megalomania
May 18th, 2003, 03:44 PM
Bitter
Frequent Poster
Posts: 290
From: 11 Downing Street, London, England
Registered: SEP 2000
posted 04-04-2001 10:55 AM
--------------------------------------------------------------------------------
Can PETN be detonated without using any other primary explosive ? Will, say, a confined chlorate/sugar/aluminum mix be sufficient to set it off ? I know it's alot easier to detonate than RDX...
Anthony
Moderator
Posts: 2306
From: England
Registered: SEP 2000
posted 04-04-2001 05:18 PM
--------------------------------------------------------------------------------
The Blasters Training Manual claims there hasn't been a reported case of det cord (petn filled) being detonated accidentally (by shock or impact). For the military to use it, it must be pretty insensitive - what with all those bullets flying around...
(All IMHO)
wantsomfet
Frequent Poster
Posts: 236
From: EU
Registered: JAN 2001
posted 04-04-2001 05:23 PM
--------------------------------------------------------------------------------
What amount & density do you think of? Perhaps larger quantities with a flash charge... (there it is again)
But i don't think it's reliable. But who knows...
------------------
for best catfood visit:
catfood.tsx.org
c0deblue
Frequent Poster
Posts: 229
From:
Registered: JAN 2001
posted 04-04-2001 11:37 PM
--------------------------------------------------------------------------------
Found the following reference, if this helps answer the question:
"Acetone Peroxide: Impact sensitivity - 4" with 500 gram weight. Initiation capability - 0.05 grams compressed at 250kg/cm2 initiated PETN."
The other non-primary method is to use an "Exploding Bridge Wire" or EBW. This requires an extremely high current pulse and is thus beyond the capabilities of normal electric detonating equipment.
Bitter
Frequent Poster
Posts: 290
From: 11 Downing Street, London, England
Registered: SEP 2000
posted 04-05-2001 10:05 AM
--------------------------------------------------------------------------------
The reason I started this tread was because I did not like using short-lived primaries like AP in my blasting caps.
I was thinking of something like mercury fulminate, but I was concerned with the sensitivity of the stuff causing an explosion during compression. I can compress it quite safely, but I don't want to waste any. Also, I am not sure if it is 'compatible' with main charge of PETN already in the detonator.
J
Moderator
Posts: 602
From: United Kingdom
Registered: SEP 2000
posted 04-05-2001 02:08 PM
--------------------------------------------------------------------------------
C0deblue, do you have any more info on the EBW (current required, minimum voltage, type of wire)? Could a large enough capacitor bank be constructed without the need for specialist equipment? I'm thinking along the lines of a large bank of surplus high capacitance electrolytic caps. Could this method be used to detonate other HE's?
The main problem I can see is a suitable switch for the huge current. I remember reading in alt.eng.explosives that 1000's of amps were required.
J
------------------
"If the aquarium water has to be drunk don't waste the fish. In fact they'll probably be the easiest to eat even if you don't need the water. The cat is next in the pot." - John 'Lofty' Wiseman
c0deblue
Frequent Poster
Posts: 229
From:
Registered: JAN 2001
posted 04-05-2001 09:40 PM
--------------------------------------------------------------------------------
It would probably be pretty simple to build an EBW system with nowhere near the difficulties you're envisioning. Thousands of peak amps might be needed for some exploding foil (slapper detonator) applications, but EBW requires substantially less.
As a general rule, commercial EBW detonators need about 200 kilowatts and 200 amperes for operation, with about 2 joules total energy used. However, there's no universal standard, and different EBW designs (even from the same manufacturer) may have completely different threshold burst current specifications.
Good info on various aspects of EBW systems (many references): http://www.risi-usa.com/0products/index.html
A typical EBW firing circuit charges a 1-1.5 uF capacitor to 3,000-4,000 volts and discharges it through the bridge-wire. Discharge may be automatic (i.e. spark gap breakdown occurs when the charge level reaches a predetermined flashover point) or it may be externally triggered using a pulse transformer. A 1 uF/5KV oil-filled capacitor ought to be tough enough to handle repeated fast discharges without mechanical failure.
Capacitors: http://www.highenergycorp.com/oil/hvdcratings.html
Spark Gaps and triggers: http://www.polytec-pi.fr/EGG/Eclateurs/Miniature%20Triggered%20Spark%20Gaps.htm
Burst current for the particular EBW detonator must be delivered in an extremely short period, typically 1 microsecond or less. This means that with long firing leads, special attention must be paid to overall circuit inductance and capacitance effects, either of which may degrade pulse risetime and result in failure of the bridge-wire to explode with sufficient force to cause detonation of the surrounding explosive. If the pulse is too slow the energy will not be sufficiently concentrated. This is analogous to the brisance/power tradeoff - the bridge-wire will still "explode", but will cause only deflagration of the explosive (not detonation).
