Sciencemadness Discussion Board - Using H2O as an "explosive" ?

Using H2O as an "explosive" ?

VladimirLem - 19-5-2013 at 09:33

Hi guys

i'm very intrested in torpedos and similar stuff (cause they're awsome

) and then i read that 1 kg water (1 liter) will make over 1600 liters of gasvolume - compared this with an explosive, like, lets say RDX will make "only"

around 900l volume.

so, would it work, if someone build a charge with the shape of a grid out of explosive and water around that grid, so that the extreme high themeratures of the detonation will heat the water up to the steam-phase? (lets say 2.0-2.5kg explosive for 1 liter water)

if yes, then will the steam stay long enough as gas without cooling down to the water-aggregate phase

technical datas:
energy to heat water to steam: 2257 kJ
energy of blackpowder: 2780 kJ
energy of most explosives 3000-6000 kJ

if all that would work, it would be awsome to make 2 chages of 3kg explosive - but one with containing around 1 liter water extra, and the blast/wave/whatever will be hugher when (both) detonated unterwater

question: if this would work, why dont use seamines that? i doubt it works cause of some fucking chemical/physical process i dont know about, but i must be sure...come on guys, tell me if im right or wrong

and dont worry about the fishes out there, i know a cool, fishless pond

franklyn - 19-5-2013 at 10:03

There are better things to volatilize. The latent heat of water is among
the highest of any common fluid. It is not just the gas (steam) volume
that matters but the thermodynamic conversion of heat to mechanical
force according to the gas law PV=nrt. Water serves best in it's liquid
state as a tamp or applying it's incompressibility to transmit force. As
an oxidizer for aluminum the energy is 1760 kcal /kg . The gas product
is hydrogen which has the lowest latent heat of any substance and
expands accordingly.

.

Ral123 - 19-5-2013 at 10:49

Hexogen has density of 1.8g/cm2. Water has density of 1g/cm2. Tell me how one volume of explosive/water matrix with density of 1.3 will give better performance then one volume of Hexogen at 1.8 with much higher energy? However if you have two equal volumes and equal weights of explosive, and add some water to one of them, while maintaining the same volume, some performance may be gained.

Fantasma4500 - 19-5-2013 at 10:56

Quote: Originally posted by Ral123

Hexogen has density of 1.8g/cm2. Water has density of 1g/cm2. Tell me how one volume of explosive/water matrix with density of 1.3 will give better performance then one volume of Hexogen at 1.8 with much higher energy? However if you have two equal volumes and equal weights of explosive, and add some water to one of them, while maintaining the same volume, some performance may be gained.

im pretty sure he meant as in per kg, as 1 litre of water is 1 kg of... 'gravitational force' aka weight

potentially it could work to have a ammonal or similar with tiny pouches of water in between packed airtight etc.

1 kg AN (1 kg not 1L) equals very very close to 1000 litres of gas which is among the highest gas outputs of what i remember

i think there needs to be very thin pieces of water if you can call it that, in order for this to be effective by any means..
in vietnam war they used daisy cutters, basically AN/Al with as much as 5% water in it, they used it to make clear zones without vegatation etc. so perhaps it could work this way, but you would need a big nice booster for that but it would in very large scale be worth the effort for sure

Trotsky - 19-5-2013 at 11:47

What about the ammonium nitrate water gels? Do they not gain extra power over dry AN?

caterpillar - 19-5-2013 at 12:02

Nuclear explosion under water evaporates large amount of it and is definitely much more efficient as same explosion in air for ship's destruction. But if you are talking about usual explosive, there are some of them which uses water as oxidizer (alumotol, for example- Al + TNT). They have very negative oxygen balance and content Al to reduce water. Water cannot increase total energy of explosion, but it can increase volume of gases (for example, C + H2O -> CO + H2)

VladimirLem - 19-5-2013 at 12:57

Quote: Originally posted by franklyn

There are better things to volatilize. The latent heat of water is among
the highest of any common fluid. It is not just the gas (steam) volume
that matters but the thermodynamic conversion of heat to mechanical
force according to the gas law PV=nrt. Water serves best in it's liquid
state as a tamp or applying it's incompressibility to transmit force. As
an oxidizer for aluminum the energy is 1760 kcal /kg . The gas product
is hydrogen which has the lowest latent heat of any substance and
expands accordingly.

