Tons as a measure of bomb yield?

[athelas]

One hears of bombs (usually nuclear, but sometimes conventional as well) having yields of x kilotons, or megatons for very large ones. What is the meaning of the unit "tons" here? Equivalent tons of TNT? Equivalent amount of kinetic energy of a mass dropped from orbit? Tons of trouble it causes the people it hits?

[Shagnasty]

It means the equivalent of a given amount of TNT detonating. The size of the bomb can also be expressed in joules.

http://hypertextbook.com/facts/2000/...adKaleem.shtml

[Rhubarb]

Your first guess is correct. Generally speaking, a one kiloton yield thermonuclear device has the same explosive power as one thousand tons of TNT. Big boom. Do not try this at home without adult supervision.

[msmith537]

Originally Posted by athelas

One hears of bombs (usually nuclear, but sometimes conventional as well)

When you hear conventional bombs measured in weight, it's usually as in "2000 lb bomb", "500 lb bomb". Litterally it's the weight of the (usually aerial) bomb.

A conventional bomb cannot denonate with the force of 1 kiloton because a 1000 ton weapon is not practical.

[Hail Ants]

A few months before the very first A-Bomb was tested they detonated a 100-ton pile of TNT near the Trinity site to calibrate the instruments for the nuclear blast.

[Chronos]

When you hear conventional bombs measured in weight, it's usually as in "2000 lb bomb", "500 lb bomb". Litterally it's the weight of the (usually aerial) bomb.

But then, conventional bombs are generally made out of something at least roughly comparable to TNT, so a 2000 pound bomb should be expected to have a yield of approximately 1 ton.

[UncleRojelio]

Originally Posted by Hail Ants

A few months before the very first A-Bomb was tested they detonated a 100-ton pile of TNT near the Trinity site to calibrate the instruments for the nuclear blast.

[slight hijack]Why would they use 108 tons for the 100 ton test?[/SH]

[chrisk]

According to wikipedia, they adopted a roughly average value for the energy in a 'ton' of explosive energy, since batches of TNT vary by about 10% either way.

[/fun probably-fact]

[UncleRojelio]

Originally Posted by chrisk

According to wikipedia, they adopted a roughly average value for the energy in a 'ton' of explosive energy, since batches of TNT vary by about 10% either way.

'nother words, "Close enough for government work"?

[bonzer]

Originally Posted by UncleRojelio

[slight hijack]Why would they use 108 tons for the 100 ton test?[/SH]

My reading of Kenneth Bainbridge's official report on the tests (a pdf) is that the stack was actually 100 tons, but it's the yield that was 108 tons. In other words, the particular variety of TNT they were using was slightly more powerful than the nominal stuff. See p58, where it's stated that it was "108 tons TNT equivalent neglecting any effects of wood boxes". Everywhere else the report merely describes the amount of explosive as 100 tons.

[SCSimmons]

Originally Posted by Rhubarb

Your first guess is correct. Generally speaking, a one kiloton yield thermonuclear device has the same explosive power as one thousand tons of TNT. Big boom. Do not try this at home without adult supervision.

Yes-number one rule in my household: the children do not get to play with the weapons-grade uranium unless Dad or Mom is there to supervise. Can't be too careful!

[Fear Itself]

Originally Posted by Hail Ants

A few months before the very first A-Bomb was tested they detonated a 100-ton pile of TNT near the Trinity site to calibrate the instruments for the nuclear blast.

On June 2, 2006, the Dept. of Defense will detonate the largest non-nuclear explosion ever:

One of the largest conventional explosives tests ever is going to be set off at the Nevada Test Site in June. Original reports saying it might trigger a mushroom cloud over Las Vegas sent a shock wave through the offices of some Nevada's congressional delegates.

A 700-ton explosive charge is set to be detonated at the Nevada Test Site on June 2. When asked to comment on the test, a senior defense aid was quoted in an Internet news article today saying, "It's the first time in Nevada that you'll see a mushroom-shaped cloud over Las Vegas since we stopped testing nuclear weapons."

