take that force being applied over a 20'x15' surface and instead have it be applied over a 10" diameter surface.


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## Nagol (Mar 1, 2012)

jonesy said:


> Maybe they could try and build something similar to the A-10, built around a later smaller more advanced version of this. That would make a terrifying anti-armor plane.




1) Rail guns require long "barrels" for acceleration so plane mounts would be problematic.

2) The recoil would knock the plane below stall speed I expect.


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## Nagol (Mar 1, 2012)

Thunderfoot said:


> While this looks all well and good, I have a couple problems, namely is the acceleration capable of penetrating armor plated steel ship hulls?  If so, then this becomes a great weapon in close support of ships as the magazine can be removed an secondary explosions caused by direct hits could be a thing of the past.
> 
> If I'm reading the technology right, basically this is a very high powered catapult, meaning it's fire and forget, straight line trajectory so anti-aircraft and missile defense uses are neigh unto impossible as there would be no way to "direct" the round or have it home like radar, sonor, laser, video and fly by wire munitions.
> 
> ...




For anti-air/missile, I suspect they're hoping for something like the phalanx system.  Railguns should produce less heat per shot and nothing would prevent a "gatling" version other than the power demand.


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## Umbran (Mar 1, 2012)

Thunderfoot said:


> If I'm reading the technology right, basically this is a very high powered catapult, meaning it's fire and forget, straight line trajectory so anti-aircraft and missile defense uses are neigh unto impossible as there would be no way to "direct" the round or have it home like radar, sonor, laser, video and fly by wire munitions.




The need to steer is largely dependent on relative speed and distance to target.  If the target's pretty much sitting still, a straight-line path is fine, as the target can't get out of the way before the projectile gets there.  And these projectiles are intended to go twice as fast as an SR-71.

That being said, the article makes it seem that these are intended to take the place of standard cannon and ship to ship guns and ship to shore missiles.




Kzach said:


> So, math whizzes, the article says that one 'megajoule' of kinetic energy is the rough equivalent of a one-ton car travelling at 100mph. So does that mean a 33mj rail-gun is the equivalent of a 33-ton car travelling at 3,300mph or a 33-ton car travelling at 100mph?




In terms of energy, the 33Mj railgun would be like a 33 ton car, moving at 100 mph. 



> If it's just 100mph, then that's not exactly impressive.




Ah, but there's two things you're probably not taking into account - the projectile isn't a car, and there's more to impact than energy.

A car is a relatively lightweight framework made to crumple if it hits something - the car absorbs a lot of it's own energy of collision.  A 33 ton car would be like.. a stack of cars 2 cars high, two cars wide, and eight cars long.  Move that at 100 miles per hour.

And now put that in a solid slug that you can hold in your hands.  Instead of an impact area of something like 100 square feet, the impact area is the size of your palm.  Rather than weighing 33 tons, you can lift it.  And instead of moving at 100 mph, it is moving several times the speed of sound.  That energy is *concentrated*.

The car analogy speaks to energy, but the energy of collision is by no means the only issue.  Momentum also matters, and how that momentum and energy is transferred to the target also matters.  For example:

A one-ton car, moving at 30 mph has over 75000 Joules of kinetic energy.  If it hits a human dead on, that human may well be dead, but might just be seriously injured.   Folks survive getting hit by cars.  

A bullet from a .357 magnum has only 750 Joules of kinetic energy when it leaves the gun.  That's 1% of the energy of the energy of the car, but with a hit dead on, a human is still grievously injured, quite possibly dead.  

How that energy is delivered matters.  A lot.


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## Janx (Mar 1, 2012)

so we knwo the bullet is like 33 tons hitting at 100mph.

But if the bullet is so small, how is it going to damage a large area and not just punch a fist sized hole in the side of the target?


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## Thunderfoot (Mar 1, 2012)

Nagol said:


> For anti-air/missile, I suspect they're hoping for something like the phalanx system.  Railguns should produce less heat per shot and nothing would prevent a "gatling" version other than the power demand.



But let's crunch some numbers - accuracy in a conventional sense is measured in milliseconds when discussing ship to air, the Phalanx has a radar/sonor/laser tracking system that can lock on, aim and fire several hundred armor piercing HE cannon rounds (automatically) in a matter of seconds in a package that is roughly 60' x 100' of ship space to include gun mount and armory for ammunition storage (its a self contained unit).  T

The railgun is a large hand fed cannon that uses a high-energy propulsion system (ie an engine (which would need to be separate from the ship's engine.))  Even assuming a "Gatling" version of the weapons system, with a computer controlled guidance and firing system similar to the Phalanx, the size would make it closer to a conventional gun turret instead of the compact Phalanx.  

So, more space required to mount, a gun crew to load.  While I can see this as a great replacement for a ship to ship weapon, and just possibly a dumb ship to shore armament (though I find that application highly suspect), as for air intercept, this thing screws the pooch.


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## Thunderfoot (Mar 1, 2012)

Umbran said:


> The need to steer is largely dependent on relative speed and distance to target.  If the target's pretty much sitting still, a straight-line path is fine, as the target can't get out of the way before the projectile gets there.  And these projectiles are intended to go twice as fast as an SR-71.
> 
> That being said, the article makes it seem that these are intended to take the place of standard cannon and ship to ship guns and ship to shore missiles.



I agree the ship to ship application looks great, and if ship to shore attacks were still conducted like they were in WWII, this thing would be great for that, the collateral damage caused  by dumb weapons means this thing is dead on arrival except on maybe a few cruisers. (remember, we only have two battleships in reserve as floating museums and 2 have been mothballed (floating in a harbor with no personnel, munitions or fuel on board.)

These would be great to replace the main guns on a battleship, but the question is why?  We don't use them anymore.  When you have every human rights organization complaining when a civilian target is hit in a smart weapon application.  I just can't see the Military approving a weapon that is akin to giant catapult (even an effective one) being mounted as a viable ship to shore system.



Umbran said:


> In terms of energy, the 33Mj railgun would be like a 33 ton car, moving at 100 mph.
> <SNIP>
> How that energy is delivered matters.  A lot.



Which is why that ship to ship application makes much more sense.


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## Thunderfoot (Mar 1, 2012)

While the Navy is researching this, the Army and Marines would have a much better use for this thing; Drag along artillery.  A dumb weapon firing projectiles at around Mach 8 with 33Mj of impact.  An artillery barrage of one battery firing once could devastate a brigade sized force in seconds, even under "hard" cover.

And while it being a powered system does have it's drawbacks when compared to a conventional weapon, the margin of error on the battlefield for self-inflicted accidents (cooking a round in the chamber, igniting your ammunition, etc.) seems to drop considerably.  Friendly fire accidents, though, would be simply horrific.


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## Thunderfoot (Mar 1, 2012)

Janx said:


> so we knwo the bullet is like 33 tons hitting at 100mph.
> 
> But if the bullet is so small, how is it going to damage a large area and not just punch a fist sized hole in the side of the target?



So far, all we have seen is a shell approximately the size of 100-pounder. 
The hole would be significantly larger than fist sized, closer to Shaq sized or, if they can rig it to tumble on impact, Dumbo sized.


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## Umbran (Mar 1, 2012)

Janx said:


> But if the bullet is so small, how is it going to damage a large area and not just punch a fist sized hole in the side of the target?




Do you want to damage a large area on the surface of a target, or do you want to damage critical systems or supports *inside* the target? 

Punching through the side of the target is just fine.  Having penetrated, your metal slug is now fracturing, rolling, tumbling and ricocheting around inside a big metal or concrete box.  Mayhem ensues.  

