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Fnord

Tue Nov 16 2010, 08:15PM

Registered Member #2004 Joined: Sat Feb 28 2009, 11:43PM
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Posts: 39

(Not sure whether this should go here or in high voltage, though I guess technically it's electromagnetic)

I've been looking at ion guns lately and have found a few references here and there on the internet, but as far as a solid documentation on the subject I've seen nothing.

I understand how they work in theory, though I don't know much about their real-world effects.
If anyone has any experience in this area I'd like to hear from you.

Questions*:
-Do they actually have any practical uses? (besides ion engines)
-How potentially dangerous would it be to get hit with a discharge from one?
-What speed can you actually accelerate ions to with such a device?
-Is there a formula for figuring acceleration?
-How quickly do ions disperse/lose velocity in atmospheric air? (range?)
-Is the output of such a device more dependent on the voltage or the current used, or is it about even?

In a typical design,
(Corona emmiter(-) Attractive grid(+) Repulsive grid(-))
wouldn't the repulsive grid tend to bounce ions back to the attractive grid, rather than letting them pass and giving them a 'kick' on the way out?

And wouldn't the repulsive grid tend to leak corona/ions also? (causing backwards firing)

*Most devices I've heard about were relatively low power, meaning perhaps the voltage and current of a flyback with a decent driver circuit. I'm asking these questions with such a device in mind.

Neuuubeh

Tue Nov 16 2010, 09:41PM

Registered Member #3411 Joined: Sat Nov 13 2010, 08:25PM
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Posts: 33

Any kind of charged particle accelerators tend to be useless in the atmosphere. It is a huge problem with pretty much any high energy "energy" weapons as a matter of fact, be it lasers, particle accelerators or even railguns. The atmosphere offer too great of a resistance/defocussing on those high kinetic/electromagnetic energies.

Go at least in an orbit around Earth and its going to be a whole different store. Deep space even more so. But yah, i doubt we will be seeing such advancements in our lifetimes..

At least my opinion on the matter :).

Fnord

Wed Nov 17 2010, 09:27PM

Registered Member #2004 Joined: Sat Feb 28 2009, 11:43PM
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Posts: 39

Long range lasers are already in use, and railguns have bigger problems than atmosphere to deal with.

Turkey9

Thu Nov 18 2010, 12:01AM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

The reason ion accelerators don't work in atmosphere is based on their charge. The field only accelerates the ion as long as it has a charge. The instant that that particle interacts with a non charged particle, the ion loses it's charge and it stops being accelerated. The average length a particle can travel interaction free in atmosphere is on the order of a micro millimeter (excuse my sloppy units!). As pressure decreases, the distance between the non-charged particles increase and thus the distance an ion can travel without interacting with them increases.

The type of accelerator you're talking about with have basically no affect on a person, even if the ion made it to them. Higher energy accelerators can cause radiation type injuries when a person is exposed for extended periods of time.

Accelerators do have uses but you have to get the particles going much faster first. a PET scan uses antimatter accelerated into the body to image. When I say antimatter, I mean single positrons. The annihilate in the body when they slow down and release a photon which is how the image is captured.

You could build an ion engine in theory with a flyback type supply. The current will be low since it is an electrostatic device.

Neuuubeh

Thu Nov 18 2010, 08:28AM

Registered Member #3411 Joined: Sat Nov 13 2010, 08:25PM
Location:
Posts: 33

Fnord wrote ...

Long range lasers are already in use, and railguns have bigger problems than atmosphere to deal with.

Sure, as demostrators. Beam absorption and blooming is and will always remain an issue. Any dust/steam/whatever impurity along the path of the photons reduces the energy which gets to the target. Ever seen a demonstration in a rainy or even overcast day? All I can remember is nice clear skies and relatively hot temperatures with low humidity

Railguns do have other issues, no doubt (but nothing that hasnt been quite solved really?). But dont tell me a railgun wont work THAT much better in absence of atmosphere - the simple equation of aerodynamic drag suggests otherwise.

PS Heard the statement of the secretary of defense on those first boeing lasers?

"I don't know anybody at the Department of Defense, Mr. Tiahrt, who thinks that this program should, or would, ever be operationally deployed. The reality is that you would need a laser something like 20 to 30 times more powerful than the chemical laser in the plane right now to be able to get any distance from the launch site to fire."

Use against ground targets seems unlikely. Aside from the difficulty of acquiring and tracking a ground target, firing through the dense atmosphere would weaken the beam. Ground targets such as armored vehicles are not fragile enough to be damaged by a megawatt-class laser

Railguns look more mature to me...

Anyhow, enough with the offtopic. Ion experiments can be cool, you can either make an engine as already suggested, or try making one of those ion wind lifter platforms. Neither requires high power :)

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