Navy Railgun Tests Leading to Ship Superweapon by 2020

Starman · Mar 1, 2012

Now if they can just figure out the power issue.

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.

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]

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.

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.

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.

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.

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.

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.

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.

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?

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.