Imagine a metal canister capable of holding massive amounts of air or some other compressible substance. If it were filled with enormous amounts of said fluid and dropped from a plane, how destructive would it be?

I am aware of "lazy dog" weapons that were destructive just because of the weight (and this would be a very heavy canister), but I was thinking the force of the air rushing out of it would be powerful. I can think of three possibilities:

  • The canister would have to be so strong to resist the pressure that a drop from a plane wouldn't break it

  • The "explosion" would be loud, but do nothing but scatter dust and shrapnel

  • A deadly and powerful explosion would ensue as the pressurized air rushed out and created a deadly shockwave of energy

I have tried to research it on Google, but the only results I can find are deaths by exploding whipped cream canisters. And they say sugar won't kill you.

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    Someone with a physics background might know the exact definitions, but I don't think there's any meaningful difference between 'explosion' and 'high pressure canister being opened'. Both just cause a rapid and destructive expansion of stuff, except one may have more fire than the other. You should probably add some concrete numbers and info on exactly what this bomb is made of: what's in it, how much pressure it has, etc. – Giter Oct 3 at 15:13
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    @Giter The difference lies in the rate of gas expansion, much slower with a breached pressure vessel than a high explosive where the reaction exceeds the speed of sound. – Ash Oct 3 at 15:45
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    "Imagine a metal canister capable of holding massive amounts of air or some other compressible substance." Imagine a pressure cooker bomb. en.wikipedia.org/wiki/Pressure_cooker_bomb They're stunningly common. – RonJohn Oct 3 at 17:49
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    A canister that suddenly releases extremely high internal pressure would be pretty close to the definition of a bomb much less being like one. – John Oct 3 at 23:42
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    The OP is not asking about a pressure cooker bomb, That is a pressure cooker filled with conventional explosive as opposed to a compressed gas. en.wikipedia.org/wiki/Pressure_cooking – Paul Johnson Oct 4 at 8:03

10 Answers 10

up vote 7 down vote accepted

It definitely could act as a bomb. Many teenagers when I was growing up would make "dry ice bombs" by putting dry ice in tepid water in a 1 liter plastic bottle, quickly closing the lid & retreating to a safe distance to watch it explode from the pressure. They were about as powerful as an M-80* w/ < 1 liter of compressed volume & only the thin plastic of the beverage container to build up pressure.

With high performance materials & ultra high compression, you could achieve huge explosions. As the vessel will be under enormous tension & hit the ground w/ great force, it should be relatively easy to ensure failure is abrupt & catastrophic ('an explosion')

A lot will depend on what gas you are compressing & what material your pressure vessel is made of. If you're compressing regular air, the oxygen will be a stronger & stronger oxidizer the more you compress it (even if you do it slowly so the temp doesn't spike). I can't find the specifics on this effect, but I'll hazard a guess that by 3500 Bar/50K PSI** you would have reached the limits of stainless steel or aluminum corroding if not combusting, but it may be feasible w/ high performance ceramics or fluorine passivized steel or something to hold pressures there or higher.

The ultimate theoretical limit of a device like you suggest would probably be if you could somehow use metallic hydrogen. That is, fill your vessel w/ hydrogen, the lightest gas, compressed until it's literally solid metal. It may never be possible in practice, but if you could use metallic hydrogen your bombs would be at least tens or hundreds of times stronger than conventional bombs of similar size.

*An M-80 is a firecracker too strong to be legal anywhere I know of

**These numbers are a wild-ass guess, outside my domain of expertise. You've been warned!

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    Honestly, this answer is exactly what I'm looking for! – Redwolf Programs Oct 4 at 23:38
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    There's a mythbusters episode, where they tried to turn a gas bottle into a rocket. They failed more than once, because pressurized containers make excellent bombs. (@NSA: This is only theory) – Alexander von Wernherr Oct 5 at 8:53

In the world of Hazmat and fire fighting, there is a commonly-known acronym which is related to your question: B.L.E.V.E.: Boiling Liquid Expanding Vapour Explosion - although most commonly planned for with flammable vapours such as petroleum distillates, it can absolutely occur with non-flammable gases such as Nitrogen.

