Dissolved Corn Starch As Explosive Confinement?

[evilgecko]

I have been experimenting with different ways of exploding pipe bombs (approx 70g BP in sealed metal pipe) lately and are wondering if dissolved cornstarch would have the interesting effect of confining the pipe bomb?

Say immerse the pipe bomb in the middle of a 4L paint can filled with a saturated solution of cornstarch in water. I'm sure everyone knows how corn starch solution transforms into a malleble solid under pressure. Related to the experiment, would the cornstarch solidfy as the pipe bomb explodes from BP overpressure and reinforce the explosion by extra confinement?

Also, after the pressure as ripped the can to shreds and propelled the cornstarch through the air, would the cornstarch penetrate close objects like a solid or would it just splash against them like a liquid?

[DONMAN]

Wow, that is an interesting concept.... I dont think anyone could say for sure, why don't you test it out for us. Put the bomb in the paint can with the cornstarch. Then set up 4 pieces of plywood 1cm thick around the bomb about 4 ft away and let it rip. Then observe if any of the starch penetrated the plywood.

[evilgecko]

I discovered that I'll need to buy some more corn starch (aka corn flour in NZ). I dissolved all I had, but it wasn't enough to fill the can. Since corn starch can go off if left in solution I added a small amount of bleach (sodium hypochlorite) to the solution hoping to sav for when I buy some more. To my dissapointment the solution lost much of its soldifying effect! I'm trying to figure out if a chemical reaction took place (unlikely since their was only a very small amount of bleach added), or the change was because the extra ions changed the structure.

I'll be able to get alot more cornstarch in the next few days and test it.

[nbk2000]

I remember someone long ago tested an idea similiar to this one, using pipes.

He plugged both ends of a pipe with cornstarch putty and ignited the filler (BP, I think), and the pipe shattered.

So, yes, cornstarch putty will solidify sufficiently under shock to allow BP to rupture a pipe, but that's INSIDE the pipe, not outside.

If it was outside, I'd expect the starch to solidify and greatly reduce the speed of the pipe fragments, before blowing apart into a gooey mess.

Only a test can tell for sure. :)

From my own test using Silly Putty (http://roguesci.org/theforum/showthread.php?t=5293), I know that it'll 'shatter' like a solid, but the pieces are too soft to penetrate a plastic soda bottle at contact range.

[hereno]

The previous topic on cornstarch tamping: http://www.roguesci.org/theforum/showthread.php?t=1726

[Alexires]

I have thought about this idea before and I am I two differing beliefs.

When a pipe bomb "detonates" all that is happening is that the pipe cracks in one place and releases the pressure. If this was surrounded in cornstarch/water I'm fairly sure you would have chunks of cornstarch flying around. Whether these would be effective in hurting someone depends. See, it will never be the same as having nails/bb's/or some kind of metal, but maybe as a stun round....

As the shock wave travels through the cornstarch/water media it stress fractures the cornstarch. The more brisant the "explosive" then the greater the stress, thus the smaller the pieces thrown off. The smaller the pieces, the greater the air drag thus less range.

Either you will have some kind of cornstarch goo thrower or a kind of stun contraption that throws out very painful bits of goop...

[evilgecko]

I tested it today. Dissolved 600g of corn starch into as little water possible and placed a small 50g BP pipe bomb in the middle of it. It sounded muffled and large strands of goop could be seen flying through the air.

But it also did make a few nice holes in the boxes surrounding the tin. Take in mind it was only 50g of BP at work here.


This is the video (sound and picture out of sync).
http://www.youtube.com/watch?v=loS7GG4yYng

This is the damage it did to the box which was about half a meter away. Notcie the very small pinhole punchmarks and the big huge gaping holes.

http://i5.photobucket.com/albums/y171/evilgecko_nz/DSCF0988.jpg

http://i5.photobucket.com/albums/y171/evilgecko_nz/DSCF0986.jpg

[Khalnath]

I'm curious to see whether there's a difference in the effectiveness of the corn starch as a tamper depending on whether you use a low explosive like BP or a high explosive. It seems to me that since the corn starch solution gets "harder" the more shock you apply, its effectiveness would increase with increasing brisance.

I'm afraid I don't really see the point in this if you're going to use a pipe bomb... (then again, I'm a clueless newbie) but on the other hand, I can definitely see applications if you're using a cast charge (of something not water soluble of course), or something wrapped in a light waterproof covering like wax paper.

I'd also be interested to see if corn starch would make a difference in an Alford Strip (http://www.roguesci.org/theforum/showthread.php?t=6273). If so, sounds like a cheap and easy way to improve effectiveness.