Also, remember, the projectile itself is just a metal slug.  Compared to a missile or rocket, it is probably cheaper than dirt, small as a speck, light as a feather, and free of explosive risk.  You can carry a bazillion of them, and shoot them all day long, so long as you have power in your vessel.


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## Umbran (Mar 1, 2012)

Thunderfoot said:


> The railgun is a large hand fed cannon that uses a high-energy propulsion system (ie an engine (which would need to be separate from the ship's engine.))




Two things:

1) The *test* version is hand fed.  Don't expect it to stay that way in a fully weaponized production version.  Automating the loading of solid slugs is child's play by comparison to getting the launch system to work.

2) The energy source does not need to be separate from the ship's engine.  If the ship's engine can be used to just generate electricity, rather than motive power, then the ship's engine does just fine.  

Yes, there is a collateral-damage argument for ship-to-shore applications, in general.  But don't think "bombardment", but instead tactical strike at range.

Typical ship-to-shore these days is usually done with explosive rounds or missiles, right?  Rounds are fired in ballistic arcs, and from a moving ship accuracy is an issue.  And missiles are steerable, but depend on explosive power, and so do a lot of collateral damage.

This thing's round is flying faster than either of the other munitions.  Motion of the launching platform is thus less of an issue, and lack of explosive power means that you'll damage what you hit, and less of anything else.

So, there's a tank or gun emplacement on the shore?  Not for long!


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## Umbran (Mar 1, 2012)

Thunderfoot said:


> And while it being a powered system does have it's drawbacks when compared to a conventional weapon




I think you underestimate the power requirements here.

A single one of these rounds carries enough energy to melt 70 pounds of room-temperature iron.  Let me crunch some numbers...

Okay, an M1 Abrams tank has a 1500 horsepower engine.  If I have my math right, if you put the entire output of that engine into one of these guns, you could fire one round every 30 seconds or so.


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## Thunderfoot (Mar 1, 2012)

Umbran said:


> Two things:
> 
> 1) The *test* version is hand fed.  Don't expect it to stay that way in a fully weaponized production version.
> 
> ...



But see that's the issue the Navy doesn't shoot tanks or gun emplacements anymore, that tactic went out in the Korean war.  They are either hit from airborne weapons (tactical bomb runs) or land based artillery.  And the collateral damage from an exploding munition has been offset by the steerage issue.  Ships no longer use ballistic arcs in weapons delivery,it isn't needed.   Which is why I said as a ship weapon this thing is okay, but would be better suited for land based artillery, where all of the things you described are still a real world consideration.  

As for tactical strike at range versus bombardment, I call BS - there is no such thing with dumb weapons, that's why ships don't bombard anymore, you can't control the variables: wind, weather, magnetic pull of the earth, low flying hippopotamus, whatever.  When you have a steering system you can ignore the variables and destroy your targets at will.




> Typical ship-to-shore these days is usually done with explosive rounds or missiles, right?  Rounds are fired in ballistic arcs, and from a moving ship accuracy is an issue.  And missiles are steerable, but depend on explosive power, and so do a lot of collateral damage.



 Wrong.  There is no explosive round shore bombardment - THAT is my point.   Also, ships stop moving when bombarding a shore anyway.  It was never an issue about accuracy in a bombardment role.  One of my favorite weapons demonstrations was the USS Iowa demonstrating the power of it's naval guns, it opened up a barrage on the top of a mountain on a target island and left a "flat" area where the mountaintop was.  Your concept of what a naval bombardment is capable of is woefully underestimated, something that surprises me greatly.

Like the issue about wholesale slaughter to achieve tactical means in another thread, where you rightfully stated that you cannot kill indiscriminately for tactical means.  That's why shore bombardment went from guns to missiles, it doesn't eliminate it, but it reduces it to an acceptable level.


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## Thunderfoot (Mar 1, 2012)

Umbran said:


> I think you underestimate the power requirements here.
> 
> A single one of these rounds carries enough energy to melt 70 pounds of room-temperature iron.  Let me crunch some numbers...
> 
> Okay, an M1 Abrams tank has a 1500 horsepower engine.  If I have my math right, if you put the entire output of that engine into one of these guns, you could fire one round every 30 seconds or so.



Again, artillery - an M1A3 Abrams is a tank, not the same thing.   You set up a portable power station that power four guns in a "drag mobile" battery and have your way with the enemy.  You are effectively reversing your position on the ships engine argument from a few posts ago.


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## Umbran (Mar 1, 2012)

Thunderfoot said:


> But see that's the issue the Navy doesn't shoot tanks or gun emplacements anymore, that tactic went out in the Korean war.




Yes.  My point is that new weapons, with new performance characteristics, may change that.



> As for tactical strike at range versus bombardment, I call BS - there is no such thing with dumb weapons




There is no such thing with *current* dumb weapons.  My point is that this round will behave differently than the cannon shells you're thinking about, and so may be useful for other tasks.

Let's do a bit of comparison:

The 16" main guns on an Iowa-class battleship fire a round that weighs well over a ton, with a muzzle velocity of 820 m/s.  And...

_"The large caliber guns were designed to fire two different 16-inch (410 mm) shells: an armor piercing round for anti-ship and anti-structure work, and a high explosive round designed for use against unarmored targets and shore bombardment." _

(So much for not using explosive rounds!)

The rail gun should fire a round that weighs a mere 40 pounds, at three times the muzzle velocity of the Iowa guns.



> that's why ships don't bombard anymore, you can't control the variables: wind, weather, magnetic pull of the earth, low flying hippopotamus, whatever.  When you have a steering system you can ignore the variables and destroy your targets at will.




Yes, but having to carry a precision steering system makes the round far, far more expensive.  

The railgun round is *tiny* by comparison, and for the same range, spends a third of the time in flight.  This should drastically reduce inaccuracy due to environmental factors, or motion.  It may be able to do the work of a guided round, without the expense of guidance!



> Also, ships stop moving when bombarding a shore anyway.  It was never an issue about accuracy in a bombardment role.




Well, in explosive bombardment, accuracy isn't really that big a deal.  You carpet an area with 1-ton explosive bombs, everything's going down.

However, despite your claim, no ship on the sea is ever really "stopped", especially when they're tossing out major ordinance.  When you're considering hitting a target miles away, small motions matter.  And Iowas certainly do rock when they open up with those guns, do they not?



> Your concept of what a naval bombardment is capable of is woefully underestimated, something that surprises me greatly.




My point is that this gun isn't useful for that classic "bombardment" - which, as noted above, did use explosive rounds (there's "bomb" in "bombardment", you know  ).  It is a different weapon, with different capabilities.  Stop thinking of it like a standard cannon, because it isn't one!



Thunderfoot said:


> Again, artillery - an M1A3 Abrams is a tank, not the same thing.   You set up a portable power station that power four guns in a "drag mobile" battery and have your way with the enemy.  You are effectively reversing your position on the ships engine argument from a few posts ago.




My point is that this weapon has power requirements equivalent to a tank.  Somehow, you're going to have to carry along tank-scale engines.  So, why drag the gun behind, and have the risk of a separate power source? 

Mount it on an un- or lightly-armored chassis with an Abrams engine.  When it isn't firing, the engine drives electric motors to move the thing.  When you need artillery, drop the stabilizing legs, shift that engine to charging capacitors, and fire away!


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## Dannyalcatraz (Mar 1, 2012)

Janx said:


> so we knwo the bullet is like 33 tons hitting at 100mph.
> 
> But if the bullet is so small, how is it going to damage a large area and not just punch a fist sized hole in the side of the target?






