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."

Comments

95 miles altitude is space..Way Cool

[lecithin]

But I was thinking, is this a possible way to launch orbiting vehicles? I first think no, as the initial force necessary to 'shoot' something into orbit would probably destroy any delicate instruments needed for a working satellite.

  However, this seems very interesting as an Anti Satellite/"Star Wars" platform. If they can get the software working to intercept, this should (scaled up version) be able to knock out satellites, ballistic missiles, etc - shouldn't it?

Re: 95 miles altitude is space..Way Cool

[Maximum Prophet]

$1000 to launch 3.2 kilos into space. Damn straight. The price has to come down with volume. You just need to install the thing up the side of a mountain. You don't even need the fins and electronics onboard, just some end of the muzzle steering pushes should be enough to change the orbit the thing arrives in. Use it for fuel, water, and supplies that can take the G's, making it that much safer for the astronauts.
You'd need to build a space tugboat that can hunt down and gather the payloads, then boost them to a higher orbit. No biggy, you can use robots with ion drives for that stuff.

Re: 95 miles altitude is space..Way Cool

[Yvanhoe]

Well the most intelligent use of a mass driver I have seen in SF (and envisioned real space projects) is to use a mass driver to send the product of moon or asteroid mining back to the earth. IIRC, it requires more than 100 times less energy to send something out of moon's gravity well than to send it out of earth's, so a shot of 100 tons of titanium a day could well make a moon mining facility profitable.

Re: 95 miles altitude is space..Way Cool

[ceoyoyo]

The projectiles have to be made out of metal, so you can track them with radar, and they'll be smoking hot after slamming through the atmosphere so fast. Since they're purely ballistic once you detect them you can figure out where they came from using high school math.

I don't see them replacing crusie missles

[winkydink]

if you can only fire 10 per day.

Re:I don't see them replacing crusie missles

[drinkypoo]

Ten a day per launcher, yo. A cruise missile costs a million bucks plus. These projectiles will cost about a thousand dollars (projected, maybe it'll be $2000, still negligible in comparison.) With the amount of money you save not launching cruise missiles, you can afford to build more launchers. Let's say the launcher costs a billion dollars and the projectiles are $2000. You will then "save" $998,000 every time you launch a railgun projectile and you need launch only 1002 projectiles to get your launcher and the ammo for "free". Wikipedia claims the cost of a tomahawk is 1.3 million, so depending on who's right it could be an even shorter period of time. Something like 4500 of these missiles are known to have been made, so assuming an average cost of $1M that's what, 4.5 billion dollars spent so far? Just to put things in perspective. Also, even cheaper munitions could be used for short-range firings where windage will not make a substantial difference and guidance is not needed.

Re:I don't see them replacing crusie missles

[dan828]

GPS and computer controlled fins. It'd just be a matter of developing a system that can withstand launch Gs and the electromagnetic forces. Maybe difficult, but probably not impossible.

Re:I don't see them replacing crusie missles

[physicsphairy]

I'd be very careful accounting for winds over a distance of 200 miles

"they will apex at 95 miles altitude, well into space."
There are no winds in space. For that matter, the atmosphere thins out considerably before then. If it didn't these long range railguns would be pretty useless because most of the kinetic energy would be lost. And at the velocities we are considering the time spent in the deeper atmosphere is miniscule. Neither do we know how much spin the projectiles will have (a major stabilizing factor). But it's hard to imagine any such simple and fundamental thing would be overlooked by the scientists involved.

Re:I don't see them replacing crusie missles

[Kadin2048]

They already have such systems for conventional artillery. I'm not sure of the G forces involved on a railgun projectile versus a conventional one, but we've managed to put fairly sensitive electronics in the noses of conventional artillery projectiles since World War II, so I think we can probably figure it out.

The GPS-guided artillery shells that I've seen actually don't use "fins" in the same way that a missile does, but little pop-up retarders that change the shape and aerodynamic characteristics of the projectile just enough to produce a change in direction. Allegedly they can be quite accurate.

I think the technology where I heard about the GPS-guided artillery was something to do with the Crusader mobile artillery system. Basically, it was the Army's way of competing with the Air Force as a "surgical strike" capability. Unfortunately then Iraq really happened, and people's interest in surgical air-strikes went out the window with "shock and awe," or at least it seems like it.

Re:I don't see them replacing crusie missles

[arivanov]

10 a day is better than ten in total. You will be surprised how few Tomahawks (or Granits in the Russian case) are actually carried by most ships capable of launching them.

The contract is awarded to a nuclear shop so I suspect that the thing will have an integrated reactor which makes it even more interesting.

