Big Damn Gun.

Conventional cannons typically have an upper range limit of 50 miles or so, due to the limits of using chemical explosives as propellants.  But the military is developing cannons that use electromagnets instead, and the latest one built by the navy (below) can fire a 7 pound projectile at 2.4 kilometers per second, more than twice the velocity of the fastest bullet and over 7 times the speed of sound.  

The entire shot above happens in a fraction of the blink of an eye and the projectile is only visible with ultra-high speed cameras.  And using an online projectile distance calculator (which doesn’t factor in wind resistance), it would, at a 45 degree angle, dip into outer space and travel approximately 364 miles.

Hooyah.

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About agnophilo

Nerd.
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13 Responses to Big Damn Gun.

  1. anaraug says:

    Cool stuff.  I didn’t realize that we had working railguns on that scale.  Still I’d be surprised if they remotely approach “cost-effective” yet.

  2. agnophilo says:

    @YouTOme – : )@anaraug – Well we’re not gonna have big guns like that on tanks any time soon, but I wouldn’t be surprised to see them replace the long range guns on naval vessels, given that many are nuclear powered and can easily meet the energy requirements, and would be significantly less vulnerable without huge quantities of explosives stored in the ship.  And the fact that they’re also working on railgun-propelled rockets that fire magnetically then ignite and travel even further.  Plus railguns aren’t that complicated, highschool students build small-scale ones.  The main thing is the power source and the capacitors.@TheSaltMine – : )

  3. The_ATM says:

    The capacitor banks they use for this are freaking massive.  They plan on putting these on cruiser ships some day, but looking again at the comments I notice you already mentioned that.I think they take too much energy to fire, but if they couple that with new artillery technology they accuracy could be wildly improved.  Something they already use “has an accuracy of less than 10 meters at ranges out to 14 miles.”  I am not sure if this uses dgps or just gps, but the potential for accuracy improvement with already existing technology can give wildly improved results.  ( dgps at its best can give about 2cm error global accuracy. )  The prospect of being able to spot tanks or enemy buildings by satellite and take them out with a rail gun 200+ miles away is pretty exciting.Considering that we tend to started wars in which we will probably never encounter the opportunity to use these, all the money goes to waste.

  4. helvetebrann says:

    I kind of always thought it was Hoorah, not Hooyah?

  5. anaraug says:

    @agnophilo – I guess what I have a hard time imagining is a railgun projectile that has a rocket inside it that still manages to function after the projectile passes several kiloamps (megaamps?) of current.

  6. agnophilo says:

    @The_ATM – You can also use things like laser targeting with line of sight, but I’m sure GPS is used to attack land targets.  And yeah the capacitors are pretty big, but puny compared to the long range guns on big military ships (like so), which can fire a fraction of the distance and require carrying thousands of tons of explosives, making the ship vulnerable to even high caliber bullets which can detonate an ammo store and take down an entire ship.  As far as too much energy to fire, it requires, I believe, 8 megajoules to fire, and it is my understanding that large nuclear powered ships generate hundreds of megajoules.  So several ships firing continuously would take a fraction of the total energy potential of modern ships, and in theory you could even power them with direct current from the nuclear generator, negating the need for capacitors altogether. And who needs 2 centimeter accuracy at 10 miles away where they can fire back when you can bombard them with hundreds of rounds from 150 miles away?  Also if the impact velocity is high enough the projectile will melt or vaporize on impact.  It doesn’t even need to contain explosives to be devastating.@helvetebrann – Hooyah is the “official” exclamation of the navy.  I thought it appropriate, the blog being about a navy prototype.@anaraug – Actually the projectile must be made of non-conducting material or the railgun won’t work.  But yeah I don’t know how or if that would work.  I just know they’re working on it.  They already have cannon rounds that ignite into guided missiles after x miles if I am not mistaken.  If they can do that…

