DIY Railgun Projects

Rhett writes: "Straight out of Quake it's a couple of EE projects for building railguns: Working railgun by Texas Tech students and a project by MIT Students." Now if only we can get enemy ICBMs to pass through Texas Tech on their way to dropping nuclear weapons on the U.S., we'll have a working missile defense system.

Comments

This could be interesting

[darkmayo]

Yes pranks taken to the next level with almighty rail guns.. I can see the headlines now.. "MIT rails Caltech" .."I OWNz J00" was the battlecry from MIT when the they opened fire from a mile away punching holes in Caltech. Caltech responded by saying "Oh yea just wait til we get our BFG10k working then we will have the last laugh." then caltech was railed again and responded once more.. HEY I WAS TYPING..

Ender's Game

[Scot Seese]

Now the system platform needs to be connected to a very fast moving servo controlled aiming system controlled using the galvanic skin response/ musculatory pressure sensing sleeve Boeing is developing to fly aircraft - WITH the final assembly being connected to the most sophisticated, accurate weapons guidance system in the world: A thirteen year old boy with a case of Cherry Coke and Doritos.

When the fire test fails in front of the review board, perhaps he can yell "LAG!!"

Applications?

[Caid Raspa]

These are only toys, as this 200 feet per second the Texans get is a lousy projectile speed. Have they heard about gunpowder?

An AK-47 gives about 2000 feet per second, it weighs about 15 lbs, and it is more than 50 years old design.

The new German G-3 punches about 10000 feet per second, which is enough to pierce about one foot of steel, and it should be about the same weight as an AK-47.

For infantry, railguns will never be better than the ordinary chemicallly powered ammunition.

OTOH, put a railgun in a submarine. It could be about the same length as the sub, of the order 100 meters, with not much extra weight added. Normal ships could also use this.

Railguns vs Orbital Platforms

[Alien54]

I once toyed with a story idea where some of the locals of a planet used rail guns against visitors from other systems. [Sort of like hillbilly geeks vs revenuers]

The bottom line on these is that for dumb payloads the first shot or two will likely hit depending proper leading of the target. but dodging the shots is relatively easy, since even with projectiles going at ten miles per second, shooting at target one hundred miles up means that the target is at least ten seconds away. This is plenty of time for alarms and manual menuvering. (Take evasive action Sulu!) This depends on detecting the characteristic magnetic flux from a rail gun shot at the time the shot is fired. a little dicey, but not that impractical.

Given atmospheric turbulence, etc. We should probably have something like a rapid fire rail gun to be really effective - something like machine gun speed.

I can see the black budget people working on this now.

What about COIL Guns?

[Raetsel]

I remember, years ago, during the (seeming) height of the US military's interest in rail guns (and Popular Science, etc., etc...) a small group of college students with a more efficient answer...

• it was a COIL Gun.

Really the same basic idea as a rail gun, but they 'wrapped' the rails around the payload to get more efficient use of the electromotive force -- more 'bang for your watt,' so to speak.

That, and it looked more like a gun barrel. It was so much cooler looking!

Google turns up some interesting things, from someone trying to sell handheld weapon plans, to science-museum, brick-destroying, 900 foot-per-second Coaxial Electromagnetic Mass Accelerators. The second one is rather small, too -- something like that should scale up without too much trouble...

God, that looks like fun. This brings back that feeling I had 10 years ago when I really wanted to build one of these things. Maybe now I'll pull my head out of the computer long enough...

Oh, wait. Jet boat first.

Physics Question

[dschuetz]

So, basically, these are self-acting/modifying magnetic loops? In a sense, it's a single-turn coil that collapses on itself, and the motion of the collapse is used to fire the projectile.

I'd always assumed that a railgun was more solenoid-like -- a long coil with many windings, and a magnetized firing slug that pushes the projectile out. Maybe implemented as lots of smaller coils, computer-controlled to fire at just the right moments.

