It’s a repeat, but it has been a while so it’s probably new to some of you!
The GBU-39 Small Diameter Bomb is a 250lb class GPS/INS guided weapon with wings to extend its range. It has multiple fuzing options allowing it to attack both hardened targets via penetration, and soft targets via instantaneous or airburst fuzing. Depending on release altitude and speed, it can have a range of up to 40km.
Being a relatively small weapon, fighters can carry more SDBs than conventional guided bombs. A special carriage rack allows four SDBs to be mounted on one weapons pylon.
I’ve read a couple places where, despite its great accuracy, the SDB isn’t a particularly favored Close Air Support weapon. The reason is that gliding range. It takes a while for the bomb to fall to earth. A JDAM or LGB gets there a bit quicker.
But if you’re trying to suppress or defeat an integrated enemy air defense network, then the SDB is just what you want. You would use your Electronic Attack aircraft to jam and spoof enemy air defense radars, AGM-88 HARM missiles to knock them off the air or damage their antennae’s, and then stand off and destroy the launchers and control facilities with SDBs.