.

interesting

so, what would be a good choise? stuff like ethanol/acetone/methanol?

acetone have a boiling point of 56 C and a high molecular mass of 58 (sould bring more gas than the others with low value, right)
density is just 0.8g/ml :/

@Ral123:
the size and overall-density of the charge is secondary. no doubt, that 1kg cast-RDX will beat the shit out of some home made amateur-water containing stuff, i'm just interested, if its possible to exchange explosive material with fuckin water and getting the "same" performace

Quote: Originally posted by caterpillar

Water cannot increase total energy of explosion, but it can increase volume of gases (for example, C + H2O -> CO + H2)

thats what i was asking, sure the power of the explosion wouldnt be increased, but at unterwater-devices the release of gasvolume is very important, and so i started this thread

[Edited on 19-5-2013 by VladimirLem]

Ral123 - 19-5-2013 at 13:06

Quote: Originally posted by caterpillar

Nuclear explosion under water evaporates large amount of it and is definitely much more efficient as same explosion in air for ship's destruction. But if you are talking about usual explosive, there are some of them which uses water as oxidizer (alumotol, for example- Al + TNT). They have very negative oxygen balance and content Al to reduce water. Water cannot increase total energy of explosion, but it can increase volume of gases (for example, C + H2O -> CO + H2)

First the TNT detonates. Then the Al finds itself surrounded by carbon oxides, hydrogen oxides, it doesn't care will it take it's oxygen from the water or from the TNT. The energy output and the final products are the same.

@VladimirLem
I made few tests, they are on youtube.
Pressed AP explodes with a bit more brisanse.
AP, wetted with AN solution explodes with a bit more gases given off it seems.

VladimirLem - 21-5-2013 at 02:56

Quote: Originally posted by Ral123

nice to know - i allways wondered why Torpex and other Underwater-Compositions are containing so much AL (and fucking the OB up)...i only read, that it will make a stronger blast, but that the AL reacts with the water/steam at the Detonation was unknown...

are there other, better avaible substitutes for AL ?

and, does anyone know which liquids could be better than water, that "franklyn" (2nd post in this thread) said...
im not sure if flamable liquides are a good choise^^

papaya - 21-5-2013 at 03:17

Quote: Originally posted by VladimirLem

i doubt it works cause of some fucking chemical/physical process i dont know about, but i must be sure...come on guys, tell me if im right or wrong

Perhaps that law is the conservation of energy. Another thing is that gasoline contains more energy than any explosive practically used, so 'strength' is more associated to power (energy/time), introducing water adds lot's of inertia thus 'time' is bigger, so I don't understand why this will be more powerful.
Btw, it would be very interesting to see a very fast thermite (like CuO/Al) set off underwater

Fantasma4500 - 21-5-2013 at 05:10

Quote: Originally posted by papaya

Quote: Originally posted by VladimirLem

i doubt it works cause of some fucking chemical/physical process i dont know about, but i must be sure...come on guys, tell me if im right or wrong

i could plausibly try CuO + MgAl sensitized with Ferrocerium, it would plausibly not show much results tho as it would be a very small amount (yes.. inside...)

im just abit unsure of what container and how large it should be for a 0.03g charge or so..
wires
steel wool
NC
CuO thermite
duct tape
should work

papaya - 21-5-2013 at 05:36

Isn't 0.03g too little ? Instead I would take some 30g and maybe some 3L of water (numbers out of the air

). Of course glass must be excloded !
Anyways, if you decide to try in any quantity photos or even a 2h long movie is welcomed!

