Wallis Barnes, inventor of the famous bouncing bomb, turned his attention to more conventional gravity bombs, but of tremendous size. The results were the Tallboy and Grand Slam (above) penetrators, the Earthquake bombs of World War II.
Conventional air dropped ordnance, both bombs were distinguished by their size and potential destructive power. The Tallboy, was the first large bomb of the duo, weighing in at 12,000 lbs. Of that overall weight, over 5,000 lbs were explosive filler. And of its 21 foot length, ten feet were the hard steel bomb casing.
Dropped from 20,000 and impacting soft earth it could create a crater that would require 5,000 tons to fill. And when dropped on a concrete hardened target, the Tallboy could go through 15 feet of cement and rock. And while a driect hit would be destructive, need for pinpoint drops were softened by the tremendous explosive power of the bomb itself. Impacting near a target would transfer energy through the earth, searching for a void (ie bunker, etc) creating a cavern that would than collapse to devastating effect.
So valuable were the Tallboys, that unlike conventional bombs armed and unused in a raid, they were not dumped but kept for future use. Landing a bomber with a 12,000 lbs armed bomb was not a riskless procedure.
The Tallboy, meticulously made by British ordnance workers, saw vigorous use against Nazi targets throughout Europe. Tallboys were dropped on German prep-and-storage facilities for the Vengeance series of weapons. They were dropped in numbers on V-1, V-2 and even the V-3 cannon site.
In addition to German U-Boat pens, the Tallboys were used on the famous Nazi battleship Tirpitz. In the first raid, a Tallboy landed near the battleship knocking out its engines. A second raid resulted in no damage, but a third sortie two months after the first scored two direct Tallboy hits on the Tirpitz sinking the battleship.
Tallboys were also dropped with some success on the targets on and around Hitler's "Eagle Nest" home.
And then, there was the Grand Slam. Weighing in at 10 tons, it was the big brother to Tallboy and used to pummel U-Boat pens, aqueducts, railways and other targets.
Both deemed successes, the United State tested Grand Slam bombs after the war. And in the late 1990s and into this century, the USAF fielded ordnance designed as hardened target penetrators, continuing the legacy of Wallis Barnes' designs.