What goes around, comes around. After realising that missile tech is too expensive, Iraq tried to build the Babylon gun with a 1000 miles range. For the same reason (the missiles being too expensive) Russians have now developed a gun launcher (forgot the name) to fire high altitude atmospheric probes instead of the old missile system . US nearly did that with the HARP, but heavy lobbying by the aerospace industry killed that. And now we come full circle with US looking at long range guns for cost reasons.

Re:I don't see them replacing crusie missles

[Kadin2048]

*grumbles something about failure to improve nuclear generators for destroyer use*

There's nothing wrong with the nuclear reactors we have now; you could easily fit one of them into a destroyer without any problems. I'm sure Westinghouse Nuclear would be happy to draw you (assuming 'you' have a few billion bucks to spend) some plans of how it could be done. Much of the space optimization has already been done, for submarines. There are several basically standardized designs that you could build the ship around, and then plop one in when you got everything else ready. It's totally doable.

The Russians have several nuclear powered ice breakers that aren't much larger than destroyers, and they used to have several nuclear-powered cruisers as well (although I think they've all been decommissioned).

The reason that surface ships haven't been built with nuclear reactors has more to do with the perceived economics of fossil fuels, rather than any real technical limitations. And for that matter, I've seen analyses that show that bulk supertankers could be economically driven by nuclear reactors -- if the NS Savannah was around today, and upgraded to use containerized cargo instead of manually loaded stuff, it would probably make money due to the high cost of bunker and diesel.

If it's really electricity that's the problem with the rail gun, putting a nuclear reactor on a smaller ship wouldn't be more work than breaking out some old plans, or making a long-distance phone call to a retired-engineer's home in Russia.

Re:I don't see them replacing crusie missles

[drinkypoo]

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.

Solar won't help with this to any significant degree - at least not anything mounted on a ship. On the other hand, you could theoretically make a bunch of little floating hockey-puck shaped robots that would be just smart enough to connect to one another and had just enough propulsion for the job, that would make a sort of "floating carpet" of solar collectors. When you were done, you'd just command them to separate into strips, and you'd reel them in like a rope.

Re:I don't see them replacing crusie missles

[krisp]

the new year's 3 hour long episode of "Future Weapons" on Discovery Channel had a segment on GPS-guided artillery. They fired it at 16,000 Gs and it hit a target 25 miles away or so within 2 yards. And this was with the shell fired 40 degrees off course. Still not close to the "hundreds of thousands" of Gs the article quoted, though.

Projectile distortion?

[ackthpt]

What happens to the projectiles in these things? Such a gauss density I would assume, beyond simply the accelleration of the projectile has to be considerable. The coin shrinker is only 1600-2500 J

Assuming 2500 J in a space of 3 mm does to an object the size of a quarter, 8 mega Joules would have an equivilent magnetic density spread over a gun 96 metres in length. Or me math is fscked...

I wonder.....

[Prysorra]

Perhaps a sufficiently high arc can disguise this as a meteor* strike if it goes unannounced and unnoticed by radar.

*Meteorites leaves evidence. Meteors can explode in midair.


Cool to think about....

Launch Loop

[cutecub]

You're talking about a Launch Loop.

Basically, its a magnetic rail gun for launching space-craft into orbit. And in order to avoid the crushing G-forces involved, it has to be hundreds of miles long. So, while it may not be economically or politically viable, it is technically feasible. We know how to build a launch loop, as opposed to a Space Elevator, which can't be constructed with current technology.

-Sean

Amount of power (energy really)

[Beryllium Sphere(tm)]

32 megajoules is less than 9 kilowatt hours.

Heat might be more of an issue. That would be over 30,000 BTUs, or a 60 degree rise in a quarter ton of cooling water.

Return of the Battleship

[Black-Six]

With this new rail gun technology, the US Navy now has a serious fire support asset in its Iowa and North Carolina class battleships. All they have to due is overhaul the power generation systems to handle these things and an Iowa class battleship would be capable of launching 90 16" projectiles and 200 5" projectiles a day via modifying the the main and secondary batteries for rail gun tech. In much more significant terms a Iowa class battleship would be able to deliver a broadside salvo of 9 16" rounds and 10 5" rounds on a target. Thats a lot of firepower!

Re:Return of the Battleship

[Anonymous Coward]

Modify the batteries for rail gun tech? At best they'll be able to keep the crew! Railguns don't use gunpowder, the aiming system will have to be completely new, and the barrel of a rail gun is a rather important part of it, too. Obviously they'll need new shock absorbers. Dunno, what were you thinking they'd actually keep?

power not the problem

[EricBoyd]

Running a few quick calculations shows that power is not likely the cause of the delay between firings. If you have 10kW to power your system, you can fire a 64MJ blast every 1.78 hours. If you have 100kW, time to fire is only 10.7 minutes. Obviously for the smaller railguns the power requirements are even less. I'm no expert on how much power is actually available on those big boats, but somehow I doubt that 100kW is out of reach.