Thunderfoot said:


> So far, all we have seen is a shell approximately the size of 100-pounder.
> The hole would be significantly larger than fist sized, closer to Shaq sized or, if they can rig it to tumble on impact, Dumbo sized.






Umbran said:


> Do you want to damage a large area on the surface of a target, or do you want to damage critical systems or supports *inside* the target?
> 
> Punching through the side of the target is just fine.  Having penetrated, your metal slug is now fracturing, rolling, tumbling and ricocheting around inside a big metal or concrete box.  Mayhem ensues.
> 
> Also, remember, the projectile itself is just a metal slug.  Compared to a missile or rocket, it is probably cheaper than dirt, small as a speck, light as a feather, and free of explosive risk.  You can carry a bazillion of them, and shoot them all day long, so long as you have power in your vessel.




If it helps, think of this as an AP round.  A very nasty AP round.

If a small enough version could be made- as in smaller caliber & thus power requirements and recoil- this could be a great weapon for tankbusting aircraft.

In addition to the effects Umbran mentioned, even if the round doesn't actually penetrate, it could kill via spalling.  We also know that plasma is generated at launch, so the round itself is likely to be quite hot...hotter than conventional rounds.  It may be able to deliver some of that heat energy as well as its kinetic energy, making it a de facto incendiary round as well.

And remember, this is still early-stage stuff.  It is possible that, just as in gunpowder weaponry, they may be able to develop special rounds for these weapons.  A railgun version of grapeshot could be hideous, for instance.

Not only would that be nasty for antipersonnel purposes, but if used in AA emplacements, accuracy becomes a non-issue- point at an area of the sky and hit everything in it with Mach 10 slugs, and most of that stuff will fall down.


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## Jack7 (Mar 1, 2012)

It's a high acceleration kinetic weapon. In addition to all of the other forces being employed to project the weapon and traveling with the warhead, the projectile is dragging gravity and the accumulated g-forces with the projectile. Nothing solid wants to get hit by that because it will re-transfer those same g-forces to the target.

In addition to all of the other kinetic and physical forces.


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## frankthedm (Mar 1, 2012)

Dannyalcatraz said:


> A railgun version of grapeshot could be hideous, for instance.



A warship mounted shotgun... why am I imagining Cthulhu & Gojira having a _Rabbit Season / Duck Season_ argument?


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## jonesy (Mar 1, 2012)

Nagol said:


> 1) Rail guns require long "barrels" for acceleration so plane mounts would be problematic.
> 
> 2) The recoil would knock the plane below stall speed I expect.



But, it's a railgun. Magnetically accelerated. I thought those things didn't have any recoil?


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## frankthedm (Mar 1, 2012)

I'm no scientist, and I'm just guessing but while the mechanism might not generate traditional recoil, the projectile leaving the gun at such high velocities might make some sort of physical interference.


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## Umbran (Mar 1, 2012)

jonesy said:


> But, it's a railgun. Magnetically accelerated. I thought those things didn't have any recoil?




Newton's Third Law still applies.  For every action, there is an equal and opposite reaction.  A force is applied to the projectile, so a force in the other direction is applied to the launcher.  That electromagnetism is used to apply forces to the object does not change that most basic of facts.

So, there will be recoil.



Jack7 said:


> In addition to all of the other forces being employed to project the weapon and traveling with the warhead, the projectile is dragging gravity and the accumulated g-forces with the projectile.




The thing only weighs 40 pounds, and while it is moving at high mach numbers, it is not moving at relativistic speeds.  This thing will have no noticeable gravitational effects.

You don't want to get hit by it, because it has a lot of kinetic energy and momentum, and if it hits you it will transfer some of those to you in a very short time, and that will hurt.


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## jonesy (Mar 1, 2012)

Umbran said:


> Newton's Third Law still applies.  For every action, there is an equal and opposite reaction.  A force is applied to the projectile, so a force in the other direction is applied to the launcher.  That electromagnetism is used to apply forces to the object does not change that most basic of facts.
> 
> So, there will be recoil.



That doesn't directly translate to recoil. Equal and opposite reaction as a concept is misleading in some cases. A bazooka has practically no recoil at all in comparison to with how much power it unleashed its projectile with, and yet equal and opposite reaction fully applies. There are guns which are designed to dissipate the 'opposite' force so that when you fire them the accuracy isn't affected, because the 'recoil' isn't all in the backwards direction. They call it recoil reduction.

Equal and opposite when talking of amounts of power unleashed, sure. But the direction of the reaction isn't always directionally opposite.

So, when I think railgun, I think it should be possible to design one the way they design wingtip missile launchers which have about as much recoil as a bazooka. Even more so since the projectile isn't 'touching' the tube it's launched from when it's launched. Right?

Edit:
And when I say 'the way they design wingtip missile launchers' I mean positionally, not mechanically. Obviously.


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## El Mahdi (Mar 2, 2012)

Thunderfoot said:


> If I'm reading the technology right, basically this is a very high powered catapult, meaning it's fire and forget, straight line trajectory so anti-aircraft and missile defense uses are neigh unto impossible as there would be no way to "direct" the round or have it home like radar, sonor, laser, video and fly by wire munitions.




From the article:



> U.S. Navy commanders ultimately want a weapon capable of firing up to 10 _guided_ projectiles per minute at targets up to 100 miles away.




Not _aimed_ projectiles, _guided_ projectiles.  The only propulsion they would have would be that which they get from the initial firing.  But they can still be guided projectiles in much the same way we have guided gravity bombs.  They could use camera, radar, laser targeting, ground mapping with inertial nav, GPS, or a combination of these for guidance (like Boeing's JDAM package).

Railgun projectiles could look something like this:






For comparison, a MK-84 JDAM.  A 2000lb _guided_ gravity bomb with GPS/Inertial Nav and Laser Targeting.







Umbran said:


> Punching through the side of the target is just fine. Having penetrated, your metal slug is now fracturing, rolling, tumbling and ricocheting around inside a big metal or concrete box. Mayhem ensues.




Yup!  In mechanical and military parlance, we call it _"spalling"_.




jonesy said:


> That doesn't directly translate to recoil. Equal and opposite reaction as a concept is misleading in some cases. A bazooka has practically no recoil at all in comparison to with how much power it unleashed its projectile with, and yet equal and opposite reaction fully applies. There are guns which are designed to dissipate the 'opposite' force so that when you fire them the accuracy isn't affected, because the 'recoil' isn't all in the backwards direction. They call it recoil reduction.




Well, a bazooka has very little recoil because 1) the propelling force is internal to the projectile (unlike the rail gun); and 2) the rear of the launch tube is open, so the force of the rocket engine does not directly interact with the launch tube - if the back of the tube was closed, then the person holding the weapon would experience the full recoil of the rocket (which would be extreme to say the least, at least until the launch tube exploded...)

With the rail-gun, the force to propel the projectile is coming from the rails affixed to the inside if the weapon.  Picture it this way, in much the same manner as a balloon squeezes out the air inside it (though equalization of pressure is also involved), and thus propels itself in an opposite direction - the magnetic fields of the rails are squeezing out the electfrified projectile (which now has it's own magnetic field), while much like the balloon, the weapon itself is propelled in the opposite direction (except that the gun is affixed and has mechanisms to disipate the recoil).


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## jonesy (Mar 2, 2012)

El Mahdi said:


> With the rail-gun, the force to propel the projectile is coming from the rails affixed to the inside if the weapon.  Picture it this way, in much the same manner as a balloon squeezes out the air inside it (though equalization of pressure is also involved), and thus propels itself in an opposite direction - the magnetic fields of the rails are squeezing out the electfrified projectile (which now has it's own magnetic field), while much like the balloon, the weapon itself is propelled in the opposite direction (except that the gun is affixed and has mechanisms to disipate the recoil).



