Navy Gets 8-Megajoule Rail Gun Working

prototypo writes "The Free Lance-Star newspaper is reporting that the Navy Surface Warfare Center in Dahlgren, Virginia has successfully demonstrated an 8-megajoule electromagnetic rail gun. A 32-megajoule version is due to be tested in June. A 64-megajoule version is anticipated to extend the range of naval gunfire (currently about 15 nautical miles for a 5-inch naval gun) to more than 200 nautical miles by 2020. The projectiles are small, but go so fast that have enough kinetic punch to replace a Tomahawk missile at a fraction of the cost. In the final version, they will apex at 95 miles altitude, well into space. These systems were initially part of Reagan's SDI program ("Star Wars"). An interesting tidbit in the article is that the rail gun is only expected to fire ten times or less per day, presumably because of the amount of electricity needed. I guess we now need a warp core to power them."

Re: 95 miles altitude is space..Way Cool

[Phanatic1a]

But I was thinking, is this a possible way to launch orbiting vehicles?

No, because when you shoot a projectile, you're putting it into a orbit that intersects the earth. You need some other impulse source to circularize the orbit.

More nuclear ships?

[TheWoozle]

So, do the electrical power requirements for this mean that the Navy will once again be building nuclear-powered ships?

Well

[everphilski]

How many million-dollar cruise missiles are you firing a day?

Most likely it will end up as an augment. One of the virtues of this system being, though, it can set up a shot quicker than a Tomahawk.

Slight correction?

[Civil_Disobedient]

The Navy isn't estimating a price tag at this point, with actual use still about 13 years away.

I think they mean deployment, unless the Navy knows something Congress doesn't. Which wouldn't surprise me.

Re:I don't see them replacing crusie missles

[Smidge204]

I doubt the actual rounds used in a battlefeild scenario would be dumb-fire lumps of metal, for just that reason. They already have laser guided munitions that an aircraft (or unpiloted drone) can spot for, so adding GPS to get within a mile of the target then using laser guidance the rest of the way seems prefectly doable.

=Smidge=

Re:I don't see them replacing crusie missles

[SydShamino]

Well, that's each rail gun that can fire just 10 times a day. Even if they cost $100 million each, there's little stopping the military from buying 50 of them for each coast.

(I'm ignoring whether they are practical or not, or if they cost too much, compared to alternatives. I'm just pointing out that the military can solve many limitations by throwing money at them, and no one in the government is embracing plans to limit military spending at this time.)

Re: 95 miles altitude is space..Way Cool

[Itchyeyes]

No biggy, you can use robots with ion drives for that stuff.

Ion drives would be worthless for your proposal. From Wikipedia:

In practice, with currently practical energy sources of perhaps a few tens of kilowatts, and given a typical Isp of 3000 seconds (30 kNs/kg), ion thrusters give only extremely modest forces (often tenths or hundredths of a newton).

Hardly the kind of propulsion you want to use for something that would be constantly stopping and changing direction. Ion drives are best used for crafts that travel extremely long distances with no need to change direction.

Re:Amount of power (energy really)

[D4rk Fx]

It's not all converted to heat. Well, assuming the projectile actually does leave the muzzle... Some early experiments ended up vaporizing the projectiles inside of the rails.

Think twice.

[Wilson_6500]

...these would almost replace Navies.

I believe a Navy does a lot more than just throw shells at buildings. That aside, you'd probably have a hard time hitting an even slightly moving ship with one of these at any range, let alone finding the ship in the first place without any of your own. After all, if the ship makes a slight random adjustment to course every six minutes or so (travel time of the shell at maximum range), then they're reasonably safe--especially if we assume that each gun could only fire at the maximum noted rate of ten shots a day, which means they get a shot every few hours or they blow all their shots in a few hours. Mounting these on shorelines is a waste.

Accuracy?

[chiph]

Being able to launch one is a great accomplishment. The question is: Where will it hit? Unlike a Tomahawk, it's unlikely you can install a GPS receiver in the "bullet" because of the high launch g-forces, so using terminal guidance is probably out. You'd have to rely on the initial launch trajectory, which at a range of 200+ nautical miles, means the result will likely be a miss, rather than a hit.

Of course, if they get the rate of fire up high enough...

Chip H.

Re:I don't see them replacing crusie missles

[UnknowingFool]

That's 10 per gun. A cruise missle takes about 2 months to build, I think. And a ship/sub only carries a limited number of them. It might augment cruise missile in that the missiles would be for highly selective pre-planned attacks while a rail gun is for close support like artillery.

Re:I don't see them replacing crusie missles

[Chyeld]

If the limitation in firing these is generating the power to fire, it won't matter if you have 60 launchers or just 1, you still will only get ten shots off in a day. Unless you are including the cost of a whole need power plant for each launcher.

