# Conventional Bomb - upper size limit?

A few days ago I read a UK newspaper report claiming that American commanders are seriously suggesting using small nuclear weapons to kill Bin Laden - should his location ever be determined.

I don’t know weather to laugh or cry, but that is not my questions. The report set me thinking: well what is the upper limit of the size of a conventional bomb? Would it be possible to load an aircraft the size of a large passenger jet with a huge bomb and fly it to the detonation point by remote control? Such a weapon could perhaps be as devestating as a small nuclear weapon. Just how big a bang is possible, is there a law of diminishing returns as conventional bombs get bigger.

Perhaps you remember 9-11? Although the jets were not loaded with conventional explosive, the effect was not dissimilar.

In theory, there may be a physical limit to how large a bomb could be, but we would probably be talking volumes so large that assembling the sheer quantity of explosive would be as much of a problem as setting off the whole shebang <so to speak>

Nuclear weapons are just more efficient, in terms of yield per pound of bomb, than non-nuclear explosives.

Much of the weight, if not the majority, of a conventional bomb is in the casing. I first thought that making a larger bomb would result in a heavier case with the warhead making up a smaller percentage of the total weight. But, comparing some American bombs at fas.org, I found that’s not the case. The Mk 82 500 lb. bomb is 38% explosive, the Mk 83 1000 lb. bomb is 39% explosive, and the Mk 84 2000 lb. bomb is 48% explosive. And the BLU-82 ‘daisy cutter’ bomb, which weighs 15,000 lbs, has 12,000 of explosives (80%). So it actually looks like the weight of the case is not going to be a limiting factor, though it may be necessary to use different bomb designs and different explosives.

Currently, the USAF is looking into the 30,000lb “MOP”:
http://209.157.64.200/focus/f-news/1274490/posts

http://www.tallahassee.com/mld/democrat/2004/11/10/news/local/10132620.htm?template=contentModules/printstory.jsp

There really isn’t a limit on the size of a conventional bomb, assuming you have some way of delivering it. In past wars, miners have dug tunnels under enemy positions and deposited huge quantities of explosives, to be detonated when the time was right.

Even with nuclear weapons, you are usually better off using multiple small-yield weapons rather than one Tsar Bomba. Five properly targeted 200-kiloton weapons will cause more damage than a single 1-megaton weapon. Increased yield brings diminishing returns.

I don’t know where you read the story, but I’m guessing that the bomb in question was a Robust Nuclear Earth Penetrator which is basically super bunker buster. It’s designed for deep penetration (useful if OBL was in a cave somewhere). Co-incidentally, the program to develop these was scrapped two days ago.

The largest conventional bomb today is the “daisy-cutter” BLU-82B which weighs 15,000lb. A bigger bomb, the Massive Ordnance Air Blast Bomb, or MOAB,GBU43/B (21,700lb) is being developed. The biggest bomb ever used was the 22,000lb Grand Slam. The biggest bomb ever built was the T-12 which weighed in at a hefty 44,000lbs.

As to an upper theoretcal limit, I don’t know.

The theoretical upper limit of a conventional, thermobaric, or even nuclear, weapon is determined only by the available means of delivery. Basically, how much weight/volume can you transport all at once[sup]*[/sup]? That’s your limit. That means, of course, that the theoretical upper limit is changing all the time. I’d guess that a supertanker loaded with the right chemicals would be your upper limit, these days…

[sup]*[/sup]I don’t consider large piles of explosives built up over a period of days to be a ‘bomb’ - That excludes sapper-built mines, EOD disposal explosions, and nuclear simulation explosions using massive stacks of TNT crates.

I don’t know… Wouldn’t the burn rate of the conventional bomb’s explosive material also set an upper limit? If I had a bomb 500 ft across, and tried to detonate it, I’d imagine that it would explode while a lot of the explosive was still unburned. You’d get a bigger fireball, but no more overpressure than with a smaller bomb.

I suppose you could improve that greatly with strategic placement of detonators through the material, but there must be SOME limits.

That is the sort of problem I had in mind, that it may be very difficult to get a huge bomb to detonate efficiently. Perhaps the problem is actually rather similar to that of nuclear detonation - it is very difficult to contain the main explosion for sufficient time for it to go off properly.

BTW, my thought of delivering a bomb by filling a aircraft with explosives was simply a way getting the largest possible bomb to its target - no mucking about with release mechanisms etc. Any allusion to the events of September 11th were quite subconscious. However, on reflection, using such a weapon to kill Bin Laden would have a certain poetic justice.