I hate living in the city. I want to test this stuff myself. :(

[mizzu]

Corn starch shaped charge kit for horizontal use.
1) 12" X 12" cardboard box
2) 6" Metal Funnel
3) 5 lbs cornstarch
4) 2 qts water
5) 12" roll of aluminum foil
6) explosive & detonator of choice
7) Tennis ball sized piece of clay or wax

Unpack contents near objective. Line box with tin foil. Insert detonator & fuse, wires etc. upturned funnel. Close small end with wax, Pack explosive into large end of funnel. turn box on it's side & insert large end of funnel to flushfit to bottom, seal around mating edge of funnel & box with wax, place box over objective, sprinkle 2lbs of cornstarch into box, add water & mix, add more water & remaining cornstarch in equal amounts until mixture has consistency of heavy slurry. Back off detonate & enjoy. Funnel reinforced by cornstarch will focus blast in tight circle. Nice thing about this package is you carry it in & have nothing to carry out except your goal.

[KrIsPy]

I'm curious to see whether there's a difference in the effectiveness of the corn starch as a tamper depending on whether you use a low explosive like BP or a high explosive. It seems to me that since the corn starch solution gets "harder" the more shock you apply, its effectiveness would increase with increasing brisance.
:(

I Recently tested a corn starch end cap with APAN. It was the end of a pen casing with one end sealed normally and the other with a corn starch end cap.

I didn't get a full det, probably because of the small size (critical diameter issues for not powdered enough AN), but the end cap of corn starch was effective.

On the other hand, HE gasses expand at supersonic speeds, and therefore, the pen casing probably would burst before it reached the end where the corn starch was serving as an end cap. After all, HE 's don't need cnfinement because of this.

I'll upload the video soon. You can't see much but it may help.

- One last question: (Kind of OT): I understand you dont NEED confinement for HE 's, but from personal testing with lower VoD and briscance explosives like APAN, I have usually found that confinement in metal pipe tends to increase the destructive power against soft targets (like mud). Is it true that confinement helps? I researched this and red some patents and other article, but they were either too broad or didn't simply said HE don't need confinement.

[nbk2000]

UTFSE would find relevant threads to post your OT question in. Please do so in the future.

[evilgecko]

A problem with a shaped charge with cornstarch reinforcment is that you'd need huge amounts of powdered cornstarch. I found this out when I was dissolving corn starch before. 600g of cornstarch in water at sloppy slurry state was able to fit it a cat-food tin. Can't remeber the exact volume of the cat-food tin but it was small.

[KrIsPy]

UTFSE would find relevant threads to post your OT question in. Please do so in the future.
My bad NBK. I searched and I found a quote from an experienced member :D
"Confinement of any charge improves efficiency and reduces the weight of explosive needed to perform the same work." -NBK I assume this is more for LE's than HE's because LE's don't detonate, but I'll keep confining my smaller charges, because I always see power increases.

Anyway, I uploaded a video from a little while back of APAN in a pen casing with a corn starch end cap. I think the casing may have shattered before the APAN near the end cap detonated, but it seemed to work... It was an incomplete detonation though.
Go HERE (http://rapidshare.com/files/28284641/ANAP_pen_casing_cornstarch.mpg.html) to see it, if you want.

[nbk2000]

LE's benefit the most from confinement, but even HE's get a boost, unless you're going for pure blast effect, in which case confinement is counterproductive by using energy from the blast to break the casing.

Confinement matters most when you're trying to get the explosive to do directional work, such as EFP or SC, since the case prevents the gases from the explosion from venting into the atmosphere before it has a chance to work upon the SC/EFP cone/platter.

There is a point of diminshing returns, where more confinement doesn't increase effectiveness, and that is determined by experimentation.

[KrIsPy]

Wow. Thank you. That was explained extremely well.

I figured it had to do with expanding gases for HE's and I have found that metal confinement for weaker high explosives (if you consider them HE's) like APAN, AP or ANFO are especially benefited in terms of destructive power, partially, I'm sure, due to the huge amounts of gases released in all three of these explosives.

To try to get this back on topic (sorry I led it astray), if confinement benefits HE's, and considering the fact that pipes are very convenient for confining charges, but end caps are a pain in the ass to get, do you think that corn starch/water end caps would be a cheap and effective solution?

LE explosives have been tested in this use, and I attempted to test a weak HE, but without great results. I think this really has potential. I'll try it again as soon as possible (maybe with PA or ETN or something more brisant.