That said, the point of "How many cruise missles do we expect to actually fire in one day?" is a good one.

Knocking out satellites?

[grumpyman]

Wait a second... I guess the country who has the most prolific use of satellite for military is the states. So could this technology comes back and bite our own ass?

Probably sufficient for a first stage.

[HighOrbit]

No, because when you shoot a projectile, you're putting it into a orbit that intersects the earth. You need some other impulse source to circularize the orbit.

Or, the rail gun could just be used as the first stage, second stage would be a solid chemical rocket which would take it the rest of the way and shape the orbit. The hard part then is getting the rocket engine, fuel, and nav-instruments to take the inital g-force of the rail-launch. The article mentions this:

"When this thing leaves, it's [under] hundreds of thousands of g 's, and the electronics of today won't survive that," he said. "We need to develop something that will survive that many g 's."

From the above, I'm assuming they have a reasearch project underway that would directly translate into launch survivability for the hardware. I'm not a electrical or mechanical engineer, but I'm going to guess that electronics embedded in high-impact composite ceramics (a la tank armor) might be the ticket here. The rocket engine and the fuel are another story. My understanding is that solid rockets are relatively simple construction (compared to liquid) so they would be the best candidate for survial. Pretty much every weld or joint I can think of would come apart under those kind of forces, so the fewer parts the better.

Re:Useless?

[king-manic]

I think it's great that research is being undertaken since this could be useful for other applications, but am I the only one scratching their head as to why the military is making a big push for these?

I assume a gun like this would go onto a destroyer. I can't think of the last time a destroyer was used in any meaningful way in combat since WW2. If I remember correctly, the only reason the navy even keeps destroyers is because congress forces them to. I guess you could put it on a tank or something, but most conflicts that are fought now are on the ground and are more guerilla tactics than formal engagements. It's being shown in Iraq and Afghanistan that all the fancy new technology that the military keeps buying doesn't really mean squat when it comes to fighting a war.

Am I missing something here?

In open engagements, tech matters. Having armour that is light and can stop small arms fire forces the other side to carry rifles. Having a higher rate of fire, higher tolerance for enviromental factors and lighter rifles of the same cilibre also help. Having good camo, being well provisioned and simpyl being well fed matter. All of that means tech. Where it fails is ambushes. Even then it forces ambushes to use mroe firepower. The kill rate between insurgents and US forces is still lop sided. If the US was commited as a society to this war, the insurgents would have no hope regaurdless of their gurilla tactics. But since the US is so splintered and anti-war to start. The Maoist gurilla tactis work.

Just a note: I'm canadian and thought the US stepping into Iraq was a mistake. They didn't have enough home grown support nor sent enough troops. They also should have been more upfront with their motives and the importance of what their doing. Their not fighting terrorism, their trying to establish control of the last remaining megatons of oil in the middle east to keep economic supuriority over the other emerging world powers. Or so it seemss from here.

Re: 95 miles altitude is space..Way Cool

[Anonymous Coward]

No, because when you shoot a projectile, you're putting it into a orbit that intersects the earth. You need some other impulse source to circularize the orbit.

IANAP, but that seems rather counterintuitive to me. If we could shoot a projectile arbitrarily fast and low to the horizon, I imagine a trajectory which forms a spiral around the earth with the object eventually breaking free of the earth's gravitational pull. If that's possible, then simply cut back the velocity to the right amount and that spiral becomes a perfect circle around the earth, no?

I could be completely full of shit, this is just my high school physics knowledge talking, please correct me if I'm wrong.

Re:I don't see them replacing crusie missles

['nother poster]

Nope, not even close, but lots of what is not kinetic energy will be waste heat not electricity. If you want to put enough electricity for two shots you would need to double your initial energy. If the energy doesn't go to waste heat or kinetic energy for the warhead where does it go?

Re:I don't see them replacing crusie missles

[Gazzonyx]

Let me add a few more variables to this equation, just to tick off the math junkies out there.

Let us also take into consideration that missiles are dangerous for the fact that they carry explosives! I'd wager that a good chunk of the setup time for firing a tomahawk is due to the nature of the munition. Most people tend to move a little slower and more carefully when playing with explosives, not to mention the time overhead incurred by redundant safety procedures that I'm sure the Navy has implemented. Furthermore, storage is an issue since there is fuel involved (I think they fuel right before launch - for obvious safety reasons). Which in itself involves more time and precaution.

Now we have this rail gun firing pieces of metal. I don't know about you guys, but even I'm not too afraid of moving a piece of metal. Storage of the 'slugs' should be easy since they have no inherent safety limitations, other than them not falling over on rough seas.

They take up less room, cost less, take less time to move, and now the ship no longer needs to also carry fuel for tomahawks. This reasons that there is probably more room on board. The slugs cost less, too, opening part of the budget. Sounds to me like this sets the stage for an additional amped up (sorry, I couldn't resist) power platforms on the ships in order to increase the net energy output and allow more launches per day.

