Sciencemadness Discussion Board

Underwater explosives

Blaster - 11-4-2005 at 09:52

I’ve been working on some underwater explosives lately and I thought I’d share my findings with the board.
I know there’s an aversion to practical applications of explosives by the moderators, but I don’t think this subject has been covered before and demonstrations are necessary here. I’ll move it to my Perchloric Ester site if anyone objects!

Firstly the fuse. I found all normal black powder fuses I tried went out underwater. I tried adding Mg metal etc to increase the ferocity of the burn without success. Eventually I found that the following mixture will burn. KClO3 4parts, powdered sulphur 1 part and powdered charcoal 1 part. Pretty straightforward stuff, but being a chlorate mixture just make sure you don’t grind the chlorate with the sulphur or carbon!

I then needed a waterproof case for the mixture so I used a plastic straw, sealed at one end.
Next I needed a detonator for underwater, so I put a gram or two of Lead Azide in the bottom of the straw first, then filled it up with the chlorate black powder.

Here is a picture of the straw – if you look carefully you will see the white PbN3 right at the bottom of the inside of the straw.



Next to the straw is the explosive – it needed to be unaffected by water and quite sensitive so I chose homemade Gelignite. I made some Nitroglycerin and put it in a camera film case. Then I dipped some Guncotton into the NG until a gel was formed.
Here’s a pic of the completed underwater bomb.



Firstly I tested the fuse/detonator on its own inside a plastic jar. Here’s a movie (610KB) – a broadband connection will probably be needed here!
(Its Xvid mpeg4 codec compressed if anyone has trouble)

Fuse Test

That seemed to work very well, so I now chose a large disused watertank for the explosive. It was a large steel rivetted tank about 5 feet across and 4 feet high, full of water of course. Here is the movie (980KB). I have edited out me igniting and dropping it into the water as this is going out on the Net!!!

Underwater Explosion

If you slow-mo it in whatever movie viewer you're using you may notice a reinforced concrete pillar just in front of the tank get shattered in the first few frames!

Here's a pic of the hole left behind and the shattered concrete post!



[Edited on 12-4-2005 by Blaster]

fatkangaroo - 11-4-2005 at 12:57

Very nice. I was wondering since your device was made from plastic did it sink? It looks like a film canister, how many grams did you fit into it? It does not look like a good seal where the fuse/cap enters the container. Did you glue it up? The fuse test was a good laugh. I was suprised at the amount of damage to the concrete post it does look pretty old and corroded though.

Blaster - 12-4-2005 at 00:26

It did sink easily, it was very heavy - NG is quite dense stuff. The SG is about 1.6 I think.
I filled the canister to the top, not sure how many grams but I guess about 100. (With the straw test I did tape a stone to it to make it sink).

Seal was not glued up - its not necessary. In fact, I have tried this experiment by simply molding the Gelignite around the end of the straw/detonator and throwing it into water. As you know NG is non-soluble and not affected by water. I didn't do that here as it has a tendancy to fall off and this was quite a lot of gelignite (by my homemade standards) to risk losing if it did fall off!

Madandcrazy - 22-6-2005 at 06:12

Nice ideas.

Why not the explosives filled in a tube and than the primary is ignited by carbide ;).
The water invading thrue a small culvert to the carbide wich ignited the explosive.

I guess about 100 grams ?

Lambda - 22-6-2005 at 08:25

Blaster, you used a normal 24 X 36 mm filmcanister. The internal canister diameter being 2.9 X 4.7 cm. You paked the charge about 3 mm off the rim, and compressed this would have likely have been at least 8 mm deeper. So this would leave you with a 2.9 X 3.9 cm volume space. Your volume will then be R X R X Pi X H = 1.45 X 1.45 X Pi X 3.9 = 25.76 cm square. Your explosive density being about 1.6 g/cm square X volume = 25.76 X 1.6 = 41.2 grams of explosive. You have pissed next to the toilet by a factor of ~2.5. If you make this kind of mistake in chemistry, and specially with explosives, you will get yourself killed oneday. It allso looks like you used less Lead azide than two grams.

If indeed you would have used two grams of Lead azide in a glass container without water, then these fragments would have flown several meters away, maybe hitting you. Doing this kind of stuff inside, is rather irresponsible to, with all that flamable material in the direct facinity. You, or somebody ells may allso cut themself on glass that is still laying around oneday.

Please be carefull, and do better planing infuture.

It was however, wise of you to test this fuse fist. If you just would have put a lose blackpowder fuse in a straw, then it would have burnt several meters per second.

You have made some nice photo's and filmfootage. ;)

Blaster - 25-6-2005 at 13:41

Lambda, just read this post after some time away. Bit patronising quite frankly.

Irresponsible? Maybe, but then playing with explosives on an amateur basis is by its very nature. I'm putting myself at risk alone and I enjoy it quite frankly!
This was pretty tame stuff compared to my work with Ethyl Perchlorate.

I've been doing such things for 20+ years, so I'm not some schoolboy amateur in case that's what you're thinking. I am in fact a fully trained graduate chemist and I have over 10 years experience as an industrial chemist.

I'm not in the habit of doing quantitative analysis when blasting for fun but even if I was 50 whole grams out (it was a pure guess btw) in a tank holding a vast quantity of water I doubt it would have made much difference when you consider I was standing 100 yards away at least. Maybe if I'd used 100kg then things would have been different!
Incidently, the fuse test was in a plastic container.



Madandcrazy - not a bad idea about the carbide but you would still have to ignite the acetylene generated with a fuse.

halogen - 27-6-2005 at 06:47

Well perhaps the acetylide could be mixed with an oxidiser. Thus when it is dropped underwater, H2C2 is produced which is than oxidised to produce sub-fluvial burning? Magnesium could be added to obtain arial combustion.

Lambda - 27-6-2005 at 07:54

Dear Blaster, I am very lucky to still be allive. I tickelt the tail of the Devil with a slege hammer........

So, please don't take it to personal. I had no intention of insulting you, and appologise if I have given you this impression.

Regards
/Lambda :)

V2A - 27-6-2005 at 11:37

Quote:
Originally posted by Blaster
Firstly the fuse. I found all normal black powder fuses I tried went out underwater. I tried adding Mg metal etc to increase the ferocity of the burn without success. Eventually I found that the following mixture will burn. KClO3 4parts, powdered sulphur 1 part and powdered charcoal 1 part. Pretty straightforward stuff, but being a chlorate mixture just make sure you don’t grind the chlorate with the sulphur or carbon!


one can use NaClO3/sugar mixture, too, which is safer than the one u made with chlorate and sulfur.

i put a 50:50 mixture in 6mm drinkstraws (about 15cm long).
these "fuses"burn very slow and from 5 tests none went out under water.

JrayJ - 26-2-2009 at 14:38

Or you could just use water proof fuse ;)

Polverone - 27-2-2009 at 08:29

The revival of this thread isn't as good as the original Broadway run.