Wikipedia BLEVE entry

I worked for some time as a tech writer for a company which had a large number of gas storage and flowing systems for a range of gases used in their industrial processes: Oxygen, Nitrogen and Hydrogen; I was also a Hazmat F.R.O., and part of their in-house Disaster Response Team - and I can tell you we very carefully briefed the local fire fighters about our facility and the specifics of our gas system, its shutoffs and controls, kill-points, and potentials for BLEVE and other similar pressure risks.

I think that you don't need a super-high pressure canister - I think you need a canister with a mix of fluid and flammable vapour, and a heat source directly impinging on the canister's outer skin.

  • I thought that a BLEVE is dangerous not only because the pressurised container fails, but that the flammable gas is then ignited (fireball). I don't understand how you reconcile saying "it can absolutely occur with non-flammable gases such as Nitrogen" with "you need a canister with a mix of fluid and flammable vapour". – ChrisW Oct 3 at 21:21
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    No. Please actually read the linked Wikipedia article (or in fact any other resource on what a BLEVE is) - the issue that the pressure vessel's failure suddenly drops the pressure within the vessel (as gas escapes) which causes the remaining fluid to instantaneously boil and evaporate - making for a huge expansion of the gases' volume exactly as the pressure vessel is failing. Water can BLEVE. It is of course far worse if the vapour is flammable. Most damage / injuries from BLEVEs are caused by high-velocity shrapnel from the failing pressure vessel. – GerardFalla Oct 3 at 21:41
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    As to my closing suggestion: I'm responding to OP saying that versus their proposed use of a super-high pressure canister filled with an incompressible working fluid, I think that what they actually need for their desired effect (HE results without use of actual HE munitions) is a canister filled with a high volatility flammable medium which is fluid at STP and volatizes readily at medium temperature, and attached to said canister a heat source with heat directly impinging upon the pressure vessel exterior. What a firefighter or hazmateer would call a "bad day". – GerardFalla Oct 3 at 21:52
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    @ChrisW -- yeah. while you can get a BLEVE in a nonflammable medium (water, even), the most common (and hazardous) cases are in flammable gases (LPG and friends) or volatile liquids – Shalvenay Oct 3 at 23:41
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    To give an example, a water boiler explosion is a BLEVE. Which as Mythbusters have show can demolish a small building. So take a container of water, superheat it and drop from altitude. The landing will damage the tank and cause it to rupture, releasing the water which will explosively evaporate. – ratchet freak Oct 4 at 16:14

You can use the following rough approximation to estimate the amount of energy stored in a pressurized gas:

$E_\text{stored} = p \cdot V$

That is the amount of energy that you can release upon freeing up that gas.

So, let's say you want the same energy release of 1 kg of TNT, which would occupy about half a liter volume. That would account for $E = 4.18 \cdot 10^6\ \mathrm J = p \cdot V$.

With 10 cubic meters (10000 liters) stored at a pressure of 418000 kPa (about 4000 atm) you could release the same energy.

Using a "more practical" 0.1 cubic meter (100 liters) would require a pressure of about 400000 atm.

You see it's not the most efficient way of delivering damage.

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    Also TNT releases it's energy in a fraction of a second, a pressure vessel won't dump that quickly unless something really strange is going on, normally it will breach and the gas will rush out over a couple of seconds to a few minutes depending on the size of the hole. – Ash Oct 3 at 16:06
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    100 kPa is about 1 atmosphere. So 418000 kPa is about 4000 atm. For comparison, scuba tanks typically have about 200 atm. 10 cubic meters of gas stored at 4000 atm would be a volume about 2.5 liters. – user52458 Oct 3 at 16:51
  • @puppetsock, you are right. fixed – L.Dutch Oct 3 at 17:04
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    @Cadence: Wolfram Alpha says 1 kg of TNT takes 0.0006 cubic meters, or 0.6 liters, which seems a lot more reasonable. If it were 0.06 cubic meters, it'd be 1/60 the density of water. – user2357112 Oct 3 at 17:46
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    Do note however, that liquefied gasses such as LN2 are often used to soak up excess thermal energy from standard explosives like TNT and convert it to a more powerful shockwave. – Perkins Oct 4 at 0:01

Gas rushing out of a ruptured pressure vessel has no Brisance so the vessel doesn't tend to break up into many pieces but rather develop only a single breach from which all the gas escapes. This causes reactive motion as the force of the gas escaping pushes the breached vessel away, like blowing up a balloon and then letting it go and it shoots across the room, but with steel instead of rubber. It's dangerous, flying steel is never anything else, but it won't cause a shockwave because it will be a, relatively, slow release, nor would one expect much shrapnel.