The insulation value of the wire must be high enough to withstand a fast rising pulse of 3-4 KV, but in reality the effective voltage gradient will never be that great due to the shunting effect of the bridge-wire. A good quality PTFE-insulated twin-conductor wire should do the trick for distances up to 150 feet or so (twisted pair will exhibit the lowest inductance). Beyond that distance a low-loss coaxial line would be preferable.
The question of what to use for the bridge-wire remains. This could be the traditional nichrome, or even a fine bit of copper or steel wire. Some EBWs utilize carbon film as the exploding element. A carbon resistor of the right value might work, and of course a diode when subjected to a disastrous overvoltage makes a hell of a bang. For that matter you could try using a diode "bridge-wire" and plugging the line straight into the mains. With the right diode you won't even blow a fuse.
PS - BTW, did you receive my emails with the Tesla stuff?
[Edit: On reflection, a diode or carbon resistor would only work if the carbon or silicon (as the exploding element) could be brought into intimate contact with the PETN. This would not be the case with commonly available axial lead components, since the plastic casing would act as a barrier that would interfere with the detonation wave. Surface Mount components would be a better choice, since their active elements are covered only by a very thin membrane of plastic material. Shock wave propagation in commercial detonators has been found to be unaffected if the primary/base charge separator is sufficiently thin, and Surface Mount resistors or diodes would fulfill that requirement.]
[This message has been edited by c0deblue (edited April 06, 2001).]
Jumala
Frequent Poster
Posts: 200
From: Germany
Registered: OCT 2000
posted 04-05-2001 09:51 PM
--------------------------------------------------------------------------------
Hallo Bitter,
I thought about this problem also sometimes and I also donīt like AP in a detonator.
PETN can be set off by shock with a hammer.
When this is true than it should be possible to set it off by a mix of perchlorate and Al.
Iīve seen how much power is in firecrackers which uses this mix. It is more powerful than armstrongs mix but ways more stable.
I have no possibility to test it but I believe a cartridge filled with 50% PETN and 50% of this mix should work. (The mix has much more power than a hammer)
What do you think?
Bitter
Frequent Poster
Posts: 290
From: 11 Downing Street, London, England
Registered: SEP 2000
posted 04-06-2001 09:55 AM
--------------------------------------------------------------------------------
I'll give it a go eventually, Jumala. It sounds like a good idea. I tried a confined perchlorate/aluminium mix once and it went off with quite a bang. The heat off it was enough to ignite a small quantity of thermite (although not particularly well), so it must be pretty powerful. Thanks for your help, everyone.
Frequent Poster
Posts: 290
From: 11 Downing Street, London, England
Registered: SEP 2000
posted 04-04-2001 10:55 AM
--------------------------------------------------------------------------------
Can PETN be detonated without using any other primary explosive ? Will, say, a confined chlorate/sugar/aluminum mix be sufficient to set it off ? I know it's alot easier to detonate than RDX...
Anthony
Moderator
Posts: 2306
From: England
Registered: SEP 2000
posted 04-04-2001 05:18 PM
--------------------------------------------------------------------------------
The Blasters Training Manual claims there hasn't been a reported case of det cord (petn filled) being detonated accidentally (by shock or impact). For the military to use it, it must be pretty insensitive - what with all those bullets flying around...
(All IMHO)
wantsomfet
Frequent Poster
Posts: 236
From: EU
Registered: JAN 2001
posted 04-04-2001 05:23 PM
--------------------------------------------------------------------------------
What amount & density do you think of? Perhaps larger quantities with a flash charge... (there it is again)
But i don't think it's reliable. But who knows...
------------------
for best catfood visit:
catfood.tsx.org
c0deblue
Frequent Poster
Posts: 229
From:
Registered: JAN 2001
posted 04-04-2001 11:37 PM
--------------------------------------------------------------------------------
Found the following reference, if this helps answer the question:
"Acetone Peroxide: Impact sensitivity - 4" with 500 gram weight. Initiation capability - 0.05 grams compressed at 250kg/cm2 initiated PETN."
The other non-primary method is to use an "Exploding Bridge Wire" or EBW. This requires an extremely high current pulse and is thus beyond the capabilities of normal electric detonating equipment.
Bitter
Frequent Poster
Posts: 290
From: 11 Downing Street, London, England
Registered: SEP 2000
posted 04-05-2001 10:05 AM
--------------------------------------------------------------------------------
The reason I started this tread was because I did not like using short-lived primaries like AP in my blasting caps.
I was thinking of something like mercury fulminate, but I was concerned with the sensitivity of the stuff causing an explosion during compression. I can compress it quite safely, but I don't want to waste any. Also, I am not sure if it is 'compatible' with main charge of PETN already in the detonator.
J
Moderator
Posts: 602
From: United Kingdom
Registered: SEP 2000
posted 04-05-2001 02:08 PM
--------------------------------------------------------------------------------
C0deblue, do you have any more info on the EBW (current required, minimum voltage, type of wire)? Could a large enough capacitor bank be constructed without the need for specialist equipment? I'm thinking along the lines of a large bank of surplus high capacitance electrolytic caps. Could this method be used to detonate other HE's?