On a side note... Seriously, how much surface area does a ship have that could catch solar energy? It might be relatively small, but I'd go so far as to say that near the equator, with 12 hours of sunlight every day, it probably adds up to be signifigant over the course of a day.

Rifles do produce a sonic boom

[tbcpp]

Actually it's the other way around, the sound of the shell makes very little sound compared to the crack of the bullet.

from wikipedia: [wikipedia.org]

Another important factor in sound signature suppression is the muzzle velocity of the ammunition. In weapons firing supersonic bullets, most often rifles, the supersonic bullet itself produces a loud and very sharp sound as it travels downrange. This is often referred to as a ballistic crack. For this reason, it is more difficult to hush the sound signature of these firearms effectively. Subsonic ammunition reduces sound report, but has a lower velocity than supersonic ammunition and is thus less lethal and has a shorter range.

Re:Not electricity

[Anonymous Coward]

It is not just friction, or even friction. If, as another commenter noted, your projectile is to have 9 MJ when it leaves the rail gun, which means you have to put in 9 MJ through your apparatus (or you can't impart it). Given less than perfect apparatus, losses are inevitable, and these have to be dissipated, often as heat. In addition, recall that you have now flung a projectile with 9 MJ of energy that means your apparatus has to absorb 9 MJ of recoil. Most of that energy will probably be released as heat, so you need a massive cooling apparatus to dissipate the energy, or you limit the frequency of shots. Or both.

Re: 95 miles altitude is space..Way Cool

[ceoyoyo]

I really, really doubt you could use the moon to put something in a spiral orbit around Earth. It is technically possible to use the moon to put a surface fired projectile into a more or less stable orbit, but it wouldn't be a useful one, being VERY high.

If you fire the projectile "strait [sic] up, and at the perfect velocity that it's not moving that fast when it leaves the atmosphere" then it will certainly come back down, and pretty fast at that. These naval guns are putting up a projectile that leaves the atmosphere and it's entire flight time is 6 minutes. Oh, and there's the matter of the big bang when it comes back down on your head.

You're right, it is impossible for the rail gun to hit itself from behind, but definitely not for the reason you say. Air resistance will slow down the shell, causing it to fall short. BUT, neglecting air resistance, if you fire your shell at orbital speed (for the altitude of your gun) then the shell will circle the planet and hit you from behind. That's how orbits work. It will not "fly out too far for the earth's gravity to have an effect on it." If you fired the shell at escape velocity or greater then it would fly away forever, but that wouldn't be very useful for putting it in orbit, would it?

Meanwhile...

[WhoIsJohnCleland]

...an Iraqi teenager blows your goddamn legs off with 20 bucks of explosive in a coffee can.

Re:Yeahbut....

[dbIII]

A cubic foot of seawater weighs approximately 64 pounds. A quarter ton, or 500 pounds

Somebody please add this to the metric article as an counter example for when people are talking about how easy imperial units are to deal with.

Re:Probably sufficient for a first stage.

[DerekLyons]

No, because when you shoot a projectile, you're putting it into a orbit that intersects the earth. You need some other impulse source to circularize the orbit.

Or, the rail gun could just be used as the first stage, second stage would be a solid chemical rocket which would take it the rest of the way and shape the orbit. The hard part then is getting the rocket engine, fuel, and nav-instruments to take the inital g-force of the rail-launch.

No - getting the hardware capable of surviving the G-forces is the easy part. The hard part is explaining to the beancounters why you are replacing a 50 million dollar first stage with a 10 billion (or most likely more) dollar accelerator - and not reducing your launch costs significantly because of vastly increased infrastructure maintenance and operations costs.
 
There's a reason why only the lunatic fringe of the alt.space community keeps insisting that an EM accelerator is the 'only way to go'.

Re: 95 miles altitude is space..Way Cool

[EveLibertine]

it requires more than 100 times less energy to send something out of moon's gravity

I think that means it requires less than 1/100 of the energy to fire something from the Moon compared to firing something from the Earth. Just clarification, as your wording was a bit confusing. Still, its a neat idea, but brings up some questions. Where do we safely land these things? Also, it would take some special care not to fire titanium into our other man-made satellites. I doubt it's really a feasible model at this point in time.

Titanium ore is common on Earth

[Anonymous Coward]

Why bother, there are plenty of Titanium mines on earth. Turning it into metal is the hard part.

Re:Probably sufficient for a first stage.

[GORby_]

Don't forget that conventional rockets, also have to lift their fuel. This means that the total mass that has to be lifted is many times more than the userful payload. With a rail gun, the only losses you have are due to the inefficiency during the creation and transport of electricity, and the friction of the projectile in the barrel and with the air.