  • Like a missile. This should be a more correct answer than the accepted one. – Edwin Chua Oct 5 at 5:48

I've never seen sugar do that

There are a few reports of non-flammable gases expanding (not exploding) in such situations and places that they can kill.

For example in late 70's in Poland storage of non-flammable helium had an explosion while filling typical container (the ones used to fill balloons) which created chain reaction that resulted in 5 deaths.

Remember that what the gas is doing is rising the pressure. If there is a space for that pressure to run out there will be no shockwave (or it will be very short in range). But if he place is small the pressure can be lethal. Like my nephew who punctured rather large helium balloon in home which resulted in destruction of all windows.

The main thing is that such bomb would be far less usable than real bomb. That can be made from a gas canister you attach to your grill. Because here you not only have expanding gas. You have expanding flammable gas. So pressure + flammable + taking out oxygen. And it's cheap and easy to use.

  • I want to add that the flammability of the gas increases the pressure even further, both from the heat and from the fact that the combustion products tend to be less dense than the fuel that made them. – Ryan_L Oct 3 at 16:26
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    Yours is one of two answers who both cite a statement ("I've never seen sugar do that") that doesn't (and never did) exist in the OP's question. Where did you see the quote? – JBH Oct 4 at 0:21
  • That must have been a huge helium balloon for it to have resulted in the destruction of all windows! – Michael Oct 4 at 1:33
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    @Michael It was the size of those "gender reveal" balloons. Flat was 52 sq metres with 8 people in and pretty warm (kid birthday). – SZCZERZO KŁY Oct 4 at 7:46
  • Do you have a source for the disaster in Poland? I did a Google search for poland helium storage explosion and the only relevant result was this very page. – Tanner Swett Oct 4 at 22:03

Possibly Not

Here at STAQXchange Pseudoscientifix, we spare no expense every day to answer your scientological queries. Here are Jen and Lisa, our two highly qualified, intelligent & inquisitive girl scienticians who have taken on the assignment of testing out your query. Jen is up on the mountain throwing a propane tank from the heights down onto Lisa, waiting in the sharp rocks below. Notice how nothing happens to the tank.

Smart Girls Play With Bombs!

  • RESULT: Not a bomb, sorry!

But our Scientological Review Committee thought that perhaps the initial experiment was invalid due to the fact that Jen's canister "bomb" bounced and rolled a lot on the way down, softening the blow. So, here we have Billy-Joe-Rufus-Dean, another one of our highly ejuckated and certifiable boy scienticians, who is going to drop the canister "bomb" from STAQXchange's beautiful downtown Miami corporate headquarters building. Don't mind the warning sirens --- today we're also testing several other astute queries from our admiring public and we feel it is our civic duty to warn pedestrians before we drop heavy objects onto the street below!

Look Out Belooooowwww!!

  • RESULT: Hmm. Still not a bomb, sorry!

Never deterred by two consecutive failures to obtain the right answer, STAQXchange's Review Board Committee decided to give your query one more good old college try! Again, sparing no expense we decided to send Boo, Sticky-G & Ling-a-Ding, our Crack(ed) Team of PhD candidates (Univ. of Cracker Jack) to the very ends of the Earth to perform a final test of your query by, yes, you guessed it! --- throwing a pressurised gas canister into an actual erupting volcano! They figured that would simulate the extreme conditions of being thrown out of an aeroplane. Plus the little pyros got to play with fire.

Hot Stuff Comin' Through!

  • RESULT: Drat. Still no explosion --- still no bomb, sorry!

REALITY CHECK

At best, if you drop the canister and it lands in just the right way that the valve & regulator are shorn away from the tank body, the tank can be turned into a slightly damaging missile:

Notice that the tank cum missile managed to punch a nice round 10 inch hole in a hollow block wall, plus cause some minor damage to a similar wall a short distance behind the first.

How It's Really Done!

A bomb? Not well. You have the problem of making the container go from sufficiently strong to contain all the pressure to insufficiently strong to contain any of the pressure in a very short period of time. If you just punch a hole in it, you won't get a bomb, just a rocket.

