US Navy Testing Hypersonic Railguns

[Schneibster]

23 pounds, delivered at Mach 7 a hundred miles away. This explodes like a nuclear weapon, without the radiation or the fallout. No explosives. It's just the kinetic energy of the slug. All heat nothing more. Iron is presumably the best material. It's highly magnetic and therefore ideal for railgun acceleration.

 

http://complex.foreignpolicy.com/posts/2014/04/07/watch_the_navy_s_futuristic_star_wars_railgun_blow_things_up

 

This article is from my favorite foreign affairs site. You will have to register, but you will be able to view ten free articles every month, and comment on them.

 

If you don't want to register, then here is the direct Vimeo link:

 

 

Bear in mind that actual use of the weapon against targets has never before been shown on any medium. I doubt this has seen public viewing on a science site up until now. Enjoy.

Edited April 8, 2014 by Schneibster

[swansont]

In the video here it looks like aluminum for the sabot. I would expect the projectile to be denser, perhaps depleted uranium.

 

Nuclear weapon? The demonstrated muzzle energy is a few tens of Megajoules.

[John Cuthber]

Mach 7 is about 2310 m/s

So 1/2 m v^2 is about 60MJ

About the energy of 10 Kg of TNT

Or roughly half a (US) gallon of gasoline.

So, re

"This explodes like a nuclear weapon, without the radiation or the fallout. No explosives."

 

Nope, not really.

 

 

"This article is from my favorite foreign affairs site. ."

I invite you to consider changing your favourite site to one which can do elementary physics.

 

"You will have to register, but you will be able to view ten free articles every month, and comment on them"

Why would I bother?

[swansont]

Thought some more about the "nuclear" bit. The system isn't 100% efficient at launching, and probably not even 50% efficient, so one probably needs to dissipate at least as much energy at the point of launch as has been imparted to the projectile (which loses energy as it flies owing to air resistance) Also, momentum is conserved, so there's recoil to consider. So I hope that we're not launching something that is anywhere close to nuke-scale, because it would likely destroy the launch platform, i.e. the ship.

[Schneibster]

I couldn't listen to the video, just watch it; something funny with my system no doubt. I read the article and extrapolated from "rail gun." Whatever they're doing, it's not technically a rail gun, which is purely electromagnetic. I'm still trying to figure what's making flames come out the muzzle.

 

The sabot trick was what they used for the penetrator DU rounds in tanks; I guess you're familiar with the details of that, swansont.

 

Obviously what they're doing there is barely capable of hitting a single hard target, a tank or (in the video) truck.

 

Thanks for running the numbers, John Cuthber. I was gonna get up today and do that. You're right, it'll take a heckuvalot more velocity, or mass, to hit hard enough to outperform, say, the New Jersey's main guns which throw a projectile the mass of a Volkswagen some twenty miles or more. (I'll go look up the details if anyone's interested.) This thing they're playing with in the video is a toy compared to that.

[John Cuthber]

The "flames" might be the result of a light gas gun (burning H2) , but they call it a rail gun.

Who cares?

It doesn't seem to pack much more punch than an anti tank weapon.

[Schneibster]

I think it's pretty clear from the way they're talking to the reporters from FP that they figure to make them a lot bigger.

 

I'm interested in the magnetic engineering, actually. It has applications in space flight and fusion. A true railgun uses electric or magnetic linear acceleration. I would expect the accelerator to run half the length of a ship or more, with a final (comparatively) short barrel to provide final direction. I wouldn't expect more than a few degrees' off-axis aiming from the main axis of the ship. I'd expect a projectile in the neighborhood of a ton.

 

I'm thinking this may be more of a rail-boosted gun, with a sabot penetrator. Sexy, but not really a "rail gun." Just kind of a hand-wave at it.

[swansont]

The "flames" might be the result of a light gas gun (burning H2) , but they call it a rail gun.

Who cares?

It doesn't seem to pack much more punch than an anti tank weapon.

 

I think the advantage is in the smaller cost of the projectiles as compared to missiles, since there's no propellant or warhead. Put this on a nuclear-powered ship, and then it's just a question of how much metal you can carry. Much more bang for the buck, if it works as advertised.

[Schneibster]

It's a justification for these small ones. However I think they've got big ones we're not seeing any videos of.

[imatfaal]

Just from back of the envelope calcs the 16inch guns of World War Two battle ships launched shells with about ten times the kinetic energy.

