The BLU-97 has become the most well known and the most notorious of submunitions. This may be because it has been deployed more than others by US forces in recent years. It may be because their fuze system can be so sensitive to movement that accidents with unexploded examples are hard to avoid. Generally air dispersed from CBUs, the BLU-97 has caused deminer fatalities after Gulf War 1, Kosovo, Afghanistan and Iraq following Gulf War 2.
Dropped at the same time as bright yellow food packages in remote areas of Afghanistan, it was a public relations disaster for those keen to present the invading allied forces as "humanitarian", with many anecdotal reports of civilian casualties. With demining groups reporting failure rates of more than 30% in Afghanistan (more than 60 for each cluster bomb), the reports of civilian injury seem credible.
When unarmed, the BLU-97 looks like an elongated yellow beer-can with a serviette attached to one end. The cloth drogue may be many colours and is not a full parachute, merely a drogue to orientate the munition as it falls.
A shows an unarmed BLU-97, where the casing has not expanded in length.
B shows an armed BLU-97. The two fuzes are inside the part that has pulled out.
C shows fragmentation recovered from a crater after a BLU-97 detonated during clearance.
D shows BLU-97s littering the ground in Iraq after being dropped from a height that was too low for them to arm as designed. Their damaged state means that they are now unpredictable and so must be considered highly dangerous.
The BLU-97 contains:
High Explosive charge: 290g of TNT/RDX
Anti-armour shaped charge liner
Pre-scored fragmentation jacket
Zirconium sponge incendiary
An impact fuze system designed to detonate on impact and a secondary "all-ways" acting fuze intended to ensure detonation if the impact system fails. It is the latter (a ball-bearing in a chamber with sloping sides) that makes the unexploded munition so sensitive to movement.
The picture below shows a rooftop in Iraq illustrating that buildings will be targeted in conflict. Iraqi troops were stationed there and may have had vehicles that presented a "legitmate" target, but the submunitions entered the fabric of the building
and many did not detonate, causing a persistent problem when civilians later occupied the building.