I believe that the time to fire is more likely dominated by the maintenance issues - making sure that the rails are perfectly straight, the warhead is correctly placed, etc. If you're off by even a little bit that sucker could destroy the railgun on the way out, costing you millions and making it inoperative until you're back home.

Re:Replace tomahawk?

[gnasherspants]

Its advantages are obvious - each round is cheap, it doesn't get lost and end up as a technology or a munition 'giveaway' (or bad press), and as the article says, reaction time can be rapid. It means that the next class of boats are merely floating powerstations with all the 'goodies' held far away from the action. Besids, a rail gun is not just line of sight, as with any ballistic weapon, unless you can see over the horizon. I guess the main limiting factors in use would be those of ablation - both to the rail and projectile.

Comment removed

[account_deleted]

Comment removed based on user account deletion

Re:physics of railguns

[sjaskow]

Well, a little googling turned up this which seems to explain it better without of the nasty physics technobabble. And this is how to do it yourself.

Re:More nuclear ships?

[Protonk]

Eh. The reasons for dropping nuclear powered surface ships were that the regulatory and maintenance costs didn't justify the independence that nuclear fuel offered. Also, in the wake of TMI, cruisers like the Long Beach found fewer and fewer foreign ports willing to invite them.

The Navy keeps nuclear power on submarines because the air independence is too valuable (notwithstanding the nuke/diesel arguments) and on carriers because it makes for a ready source of steam (think catapults), hot water, etc.

Power required in electrical form was never really an issue. Modern gas turbines can produce power more quickly and in a denser fashion (think fuel + turbine + cables vs a whole steam engine room) than naval nuclear reactors.

Unless they decide on HUGE engine rooms and prioritize power use, i wouldn't see nuclear powered sruface ships coming back.

Power is relative, I guess.

[LordByronStyrofoam]

When I worked on General Atomic's Doublet-III experimental fusion rector, in the early 80s the energy for the machine was supplied by a three-story motor-generator constructed below-ground at the site. The motor ran off 440V mains and when powered spun itself, the generator and a 400-ton flywheel at 480rpm. It took twenty minutes to get the thing up to speed.

During a 5-second 'shot', when the stored energy was released, the motor, generator and flywheel would go from 480 to ~100 rpm, and dump 960 mega joules of energy into the coils of the experiment. You could feel the vibration in your feet anywhere you stood at the site, all the CRT's images would collapse due to the intense magnetic field generated. Then it was another twenty minutes before they could do it again.

Useless?

[SparkyTWP]

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?

alternative to nukes

[2ms]

Hmm, I wonder if, instead of nuclear missiles, we could just have nuclear generation powered railguns that could lob comet-like projectiles, thereby have the same kind of initial devastating effect, but without all the problems of nuclear fallout and radiation.

I mean, it's true that nuclear weapons have basically brought peace to modern nations through the principle/doctrine of mutually assured destruction (thats why, for example, all of Europe isn't Soviet Union now -- Russia forced to stop taking over stuff and be peaceful or else get nuked).

Maybe a new doctrine of mutually assured destruction through the crushing of cities through colossal projectiles with ungodly kinetic energy would still provide the umbrella of traditional MAD, but without that tiny little problem (which will never go away as long as there are nuclear weapons) of the potential of some lunatic dictator, who cares more about being in power than he cares about whether or not the rest of life on planet gets wiped out by radiation poisoning, getting his hands on nuclear weapon.

Re:Platform instability

[superstick58]

Take the example of the M-1 Abrams. The main gun on this tank is stabilized in some way to allow accurate shooting while on the move. I'm not sure of the details behind this, but I'm sure mounting the railgun on some actuators controlled by some gyros will be able to minimize the pitch from the ocean.

Re:Probably sufficient for a first stage.

[ceoyoyo]

The other problem is finding some sort of material that can survive the heating. If you're going to reach an orbit that doesn't take much fuel to circularize you're going to have to be going at more than orbital speed coming out of the barrel and fly at a fairly shallow angle to the surface -- through dense air. That's going to make the space shuttle's reentry look like child's play.

Re:How fast is this thing travelling???

[Oswald]

Funny you should ask. Mythbusters did research into the deer-rifle equivalent of this problem and came up with several documented cases of people who had (accidentally) been shot from over a mile away. The bullets were still dangerous at that range because they had not been fired at an angle steep enough to cause them to expend all their energy fighting gravity (around 45 degrees?) If the bullets were fired straight(ish) up, their terminal velocity when they fell back wasn't nearly high enough to kill a person; if they arced up and arced back down like a throw to home from the outfield, they were still moving real fast and could do real damage when they landed.

The most surprising thing to me was the terminal velocity of a lead bullet--around 80mph. I would have expected higher from such a dense metal.