I can always get behind a good balloon analogy.


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## Jack7 (Mar 2, 2012)

> The thing only weighs 40 pounds, and while it is moving at high mach  numbers, it is not moving at relativistic speeds.  This thing will have  no noticeable gravitational effects.
> 
> You don't want to get hit by it, because it has a lot of kinetic energy  and momentum, and if it hits you it will transfer some of those to you  in a very short time, and that will hurt.




No, I'm not talking about relativistic speeds obviously. I'm talking about how g-forces build in the warhead projectile which will be concentrated, along with all other relevant forces against a very small area. 

I'm talking about the g-forces, along with all of the other forces, that are generated by an object at high acceleration (within a gravitational field) stopped suddenly by impact against solid surfaces. Though it won't be stopped by the solid surfaces it will targeted against. But all of those energies will be concentrated in a very small impact area, though exactly how those forces are transferred to the target will vary by the actual nature of the target (and the warhead). 

But I'm not talking about planetary g-forces, I'm talking about the g-forces generated by small but massive objects accelerating at high speeds and impacting other objects at tight impact points. Again though, that's just one of the forces that will actually be involved. 

And of course much will depend upon the shape and nature of the matter of the target and the shape and matter of the projectile.


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## Kzach (Mar 2, 2012)

There's a blatantly obvious application that you're all overlooking here and so I feel bears pointing out: space-guns!

We're one-step closer to ruling the galaxy, humans!


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## Dannyalcatraz (Mar 2, 2012)

They've been talking about rail guns in space for decades now...But issues about recoil damping are even more important there than here on the ground.


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## jonesy (Mar 2, 2012)

Dannyalcatraz said:


> They've been talking about rail guns in space for decades now...But issues about recoil damping are even more important there than here on the ground.



Just make a remote gun that fires a salvo. It runs away with the same power it uses to fire itself empty.


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## Mustrum_Ridcully (Mar 2, 2012)

Kzach said:


> There's a blatantly obvious application that you're all overlooking here and so I feel bears pointing out: space-guns!
> 
> We're one-step closer to ruling the galaxy, humans!



Unlike in Firefly, real world firearms ammunition actually provides its own oxygen and would probably work unaltered in vacuum. 
Maybe some issues with recoil compensation may remain if there is no regular air in the gun. Maybe some automatic weapons would not work as well (they use pressure build up in the gun barrel to reload themselves automatically, but I suspect that most of that pressure comes purely from the explosion itself and whether air is in the barrel before doesn't matter at all.)



Dannyalcatraz said:


> They've been talking about rail guns in  space for decades now...But issues about recoil damping are even more  important there than here on the ground.



Why is recoil damping more of an issue? Sure, your spaceship/satellite will get brought off course a little every time it fires, but that's what your engines are for. I would expect the craft firing the weapon still be heavier, so it would be accelerated a lot less than the projectile (and we're not talking about relativistic weapons).

I would expect that heating could become a larger issue, as without air to help transfer heat, it radiates only very slowly. And the craft itself has the same issue.


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## Dannyalcatraz (Mar 2, 2012)

> Why is recoil damping more of an issue? Sure, your spaceship/satellite will get brought off course a little every time it fires, but that's what your engines are for.




Well that's it right there.  A terrestrial rail gun- regardless of type- has all kinds of friction, anchors, and mass that can be used to keep it in place and on target.

A space-based railgun cannot rely on those things.  Each shot will move it, changing orbit & velocity, and thus targeting.  Sure, you can use fuel to re-orient, but that takes time and a non-renewable resource.

So the better your railgun's recoil damping, the more accurate & fuel efficient your killer sattelite is.


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## Kzach (Mar 2, 2012)

Mustrum_Ridcully said:


> I would expect that heating could become a larger issue, as without air to help transfer heat, it radiates only very slowly. And the craft itself has the same issue.




Heat? A problem in space? Really?

So, umm, how does that big ole star warm us up without an air conduit between us? Or are you one of those 'old testament' types?


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## Dannyalcatraz (Mar 2, 2012)

Thermal control in space is always an issue- depending on exposure, stuff can freeze or get boiling hot.  Things that go from light to dark a lot can experience thermally induced metal fatigue.


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## El Mahdi (Mar 2, 2012)

It's just like putting things in a thermos. A vacuum is an awesome insulator.

Now imagine that the contents of your thermos is generating it's own heat, heat that's dangerous to survival and equipment operation, but that heat has no where to go because it's so well insulated...that's the problem with space.

Ever wonder why the shuttle craft is always shone with it's bay dooors open while in orbit...? They open the doors to assist in bleeding off heat from equipment. Once the doors are closed, they only have so much time to begin re-entry, or heat build-up starts becoming a problem. Believe it or not, one of the things that would instantly cause a mission abort and a need to return home is an inability to open the bay doors.


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## Dannyalcatraz (Mar 2, 2012)

Hence Dave's annoyance at Hal...


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## Kzach (Mar 3, 2012)

Dannyalcatraz said:


> Hence Dave's annoyance at Hal...




To be fair, Hal was never much of a team-player.


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## Dannyalcatraz (Mar 3, 2012)

Good point.


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## El Mahdi (Mar 3, 2012)

I heard that Dave Kzach and Danny...


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## Olgar Shiverstone (Mar 3, 2012)

I'll have a post on this up on my blog tomorrow, but I'll preview a few items for discussion here.

This isn't the first weapon-packaged test, not by a long shot.  PM EM Gun at Picatinny Arsenal and UT Austin had a long-running program to use railgun technology for anti-tank use, until the program was shuttered and transferred to the Navy in 2009.  The problem for Army use was the poor rail durability and inability to reduce the power source size sufficiently for ground application; it needed about a decade of development for that.

In naval use, when combined with a guided projectile like an Excalibur 155mm round (well, it's hypersonic GPS-guided equivalent, of course), it could provide anti-ship or naval gunfire support to a range of over 100 nautical miles, which means a ship over the horizon could accurately engage targets well inland.  MAXORD for a projectile at that range is in low-earth orbit, so the shipboard model had some potential use for anti-satellite and anti-ballistic missile applications.  

Still, a lot of work has to be done yet on power supplies and rail durability, so don't expect a ship mount any time soon.


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## Umbran (Mar 3, 2012)

Mustrum_Ridcully said:


> Why is recoil damping more of an issue? Sure, your spaceship/satellite will get brought off course a little every time it fires, but that's what your engines are for.




We are not yet at the Star Wars and Star Trek level, where space engines have nigh-unlimited fuel, and you can drive around willy-nilly.  Every ounce of propellant on your ship has to be lifted from the ground into orbit - it is heavy and expensive, and so limited.  




Kzach said:


> Heat? A problem in space? Really?
> 
> So, umm, how does that big ole star warm us up without an air conduit between us? Or are you one of those 'old testament' types?




First off, please leave the religious commentary out next time, thank you.

Second of all, yes, heat.  The Sun warms us through electromagnetic radiation.  So yes, you can use radiative cooling in space.  But, compared to the convective and conductive cooling options available on the ground, radiative cooling is typically very slow, and/or requires huge radiating fins

Huge fins radiating heat means "huge target that is super-easy to detect in space".   Not exactly what you want from a weapons platform.


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## Kzach (Mar 3, 2012)

Umbran said:


> First off, please leave the religious commentary out next time, thank you.