Now that will blow up real good.

[Bryan Ekers]

Originally Posted by UncleRojelio

[slight hijack]Why would they use 108 tons for the 100 ton test?[/SH]

It's those damn imperial units.

[matt]

Originally Posted by bonzer

My reading of Kenneth Bainbridge's official report on the tests (a pdf) is that the stack was actually 100 tons, but it's the yield that was 108 tons. In other words, the particular variety of TNT they were using was slightly more powerful than the nominal stuff. See p58, where it's stated that it was "108 tons TNT equivalent neglecting any effects of wood boxes". Everywhere else the report merely describes the amount of explosive as 100 tons.

That makes sense. The nominal energy value of TNT, as used for the SI energy units kiloton and megaton , is 1000 calories per gram, which is both a nice round number and conveniently falls within the reported range of values measured for TNT.

The variation in measured TNT energy is presumably due to contamination by other organics in the toluene, and/or some partially nitrated toluene content. Pure TNT actually yields 1080 calories per gram, which is why a pile of high-purity TNT that weighs 100 tons would release as much energy as 108 tonnes of lower purity, 1000-calories/gram TNT. (TNT was first synthesized in 1863 and pure TNT in 1880, so I'm guessing any 20th Century TNT was the good stuff!)

[Antonius Block]

Originally Posted by Fear Itself

On June 2, 2006, the Dept. of Defense will detonate the largest non-nuclear explosion ever

I don't think that's going to surpass the 1985 Minor Scale test at White Sands NM, of which the ammonium nitrate/fuel oil mix was intended to "simulate the effect of a four kiloton nuclear device".

There have been some fairly large man-made non-nuclear explosions. Many of those were not intentional [usually the accidental ignition of munitions, such as at Halifax (1917), Bombay (1944), Port Chicago (1944), RAF Fauld in England (1944), and Texas City (1947)], but others were strategic actions, such as the Battle of Messines (1917) in which several hundred tons of explosives -- buried in tunnels by the British -- killed 10,000 German soldiers in the trenches above.

[Antonius Block]

Originally Posted by Chronos

But then, conventional bombs are generally made out of something at least roughly comparable to TNT, so a 2000 pound bomb should be expected to have a yield of approximately 1 ton.

The casing enclosing the bomb may also add a fair amount to the weight: for instance, in the most powerful conventional bomb ever used in warfare (Barnes Wallis' 10-ton Grand Slam, itself an update of his 5-ton Tallboy), the Torpex explosive was less than 50% of their total weight -- although since Torpex was 50% more powerful per unit weight than TNT, the Grand Slam would have had a yield of about 7 tons of TNT (i.e. 0.007kT).

[LSLGuy]

Former USAF pilot & bomb dropper here.

Non-nuclear aerial bombs are traditionally (and currently) described by their complete weight. A "2000 lb bomb" (http://www.fas.org/man/dod-101/sys/dumb/mk84.htm) weighs ~2000 lbs.

For very round numbers the weight is about 1/2 explosives and 1/2 casing, fins, fuzes, etc. By volume it's more like 90/10, but explosive is much less dense than metal.

This naming convention extends to typical cluster bombs, FAEs, etc. Usually those are refered to by a desgnator, ie CBU-52, but if someone says a CBU-52 weighs 750 lbs, they mean total weight on a scale, not the weight of the contained explosives.

Special purpose "earth penetrator" bombs have been built in the last 15 years that change that ratio a bunch. The BLU-113 (http://www.fas.org/man/dod-101/sys/smart/gbu-28.htm) is a 5000# class weapon that is barely 13% explosive by weight.

[Chronos]

Hm, I hadn't realized that as half or more of a bomb's weight could be casing, etc. I did realize that not all explosives have exactly the same efficiency as TNT Still, in my line of work, a factor of 2 still qualifies as "approximately".