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Storing Data on Projectile

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Ash Small

Thu Sept 17 2015, 04:37PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Steel can be soft or hard. This, I think, mainly depends on grain structure, and the easiest way to alter the structure is generally heat treatment.

Transformer steel, for exampl;e, needs to be soft, whereas permanent magnets are hard.

2Spoons

Fri Sept 18 2015, 05:19AM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615

Wow, so fixated on one solution, and so hostile to alternatives. You do realise we are trying to help you find a workable solution?
I think your magnetic imprinting method is likely to fail because:
You will have to overcome a large remanent field in the projectile, resulting from its travel through a bunch of solenoids, unless you can provide a demagnetising coil at the muzzle.
Skin effect will prevent field penetration into the projectile at speed, so if you are very, very lucky you may get a magnetic imprint 5 to 10um deep (based on your 200kHz above).
I think reading that back is going to be exceedingly difficult.
Still, if you want to try then I wish you good luck and success.

And before you dismiss RFID out of hand consider putting the chip on a small plastic standoff on the rear of the projectile to get it clear of the iron, and the read/write coil is mounted in the breech so that data can be written as the projectile is loaded.

hen918

Fri Sept 18 2015, 07:13PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

2Spoons wrote ...

Wow, so fixated on one solution, and so hostile to alternatives. You do realise we are trying to help you find a workable solution?
I think your magnetic imprinting method is likely to fail because:
You will have to overcome a large remanent field in the projectile, resulting from its travel through a bunch of solenoids, unless you can provide a demagnetising coil at the muzzle.
Skin effect will prevent field penetration into the projectile at speed, so if you are very, very lucky you may get a magnetic imprint 5 to 10um deep (based on your 200kHz above).
I think reading that back is going to be exceedingly difficult.
Still, if you want to try then I wish you good luck and success.

And before you dismiss RFID out of hand consider putting the chip on a small plastic standoff on the rear of the projectile to get it clear of the iron, and the read/write coil is mounted in the breech so that data can be written as the projectile is loaded.

I think, for the purpose of identifing a coil-gun projectile that is used in a crime, the NFC/RFID idea is flawed: It can be erased too easily, a distance from the projectile.

Signification

Sat Sept 19 2015, 10:18AM

Registered Member #54278 Joined: Sat Jan 17 2015, 04:42AM
Location: Amite, La.
Posts: 367

Yeah, simplicity of countermeasures virtually kills this idea.

DerAlbi

Sat Sept 19 2015, 03:35PM

Registered Member #2906 Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727

Sry 2Spoon, the possibilities are obviously infinite to approach any given problem. The more offtopic it gets the harder it is to get someone who could contibute here to read the thread.

For now: How to design a magnetic writer?

i mean.. somehow the flux needs to go through the projectile thats up to 0.5mm away. (the air gape size due to the barrel)
I think i need something like a horseshoe shaped core. Made from... Ferrite? But i think to store the best possible remanent field, i should dirve the iron to saturation. which will not happen with a core material that saturates earlier than iron. Pure Iron will not work as a core at those frequencies. But if that does not work.. will the projectile work?
The closed loop through the overall 1mm gap must be more attractive to the flux than closing directly inside the horeshoe.
The size alone to satisfy such condition puts a limit on the bitsize.
Also: how to to choose the orientation? Make the field lines parallel to the projectile direction? That would lead to really big physical bits. Or the horseshoe is oriented in such a way that the field lines are perpendicular to the projectiles direction. That could allow for smaller bits but it does not benefit from the previous magnetic imprint of the last acceleration coil.

Bored Chemist

Sat Sept 19 2015, 08:46PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

If I got a magnet and shot it from a compressed air cannon into a solid target, I would expect the shock to demagnetise it.

So...?

Hazmatt_(The Underdog)

Sat Sept 19 2015, 10:44PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

1. Duplicate the magnetic head from a tape deck, but beef it up for high current
2. You need pulsed DC to write not AC
3. You will need to pulse several amps of DC at very high speed to write to the slug (H-Bridge)
4. You will need to "Erase" the slug before writing to it, so that requires an erase head.
5. You will need an optical gate for the slug to pass through to start the write cycle, its moving pretty fast so spacing is critical
6. Impacts will distort the slug, reading back may be worthless, but that depends on how wide the magnetized section of the slug is, doesn't it?
7. Results?

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