  7. The_ATM says:

    “And who needs 2 centimeter accuracy at 10 miles away where they can fire back when you can bombard them with hundreds of rounds from 150 miles away?”Because if you are firing 364 miles, a 0.25 degree error in your yaw axis of fire would result in the projectile hitting off the target by about 1.6 miles.  Awfully difficult to melt through the armor of a tank with a high speed projectile when you end up hitting a school yard full of children miles away.  Even if you get your launch angles absolutely correct, wind and other completely unpredictable factors affect your accuracy.  The reason I mentioned the artillery was because the electronics to correct itself are on the projectile.  This can make the projectile land accurately regardless of the distance it is fired at.  I was not mentioning the artillery because it is explosive.”Also if the impact velocity is high enough the projectile will melt or vaporize on impact.”Well, probably not with your 45 degree firing angle.”and in theory you could even power them with direct current from the nuclear generator, negating the need for capacitors altogether.”The capacitors are there for the instantaneous demand for energy.  The capacitors are working essentially as large batteries that can both charge and discharge more instantaneously. Wikipedia says the largest naval nuclear reactors make 165 MWatts of electrical power.  So that would be 165 MJ per second.  But if it takes 0.05s to fire an 8MJ round, firing it will demand far almost all the energy the reactor could produce in that 0.05s.  So directly running off the reactor probably wouldn’t work so well.  Either way, the capacitors are there to store energy for the high instantaneous demand.  I guess now that you mention how much power the nuclear reactors produce and with some extra reading it does not seem immensely impractical.  I guess I was going with my initial impression and my fondness for electronics that do not consume much power.

  8. helvetebrann says:

    @agnophilo – No, yeah, I got the reference.  I guess I’d always imagined the spelling of it differently in my head.

  9. agnophilo says:

    @The_ATM – “Because if you are firing 364 miles, a 0.25 degree error in your yaw axis of fire would result in the projectile hitting off the target by about 1.6 miles.”  Good point.  But I wasn’t suggesting using it to hit things at maximum range necessarily, that was just to show how much more powerful than a conventional cannon it is.  We got into practicality in the comments.  But I see your point.  Though even if you could hit a target 20 miles off instead of 7 it would be a huge advantage. “Awfully difficult to melt through the armor of a tank with a high speed projectile when you end up hitting a school yard full of children miles away.”  Haha, point taken.”Even if you get your launch angles absolutely correct, wind and other completely unpredictable factors affect your accuracy.  The reason I mentioned the artillery was because the electronics to correct itself are on the projectile.  This can make the projectile land accurately regardless of the distance it is fired at.”  Didn’t know artillery could self-correct, I thought only missiles did that and artillery was just meant to blanket an area until the target was hit.  Cool.  Though in principle with the right materials you could insulate electronics.”I was not mentioning the artillery because it is explosive.”Didn’t think you were.”Also if the impact velocity is high enough the projectile will melt or vaporize on impact.Well, probably not with your 45 degree firing angle.”Well no, with that trajectory it would burn up in reentry.  Also was just trying to illustrate how powerful it was.”The capacitors are there for the instantaneous demand for energy.  The capacitors are working essentially as large batteries that can both charge and discharge more instantaneously.” I know.”Wikipedia says the largest naval nuclear reactors make 165 MWatts of electrical power.  So that would be 165 MJ per second.  But if it takes 0.05s to fire an 8MJ round, firing it will demand far almost all the energy the reactor could produce in that 0.05s.  So directly running off the reactor probably wouldn’t work so well.”  Well, a ship that could fire 20 rounds per second at almost 8 times the speed of sound would still be impressive.  And lets say a ship has 4 cannons that fire once per second, it would require only 32MJ and could fire as fast and as often as power is produced beyond what is needed for other active systems.  Shutting or slowing down propulsion temporarily would give it a big boost of course.  If all power was diverted temporarily to the railguns that reactor could potentially fire 20 rounds per second.”Either way, the capacitors are there to store energy for the high instantaneous demand.”  They could also expand the initial firing rate by having more capacitors.  They could charge capacitor banks while approaching a target, then release a barrage of ammo at a a high firing rate, which would then slow to a moderate firing rate.  These ships already have large battery capacities which are used for backup emergency power for propulsion when the ship’s main generator is offline or damaged, so they can usually run a few days on batteries.  I don’t know how long a capacitor can hold a charge, but they could merge the two systems and tap into the backup propulsion system to lengthen the time they can fire at a high rate.”I guess now that you mention how much power the nuclear reactors produce and with some extra reading it does not seem immensely impractical.  I guess I was going with my initial impression and my fondness for electronics that do not consume much power.”Well I did more reading after the initial blog from your comment too.  Very interesting stuff.  I’m not a fan of violence, but the technology is very cool.  And yeah things that use little energy are good, but I’m more fascinated by the technology to generate huge amounts of juice : )

  10. agnophilo says:

    @helvetebrann – I was surprised it was spelled that way too.  I think it just looks stupid in text without the attitude it’s said with.

  11. The_ATM says:

    @agnophilo – “I’m not a fan of violence, but the technology is very cool.”Technology and violence are hardly able to solve our international relations problems.  It bugs me to think we are spending probably 1 million times the amount of money the enemies we are fighting spend.  Of the money they spend, much of it is our own money.  With the field I work in I am very likely to get a job working in “defense” research; I would, however, very much like to avoid it.  Good blog and discussion.

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