Why? It's perfectly relevant to the question I was asking.

And who's talking weapons platforms? I'm talking ships! The Yamato Cannon, for instance, was an energy-based rail-gun


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## Umbran (Mar 3, 2012)

Kzach said:


> Why?




*Because the EN World Rules say, specifically, that real-world politics and religion are deemed inappropriate for these forums, however relevant you feel them to be.

Moreover, they also forbid discussion of moderation in-thread.  So, from here, if you have further questions, you can take it to e-mail or PM.  Thank you.*


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## Mustrum_Ridcully (Mar 3, 2012)

Kzach said:


> Heat? A problem in space? Really?



Yes, really. I expected you to have been in enough of this type of discussion to know this already. 

It is a common myth that the vacuum of space is cool. But it actually can be better described as lacking any temperature at all, as it lacks what could have a temperature. 



> So, umm, how does that big ole star warm us up without an air conduit between us? Or are you one of those 'old testament' types?



As I mentioned, you can try to radiate heat (well, it's not trying. You will do that). But it is a far slower process. The sun is so incredibly big and hot that radiation is enough to heat up Earth.
But, you may notice, the sun isn't exactly getting cooler while doing so either.

Temperature is movement of small particles (e.g. molecules, atoms). This type of movement generates radiation, which takes energy from the movement and reduces the temperature. But a far more effective way to cool a bunch of particles moving is to bring them in contact with a bunch of particles moving slower (e.g. being cooler). The particles will transfer their movement energy and the slower particles with get faster, the faster get slower, and the temperature drops (for the hotter particles).

The vacuum of space lacks all these other particles to collide with and transfer energy with. So all that is left is radiating heat. And that's a slow process. If your satellite or space ship is producing too much heat, it can't cool it down that way, and it will get hotter and hotter until it stops functioning.


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## Kzach (Mar 3, 2012)

Mustrum_Ridcully said:


> Yes, really.



You're much more fun than Umbran. He's such a McGrumpy Pants.



Mustrum_Ridcully said:


> I expected you to have been in enough of this type of discussion to know this already.



And you should have much lower expectations of me by now.



Mustrum_Ridcully said:


> As I mentioned, you can try to radiate heat (well, it's not trying. You will do that). But it is a far slower process. The sun is so incredibly big and hot that radiation is enough to heat up Earth.
> But, you may notice, the sun isn't exactly getting cooler while doing so either.



Well that's just great; so the Earth is a giant Greenhouse stuck in a giant vacuum! We're so screwed.

Also, I think you may have hit upon the best concept for a space-gun! The transferral of energy through a plasma conduit propelled at relativistic speeds, ie. the Yamato Cannon!


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## Plane Sailing (Mar 3, 2012)

Thunderfoot said:


> If I'm reading the technology right, basically this is a very high powered catapult, meaning it's fire and forget, straight line trajectory so anti-aircraft and missile defense uses are neigh unto impossible as there would be no way to "direct" the round or have it home like radar, sonor, laser, video and fly by wire munitions.




I'm afraid you're not reading it right!

The article says (my emphasis)

_U.S. Navy commanders ultimately want a weapon capable of firing up to 10 *guided projectiles *per minute at targets up to 100 miles away_


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## TanisFrey (Mar 4, 2012)

Plane Sailing said:


> I'm afraid you're not reading it right!
> 
> The article says (my emphasis)
> 
> _U.S. Navy commanders ultimately want a weapon capable of firing up to 10 *guided projectiles *per minute at targets up to 100 miles away_



That indicates the navy wants to be able to use a round that is large enough to have a guidance package.

Earlier, several of you were talking about recoil.  A rail-gun should be able to minimize it.  In a traditional gun/cannon/rocket launcher the ammo rests upon the barrel.  When it is fired it must over static and dynamic friction of the barrel/rocket tube and the air in the way.  The first thing a rail gun does in preparing to fire is to generating magnetic field.  This will suspend the round in the middle of the chamber and not touch the "barrel wall" at all.  This will eliminate the need for extra force needed to over come it.  This is why they are talking much longer ranges then a gun powered system.

The other eventual use of this system I see it too fire missiles.  Even with mass manufacture of missiles you still get the occasional failer to lunch from the tube or explosion of a missile in the rocket tube.  This creates a potential dangerous situation for our sailors.   If we have one rail gun that tosses out a missile so that the rocket engine fires in midair.  We can eliminate the occasional dangerous misfire and extend the range of the missile in question.


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## Plane Sailing (Mar 4, 2012)

TanisFrey said:


> That indicates the navy wants to be able to use a round that is large enough to have a guidance package.




But just how large does that have to be? Since military technicians are now seriously talking about rifle rounds with terminal guidance(!)


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## Dannyalcatraz (Mar 4, 2012)

> A rail-gun should be able to minimize it.




It does, but even so, you can see a good 6" of recoil (on something anchored to the _Earth_) in the demo video.  That may not sound like much, but for a space-based weapons platform- the context in which we were discussing recoil- that is quite significant, both from a targeting and maintaining orbit standpoint.

Yes, such a weapon would doubtlessly be smaller than _that_ thing, but even so, it's a factor that needs to be taken into consideration.


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## El Mahdi (Mar 4, 2012)

TanisFrey said:


> Earlier, several of you were talking about recoil. A rail-gun should be able to minimize it. In a traditional gun/cannon/rocket launcher the ammo rests upon the barrel. When it is fired it must over static and dynamic friction of the barrel/rocket tube and the air in the way. The first thing a rail gun does in preparing to fire is to generating magnetic field. This will suspend the round in the middle of the chamber and not touch the "barrel wall" at all. This will eliminate the need for extra force needed to over come it. This is why they are talking much longer ranges then a gun powered system.




You're forgetting that the projectile also has a magnetic field.  It's the opposing magnetic fields between the projectile and the rails that propel the projectile.  The magnetic field generated by the rails is essentially "fixed" to the barrel.  The force generated by the two fields both push the projectile out (at an extreme velocity) and also push the weapon back (recoil).

Recoil is very much a consideration.  The larger the projectile (such as a larger guided projectile vs. a simple slug) the more recoil there is.


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## jonesy (Mar 4, 2012)

What would happen if you placed two of those railguns in space fixed together so that they were firing opposite of each other? Would they just break apart, or could one build a space bazooka (with a "backblast" that was exactly as lethal as the other direction)?


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## Dannyalcatraz (Mar 4, 2012)

You could, but that just makes targeting more complex- imagine having a target in your forward gunsights just as one of NOAA's satellites goes into range on the second one!


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## Umbran (Mar 5, 2012)

TanisFrey said:


> In a traditional gun/cannon/rocket launcher the ammo rests upon the barrel.  When it is fired it must over static and dynamic friction of the barrel/rocket tube and the air in the way.  The first thing a rail gun does in preparing to fire is to generating magnetic field.  This will suspend the round in the middle of the chamber and not touch the "barrel wall" at all.  This will eliminate the need for extra force needed to over come it.  This is why they are talking much longer ranges then a gun powered system.




No, on several counts.

The railgun round has longer range because (as I noted upthread) it leaves the barrel moving faster than the conventional round (up to three times faster, by the article).  The range is directly proportional to muzzle velocity.

The force required to overcome friction in the barrel should be small compared to the force required to get the round up to that speed in such a short distance.



> If we have one rail gun that tosses out a missile so that the rocket engine fires in midair.  We can eliminate the occasional dangerous misfire and extend the range of the missile in question.




That's a boazooka as a flyswatter.  You can toss the missile overboard with far more conventional means.


