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Rail Guns Closer to Reality
emtboy9 writes "Yahoo News is reporting that scientists at Sandia National Labs have created a magnetic pulse gun (rail gun) that can accelerate small aluminum plates at 34 kilometers per second, faster than the Earth travels through space.
The accelerated plates strike a target after traveling only five millimeters, or less than a quarter-inch. The impact generates a shock wave -- in some cases, reaching 15 million times atmospheric pressure -- that passes through the target material turning matter into various states almost instantly (solids into liquids, liquids into gas, and even gas into plasma)."
This is a non-military use. They are using it to simulate conditions deep within giant planets. Also this isn't really a rail gun. For one it doesn't use rails, and the whole aim of this experiment is unrelated to rail guns.
what sig?
The Sun circles the center of our Galaxy at about 250 km/s, but the Local Group of galaxies moves at about 600 kilometers per second relative to the primordial radiation of the big bang.
Clearly a solar centric frame of refernce, as (1 AU * 2 * pi) / (1 year) is roughly 29,700 m/s. Which is close to, but less than, the speed quoted.
Faster, measured against what frame of reference? A marker on the equator versus the center of mass? As seen from the moon? Sol? Alpha Proxima? Vega? The center of Andromeda's galactic core?
Probably the Earth's orbital speed around the Sun.
It's far too small to be in reference to the cosmic microwave background radiation. The temperature of the CMBR varies as a dipole across the sky, with a temperature difference of 7.7 mK, because the Sun is traveling toward the Leo constellation at about 370 km/s relative to the CMBR radiation itself. It would be traveling faster but the galaxy as a whole is moving at about 600 km/s in the direction of Centaurus.
This is unneed pendantry. If you are not only able to list off these places as frames of referrence but also think of them in the first place, odds are you already know the answer.
Most sensible people would take it as being the sun spinning around the sun, and leave it there.
Since there is no pleasing you therein, the earth is more or less 149,668,992 km from the sun, which gives a circumfrence of around 940,398,011 km which over 365 days gives 29.8 km/second.
So, there you go, it's around the sun.
Let's hear it for reading comprehension! Between yahoo news and he submitter, we're somehow left with the impression that this is a rail gun. It's nothing of the kind. It's an implosion machine. As described in the LiveScience.com article linked: "The Z uses a short burst of intense electricity - only a few 10 billionths of a second long - that forces an ionized gas to implode." So we can stop the handwringing over the morality of this "weapon", as to use it as such would require luring the enemy into a chamber the size of a soup can and asking him to hold still while you blast him.
If a job's not worth doing, it's not worth doing right.
Housed at Sandia National Laboratories, the Z machine attracted a lot of attention eight years ago when its energy output more than quadrupled - raising hopes that the reactions in the Z could provide a new source of clean, abundant power. To help further progress towards this end, the machine is getting a $61.7 million upgrade, officials announced recently.
.45 ACP.
The fact that several mods decided that you post was insightful makes me very uncomfortable with the quality of mods lately. If you read ANY of the TFAs linked, you would see that in this case the gun in question has nothing to do with "maim and kill." In this case, the "rail gun" (it's not really even a rail gun, but that's a whole different issue,) has more in common with a staple gun than my trusty
I believe this link better describes what the Z Machine has to do with rails guns.
I work at Sandia, on this very topic. These are just flyer plate experiments, using the Z-machine's Marx Generators to isentropically accelerate small aluminum flyer plates up to high velocities, in order to better understand the behavior of metals at high pressures/densities/temperatures. This has been around for a while now. The only difference is they've recently attained these higher velocities by having the Marx Generators switch at slightly different times, rather than all at once.
Nothing to see here, move along. (and pay no attention to the man behind the curtain)
It's accelerate to 34 km/s. I forget what the actual acceleration is, but I figured out that the flyer plate goes from 0 to 60 (mph) in something like 0.002 nanoseconds.
You may have also seen aluminium egg rings fired off older rail-gun devices. The actual material doesn't have to be magnetic, it moves forward because of its own magnetic field induced by current flowing through it. Aluminim is a GREAT conductor of electricity and so makes a similarly great magnetic field. This field, when interacting with the rail gun's, makes it move, NOT the fact that the material itself has (unenergized) magnetic properties. Pretty simple really.
The article's title is extremely misleading.
This does not bring rail guns any closer to reality, by which I mean it does not bring military rail guns any closer to reality.
The Z-machine is a hanger-sized experimental device akin to a particle accelerator. This was an experiment designed to study extremely high pressures, such as those thought to have been important in Jovian planetary formation.
Saying that this experiment brings rail guns closer to reality is like saying that the Large Hadron Collider (LHC) at CERN brings PPCs closer to reality.
It MAY also have implications for subway systems built along similar lines as the Japanese Bullet Train.
snip
Instead of having a moving magnetic field pulling the train, as with the Bullet Train...
The Japanese bullet train is just an ordinary train. You're speaking of the Linear Motor Train project that's been around for ages and doesn't seem to be going anywhere.