I suppose there might be some upper limit to shock-front propagation vs. burn rate, but that can be overcome by multiple centers of ignition all set to the same fuse. I’d note that there have been nuclear blast simulations done with stacks of TNT larger than moderate-sized office buildings - Certainly larger than you’d ever fit in any aircraft, and they didn’t suffer from any problems with ignition. So, seeing that several thousand tons of conventional explosives have been sucessfully detonated all at once, the real upper limit is still your delivery mechanism.

THIS was a coventional explosion.

A ship/bomb is quite possible.

G*****mn Internet Explorer ate my first post.

As for loading an aircraft full of explosives and using it as a remote-controlled Kamikaze, even that’s actually been done, in practice—in “Project Aphrodite,” B-17 and B-24 bombers were stripped-down and crammed full of explosives, and were launched with aircrews onboard who were to bail out over friendly territory, at which point the aircraft would be flown by radio commands into German targets. (A V-1 launch site, for one.)

In practice, though, it didn’t work—a couple of the planes exploded with the crews still on board (including one Lt. Joseph Kennedy, Jr.), and the rest either crashed or were shot down.

Nowadays, of course, the remote control system could be made to work a lot better—an you might be able to, say, load a modified AN-225 with a couple of hundred tons of explosives, and fly it into a target. But, again, it’d just be more efficient to simply drop a few hundred conventional bombs on a target.

The British commandos used a ship bomb in their Operation Chariot.

There are generally considered to be three types of explosives:
[ul][li]Low Explosives - Black powder or gun powder, fireworks[/li][li]High Explosives - Nitroglycerine, TNT, Dynamite, Gun cotton (modern ammunition is a high explosive)[/li][li]Nuclear Explosives - Fission and/or Fusion bombs[/li][/ul]
They are defined by how they react.

Low explosives like black powder essentially just burn quickly. If you contain the expanding, burning gasses you can get some kind of explosion. Black powder requires external oxygen to burn.

High explosives react on a much lower molecular level. Nitro is chemically unstable. Kinetic energy (i.e. shaking) will initiate a powerful chemical chain reaction (chemical, in that in only involves the electrons). Because the chemical reaction is much faster than simple burning high explosives are much, MUCH more powerful pound for pound than low explosives.

Nuclear explosives go beyond chemical reactions and involve the nucleus itself. Consequently it is many orders of magnitude faster and more powerful than high explosives.

Basically, if the explosive reaction is faster than the pressure wave it generates than there is no limit to the size of the bomb. This is true for nuclear and high explosives, but not for low ones. Black powder burns slowly enough that at some point making it bigger isn’t going to help. The shock wave will eventually overtake the burn rate and simply scatter unburnt material.

Just as a matter of morbid curiosity, which was the bigger explosion: Halifax or Texas City?

The Halifax explosion wins hands down. In Texas City there were two seperate explosions. The two ships had approximately 2300 and 1000 tons of ammonium nitrate on board.
The Mont-Blanc had 226 tons of TNT - and this wasn’t much more than the primer for the 1000+ tons of picric acid.

TNT, picric acid and guncotton are a lot better at exploding that ammonium nitrate.

It’s not neccesarily the size, it’s the yield. For example the USAF uses a fuel air bomb which basically sprays jet fuel out of nozzles from a parachute when it’s a few hundred feet off the ground, then it ignites the fumes just before impact. I’m told this saturation explosion has a rediculous yield… but the biggest and baddest is the MOAB or BLU-82… (replacing the fuel air bomb)

a quote:

The force of a MOAB explosion is sufficient to knock over tanks and kill any people within several hundred meters of the detonation.

http://www.strategypage.com/gallery/?target=moab.htm

it has the ability to clear a 3-mile-long path. Dropped from huge transport aircraft, “Big Blue” releases a cloud of inflammable ammonium nitrate, aluminum dust, and polystyrene slurry which is then ignited by a detonator. The result is a firestorm that incinerates an area the size of five football fields, consumes oxygen, and creates a shock-wave and vacuum pressure that destroys the internal organs of anyone within range.

Come get some!

D.

This is the largest conventional explosion recorded to date.

Given that it involved 3.5kTons of bombs it can be directly compared to Nagasaki and Hiroshima in terms of explosive power, even if the result was diminshed by it occuring largely underground…

http://www.hanbury-village.co.uk/hanbury_history/fauld_disaster.htm

http://www.healeyhero.info/rescue/individual/fauld.htm

http://www.carolyn.topmum.net/tutbury/fauld/fauldcrater.htm