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Rail Guns

jj said:

Otherwise, accuracy through the atmosphere at 200 miles is going to be, well, nonexistant.
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I agree, but the specification calls for suborbital re-entry... arc up, out of air, curve down, nose to target... all you really need is solid aerodynamics that will keep the projectile from wandering.

Guidance systems wouldn't be impossible, of course... but heck, the old battleships with their 16 inch guns had some pretty darned good ballistic accuracy.

Here's some statistics.

They fired shells slightly at a target slightly over 19 miles away, and 14 out of 15 shells landed within 250 yards of the target... 8 within 150 yards.

Now, there are inherent issues with this type of weapon... one is that the explosive charges being used aren't exactly the same, although they're as humanly close to identical as possible. This causes some variation in the trajectories.

Another issue is that the ship rocks during firing... so even when 5 shells are fired at a time, there's some variation between shells. Then, of course, the barrels are hot after firing... which changes the weapon characteristics slightly.

So in the end, you get a shotgun spread pattern effect. (Still, 14 shells within 250 yards from 19 miles away is amazing for an unguided ballistic attack!)

A rail gun would be a lot more accurate. No explosives... no "rocking" of the ship due to explosive firings; and lastly, no changes in characteristics from heating.

If you add to that an almost verticle launch with a suborbital parabola, I'll bet you could land an unguided kinetic weapon within 100 feet of a target 50 miles away or more. :)

And if launched from space, the calculations would be even easier.
 
Another thing to consider. Rail guns have the advantage of being capable of producing a "softer" launch than an explosive-powered weapon (such as cannon), which gives a lot of versatility in projectile type. More sensitive electronics and guidance systems are possible, as they can launch without being damaged by inertia. You might even see things like railgun launched EW packages, or a scarier thought, railgun launched UAVs or USVs (fire a swarm close to the target, they "activate" in the air or upon entering the water, and then go into a "seek and destroy" mode...imagine firing a dozen or two of these little terrors into an enemy fleet formation).
 
Great ideas, Huntsman. Have to EMP harden-them, given the method of launch. Also - given the requirement for the amount of metal that must be present - I would expect their life-expectancy during the SAND (Seek And Destroy) phase to be limited.

OTOH, you could insert these buggers in a minute or two from 100 miles away. :D
 
Ooo! I take it back!

You might not have to EMP-harden them, nor worry about their SAND duration!!!

I just realized - put the vehicles inside a metal casing. Shoot the metal casing out. Time on Target fuse blows the casing apart, releasing the UAV/USV. This way you'd get the speed, accuracy and retain the duration. Plus the shell would protect the contents from EMP as a bonus.

:bowl:
 
I did a bit of googling, and it appears that naval use is one of the prime areas of research. Primarily to replace the typical 5-inch gun mounted on destroyers and such.

The idea is to attain the same destructiveness with a weapon firing a lighter, smaller projectile. This would be a line-of-sight weapon.

Some of the research involves using graphite instead of aluminum for the "sabot" (the device that holds the projectile) to eliminate or greatly reduce wear on the rails.

One webpage said they were experimenting with rather a rather compact weapon with rails only 3 feet long.
 
Hmm... I dunno. Have to see what the kinetic potential is for a given projectile. I mean, explosive shells are pretty darned powerful. A railgun would mostly rely on kinetic energy as it's destructive power, no?
 
The depleted-uranium penetrator round that's standard for the Abrams tank is non-explosive, just a long needle of the heavy metal.
On impact, (at a mere 4500 fps) it essentially liquefies any known armor, throwing molten fragments all over the interior of the enemy vehicle. Truly horrific, BTW.

I imagine a similar projectile, at several times this velocity, would penetrate the armor of most smaller vessels, and do a lot of damage to the interior.
 
Yes, at very high speeds you get liquification at impact. At even higher speeds one can even expect vaporization.:)


It is really an efficient way to transfer energy to a target.
 
On explosive versus kinetic projectiles. The idea is, as AWP says, to transfer energy to the target. You can do that by bringing an explosive charge next to the target and detonating it. The delivery speed is essentially unimportant.

Or you can impact a projektile with sufficient kinetic energy. At speeds above MACH 4 or so, the energy released by the impact of a heavy-metal projectile is comparable with that of a similar weight of HE. At MACH 8 it is considerable higher :eek:. As a bonus, you get penetration power.

