90 meters of stone - a bomb too far ?
617 sq dropped Tallboys & Grandslam bombs during WWII (after the famous dam raids),
tallboy = 12,030lb,
grandslam = 22,000lb (10 tons)
These were dropped from Lancaster Bombers (empty weight 36,828 lb) from a height of 15-20,000 feet (service ceiling of a Lancaster is 23,500 ft)
On the 7th June 1944 several Tallboy bombs were dropped from 10,000 ft onto the Saumur Railway tunnel in France - most landed round the tunnel mouth creating craters 100ft across, one missed the tunnel mouth by 60 yards, and after penetrating 21 meters of rock and clay exploded in the middle of the tunnel. The resulting "earthquake" shifted an estimated 10,000 tons of rock and clay, completely blocking the tunnel.
On the 14th March 1945 a Grandslam bomb was dropped on the Bielefeld viaduct , it missed by 30yards. It is estimated that it penetrated mud and clay to the depth of 30m, blasted a massive subterranian cavity and 100 yards of the viaduct simply vanished into the hole.
On 27th March 1945 grandslams were dropped on the U-boat Pens at Farge near Bremen, they went through 4.5 meters of solid reinforced concreate, before exploding.
I'm always surprised that a "dambusters" follow up film was never done, 617s sqds exploits with impossibly large ordinance and their almost pinpoint accouracy (considering propeller driven planes and fairly rudimentary bomb sights) certainly deserve mention.
So could a 15 ton bomb penetrate 90m of rock if dropped from 40,000 feet, more importantly, would it need to?