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 Post subject: dam busters
PostPosted: Fri Aug 04, 2017 9:31 pm 
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Joined: Fri Apr 04, 2008 10:48 am
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Location: Broomfield, Colorado
The story turns up in every WWII history: eccentric genius Barnes Wallis invents a bomb that will skip over a water surface, hit a dam, sink to a prescribed depth, detonate, and – the dam’s busted. Author James Holland was asked why he wanted to tell this yet again; he pointed out that the previous book about the raid dated from 1951 and was made before many of the records were declassified, and most people’s ideas about the raid came from the 1955 movie, not the book. (The second question he got asked was “What are you going to call the dog?”; Guy Gibson’s black Labrador was renamed “Digger” for the movie, but Holland keeps the original name).

In his background, Holland spends considerable time discussion Barnes Wallis, whose reputation as “eccentric genius” came from:

  1. The airship R101, which featured his geodesic frame system. The R101 crashed and burned on its first operational flight, killing most aboard; however, the crash was not attributed to the geodesic framework.
  2. The Wellington bomber, again using a geodesic framework; quite successful. There was a follow-up, the four-engine Windsor bomber, but only three prototypes were built.
  3. The Tallboy (12000 lb) and Grand Slam (22000 lb) ultraheavy bombs. These were also considered successful; however, Holland notes they were not used according to Barnes Wallis’ original plans. Wallis envisioned the Germans dispersing and hiding their industrial facilities, but observed they could not do this with coal mines and other natural resources. Thus the ultraheavy “earthquake” bombs were to be used to collapse mines. This required dropping them from high altitude, and the above-mentioned Windsor bomber and a new six-engine bomber, the Victory, were to be used. (Web images of the Victory usually show it as a canard design but the surviving wind tunnel models are conventional wing-forward). Tallboy and Grand Slam bombs were eventually used against railway viaducts and U-boat pens, with fair success.
  4. The dam-breaking Upkeep bomb. These were inspired by Barnes Wallis watching stones skipping across a pond; the idea was the bombs would bounce over torpedo nets, sink in contact with the dam, and detonate using depth-charge fuses.

Barnes Wallis had some difficulty getting the idea accepted. Air Marshall Arthur “Bomber” Harris was notoriously dismissive of “panacea mongers” – people with ideas for specialized bomber attack methods or unique targets, and Barnes Wallis “bouncing bomb” met both criteria. However, the Royal Navy got into the act, seeing the bombs as a way to attack anchored warships protected by torpedo nets – specifically the Tirpitz – and Harris gave grudging assent. A special squadron was set up, Lancasters were modified, and training missions targeted obsolete dams in Wales and a surplus French battleship in Scotland. It didn’t go very well. The original design called for a cylindrical bomb in a spherical shell, dropped at a tightly controlled altitude, airspeed, and distance from the target. The spherical casing kept breaking up on impact with the water, and was eventually abandoned, even though it was feared a cylindrical bomb wouldn’t bounce straight. There were tight time constraints; the raid had to be conducted under the proper moon illumination and with the right amount of water behind the dams; that meant May 16,1943. Plus, the Admiralty wanted a simultaneous raid on the Tirpitz so the Germans would have time to adapt to the bomb design. The Admiralty eventually gave up on its plan, and the dam raid went ahead with only one successful test of a live Upkeep bomb; half the squadron hadn’t even dropped a practice Upkeep.

In the British tradition of muddling through, the raid was a success. The Möhne and Eder dams were breached – although it looked pretty grim at first, as it took five bombs on the Möhne and three on the Eder. The secondary targets – the Sorpe and Ennepe dams – were only slightly damaged; it’s something of a mystery why the Sorpe dam was a target and Holland doesn’t explain it; this was an earth dam rather than a concrete one like the others, and the Upkeep bomb wasn’t suited for an attack on it. As a result, it was attacked without spinning the bombs and along the length rather than face on.

Casualties to the bomber crews were horrendous. Five Lancasters out of 19 were lost before reaching the target – with one survivor. Another, with two survivors, was lost during the attack, and two more were lost, with no survivors, on the return. (Three Lancasters had to abort and returned to base, one with a live bomb). Casualties on the ground were also ugly; around 1600 civilians were killed by the floods (but most were foreign slave laborers impressed by the Germans). Holland notes that the raid cut off or greatly reduced the water supply to the Ruhr for some time, and a follow-up incendiary raid might have been successful. In later years, it was argued that the raid was of limited impact, because the Germans were able to repair the dams very quickly; however, Holland comments this was done by taking workers and resources from other areas – notably 7000 workers were withdrawn from the Atlantic Wall. Barnes Wallis was reportedly horrified by the casualties to the bomber crews – he’d met and talked with many of them during tests and training – and supposedly never fully recovered psychologically.

Holland’s writing is straightforward; a quick read. Appropriate photographs, line drawings of the bombs and mechanisms, and good maps, including a large scale map, a detailed map of the Ruhr, and individual maps of the attack approach for each dam.

There are some things Holland doesn’t mention. I wonder if the elaborate spinning mechanism for the Upkeep bombs was actually necessary; after all, “skip bombing” with conventional bombs was used with considerable success in the Pacific theater. Conventional bombs with time delay or pressure fuses might have worked just as well as Upkeep. The 1977 Protocol I to the Geneva Convention outlaws attacks on “stored energy structures”, such as dams, dikes, and nuclear power stations; thus a modern “dam busters” attack would be a war crime. Finally, the “trench” attack on the Death Star is supposedly based on the bomb runs in The Dam Busters movie; ironically Peter Jackson was supposedly going to a remake of The Dam Busters but left that project to do The Hobbit.

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