 

Regarding the recoil - in order to conserve momentum a battleship with 9 * 16inch guns firing a broadside would be recoiling about 8000 times more than firing the above rail gun. Purely theoretically as I think this sort of projectile launcher is completely impossible - This would put it into the rough area of launching a single projectile at speeds such that KE was equivalent to a nuclear weapon. For a single gun I expect it could be done on a large battleship size vessel - but it would be very difficult and I expect that only forward/backward facing guns would be feasible. So no broadsides - but it is one hell of a bowchaser

[Schneibster]

Sounds about right to me, imatfaal.

 

I thought up an explanation for the flames, it's just a guess but unless it's some sort of hybrid thing this explains them: they're accelerating an object to hypersonic velocity in a tube; the gas law says the air in that tube is gonna get very hot, and if the projectile is supersonic the air can't move out of the way. At hypersonic velocity, I bet it might even get plasmatized. Doesn't that make sense?

[swansont]

That's probably it, or at least part of it.

[imatfaal]

Sounds about right to me, imatfaal.

 

I thought up an explanation for the flames, it's just a guess but unless it's some sort of hybrid thing this explains them: they're accelerating an object to hypersonic velocity in a tube; the gas law says the air in that tube is gonna get very hot, and if the projectile is supersonic the air can't move out of the way. At hypersonic velocity, I bet it might even get plasmatized. Doesn't that make sense?

 

That's probably it, or at least part of it.

A year or so ago one of our members, who happened to have one of the best jobs I have ever heard of, posted this, he also happened to build possibly the world's most dangerous potato gun.

 

His explanation of the flash might apply here, only more so

 

http://www.scienceforums.net/topic/65043-vera-a-transonic-impact-gun/#entry665095

 

And InigoMontoya ("I want my father back you son of a bitch") we would love to see you posting again

[Moontanman]

I know this is supposed to be new and never before seen on public medium but I have seen this footage several years ago on a

tv program. It's still impressive and I would be willing to bet things have progressed further by now, I have seen some footage of Navel lasers that were impressive as well, makes you wonder what they have currently when you see this stuff for sure..

[davidivad]

did you guys notice that piece of aluminum is not the projectile that comes out?

my guess is that it gets replaced every shot.

a railgun is simply two rails with the projectile connecting them in the middle (and a lot of juice).

herin lies the magic....

 

for further reading on the subject of testing this phenomenon of muzzle flash check this link. while not expected from an electric gun this has been a problem for a while.

http://www.dtic.mil/dtic/tr/fulltext/u2/a156607.pdf

[swansont]

I have seen some footage of Navel lasers that were impressive as well, makes you wonder what they have currently when you see this stuff for sure..

 

Those have gone belly up.

 

 

His explanation of the flash might apply here, only more so

 

http://www.scienceforums.net/topic/65043-vera-a-transonic-impact-gun/#entry665095

 

And InigoMontoya ("I want my father back you son of a bitch") we would love to see you posting again

 

It's interesting that this transition coincides with exceeding Mach 1. I don't know if that's meaningful in its own right or not.

did you guys notice that piece of aluminum is not the projectile that comes out?

 

 

 

Most of the shots I've seen are sabot rounds, so the aluminum is the casing around the actual projectile, which falls away or is stripped soon after leaving the muzzle. The first shot in the video seems to show an aluminum part with a u-shaped back end, but the launched projectile looks the same to me.

[John Cuthber]

 

 

Navel lasers

 

The "hot gas" explanation for the flash makes sense to me.

[Schneibster]

I expect it was all the footage the reporter on FP could find on short notice. They're going through a "Hey, look at all these awesome graphics 'n' stuff on this new Internet thingie!!" phase right now. I have to close their window and only open it when I want to surf them so they don't overwhelm my CPU.

I've summarized our results back there (I'm a full subscriber to FP) and we'll see what I hear back.

 

Meanwhile I also mentioned "no explosive magazine risk" as a possible advantage; thanks you guys.

 

And I have thought about the range, which is impressive to say the least. They can hit anything in the littoral. I think the most important thing is how many projectiles they can put on target before the target can react. Even if they're small, any aircraft hit is down for days. Furthermore, there is the durandal effect on the runways; planes are no good if you can't launch them and you can't launch them if they're full of holes. If they can put hundreds of these on target in minutes, it will be like lightning raining down from Gawd guided by satellite.

 

Another important point is that they can put small force on target a hundred miles away. Never mind drones, these things are almost as small as Hellfire missiles drones use. And the drone's data showing the target location can be fed to this gun, and a projectile can land a hundred miles away that only takes out one or two rooms in a house, instead of the whole block. And no explosives.

Edited April 9, 2014 by Schneibster