The main problem I can see is a suitable switch for the huge current. I remember reading in alt.eng.explosives that 1000's of amps were required.
J
------------------
"If the aquarium water has to be drunk don't waste the fish. In fact they'll probably be the easiest to eat even if you don't need the water. The cat is next in the pot." - John 'Lofty' Wiseman
c0deblue
Frequent Poster
Posts: 229
From:
Registered: JAN 2001
posted 04-05-2001 09:40 PM
--------------------------------------------------------------------------------
It would probably be pretty simple to build an EBW system with nowhere near the difficulties you're envisioning. Thousands of peak amps might be needed for some exploding foil (slapper detonator) applications, but EBW requires substantially less.
As a general rule, commercial EBW detonators need about 200 kilowatts and 200 amperes for operation, with about 2 joules total energy used. However, there's no universal standard, and different EBW designs (even from the same manufacturer) may have completely different threshold burst current specifications.
Good info on various aspects of EBW systems (many references): http://www.risi-usa.com/0products/index.html
A typical EBW firing circuit charges a 1-1.5 uF capacitor to 3,000-4,000 volts and discharges it through the bridge-wire. Discharge may be automatic (i.e. spark gap breakdown occurs when the charge level reaches a predetermined flashover point) or it may be externally triggered using a pulse transformer. A 1 uF/5KV oil-filled capacitor ought to be tough enough to handle repeated fast discharges without mechanical failure.
Capacitors: http://www.highenergycorp.com/oil/hvdcratings.html
Spark Gaps and triggers: http://www.polytec-pi.fr/EGG/Eclateurs/Miniature%20Triggered%20Spark%20Gaps.htm
Burst current for the particular EBW detonator must be delivered in an extremely short period, typically 1 microsecond or less. This means that with long firing leads, special attention must be paid to overall circuit inductance and capacitance effects, either of which may degrade pulse risetime and result in failure of the bridge-wire to explode with sufficient force to cause detonation of the surrounding explosive. If the pulse is too slow the energy will not be sufficiently concentrated. This is analogous to the brisance/power tradeoff - the bridge-wire will still "explode", but will cause only deflagration of the explosive (not detonation).
The insulation value of the wire must be high enough to withstand a fast rising pulse of 3-4 KV, but in reality the effective voltage gradient will never be that great due to the shunting effect of the bridge-wire. A good quality PTFE-insulated twin-conductor wire should do the trick for distances up to 150 feet or so (twisted pair will exhibit the lowest inductance). Beyond that distance a low-loss coaxial line would be preferable.
The question of what to use for the bridge-wire remains. This could be the traditional nichrome, or even a fine bit of copper or steel wire. Some EBWs utilize carbon film as the exploding element. A carbon resistor of the right value might work, and of course a diode when subjected to a disastrous overvoltage makes a hell of a bang. For that matter you could try using a diode "bridge-wire" and plugging the line straight into the mains. With the right diode you won't even blow a fuse.
PS - BTW, did you receive my emails with the Tesla stuff?
[Edit: On reflection, a diode or carbon resistor would only work if the carbon or silicon (as the exploding element) could be brought into intimate contact with the PETN. This would not be the case with commonly available axial lead components, since the plastic casing would act as a barrier that would interfere with the detonation wave. Surface Mount components would be a better choice, since their active elements are covered only by a very thin membrane of plastic material. Shock wave propagation in commercial detonators has been found to be unaffected if the primary/base charge separator is sufficiently thin, and Surface Mount resistors or diodes would fulfill that requirement.]
[This message has been edited by c0deblue (edited April 06, 2001).]
Jumala
Frequent Poster
Posts: 200
From: Germany
Registered: OCT 2000
posted 04-05-2001 09:51 PM
--------------------------------------------------------------------------------
Hallo Bitter,
I thought about this problem also sometimes and I also donīt like AP in a detonator.
PETN can be set off by shock with a hammer.
When this is true than it should be possible to set it off by a mix of perchlorate and Al.
Iīve seen how much power is in firecrackers which uses this mix. It is more powerful than armstrongs mix but ways more stable.
I have no possibility to test it but I believe a cartridge filled with 50% PETN and 50% of this mix should work. (The mix has much more power than a hammer)
What do you think?
Bitter
Frequent Poster
Posts: 290
From: 11 Downing Street, London, England
Registered: SEP 2000
posted 04-06-2001 09:55 AM
--------------------------------------------------------------------------------
I'll give it a go eventually, Jumala. It sounds like a good idea. I tried a confined perchlorate/aluminium mix once and it went off with quite a bang. The heat off it was enough to ignite a small quantity of thermite (although not particularly well), so it must be pretty powerful. Thanks for your help, everyone.