Does anybody know why they weren't used in the Pacific? Seems like they would have worked well against Limestone fortifications at Iwo Jima and Okinawa.
They were a British invention and it wasn't until the USAAF saw their effectiveness against German targets, that they started to take an interest in them, by which time it was too late to modify the B-29 to carry it and for it to become operational in the Pacific before the end of the war. Post war saw the USAAF adopting the Tallboy(12,000Ib) bomb as the Tarzon guided bomb which saw some limited service in the Korean war. The USAAF also built the Grand Slam (22,000Ib) bomb as the T-14/Mk 110 and adopted the B-29 to carry it, but it as far as I'm aware it was never used operationally
In reality, British Tallboy bombs would have been practically useless against caves dug in limestone formations on the islands of the Pacific. These caves were very well camouflaged and almost impossible to see even at ground level. Hitting such a target from any reasonable altitude would have been nearly impossible, and destroying the extensive cave systems would require hundreds of direct hits. The best method of dealing with these cave systems was to locate as many entrances as possible (using smoke) and seal them with explosives delivered by engineer troops on the ground. BTW, the defensive cave systems on Iwo Jima were not limestone, but were dug into volcanic tuff (compacted ash) and porous basalt. I understand some of these caves had close to 200 feet of rock and ash overhead.
Tallboys bombs were also called 'earthquake bombs' as a direct hit was not required to destroy a target, the shockwave generated was enough to caused destructive damage to targets nearby.
True, but the shock wave wouldn't have been strong enough or widespread enough to have much effect on the caves the Japanese constructed. Damage would be limited to dozens of feet; the Japanese cave systems often extended for miles. Moreover, the "earthquake" effect of the Tallboy bombs was most destructive against surface structures like bridges, canals, and buildings whose foundations were not engineered to withstand earthquake-like shock waves.
the dambusters unit was ordered to the pacific theater for use over japan itself and not for mop-ups around the pacific. they were about to leave when the bomb was dropped an japan surrendered a few days later. as one of them said, "damn, they beat us to it!"
Devilsadvocate is correct in saying that Barnes Wallis' 'Tallboy' was designed specifically for use against man-made structures, especially reinforced concrete. Their use against other types of target ( eg Tirpitz ) was ad-hoc and less successful . Natural caves were in fact very difficult targets to pinpoint and to attack with success from the air ( such as the caves at St Leu-d'Esserent ).
While you never know how accurate internet info is, the figures most commonly quoted seem to be that a Tallboy would make a crater 80 feet deep and 100 feet across via an underground explosion, thereby fritzing anything caught in the collapse zone. If that amount of explosive force happened to intersect a cavern tunnel I would also expect it to channel along and ruin people's day out at least as far again - meaning one bomb could potentially extend to hundreds of feet rather than dozens. Or it might not connect and achieve nothing. I agree with you that it's completely the wrong weapon for taking out cave systems - for one thing it was a painstakingly hand-crafted precision weapon, taking months to make and so expensive that crews had to bring them back if not expended. Only about 700 were used in the whole war. Not suitable at all for mass use against a distributed target. Secondly it relied on a high drop altitude to get enough velocity to penetrate the ground - usually they were dropped from around 20,000 feet (Wallis designed it for a drop height of 45,000 feet). From that height, highly unlikely they'd be able to pick out the exact bit of jungle-covered crag that needed fragging, rather than a bit where the GI's were hunkering down. If there was going to be new weapon deployment for the PTO, something like an RPO-A or M202 flame rocket/grenade launcher would probably have been a much more useful tool, helping the PBI to clear opposition from around the cave mouth so they could get close enough to set demolitions.
My information didn't come from the internet, but from a book called "The Dambusters", which also describes Barnes Wallis' invention of the Tallboy bomb, and goes into quite a bit of detail as to the theories behind it and the practical application of those theories. I'm no engineer, but I think the explosive power of the Tallboy would be less effective in certain types of geological formations. The size of the crater really has little bearing on the amount of damage that might be effected, it's the shockwave it generates that delivers the destruction. Shock waves, for example, behave differently in limestone rock than they do in basaltic rock, or loosely compacted soil. Rather than being "channeled" by an excavated tunnel, the discontinuity created by an open space in the transmission medium would be more likely, in my mind, to disrupt the shock wave. It's well known that earthquake-generated shock waves propagate well in continuous bedrock, but slow down (and become much more destructive of surface structures) in homogeneous geological formations. But Wallis was depending on the shock waves created by the explosion of the Tallboy acting upon the soil or rock below a structure, and in turn acting upon the foundations of a structure, to damage or destroy the target structure. In other words, it's entirely possible that the damaging effect of the shock waves might have very little influence on a cave system excavated in bedrock. I do concur, however, with your other conclusions.
geologist here. it depends on the structure and what it's sitting on. if it's loose soil like in agricultural areas or sandy desert, a tallboy will bury itself 250 feet into the ground. upon detonating, it will create a cavity at least 5 times its volume, whereupon the loose ground will quickly compress and collapse the cavity right after. the compression will create enough ground shift to turn the footings of any large structure askew. if the bomb hit right beside a building with pile-driven supports, at least one of the piles will move down and could possibly collapse the building. if it's hard ground (meta-igneous rock) with the building's footings right on the bedrock, the bomb will penetrate less than 50 feet and cause a steep cratering (unlike a meteor crater which is shallow.) only structures nearby will suffer damage. for coral atoll ground, limestone is easily penetrated but the resulting ground shift from expansion-collapse will be difficult to estimate. limestone ground as it is already poses several problems for a builder. one has to do foundation testing and drilling to make sure no large cavity exists under the spot where you're supposed to build. on the whole, wallis designed the bomb to be a near-miss weapon that will damage the structure not due to seismic shock but rather actual ground movement. exceptions are actual hits over rail tunnels wherein the bomb penetrated right into the tunnel and collapsed it. also, the bigger grand slam was able to penetrate the armored roof of one u-boat pen and demolished it from inside.
A British Armament Research Report dated 30th July 1944 to summarize experience to date with Tallboy concluded that its' main effectiveness was against concrete structure ( caused by near-miss ). Caves could be damaged by subsidence caused by a dircect hit, and surface buildings were unlikely to suffer any damage if the bomb struck more than 70 yards away. The fullest discussion of all Wallis' bombs is Stephen Flowers' excellent book 'Barnes Wallis Bombs' published in 2004 and running to over 400 pages.
Is that the one by Paul Brickhill which covers the whole of 617's war ops? I remember reading it many years ago but none of the numbers really stuck in my mind since I was but a pimply teenager at the time:thumbsuck:.
Redcoat all but said it. From what I know, the Lancaster was the only bomber with a large enough bomb bay .
A major reason is that no US aircraft was configured to carry one. Now in Korea some were used by the USAF in modified form as the Tazon (Tallboy with AZumuth and deflectiON guidance) against North Korean targets like dams.
That is not true Poppy, The US modified a B-29-75-BW S/N 44-70060 to carry TWO Grand Slams externally. Thus its bomb bays could be used for either normal bomb storage or bomb bay fuel tanks. My money would be on bomb bay fuel tanks, because some how to external Grand Slams + bomb bays full of bombs = VERY short range. The B-29 was also capable of carrying the Grand Slam, after modifications, internally. Also, the was the US made "Tarzon" radio guided bomb based on the Grand Slam. Bell ASM-A-1 Tarzon