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## jonesy (Mar 5, 2012)

Umbran said:


> That's a boazooka as a flyswatter.



Boazooka. Indiana Jones's nemesis.


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## Umbran (Mar 5, 2012)

Dannyalcatraz said:


> You could, but that just makes targeting more complex- imagine having a target in your forward gunsights just as one of NOAA's satellites goes into range on the second one!




""Space is big. Really big. You just won't believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space, listen..."  --_The Hitchhiker's Guide to the Galaxy_.

This isn't like a firefight on the ground, you know, and despite what Hollywood shows us in Star Wars dogfights, targets in orbital combat are few and far between.  The likelihood that there's another target in that tiny volume of space behind you is very small. 

Firing backwards would solve much of the recoil issue.  However, it will take twice the energy and power, ammo, and cooling capacity to do it.

Really, the recoil issue would be that, out in space, you're taking your shots not from a mile, or tens of miles, but hundreds or thousands of miles away - over those ranges, your targeting needs to be perfect, and to do it you need to know the relative positions, speeds (and possibly spin) of both the gun and the target.  Recoil means those positions, speeds, and spin may change with every shot you take.


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## Kzach (Mar 5, 2012)

Could you propel a form of energy using a rail-gun?


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## jonesy (Mar 5, 2012)

Kzach said:


> Could you propel a form of energy using a rail-gun?



That's what it already does. It transforms other types of energy (depending on the power source electric, electromagnetic, nuclear, chemical etc.) to launch projectiles with massive amounts of kinetic energy.


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## Dannyalcatraz (Mar 5, 2012)

Umbran said:


> ""Space is big. Really big. You just won't believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space, listen..."  --_The Hitchhiker's Guide to the Galaxy_.
> 
> This isn't like a firefight on the ground, you know, and despite what Hollywood shows us in Star Wars dogfights, targets in orbital combat are few and far between.  The likelihood that there's another target in that tiny volume of space behind you is very small.




I agree, but more and more scientists and governments are discussing how crowded- "crowded" being a relative term, of course- with satellites AND debris some orbits are becoming.  

Besides, even if the odds are vanishingly small, how'd you like to be the lucky officer who won the "I just shot an expensive satellite with my backblast" lottery?  ESPECIALLY if the unintended target belonged to a hostile nation?  I wouldn't even want to be the signatory on the document that greenlighted such a design.

(Your other points about wasting ammo, energy and so forth are 100% valid, though.)


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## jonesy (Mar 5, 2012)

Dannyalcatraz said:


> Besides, even if the odds are vanishingly small, how'd you like to be the lucky officer who won the "I just shot an expensive satellite with my backblast" lottery?



Or even "I just accidentally destroyed a colony on Mars".


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## Umbran (Mar 5, 2012)

Kzach said:


> Could you propel a form of energy using a rail-gun?




A rail gun operates by running a large electric current up one rail, through the projectile, and down the other rail.  The currents create magnetic fields that interact, and the result is a force on the projectile parallelto the rails.

So, no.  Not unless your "energy" is a solid conductor of electricity.


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## Joker (Mar 5, 2012)

jonesy said:


> Or even "I just accidentally destroyed a colony on Mars".




Or even "I just started a war with the Klingons".


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## Dannyalcatraz (Mar 5, 2012)

"Dammit- Earth shot first!"


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## Kzach (Mar 5, 2012)

Umbran said:


> So, no.  Not unless your "energy" is a solid conductor of electricity.




You couldn't push a gas, like say a plasma?


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## Mustrum_Ridcully (Mar 5, 2012)

Kzach said:


> You couldn't push a gas, like say a plasma?



I am not sure, but at least plasma is ionized gas, e.g. that means it will react to electrical currents.

But while sci-fi loves plasma weapons, they aren't really practical weapons. At least not in the idea "Let's shoot tiny bolts of plasma". Plasma is gas. 
You're basically trying to shoot (hot) air. That's also ionized, which means that it will even have a stronger inherent effect to expand (more so than just hot air). It's already bad in a pressurized enviroment, but it gets worse in vacuum.

Maybe you could put that plasma into a bullet, so it doesn't expand. But then the question is - can you really create a form of plasma that significantly adds to the bullet's impact - and also be better than filling the bullet with an explosive?


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## Kzach (Mar 5, 2012)

Ah, well, the density of the plasma would matter but at the same time, the idea would be to shoot it along an ionised path, like say a laser-beam? It'd then be a sort-of ray-l-gun


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## Umbran (Mar 5, 2012)

Kzach said:


> You couldn't push a gas, like say a plasma?




Well, let's note that you started with "form of energy".  Gas and plasma (which is just ionized gas) are not "forms of energy" any more than your body, or any physical matter, is a "form of energy".

But no, you can't accelerate a gas or plasma with a rail system like you can a solid projectile.  If you jump a current through a gas or plasma, you get a lightning bolt, which heats the gas and disperses it, rather than moves it in one direction cohesively, and the next instant the current passes through *different* atoms of gas, rather than the same gas.  The projectile being able to slide, but solid, is required for the rail system to work.

There are ways to accelerate charged particles.  Every CRT TV and monitor does this.  So do the ion drives for spacecraft currently under development. They just do it differently than rail systems do.


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## TanisFrey (Mar 6, 2012)

El Mahdi said:


> You're forgetting that the projectile also has a magnetic field.  It's the opposing magnetic fields between the projectile and the rails that propel the projectile.  The magnetic field generated by the rails is essentially "fixed" to the barrel.  The force generated by the two fields both push the projectile out (at an extreme velocity) and also push the weapon back (recoil).
> 
> Recoil is very much a consideration.  The larger the projectile (such as a larger guided projectile vs. a simple slug) the more recoil there is.



There is a difference by stating a rail-gun would minimizing recoil rather than eliminate it.  I did state that a rail-gun will minimize recoil.

The projectile does not need to have its own magnetic field, alto it helps.  All you need is ferrous metal, that is metal that reacts to a magnetic field.


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## Nagol (Mar 6, 2012)

TanisFrey said:


> There is a difference by stating a rail-gun would minimizing recoil rather than eliminate it.  I did state that a rail-gun will minimize recoil.
> 
> The projectile does not need to have its own magnetic field, alto it helps.  All you need is ferrous metal, that is metal that reacts to a magnetic field.




Recoil is only dependent on the momentum gain of the projectile and other particles -- like escaping gases.  How that projectile gets its momentum boost is immaterial.

About the only way to reduce recoil is to provide an equivalent negative momentum -- like gases in a a recoilless rifle or small plastic pellets in an armbrust.


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## Mustrum_Ridcully (Mar 6, 2012)

Umbran said:


> Well, let's note that you started with "form of energy".  Gas and plasma (which is just ionized gas) are not "forms of energy" any more than your body, or any physical matter, is a "form of energy".
> 
> But no, you can't accelerate a gas or plasma with a rail system like you can a solid projectile.  If you jump a current through a gas or plasma, you get a lightning bolt,



Lightning Gun! 



> There are ways to accelerate charged particles.  Every CRT TV and monitor does this.  So do the ion drives for spacecraft currently under development. They just do it differently than rail systems do.



I thought the first probe with a ion drive is already in space? (Of course, more will be in development...)

Edit: 
An Example craft with ion drive was the SMART-1: http://en.wikipedia.org/wiki/SMART-1


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## Umbran (Mar 6, 2012)

TanisFrey said:


> The projectile does not need to have its own magnetic field, alto it helps.  All you need is ferrous metal, that is metal that reacts to a magnetic field.