Granted, this design is way simpler and super-elegant, but does the math show this as being much more efficient? (I'm certain it must, or they'd be doing a different design). It just wasn't what I'd figured it'd be...

On a more specific note, what happens to the armature as it reaches the end of the gun? Does it fly off, trailing the projectile, or do they have some means of capturing it before it exits (sending the projectile off by itself)? If so, how do you keep it from vaporizing itself? Or is the armature itself the projectile?

Finally, does anyone have a mirror set up yet? I can read all the MIT pages, but the snakeden pages seem slashdotted....

Limits of conventional weapons

[sterno]

There is a major advantage to using a rail gun. Ultimately destructive force is measured by the mass and the velocity of the projectile. Thanks to the joys of physics, the velocity has a whole lot more to do with the amount of kinetic energy you can inflict on a target.

Now, with conventional weapons, you have a serious design problem. To fire a projectile you create a small explosion in the barrel. The larger the explosion, the faster the projectile, but at some point, the explosion is so large that you cannot design a barrel strong enough to contain it (or at least not one that you can tote around on the average tank).

With a rail gun, you have a big advantage in that the force applied to the projectile is applied over the entire length of the barrel. This reduces the stress on the barrel because you can apply the necessary force over a longer period of time. This allows you to achieve higher velocities with lighter barrels which provides two big benefits:

1) more destructive force
2) guns that can be rotated and aimed faster and more accurately

Now of course there are limitations with this too, but it does get you beyond the problems inate in more conventional explosives based ammo.

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Re:Limits of conventional weapons

[jafac]

Another advantage is the acceleration curve - you can vary it by varying the amount of power you feed as the projectile travels the length of the barrel. With a bullet, the acceleration curve is loaded very heavily at the front - which means more force is applied to recoil in a shorter amount of time. In an electromagnetic weapon like a rail-gun, mass driver or gauss gun, the recoil is distributed evenly (or any way you choose) along the entire acceleration of the projectile - which has a great potential for increasing accuracy.
There's also the potential that the power-curve could be inversely wired to the reflexive muscle reaction of the firer, to provide dynamic feedback, and prevent over-compensation for recoil.

Droping In From Orbit

[Wyatt Earp]

Not true.

A MIRV from a US ICBM or SLBM, isn't "REALLY" big. They are about 4 feet long.

"As the design of the Mk 5 reentry was developed, the change to a shape stable nosetip (SSNT) was established. The nose of the Mk 4 reentry vehicle was boron carbide-coated graphite material. The Mk 5 nose has a metallated center core with carbon/carbon material, forming the rest of the nosetip ("plug"). The metallated center core will ablate at a faster rate than the carbon/carbon parent material on the outer portion of the nosetip. This will result in a blunt, more-symmetrical shape change with less of a tendency to drift and, consequently, a more-accurate and more-reliable system."

There was some talk a while ago about some of the MIRVs in US Navy SLBMs not having nuclear warheads, would it be possible to remove the nuclear bits and use a warhead like this as a kenetic kill system? How much damage would a 200-300 pound warhead do if it was dropped from 700,000 feet?

Re:The Army loves computer games.

[rjh]

1. Farming computer games for new weapons ideas is a splendid idea.
   
   Yep, except that in this case the computer games were farming Defense Department prototypes and SF literature. Railguns have existed for decades; they were even proposed as part of Reagan's Strategic Defense Initiative back in '84. So this is hardly life imitating art--art imitated life originally.
   
2. The US Army should create a department for this purpose. I really think it could reap dividends.
   
   The Defense Department already does have a department for this, called the Defense Advanced Research Projects Agency (DARPA). In a previous incarnation it was simply the Advanced Research Projects Agency (ARPA), which developed the ARPAnet to connect ARPA research labs... and that, in turn, turned into the Internet.
   
   So your ability to post your opinion on Slashdot is due largely to the very agency that you think doesn't exist yet. :)