I think the basic reason for the interest in rail guns is their potential for high velocity. The muzzle speed obtainable in a conventional gun is limited by the speed at which you can make the shock-wave from the explosion travel through the barrel. It will travel at the speed of sound, which, due to the high pressure, can be much faster than in normal air, but it is still limited, because there is a limit to the pressure you can build a barrel to withstand.

The rail-gun does not have this limit.

Hans
 
Bikewer said:
The projectile shown in the segment was decidedly not in the 5-gram range.

It was dificult to tell what the projectile was made of, it looked like aluminum. About the size and configuration of the depleted-uranium "penetrator" presently in use.

The fellow they were interviewing said the projectile in use would be of a "heavy metal" like tungsten. (I dunno why he didn't just say DU, maybe politically incorrect.)

They did mention that the copper "rails" were very strongly braced, and the "sabot" that held the projectile appeared to be cast aluminium.

They did not mention wear on the rails, but I wonder if this could not be overcome by effectively "suspending" the projectile between the rails? (Kinda like mag-lev trains)

As to naval use, I wouldn't envision this as a stand-off weapon, but rather ship-to-ship at visual range.
(A very dangerous place to be in proximity to a modern warship!)
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Arrgh me hearty! Avast ye, we ain't been shootin' at what we could see since near abouts 1917 it wuz. If ye can't hit sumthin' over the horizen ye should be keelhauled.... arrrrrrr Damn lubbers.
 
More seriously, I recall a show that showed a variation in torpedo technology that allowed for very very fast speeds under water. As I recall it had to do with extending the envelope that the thing traveled in. Anybody recall this?
 
All I know is that on the miltary-science shows you see featuring naval technology, they are always very coy about such things. "In excess of 30 knots" is a figure often cited.

Same for nuclear subs in general.
 
Completely off-topic...

I went to a large undergraduate university that had a huge (and internationally renowned) engineering college. At the time, one of my friends was working on his masters in mechanical engineering. His project was developing sound-deflecting and absorbing design, through a grant from the Navy, that could be applied primarily to submarine technology in order to make the even more sub "stealthy" to all types of sonar. The primary goal of his research was, probably not too surprisingly, to create an effective anti-sonar application for propellers. He used to make these interesting parabolic shapes and put them into an anechoic chamber then "drop" sound on them from the ceiling and look at the scatter within the room.

If you have have the chance to walk into an anechoic chamber, give it a try. The room was about 10ft x 10ft x 10ft. The walls had these large foam cones all pointed towards the center of the room. The floor also had these cones, but over which was suspended a coated chicken-wire (looking... like grated steel) covering. We had to take our shoes off to walk in.

The first thing you notice is what I can only describe as a mind-blowing silence when you step into the room and shut the door. There is absolute no ambient sound in the room. When you, for example, clap your hands, the only point of sound comes directly from your hands and, as the name suggest, the sound complete dies out immediately without propagating.

At one point when we were walking around in there, I noticed that he would always put his hand up in front of his mouth when he wanted to say something if he had to turn his back to me. I said (stupidly), "Why are you covering your mouth when you turn your back?" He replied, "Watch this." He turned his back completely to me and then slowly started turning around. At the point that his head was at about 90 degrees to mine, I heard him yelling loudly "Ahhhhhh!!!!!!" until he was facing me directly and practically screaming at the top of his lungs. It was just weird.

You don't realize how much ambient sound and directionality plays into your perception of "hearing" until you step into such a room. I think if I'd spent more than 20 minutes in there, I'd probably have started to go a little cuckoo.

-TT
 
Assuming that authors like Clancy have things even close to right, the navy can identify specific vessels by thier in-the-database sound signatures.
 
Bikewer said:
Assuming that authors like Clancy have things even close to right, the navy can identify specific vessels by thier in-the-database sound signatures.
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That's not just Clancy, I knew a few sonar techs, The good ones could get vessel type from the sound and even learn to recognize a few individual craft. during the cold war one of the guys worked near the Soviet Union and knew a specific russian "fishing trawler" that I think they called Giggling Ivan because some harmonic in the drive system made a sound like a drunk guy laughing.

They were even able to keep up with enemy sub maintanance because they could identify when things like props, pumps or drive shafts had been changed. Stuff like this required the computer, but it is quite possible.
 
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