How do you destroy a bunker made of concrete, buried 50 feet underground, especially when it’s
never been done before? That was a challenge for the US Air Force during Operation Desert Storm,
as Iraqis intelligence and command personnel were stationed inside concrete bunkers,
so deep underground, that the US and the rest of the coalition had no weapon to penetrate them.
But in an unbelievable feat of ingenuity, engineering and cooperation,
the US military designed, manufactured and successfully deployed a weapon,
in less than 4 weeks, which left Saddam Hussein with no option
but to surrender. And that weapon looked something like this, but it’s Not What You Think!
Saddam Hussein invaded Kuwait in August of 1990, with the purpose of annexing Kuwait,
acquiring their large oil reserves, and also to avoid paying back the money that
Kuwait had loaned to Iraq which had funded Saddam’s war against Iran in the 1980s.
As economic sanctions proved ineffective,
the United States led a coalition of 35 countries against Iraq,
which launched multiple air campaigns with the focus of hitting Iraq’s infrastructures. But soon,
the quantity and quality of Iraqi bunkers became a problem. According to some intelligence reports,
there were up to 40 bunkers near Baghdad, where several infantry divisions, the Iraqi Republican
Guards, and critical command and control facilities were housed. These concrete bunkers
were buried 30 to 50 feet below the surface, making them immune to direct hits from BLU-109
hardened penetration bombs, which were designed to penetrate only 4-6 feet of reinforced concrete.
A team consisting of US Air Force engineers and Lockheed Missiles and Space Company, which
had developed the BLU-109, immediately started working on a solution. To destroy the bunkers,
a new weapon was needed, and many options were considered; from a Dense Penetrator version of
the BLU-109, to an Unmanned Hypersonic Vehicle. The problem was that the development of these
new weapons would at least take months, and they needed something right away. So the US Air Force
engineers at Eglin Air Force Base proposed a heavyweight bomb that could be dropped from
a B-52, from such high altitudes that would have sufficient kinetic energy to penetrate deep into a
highly hardened target. The biggest challenge, of course, was producing the casing for the bomb. It
had to be able to penetrate through deep layers of soil and concrete without being crushed.
Someone had the idea that the Army 8-inch Howitzer barrels might just have the right
material properties to do the job. So the Eglin Air Force engineers requested that the Army
ship some of those barrels to Watervliet Arsenal. Watervliet Arsenal was renowned for their
expertise and precision in machining gun barrels, and they were soon gonna attempt turning the
Howitzer barrels into the body of the bombs. But the bomb specifications were not even yet
finalized and Eglin had to provide a go-/no-go briefing to the top brass in about one week.
It was decided that the delivery of the bomb should be done using an F-111 fighter, which meant
the 6,500 lb bomb had to be downsized to 4,700 lb. In the days to come, the Eglin Air Force engineers
worked with Lockheed … and also Rockwell, who were the maintainers of the offensive avionic suite
for the F-111. In parallel, the explosive pellets were being produced, wind tunnel time was booked
at the LTV Dallas location, and a batch of BLU-109 nosecones was on route to Watervliet Arsenal.
During the go/no-go decision on Wednesday, February 13th,
1991, Eglin air base committed to delivering two test rounds
and two operational rounds in just two weeks, and they got the go ahead. By the end of that week,
Watervliet had received the Howitzer barrels, nosecones, and some specifications from Lockheed.
At Watervliet, the machinists were working seven days a week, in multiple shifts, around the clock
to produce the penetrator's body. External hoops and rails were cut off from the barrel, shortened
to the penetrator’s rough length, and its chrome plating was stripped off. The machining of the
bomb had to proceed even though its design was not yet finalized. Spec changes were literally phoned
in, while the machining was in progress. A 30-hour precision boring operation was in progress,
while at the same time, Lockheed engineers worked to determine the final bore dimensions to ensure
it would fit the nose cone. The gun's rifling, its only remaining evidence of the weapon's former
military role, was machined away. In total, it’s estimated that 15 engineering design changes were
made during the manufacturing process, something that was only possible through total team effort.
As the transformation from cannon to penetrator progressed, the nose cone was secured onto the
body using a heat shrink operation, then preheated using special torches and welded into place in a
12-hour welding operation. Multiple wing attachment configurations were machined
on the munition body. As finishing operations were completed, the team prepared for assembly.
On the morning of Saturday, February 16th, the first penetrator was loaded onto the US
Air Force’s Air National Guard C-130 cargo plane. The paint on the bomb was still wet.
The second bomb followed a few hours later. The work on rounds
three and four began immediately at Watervliet.
Once the bomb casings arrived at Eglin Air Force base, it had to be loaded with explosives. The
13-ft casing was larger than anything previously loaded at Eglin, so it could not fit inside the
existing facilities. The loading had to be done outside, but not having a structure tall enough to
hold the casing upright, they had to dig a hole in the ground to put the nose of the bomb in.
One round was filled with concrete for a sled test, the second round was filled with
explosives in a 37-hour process. 630 lb of molten explosives were poured in using buckets and packed
by wooden rods, because the kettles were not big enough to melt all the explosives at once.
The assembled penetrator was outfitted with a laser-guided head, attached to the front of the
body, and stabilizing fins attached to the rear. The first GBU-28 was ready, and it was showtime.
On Feb 24th, 1991, the super penetrator was mounted on an F-111
and an inert test drop was initiated in the desert sands of Nevada.
The weapon hit the desert floor at supersonic speed and buried itself over 100 ft deep. It
was so deep that it was decided not to dig it up, as the expense of doing so could not be justified.
Two days later a rocket sled test was conducted at Holloman air force base in New Mexico. The
bomb was fired against a 22-foot thick stack of steel reinforced concrete slabs.
The penetrator was found over half a mile away, after having punched
through the barrier. It was obvious to everyone that the GBU-28 could do the job.
Satisfied with the results, rounds 3 and 4 were prepped at Watervliet and packed with
explosives at Eglin air force base. They were then immediately flown away to Saudi Arabia
in preparation for the drops. On February 27th, 1991, two air force F-111 fighters dropped their
laser-guided penetrators on a command and control bunker suspected of housing top Iraqi military
officials. The first aircraft missed the target. The second one, however, was a hit and if you
look closely, in a few seconds you will see smoke pouring out of the bunker’s air vents.
This suggested that the bomb had found its way deep into the bunker, which was later
verified using bomb assessment photos, showing a large hole in the top of the targeted bunker.
With only one test drop, the GBU-28 holds the current record for the minimal number of drops to
operational deployment. Most US Air Force bombs undergo about 30 drops before being deployed.
It has been argued that the hasty Iraqi ceasefire one day after the bunker was hit, may have had
something to do with Saddam Hussein learning that their last refuge had been defeated. The deep
bunkers were no longer safe. Although in the days prior, Iraqi soldiers were already surrendering or
fleeing, and the day before the bomb was dropped, Iraq had announced it’s complete withdraw from
Kuwait. But the GBU-28 bunker buster may very well have been the straw that broke the camel’s back.