The projectile being a magnet actually isn't a particular help, and the projectile does not need to be ferrous.  It merely needs to be conductive.  As the current flows, the rails and projectile become one big electromagnet.  The field of that electromagnet then interacts with the current running through the projectile producing a force on the projectile.  

It produces a force on the rails too, pushing them outwards, but you bolt them down so they don't move - the only thing that can give way is the projectile, so it takes off.



Nagol said:


> Recoil is only dependent on the momentum gain of the projectile and other particles -- like escaping gases.  How that projectile gets its momentum boost is immaterial.




Correct.  We are talking some of the most basic an inviolable physics, right up there with "a body in motion tends to stay in motion".  *SOMETHING* feels an opposite force.  If you can monkey around so that opposite force gets transferred so that it doesn't move your gun around in ways you don't like, that's good.  But, for a railgun, you have to do special work to do it - it does *not* automatically minimize it.



Mustrum_Ridcully said:


> Lightning Gun!




Well, the current would flow through the easiest path from one rail to the other rail.  Unless your target happens to be between the rails, you ain't shootin' it with lightning from a railgun. 



> I thought the first probe with a ion drive is already in space? (Of course, more will be in development...)




To my knowledge, there have been six missions from various agencies equipped with one variation of an ion drive or another.  But, for all of these missions, testing the drive was one of the major goals of the mission, so I consider them part of the development effort.


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## jonesy (Mar 6, 2012)

Mustrum_Ridcully said:


> Lightning Gun!




[ame=http://www.youtube.com/watch?v=R617vPlqinI]Tesla gun - YouTube[/ame]


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## Mustrum_Ridcully (Mar 6, 2012)

Umbran said:


> Well, the current would flow through the easiest path from one rail to the other rail.  Unless your target happens to be between the rails, you ain't shootin' it with lightning from a railgun.



Enemy of Fun you are. I knew it wouldn't really be practical.




> To my knowledge, there have been six missions from various agencies equipped with one variation of an ion drive or another.  But, for all of these missions, testing the drive was one of the major goals of the mission, so I consider them part of the development effort.



According to the (german) Wikipedia article, there are apparantly even new communication satellites in use with it. That surprised me a little. But then I just today realized that the game Startrek 25th Anniversary was made in the 90s.

Mustrum "Time Flies" Ridcully


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## Thunderfoot (Mar 7, 2012)

Umbran said:


> Yes.  My point is that new weapons, with new performance characteristics, may change that.<SNIP - for space saving sake>
> Well, in explosive bombardment, accuracy isn't really that big a deal.  You carpet an area with 1-ton explosive bombs, everything's going down.



Okay, let's just agree to disagree on this until sea trials. 



Umbran said:


> However, despite your claim, no ship on the sea is ever really "stopped", especially when they're tossing out major ordinance.  When you're considering hitting a target miles away, small motions matter.  And Iowas certainly do rock when they open up with those guns, do they not?



 lolz - yeah I was thinking the same thing.  But when you talked about movement, I assumed you meant shoot on the run, something tanks can do, and ships sort of do when fighting other ships.  They come to "stop" when bombarding. And yeah, the Germans found out about naval bombardment and ship roll the hard way. 



Umbran said:


> My point is that this gun isn't useful for that classic "bombardment" - which, as noted above, did use explosive rounds (there's "bomb" in "bombardment", you know  ).  It is a different weapon, with different capabilities.  Stop thinking of it like a standard cannon, because it isn't one!



  Now here is where we agree.  My point was one of the stated uses was classical bombardment, which I stated was foolish. Now I still think as a ship to ship this thing is awesome in a bottle of hot sauce.



Umbran said:


> My point is that this weapon has power requirements equivalent to a tank.  Somehow, you're going to have to carry along tank-scale engines.  So, why drag the gun behind, and have the risk of a separate power source?
> Mount it on an un- or lightly-armored chassis with an Abrams engine.  When it isn't firing, the engine drives electric motors to move the thing.  When you need artillery, drop the stabilizing legs, shift that engine to charging capacitors, and fire away



Ah, got it.  Actually you would mount this on a M155A3 Paladin Chassis (Self-propelled Artillery), beefier recoil suppression, larger ammo containment, better engine (for this purpose - more power less speed), less computer storage and less "super cool" tank driving mechanisms.  

But, even with self-propelled, the Military still uses drag along as well, and since you have to set up a command station when you employ a battery, a separate power station would be easy to add the mix.  And if they did employ it using both platforms, you now have standardization across the board for artillery. Something that makes the Pentagon really really happy (as well as congress because they no longer have to pay large sums for multiple weapons systems.)  So while I don't disagree with your mobile artillery usage (and in fact heartily agree that would be the most efficient usage) drag along could be revolutionized by this technology.


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## Olgar Shiverstone (Mar 7, 2012)

Thunderfoot said:


> Ah, got it.  Actually you would mount this on a M155A3 Paladin Chassis (Self-propelled Artillery), beefier recoil suppression, larger ammo containment, better engine (for this purpose - more power less speed), less computer storage and less "super cool" tank driving mechanisms.
> 
> But, even with self-propelled, the Military still uses drag along as well, and since you have to set up a command station when you employ a battery, a separate power station would be easy to add the mix.  And if they did employ it using both platforms, you now have standardization across the board for artillery. Something that makes the Pentagon really really happy (as well as congress because they no longer have to pay large sums for multiple weapons systems.)  So while I don't disagree with your mobile artillery usage (and in fact heartily agree that would be the most efficient usage) drag along could be revolutionized by this technology.




The Paladin's an M109A6 .  And the Paladin Integrated Management system (PIM), the upgrade, is based on a high-voltage 600V system.  But it in no way produces enough energy to power a rail gun.  Nothing that can fit on or be towed behind a military vehicle does -- at current technology, you need 2-3 semi-trailers worth of power generation for multiple shots.  Heck, even the supercapacitors UT Austin used in their ground-vehicle railgun were too big to fit on a ground vehicle, so right now you can't even carry the power for a since shot on a modern SPH.

The power tech needs to go a few generations before ground use is practical, which is why Naval use is a great place to start.


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## Thunderfoot (Mar 7, 2012)

Olgar Shiverstone said:


> The Paladin's an M109A6 .  And the Paladin Integrated Management system (PIM), the upgrade, is based on a high-voltage 600V system.  But it in no way produces enough energy to power a rail gun.  Nothing that can fit on or be towed behind a military vehicle does -- at current technology, you need 2-3 semi-trailers worth of power generation for multiple shots.  Heck, even the supercapacitors UT Austin used in their ground-vehicle railgun were too big to fit on a ground vehicle, so right now you can't even carry the power for a since shot on a modern SPH.
> 
> The power tech needs to go a few generations before ground use is practical, which is why Naval use is a great place to start.



I knew that - crap - it's been too long since those guys woke me up while I was trying to get sleep after a mid watch.  

As for the power - how long it would take to ramp back up using a conventional power plant, assuming a smaller shell than the Navy test?  And if the drain is that much what wouldn't that be a problem on the small diesel electric engines of naval gunships?  Only the cruisers would have the kind of power it would take to run those and the rest of their ships systems.  (My cousin was a scope dope on a destroyer - he said when they did evasive actions they had to pull power from other systems, usually lighting and environmental systems (ie, lower priority).    
Considering the 5" is the standard ship mounted weapon the rail would actually reverse the downsizing of the main gun, and even if it is a guided package, most vessels would only have one or two of these on board.  Power would still be a problem for these little ships if it takes the power plant you're describing.   That would mean that no current application is possible.  Wonder if the testing is trying to downsize the power plant?