For example: https://www.youtube.com/watch?v=tyINNUaXa8Q

Now, this could still be pretty damaging, but if you want an explosion you need a way to increase the pressure enough to cause a symmetric, catastrophic failure of the container.

I suppose opening a valve to transfer a large amount of pressure from a tank that can easily hold it to a tank that definitely cannot would get the effect you're looking for. Or mechanisms similar to paintball/airsoft grenades, only on a large scale.

Or use liquefied gasses. A relatively small change in temperature there would be sufficient to drive a large change in pressure. Or, if they're in a "supercritical" state a relatively small puncture will cause all of the molecules to attempt to stabilize into a gas form, causing a massive pressure spike and possibly an explosion. (This is why steam boiler emergency relief valves have to be not only "big enough", but also not "too big" for the volume, temperature, and internal pressure of the boiler in question. A mistake in either direction can result in an overpressure event.)

  • Really this is the best answer. – Fattie Oct 4 at 16:15
  • What about a bleve? – Aethenosity Oct 5 at 0:00
  • @Aethenosity That would be what would happen if you put say liquid nitrogen in a sealed container. It would go from practically no pressure at -200 something to roughly 60,000 PSI as you approached room temperature. But the question was asking about a compressible fluid/gas. Without a phase change in there somewhere you're not going to get the rapid pressure spike you need to violently rupture the container. – Perkins Oct 5 at 0:42

On Mythbusters, they tested this idea in a mock up of the final scene of the movie Jaws (the heroes shoot a gas canister with a rifle, and it blows up, killing the shark and sparing them). While the canister did not "explode" the resulting release of gas was powerful enough that it turned the canister into a rocket, and the shark stand-in used to test for damage was sufficiently ripped to shreds to call the shark killed.

Per their policy of "test the conditions, duplicate the results", they were able to duplicate the exploding canister using... C4. What else? The final verdict was "Busted" as the myth was specifically testing the explosive capability of the canister when shot by a gun, not its use in lieu of Bat-Shark Repellent.

Note that this myth was retested and reconfirmed as busted, but I don't have the details on the changes to the experiment.

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    The Mythbusters did many variations of this idea, my personal favourite was disabling all the safety features on a hot water tank and heating it to @ 300F, whereupon the bottom bust and it took off like a rocket. The biggest problem with this question is any container strong enough to contain that much potential energy will not shatter in a symmetric pattern, but generally fail through one weak point (valve or seam), limiting the energy release and thus potential damage. – Thucydides Oct 4 at 4:02
  • @Thucydides - you beat me to it – A C Oct 4 at 5:43

Your question really needs to first answer,

Does the released gas need to be the direct killing/destructive agent?

Because if not, your opportunities are pretty staggering in regards to,

The "explosion" would be loud, but do nothing but scatter dust and shrapnel

Just imagine it going off in an empty parking-lot full of enemies versus a small grove of dead trees filled with enemies; huge destructive and shrapnel potential. Your canister bomb could be incredibly effective in circumstances that exploit the primary means of destruction from the effects of pressure-release, such as affecting the nearby environment and its objects, transforming solids and small objects normally not moving fast enough to cause damage when it becomes deadly shrapnel at high velocities.

If the gas itself needs to be the primary cause of death, then your constraints for your designs will be context-specific to where the bomb will be used, and what it needs to compromise with pressure-release, e.g., are we dealing with spacers in EV-suites or Space Marines in powered armor, etc., so then you'd need to answer that question instead.

This isn't taking into consideration compounded effects, such as the lethality of the gas itself when not pressurized, e.g. chemical warfare.

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    Welcome to Worldbuilding.SE! We're glad you could join us! When you have a moment, please click here to learn more about our culture and take our tour. This is an excellent first answer! Thanks! – JBH Oct 4 at 19:09

I've never seen sugar do that

Clouds of finely ground sugar, flour, and most other substances that can burn, can cause a fuel-air explosion. These have destroyed mills and bakeries.

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    This response does not answer the question. The OP doesn't even ask about sugar. – elemtilas Oct 3 at 20:12
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    Yours is one of two answers who both cite a statement ("I've never seen sugar do that") that doesn't (and never did) exist in the OP's question. Where did you see the quote? – JBH Oct 4 at 0:21
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    @JBH --- the OP said, half tongue in cheek: And they say sugar won't kill you. – elemtilas Oct 4 at 1:05

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