It's off topic, but what the hell... The linear motor train does approx. 500Km/h. Impressive. However, the latest bullet train (again, just a normal train) starting tests does 405Km/h. That's pretty impressive too, and runs on existing rails. Turns out that air drag was a much, much bigger problem than originally suspected, and the means of propelling the vehicle may not be as important.
They should use some of the technology for cold fusion to accelerate small metal plates into things... That would be hella fun!
Or turn it around and try to use railgun technology to produce warm fusion. I'm not really sure if it would work (effective confinement is one *bleeping* hard thing to do), but it might offer the possibility of fusing a large amount of matter. Now how can we extract energy from the extreme neutron flux without losing the machine in the process?
Javascript + Nintendo DSi = DSiCade
There is something weird going on with the math.
First off 76,000 mph is about 38,000 m/s which agrees with the 34 km/s statement so I believe this number.
They say that the pellet achieves this speed in less than a second.
This implies an acceleration greater than or equal to 3400 g's.
Assuming a constant acceleration it also implies a track length of 17km.
Later the article states that the achieved acceleration is 1010 g! This implies an acceleration time of about 3.37 seconds and a track length of about 50km.
These two statements do not agree.
Uh, was I the only one who got the wrong article on the "magnetic pulse gun" link? It should be here.
Using rail gun on a squirrel would result in too much meat damage. A .22 is almost too much. You're better off using a .17HM2 instead. However, using a railgun on prairie dog could provide a lot entertainment. Think about how flat the trajectory would be and how far out you could hit them. Perfect for the Lubbock area. For those that need help imagining it, try http://www.dogbegone.com/.
It doesn't accellerate the flyer plate linearly. A Z-pinch machine, which the Z-machine at Sandia is an example of, implodes a thin hollow cylinder of material, a fraction of a mm thick and about 1-2 cm in diameter and roughly 1-2 cm long. The Z-pinch effect causes the cylinder walls to collapse inwards at high speed, striking a target along the axis of the cylinder.
See for example http://plasma-gate.weizmann.ac.il/ZP/
High electrical current flows through the cylinder, which causes a magnetic field whose lines of force are circular around the wire. Basic electrical physics. Also basic physics, you get a force ExB (electrical field cross product with magnetic field). The sign of the force, from the direct electrical field and its induced magnetic field, is inwards towards the center of the cylinder.
So at high enough currents, the cylinder implodes.
There's no external magnetic field necessary. If you add one, then the implosion process is more even and stable, but that isn't necessary at all for the Z-pinch effect to work.
You can even do fairly safe home experiments in Z-pinching. Take a bunch of thin wires and a couple of nonconductive disks. Put the disks on a pole, then string the wires from disk to disk so that they form a cylindrical array. Solder all the ends at the top to one electrial lead and all the ends at the bottom together. Connect up to a power source. Watch the wires move inwards.
Z-pinch is just taking that effect, and putting the equivalent of the whole world's electrical power output through it instead of a small regulated power supply. A bit more force, eh?
Calling the Z-machine a railgun is like calling a F-16 fighter a really cool drag racer. Just because they're both fast and burn hydrocarbons doesn't make them at all the same thing.
I think it should read accelerate to 34km/s, not at
Only if the aluminum slug accelerates linearly, which is almost surely not the case. Like any other inductor, the rails will need time to build up their magnetic field. This hysteresis combined with the potentially non-linear response from the capacitor bank they are likely using to power this thing, I'd imagine you could be off by just a hair.
You can't legislate goodness. Let each to his own destiny, by will of his freely made choices.
No, unneeded pedantry would be pointing out that the earth's velocity wrt the sun is roughly constant, therefore it's accelerating at 0 km/second/second. Not hard to 'accelerate' something faster than that.
That's false. There's an acceleration because the velocity is changing in direction, even if it isn't changing in magnitude. This should be obvious from the fact that there's a force (the sun's gravitational force) acting on it. Basic physics, F = ma, yada yada yada.
Although the article summary is wrong in saying that the plate was accelerated "at" 34 km/sec, perhaps accelerated "to" 34 km/sec may have been more accurate.
Or in SI units, 2 picoseconds.
"The invisible and the non-existent look very much alike." -- Delos B. McKown
From the linked Wikipedia article: Peaceful uses of railguns There is interest in using railguns as mass drivers for space exploration and mining. They would be useful for launching bulk ores into space, particularly from low-gravity bodies such as moons and asteroids; electrically powered from solar panels, they would not require any consumables such as rocket fuels. Rail guns have been proposed for use in delivering projectiles to space, especially from bodies without atmospheres (such as the Moon). Its main competitors are coil guns and ram accelerators. Also, railguns may be used to initiate fusion reactions, by firing pellets of fusible material at each other. The impact would create immense temperatures and pressures, allowing nuclear fusion to occur. However current railguns are not yet sufficient to achieve the energies required.
Well, if we're going to be pedantic, 34 km/s is a speed, not a velocity.
John
inspection of the 'scientists' link in TFA reveals that the plate is accelerated at 1010g, taking the speed (sic) from zero to the reported 34 km/s.