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## Dannyalcatraz (Mar 7, 2012)

Downsizing HAS to be at least part of the process.


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## TanisFrey (Mar 7, 2012)

Umbran said:


> The projectile being a magnet actually isn't a particular help, and the projectile does not need to be ferrous.  It merely needs to be conductive.  As the current flows, the rails and projectile become one big electromagnet.  The field of that electromagnet then interacts with the current running through the projectile producing a force on the projectile.
> 
> It produces a force on the rails too, pushing them outwards, but you bolt them down so they don't move - the only thing that can give way is the projectile, so it takes off.
> 
> Correct.  We are talking some of the most basic an inviolable physics, right up there with "a body in motion tends to stay in motion".  *SOMETHING* feels an opposite force.  If you can monkey around so that opposite force gets transferred so that it doesn't move your gun around in ways you don't like, that's good.  But, for a railgun, you have to do special work to do it - it does *not* automatically minimize it.



My bad, I did not mean ferrous (indicates the presents of iron) but relatively reactive to magnetism.  Most materials that are conductive will be reactive to magnetism.

When I speak of minimizing recoil I do not mean that it is eliminated but reduced to the minimum expected by the monument being generated in the projectile.

A standard gun has more recoil than what can be expect to be generated by the monument of the bullet.  Due to the following:
1)  The need to over come friction of the bullet with the barrel.
2)  The expanding gasses that propel the bullet.  (Automatics and semi-automatics use this to reload the weapon.)
3)  The Explosive force is in all directions including direction not directly in line with the path of the projectile.  These do get redirected into the expanding gasses.

These 3 items are eliminated be the rail gun, leaving only Newton's Laws of Motion.


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## Kzach (Mar 7, 2012)

Mustrum_Ridcully said:


> Lightning Gun!



Now you're talking!



Umbran said:


> Well, the current would flow through the easiest path from one rail to the other rail.  Unless your target happens to be between the rails, you ain't shootin' it with lightning from a railgun.



Sigh, such a buzz-kill


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## Umbran (Mar 7, 2012)

TanisFrey said:


> My bad, I did not mean ferrous (indicates the presents of iron) but relatively reactive to magnetism.  Most materials that are conductive will be reactive to magnetism.




I think you may be getting your terminology confused.  There are a small number of materials (like iron, nickel, and cobalt) that are called "ferromagnetic" - which traditionally means that they can show spontaneous magnetization, or have a magnetic moment without an externally applied magnetic field.

The phrase "reactive to magnetism" doesn't mean anything to me.  The rails and projectile need to be good electrical conductors, but that's about it.  




> 3)  The Explosive force is in all directions including direction not directly in line with the path of the projectile.  These do get redirected into the expanding gasses.




This last is not exactly true.  The round is fired in a chamber specifically so the expansion is restricted, and more of the energy of expanding gas will be transferred to the bullet.




Kzach said:


> Sigh, such a buzz-kill




An engineer friend of mine looked at fiction (with it's aliens, super-powered heroes, and such) and realized that there is a lot of cool stuff we can conceive happening, that doesn't.  He reasoned that there must be a maximum amount of Coolness in the Universe, and anything that exceeded this Universal allotment was not allowed to happen.  He dubbed this the "Too Cool Rule."

I'm not sure he was correct.  If he was, then when we suffered the losses of Johnny Cash and Warren Zevon (who were among those who are "Cooler than You" for almost all values of You), we should have seen a sudden increase in incidence of adamantium claws and aliens coming down to play Super Mario Bothers with terminally ill children.  But the idea may still have merit.

Suffice it to say, I'm dreadfully sorry the laws of the Universe don't yield your desires.  I don't make 'em, I just report the results.  If you wish, you may take a number to file a complaint with The Management.


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## Dannyalcatraz (Mar 7, 2012)

> I'm not sure he was correct. If he was, then when we suffered the losses of Johnny Cash and Warren Zevon (who were among those who are "Cooler than You" for almost all values of You), we should have seen a sudden increase in incidence of adamantium claws and aliens coming down to play Super Mario Bothers with terminally ill children.




_*snikt*_

Who says it hasn't happened?

_*snikt*_

(BTW, the myth is false- black guys' adamantium claws are no bigger on average than white guys'.)


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## Olgar Shiverstone (Mar 8, 2012)

Thunderfoot said:


> As for the power - how long it would take to ramp back up using a conventional power plant, assuming a smaller shell than the Navy test?  And if the drain is that much what wouldn't that be a problem on the small diesel electric engines of naval gunships?  Only the cruisers would have the kind of power it would take to run those and the rest of their ships systems.  (My cousin was a scope dope on a destroyer - he said when they did evasive actions they had to pull power from other systems, usually lighting and environmental systems (ie, lower priority).
> Considering the 5" is the standard ship mounted weapon the rail would actually reverse the downsizing of the main gun, and even if it is a guided package, most vessels would only have one or two of these on board.  Power would still be a problem for these little ships if it takes the power plant you're describing.   That would mean that no current application is possible.  Wonder if the testing is trying to downsize the power plant?




Those size generators and capacitors were for a 120mm APFSDS round --much smaller/lighter than a 155mm HE projectile, or a 5" HE projectile.  So no smaller scale application soon, probably not for 5-10 years.


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## Nagol (Mar 8, 2012)

TanisFrey said:


> My bad, I did not mean ferrous (indicates the presents of iron) but relatively reactive to magnetism.  Most materials that are conductive will be reactive to magnetism.
> 
> When I speak of minimizing recoil I do not mean that it is eliminated but reduced to the minimum expected by the monument being generated in the projectile.
> 
> ...




I think you're thinking of a mass driver and not a railgun.  They are similar concepts with different details.

Railguns use the Lorentz force, in effect a magnet will accelerate charged particles.  Anything conductive placed across the rails completes the circuit and carries a charge between the rails.  This creates a powerful electromagnet.  The magnet accelerates the projectile by pushing on the electrons flowing through it. The projectile could be made from conductive plastic if it wouldn't melt.

Recoil is all about momentum transfer, nothing else.  Think of it this way.  If the gun was fired and the barrel was sealed and the gases contained in a large chamber so that nothing escaped, there would be no recoil.  If the explosive were detonated with no constraints of how the force was applied (i.e. with no walls around it) the expansion would be in all directions and there would be no recoil.  Recoil happens when the expansion is directed and momentum is transferred.

Fricition in the barrel reduces recoil in that it converts kinetic energy into heat and reduces forward momentum of the bullet.  

Expanding gases affect recoil, but with proper design can be made to reduce it -- see the recoillless rifle.  Railguns lose the gases and hence lose a property that could be used to reduce recoil.  

The explosive force in a gun just a high pressure burst of gas.  That gas is directed by the walls of the chamber into expanding in a specific direction.  The bullet is in the way and pushed by the gas absorbing some of its momentum.  So the recoil of a gun is pretty much the same if a bullet is present or if the explosive charge is bare when detonated.  The momentum of the gases alone is about the same as the momentum of the gases and bullet.


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## El Mahdi (Mar 8, 2012)

jonesy said:


> I think there might be quite a line in the complaints department.




I think you have to fill out an application in quadrillioncate before even getting approval to stand in line.


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## Dannyalcatraz (Mar 9, 2012)

All this discussion has made me want to make a new Warforged PC: I don't know its class yet, but it will be some kind of blaster or ranged attacker, and its name will be Ferrous Beuller.


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## El Mahdi (Mar 9, 2012)

He does have a magnetic personality.


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## Dannyalcatraz (Mar 9, 2012)

He has a buddy you know...so much like him they might be twins.  Ronald Railgun.


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