[Edited on 21-5-2013 by papaya]

Pyro - 21-5-2013 at 06:32

torpedoes work on conc. H2O2. water is one of the hardest things on earth to heat up (4186J/KgxK) so that wouldn't be as economical. Also, the water on the outside of a ship funnels most of the energy from the explosion into the ship, making a big hole.
Also I think one would have a hard time heating water up fast enough to instantly vaporize it.

caterpillar - 21-5-2013 at 14:36

Quote: Originally posted by Pyro

torpedoes work on conc. H2O2. water is one of the hardest things on earth to heat up (4186J/KgxK) so that wouldn't be as economical. Also, the water on the outside of a ship funnels most of the energy from the explosion into the ship, making a big hole.
Also I think one would have a hard time heating water up fast enough to instantly vaporize it.

There are different sorts of torpedoes. Some of them has accumulators, some use H2O2 + fuel like kerosene, and some have fuel composition, which reacts with water (reactive torpedoes). As I remember, their fuel contents large amount of of Al + ammonium perchlorate + some binder. But Al in torpex or alumotol reacts with water, when charge explodes. It is quite clear- otherwise there would be no reason in using explosives with very negative oxygen balance like alumotol.

APO - 21-5-2013 at 15:23

I think Diethyl Ether would work much better as it is more volatile and the resulting cloud of vapor may also detonate, like a true fuel-air explosive.

phlogiston - 22-5-2013 at 00:53

If you can use the heat released by the explosive to vaporise a liquid you can get some gas. However, water appears to be a poor choice as it takes a huge amount of heat to transform cold, liquid water into steam, and you are effectively cooling the hot expanding gasses from the explosion, which may be countereffective.

What would be a good choice of liquid?

The releveant properties here are the heat capacity (energy required to raise the temperature of a substance) and the enthalpy of vaporization (the energy required to transform a liquid into a gas).

deltaHtotal = C*(Tbp-Tstart) + deltaHVap

where deltaHtotal = total energy required to heat the substance from (Tstart) to its boiling point (Tbp) and vaporise it. C=heat capacity of the liquid.
You should look for a substance with the lowest deltaHtotal you can find.

example (assuming Tstart=22 deg C / 295.15 K)

water:
deltaH = 75.28 * (100-22) + 40680 = 46551.84 J/mol

acetone (source http://en.wikipedia.org/wiki/Acetone_(data_page)):
deltaH = 125.5 J/mol * (56.6-22) + 31300 J/mol = 35642.3 J/mol

So, you can see that you can vaporise about 30% more moles of acetone with a given amount of heat. Now go and calculate for various subtances to find the best one.

However, the above does not take into account that you also get more gas volume if you use the heat release to simply heat the gasses released by the explosive itself. That may well turn out to be more effective. (Effectively, you would be cooling those hot exapnding gasses with a cold liquid. The liquid vaporises, but the gas cools and contracts. Which process has the largest effect?)

[Edited on 22-5-2013 by phlogiston]

DubaiAmateurRocketry - 22-5-2013 at 04:35

how can you turn water into gas fast enough to make an explosive ?

Dornier 335A - 23-5-2013 at 00:26

I made some quick calculations for PETN/H2O, PETN/H2O2 and RDX/H2O2 to compare gas volume (at room temperature) to the detonation temperature.
I didn't include density in the diagrams but it drops with increasing H2O or H2O2 content.

Temperature drops very quickly.

Reaches maximum temperature and minimum volume at stoichiometric ratios.

Same thing happens here, but 30% H2O2 gives same temperature and slightly higher gas volume than 0%. The density is lower though so it's most likely not a performance improvement.

[Edited on 23-5-2013 by Dornier 335A]

AndersHoveland - 27-5-2013 at 02:10

Water heater explosions, rare as they are, are surprisingly powerful. do an internet search, amazing how much destruction, and how far they can be blasted away.

Hennig Brand - 27-5-2013 at 17:55

It looks like those graphs aren't sized properly, it has messed up this thread I think.

