The "Tall Boy" and "Grand Slam" Bombs
"Tall Boy"
Type Deep Penetration Bomb
Length 6,35 meter (21 feet)
Diameter 0,95 meter (38 inches)
Weight 5.443 kg (12.000 lb)
Warhead 2.358 kg (5.200 lb) Torpex explosive *
Number used 854
These massive bombs designed by Dr. Barnes Wallis reached the speed of sound during descent being streamlined and equipped with angled fins that produced a rapid spin. Penetrating the ground before exploding they worked by setting off shock waves that would bring down nearby structures. The 5.443 kg (12.000 lb) "Tall Boy" dropped from 6.096m (20.000 feet) made a 24 meter (80 feet) deep crater 30 meter (100 feet) across and could go through 4,88 meter 16 feet of concrete. On 8-9 June, 1944 eight Lancaster bombers of No. 617 Squadron used the deep penetration "Tall Boy" bomb in an attack against the Saumur Rail Tunnel. The new weapon proved its worth, but at the cost of losing 5 of the 8 bombers on this mission. Eventually 854 Tallboy bombs were used, the most note-worthy mission resulting in the destruction of the battleship Tirpitz (77 were dropped in three attacks).

The "Tall Boy" bomb was the second biggest bomb used in WWII.

* "Torpex" means Torpedo Explosive. It was originally used for torpedoes and therefore got this name.
"Grand Slam"
Type Deep Penetration Bomb
Length 7,7 meter (26 feet 6 inches)
Diameter 1,17 meter (3 feet, 10 inches)
Tail Section length 4,11 meter (13 feet, 6 inches)
Weight 9.979 kg (22.000 lb)
Warhead 4.144 kg (9.135 lb) Torpex explosive *
Number used 41
The "Grand Slam" (Earthquake) bomb was of the same design as the Tallboy but larger and heavier weighing 9.979 kg (22.000 lb). The Grand Slam was first used on 14 March, 1945 when a force of Lancaster bombers led by Royal Air Force Squadron Leader C.C. Calder attacked the Bielefeld railway viaduct destroying two spans. In another attack against submarine pens, (Bunker Valentin) near Bremen, two Grand Slams pentrated 4,5 meters of reinforced concrete. 41 Grand Slam Bombs were dropped by the end of the war mainly against bridges and viaducts.

The "Grand Slam" bomb was the biggest bomb used in WWII at all.

* "Torpex" means Torpedo Explosive. It was originally used for torpedoes and therefore got this name.

Bombs of Professor Dr. Barnes Wallis
All photos taken at RAF Lossiemouth, Scotland exclusively for this website by © RAF, Lossiemouth and © Linzee Druce.

Tall Boy

The Tirpitz and the Tall Boy
In mid-1944 the British had to realize that with traditional weapons (torpedoes, mines and bombs) there was no way to put the Tirpitz out of commission permanently. At this time a new bomb was put into service, the "Tall Boy", a weapon developed under the direction of Professor Dr. Barnes Wallis, under whose leadership the 3.900 kg (8.600 lb) rotary water bombs, used with great success in the spring of 1943 on reservoir dams in Germany, also originated. The RAF Bomb Command thus received orders to attack the Tirpitz with the new "Tall Boy" bombs. With their weight of 5.443 kg (12.000 lb) they were the heaviest bombs ever built up to that time. In fact, the "Tall Boy" was a "Superbomb". It belonged to the category of thick-walled, teardrop-shaped GP bombs (GP "General Purpose", thus a multipleuse bomb) and were 6,35 meters (21 feet) long with a diameter of 0,95 meter (38 inches). Their warhead consisted of 2.358 kg (5.200 lb) of "Torpex", a highly explosive substance with a detonation speed of 7.600 meters (8.350 yards) per second (in comparison: the detonation speed of traditional TNT is "only" 6.900 meters (7.580 yards) per second). The ignition delay could be set to a maximum of eleven seconds. Such bombs could be carried only by the four engined bombers of the "Lancaster Mark I S" type, and then only one per plane, which also had to be rebuilt for this purpose. At the end of the war a total of 854 "Tall Boy" bombs had been dropped, of which 77 were dropped in the three attacks on the Tirpitz in September, October and November of 1944 alone. In the first attack, two direct hits on the bow was achieved, in the second only a near miss. In the decisive third attack there were three direct hits and one near miss. At the third attack, 12. November 1944, Tirpitz capsized and had to be written off as a total loss.