"Emmanuel Gustin" wrote in message ...
"Hamisha3" wrote in message
...

Not to take anything away from BarnesWallis but why does a simple torpedo
not
do the same as the boune bomb, detonate against the dam wall at a pre
set
depth?

I was just reading 'Bombs Gone', an interesting history of
British bombs. Chapter 7 (well, I had not reached that) is
devoted to the dam-busting bomb, as well as appendices
4 and 5.

Gravity dams are very hard to destroy because a small crack
will be closed by the water pressure, instead of opened.
A large hole must be made. Trials on miniature dams and
on a disused dam in Wales indicated that it would take 6,500
pounds of HE exploding in direct contact, of 30,000 pounds
exploding at a distance of 50 ft. The replacement of Amatol
by Torpex HE later allowed the bomb to be smaller. Still,
this was much more than a torpedo could contain: The Mk.XII
torpedo contained 545 lb of Torpex, about 1/10 of what was
required.

The RAF never bothered to properly document a bomb that
was modified almost every other day and was used only once,
so the best documents are apparently of German origin,
descriptions of an unexploded example recovered from
Fl.Lt Barlow's aircraft. 'Upkeep' weighed around 3900 kg
and contained 2600kg of Torpex, had three water pressure
fuses and a time fuse. Backspun at around 500 rpm and
dropped 400 to 500 yards from its targt, it bounced four
or five times before it hit the dams and sunk against it.

One of the side effects of the Dam busters on German FLAK was the
instigation of a 5.5cm FLAK cannon that could with one hit bring down
a heavy bomber and opperate effectively from short range to medium
altitudes with high accuracy and rate of fire. The weapon was to be
servo driven and automatically pointed by computer. It had a high
rate of fire and low recoil be the action of firing of the cannon
while the barrel was still returning to its home position: thus the
subsequent recoil would have to arrest the forward motion of the gun
as well as overcome the recoil shock. It was nearin completion or
entering production as the war ended.