Water absorbs energy and explosives produce energy (convert energy). When a charge has water in it that is mass and volume that is not occupied by explosive (the energy producer), which is not advantageous. Initiating secondary explosives requires very rapid heating of the explosive to high temperatures. Blasting caps generate high heat and pressure and does PV work on their surroundings when initiated in a main charge. Water heats to its boiling point temperature (which varies depending on pressure) and then a huge amount of energy is needed to vaporize it (phase change) and forms steam before any further increase in temperature takes place. Water in explosives not only absorbs/steals energy but also makes overall rapid heating of the charge more difficult. I think this is one of the big reasons why water makes explosive charges more insensitive to initiation.

The only advantage I can see is that for a given amount of energy liquid water can increase more in volume when it is converted to gas than the increase realized when the same amount of energy is added to any of the common gaseous explosive products (Unless I messed up the calculation somehow). There are advantages to using small amounts of water in slurries and emulsions but increasing energy or explosive power is not normally considered one of them I think.

[Edited on 28-5-2013 by Hennig Brand]

phlogiston - 11-6-2013 at 01:19

Interestingly, it turns out small amounts of water catalyse the explosive decomposition of some explosives:

http://www.sciencedaily.com/releases/2009/03/090320150721.ht...

However, the amount released by the decomposition of the H and O containing explosives itself is probably enough already.

[Edited on 11-6-2013 by phlogiston]

SM2 - 11-6-2013 at 05:31

Aaah, entropy, my dear Watson! ,Look at some of this elegant propulsion, militarized!

http://en.wikipedia.org/wiki/Mark_50_torpedo

Dany - 16-4-2014 at 15:55

Surrounding a chemical explosive with a liquid will not generate stronger blast. The idea that the detonation of high explosive can heat and vaporize liquid in the vicinity is wrong. The reason is that when an explosive detonate, the shock wave that is produced will interact with the surrounded liquid for a very short duration. The liquid which is on the interface (charge/liquid) will evaporate, but this is a very small quantity. The rest of the liquid mass will begin to move outward and eventually will begin to break and be dispersed away from the charge. So any liquid will serve as a confinement for the explosive charge nothing more. However, if the liquid is flammable their is a chance under certain circumstances that the dispersed liquid fuel will ignite in air generating a deflagration or a detonation which also depend on many factors (e.g., geometry of the explosive/flammable liquid charge, the power of the initiation, turbulence...). There is another method for generating strong blast wave from rapid vaporization of water. It's is called a HYDROVOLCANIC EXPLOSION

Quoted from [1]

"A hydrovolcanic explosion is generated by the interaction of hot magma with ground water. It is called Surtseyan after the 1963 explosive eruption off Iceland. The water flashes to steam and expands explosively. Liquid water becoming water gas at constant volume generates a pressure of 30,000 atmospheres"

The explosion of KRAKATOA volcano is a famous example of generation of Hydrovolcanic explosion, also from [1]:

"Krakatoa exploded August 27, 1883 obliterating 5 square miles of land and leaving a crater 3.5 miles across and 200-300 meters deep. Thirty three feet high tsunami waves hit Anjer and Merak demolishing the towns and killing over 10,000 people....The air shock generated by the hydrovolcanic explosion propagated around the world and coupled to the ocean resulting in the explosion being recorded on tide gauges around the world....The Krakatoa event released 150-200 megatons"

of course the author in [1] was comparing KRAKATOA to a nuclear explosion, so the KRAKATOA hydrovolcanic explosion generate a shock wave equivalent to a shock wave from the detonation of 150-200 megaton nuclear bomb.

Reference:

[1] Charles L. MADER, NUMERICAL MODEL FOR THE KRAKATOA HYDROVOLCANIC EXPLOSION AND TSUNAMI, Science of Tsunami Hazards, Vol. 24, No. 3, page 174 (2006)

Dany.

[Edited on 17-4-2014 by Dany]

Davin - 18-4-2014 at 21:56

Years ago, Axt posted on peroxide watergels using H2O2, Mg, and a binder. There is a section in the Encyclopedia of Explosives and Related Items about using a mixture of water and Mg as an explosive as well.