Barnes Wallis and the Earthquake Bombs of WWII

World War II brought the craziest of the inventions that perhaps humanity could ever come up with, with all manner of odd aircraft, tanks, guns, and bombs. When it comes to creative, borderline weird, and downright ridiculous inventions, the British could be considered leaders. One of their leading scientist, engineer, and inventor was Sir Barnes Neville Wallis. He was best known for inventing the bouncing bomb named Upkeep used by the Royal Air Force during Operation Chastise when they destroyed the German dams of the Ruhr Valley. Interestingly, he also had this other invention that was unprecedented: the “Earthquake Bomb.”

Earth-Shaking Idea

During World War II, most bombs were designed to maximize the amount of explosives inside the shell, usually by making the shell thin so that it could be effectively used against unarmored and unfortified targets like railyards, houses, and factories. When used against hardened targets, however, like German bunkers with the reinforced concrete walls as thick as 5 meters, the explosion would not really cause enough damage. If the explosion was just beside it, the explosion would only bounce off the walls, cause a loud noise, and probably hurt the ears of the occupants. Through 15 feet of concrete, even a 2,000 lb bomb would sound like a muffled thump.

An effective way to destroy a fortified structure was by using a shockwave that would instead do most of the heavy lifting instead of depending on the heat and shrapnel. The thing with a shockwave is that it is transmitted poorly through the air, and the better way to utilize it is in contact through the ground, you know, like an earthquake which will shatter rock like glass.

When the realization dawned on Wallis in 1941, he immediately proposed the idea in the form of a 10-ton bomb that would be dropped just beside the target, burrow deep into the ground, before exploding and causing the seismic waves. These waves would target the foundations of the target infrastructure that would be hard, if not impossible, to repair. Usually, a target hit and damaged by an explosion could still be repaired, as only certain parts or areas of it would be damaged. Another possible effect of this was it could create a cavity like a sinkhole causing the collapse of the structure near it.

Tallboys

Wallis’ idea was not really considered until 1942, with the appearance of the Lancaster heavy bomber that could carry such a bomb. With that, he began with his 6-ton version instead of his original 1941 proposal of 10 tons. It was also 6.4 meters long, thus the name Tallboys.

Inside, these aircraft-sized bombs were filled with a mixture 50% more powerful than TNT  called Torpex. Because of the aluminum powder added, it had a longer explosive pulse that would bury the Tallboys deep. Apart from that, a strengthened, high-tensile steel shell also ensured that the explosives would survive its impact with the ground at extremely high speeds. The explosive was dropped from a Lancaster bomber at 18,000 feet to achieve the speed of 750 mph before reaching the ground. Multiple fuses ensured that it would be detonated 30 seconds and 30 minutes after impact. The explosion would create a hole of 24 meters deep and 30 meters wide.

Tallboys required extreme and pricey engineering, so the bomber crew was always instructed to take them back home if they weren’t used instead of just dropping them along the way. The crews weren’t very happy about having to land fully loaded with 6 tons of high explosives aboard. Crash it on the runway and the explosion would crater the air field and kill anyone within a quarter-mile of the explosion.

When Tallboys were dropped near a huge facility in France called the Blockhaus d’Éperlecques bunker, the closest one landed about 50 meters away. Still, it caused extensive damage to the nearly finished facility that the construction had to be halted, and the building was just abandoned.

Nearly 900 Tall Boys would be dropped during the war on things like sub pens, bunker complexes, and V-1 and V-2 rocket storage sites which were located inside mountains and hills

Ten Ton Tess

After the success of Tallboys, Wallis proceeded to create a larger version of it: a 10-ton Grand Slam that he affectionately referred to as “Ten Ton Tess.” This madder version was also carried by the Lancaster that would leap about 200 to 300 feet after dropping the bomb and being rid of its weight. These bombs were so huge that the Lancaster bombers that carried them had to be modified extensively, including new engines, removal of the bomb bay doors, beefed-up landing gear and tires, the removal of gun turrets and radar system.  Trying to lighten the 32 special bombers for these missions included stripping everything they could from the aircraft including things like fire axes and even the crew access ladder.

The more powerful design of the Grand Slam was due to its goal of concrete penetration more than the Tallboy. The shells were made of hardened chrome-molybdenum and had 5 tons of Torpex. With the strength of Ten Ton Tess, nothing that was ever built during World War II could have survived its earthquake. All in all, 41 Grand Slams were dropped before the war ended. Their first use was against the Bielefeld Viaduct. This railroad viaduct was considered a prime aerial target since the beginning of the war and millions of tons of bombs had been dropped on it without success.  Its two spans were more than 1,100 feet long and nearly 80 feet high and made of stone. It was hit by just one Grand Slam about 80 feet off target and the crater it left caused a large part of the center of both of the spans to collapse.  They would not be repaired until 1965 and 1983 respectively.