American fighter jets dropped a pair of 500-pound bombs on terrorist mastermind Abu Musab al-Zarqawi on Wednesday. Does a 500-pound bomb really weigh 500 pounds?
Both weapons are considered "500-pound" munitions because they're based on a standard 500-pound bomb known as the Mk 82. The body of an Mk 82 is augmented with a fuze, a guidance system, and other accessories like wings and tail fins; all of these add to its total weight.
But the Mk 82 itself packs only about 200 pounds of explosives. It gets the rest of its weight from a steel case, about half an inch thick, that helps to penetrate targets and provides material for fragmentation.
The "500-pound" designation doesn't give you much information about how powerful a given weapon might be. It's more useful for figuring out how many bombs will fit onto your aircraft. That's because different types of 500-pound bombs have different amounts of explosive inside—one might be designed for bunker-busting and another for fragmentation. (The Mk 82 is an example of "general purpose" ordnance.) You can get a better sense of a weapon's destructive potential by looking at its "explosive yield." That tells you how strong an explosion the bomb will make, in terms of equivalent pounds of TNT. In other words, a bomb with a yield of 500 pounds will blow up with the same intensity as 500 pounds of TNT.
The "500-pound bombs" that fell on al-Zarqawi each had about 200 pounds of explosives. But their explosive yield would be 200 pounds only if they were filled with TNT. In fact, the Mk 82 makes use of a more advanced, TNT-based compound that produces a bit more energy when it blows up. Two hundred pounds of the fancy stuff might yield the equivalent of, say, 240 pounds of TNT.
Explosive yields come in handy when you're talking about nuclear weapons. A nuke that weighs about 1,200 pounds—or twice as much as the GBU-12 that was used the other day—can have an explosive yield of 14 kilotons. That's the equivalent of 14,000 metric tons of TNT, or almost 31 million pounds.
Got a question about today's news? Ask the Explainer.
Explainer thanks John Norgren of Eglin Air Force Base and John Pike of GlobalSecurity.org.
TODAY IN SLATE
The Right Target
Why Obama’s airstrikes against ISIS may be more effective than people expect.
The One National Holiday Republicans Hope You Forget
It’s Legal for Obama to Bomb Syria Because He Says It Is
I Stand With Emma Watson on Women’s Rights
Even though I know I’m going to get flak for it.
Should You Recline Your Seat? Two Economists Weigh In.
It Is Very, Very Stupid to Compare Hope Solo to Ray Rice
Or, why it is very, very stupid to compare Hope Solo to Ray Rice.
- School District Wants to Censor American History Curriculum to Make It More Patriotic
- U.S. Federal Prison Population Drops for the First Time in Decades
- Conservative Star D’Souza Avoids Jail Time for Illegal Campaign Contributions
- Moderate Chinese Intellectual Sentenced to Life in Prison After Show Trial
In Defense of HR
Startups and small businesses shouldn’t skip over a human resources department.