March 5,2008:
The U.S. Air Force is spending $1.2 billion on development and production
of its SDB (small diameter bomb). A thousand of the SDBs have been produced,
and another 23,000 are on the way over the next seven years. In addition, 2,000
special racks for all U.S. Air Force bombers, are in production. The SDB
entered mass production two years ago, and over a hundred have been used in the
last year.
The SDB is
basically a second generation JDAM smart (GPS guided) bomb design. The basic
JDAM arrived in 2001, but came in only two sizes; half ton and one ton. This
was too much blast for urban fighting. The need for less firepower compelled
the air force to quickly modify its GPS guidance kit to fit on a 500 pound
bomb. But that's still 280 pounds of explosives. The troops wanted precision,
and less bang. In response, the air force (actually, the navy) developed a 500
pound bomb with all but 30 pounds of the explosives removed. Then came a completely new smart bomb design, the 250 pound SDB (small diameter bomb). This
weapon has a shape that's more like that of a missile than a bomb (70 inches
long, 190 millimeters in diameter), with the guidance system built in. The
smaller blast from the SDB is still pretty substantial (51 pounds of
explosives). This soon led to a SDB
variant, with the Focused Lethality
Munition (FLM) warhead, which reduces the number of metal fragments created
when the bomb explodes, and increases the blast effect. This is meant to reduce
casualties to nearby civilians, but it's still a bigger bang than the
low-explosive 500 pound JDAM. Moreover, the low-explosive JDAM costs about half
as much as the SDB. The one advantage of the SDB is that you can carry more of
them, as they are much more compact than 500 pound bombs. Still, increased
competition from GPS guided rockets and artillery shells has reduced the need
for any kind of JDAM. So while the air force has more, and better, bombs, it is
called on less to use them.