Stardate 20030910.1310

(On Screen): Hamas says that Israel has crossed a "red line", and will only have itself to blame when Hamas starts to respond in kind.

Hamas on Wednesday threatened to widen its bombing campaign and target homes and high-rises in Israel, in retaliation for an air strike that flattened the house of a Hamas leader and killed his eldest son and a bodyguard.

"Targeting homes is violating all red lines," the Hamas military wing, Izzedine al Qassam, said in a leaflet distributed in Gaza City. "So the Zionist enemy from today shoulders the responsibility for the targeting of houses and Zionist towers everywhere in occupied Palestine."

"In the past, we avoided targeting housing projects and buildings, but the enemy has started this game, and they are going to face the consequences of that," the leaflet said.

The idea that Hamas had somehow been practicing restraint in selection of targets is laughable. The reason Hamas hasn't been targeting homes is that they're lousy targets for the kind of attacks Hamas has primarily been making.

Besides which, they have been targeting homes all along.

The kind of bombing campaign they are carrying out is distinctly low-resource. They cannot deliver many bombs, and the ones they do deliver are not very powerful because they must be carried by a single person without detection. That limits the size, weight and shape of the weapon, and they've settled on the "explosive belt" as the best compromise. This is a ring made up of a couple of kilos of plastic explosive around the midriff of the bomber, with a layer of metal fragments (e.g. ball bearings, nails) on top. When the explosive goes off, shrapnel spreads out horizontally in all directions. The entire thing probably doesn't weigh 10 kilos and can be comfortably worn under loose clothing (which is common there). It doesn't cause the bomber to move differently (by weight or physical obstruction) and doesn't create any unseemly lumps under the clothing. It can be reliably detonated electrically, using a simple switch.

In terms of maximizing destructive ability within the essential constraints of stealth, it seems optimal, especially if one doesn't care about the fate of the operator. But as military weapons go, it isn't really very impressive, except for the sophistication of the delivery system. It's a "smart weapon" but the warhead is tiny. The weapon's lethality range upon detonation is pretty small, and the shrapnel is easily stopped by any kind of significant physical barrier. The only way such a bomb can be effective is if it is used near (or in the middle of) concentrations of people in a single space.

When people are in residential areas, they're spread out and surrounded by walls which the shrapnel will penetrate poorly if at all. A bomb which might cause 50-100 casualties in a crowded city street would be lucky to cause 5 when detonated in a typical residential area.

Of course, their veiled threat to attack high-rise residential buildings causes us to envision those buildings collapsing, and if that happened it would indeed be a major disaster. But it isn't all that easy to bring a building down. The kinds of bombs that Hamas gives to its hapless delivery systems won't do it.

There are people who are in the business of imploding old buildings using explosives. But when they bring down any large modern building (all of which have skeletons made out of steel I-beams) they have to carefully place hundreds or even thousands of charges, and carefully control the time sequence of detonation with time-calibrated fuses. And much of what they use are shaped charges, specifically mounted in pairs on opposite sides of critical I-beams so as to cut them in half. It usually takes weeks to analyze the structure and place the charges in order to bring about the spectacular implosions we've all seen on film, and even with careful analysis and precise placement and use of shaped charges in critical cases, most of those end up involving hundreds of kilos of explosives.

Civil engineers overdesign such structures, usually by a factor of between three and five, precisely to prevent catastrophe if some of the structure is lost. No civil engineer wants his building to collapse by accident. That's why such buildings are damned hard to bring down deliberately.

The first attempt to bomb the World Trade Center involved a truck full of explosives, a couple of tons worth. It was parked next to one wall in the underground parking structure, next to some of the load bearing columns on that side of the building. And though it blew out three floors of the parking garage, it didn't significantly weaken the tower's structure. There was never any risk of collapse because of the damage.

The McVeigh attack against the Federal Building in Oklahoma City involved a couple of tons of explosives as well. It removed the front facade of the building, but it didn't actually bring the building down.

One of the problems such truck bombs have is that they're extremely inefficient. The concussion expands in all directions and most of it is wasted. And by the nature of a truck bomb, it's all in one place and not strategically located. Blast damage doesn't scale well as the amount of explosive involved increases, and one big blast does a lot less damage than a lot of small blasts involving the same amount of explosives, especially if they're placed exa