The U.S. Air Force has developed another version of the 500 pound bomb, in an effort to make the bomb less destructive. In other words, they want a bomb that can be used in urban areas, to destroy a single structure, or just part of a larger one, without injuring nearby civilians and the structures they are in. The new FLM (Focused Lethality Munition) bomb will use a composite (carbon fiber) casing and replace some of the normal 127.2 kg (280 pounds) of explosives with 93 kg of explosives surrounded by high density filler (fine tungsten powder). A regular 500 pound bomb has a blast radius (injury from blast pressure out to 13 meters, with dangerous fragments lethal out to 40 meters). The FAM would cut these distances by at least half. Meanwhile, the filler makes the bomb deadlier within the smaller blast radius. FAM, of course, is GPS or laser guided.
Three years ago, the U.S. Navy began using the LCDB (Low Collateral Damage Bomb) in Iraq. This is basically a 500 pound JDAM (GPS guided smart bomb) with 89 percent of the explosives removed, and replaced with non-explosive material (so the bombs flight characteristics remain the same.) The remaining 13.6 kg (30 pounds) of explosives give the bomb a much smaller bang, and thus less chance of nearby civilians getting hurt. Thus the LCDB has a bang that is closer to that of a 155mm artillery shell. What's interesting about that is the U.S. Army is currently using GPS guided Excalibur 155mm "smart shells" in Iraq. But Excalibur costs twice as much as an LCDB. So does the new air force SBD (250 pound Small Diameter Bomb).
The concept of the FAM and LCDB is not new. During the 1990s, the U.S. Air Force replaced all the 189 kg (416 pounds) of explosives (with concrete) in thousand pound laser guided bombs used against Iraqi anti-aircraft guns and missiles. This was because Saddam ordered his anti-aircraft weapons placed inside densely packed residential areas, in the hope that any American or British aircraft responding to fire from his anti-aircraft weapons, would also kill lots of civilians. That would make for a great photo op, as Saddam was trying to turn himself into a victim of American and British aggression. Dead civilians helped a lot. Concrete smart bombs took out the anti-aircraft weapons, but rarely hurt any nearby civilians. The LCDB is used against targets in buildings, or out in the open, who need at least a little bang, and bomb fragments, to take out the bad guys.