-  Inventors and Remarkable People
Dambusters 70 years on: Barnes Wallis - an engineer ahead of his time
A film still of a bouncing bomb trial (Photo: BAE Systems/SSPL)
It's seventy years to the day since No. 617 Squadron of the Royal Air Force returned from Operation Chastise, in which specially designed bouncing bombs were dropped in an attack on the Möhne, Sorpe and Eder Dams in Germany during World War II. Though the bouncing bomb is without doubt the invention for which Barnes Wallis is most renowned (thanks in no small part to its depiction in the film Dambusters) Wallis' other work before, during, and after World War II was of great importance, and in some cases, far ahead of its time. Gizmag spoke to Dr. Andrew Nahum, Principal Curator of Technology at the Science Museum where many of Wallis' papers are archived, about swing-wing aircraft, earthquake bombs, improbable mathematics lessons, and the geodetic Wellington Bomber.
Gizmag: How troublesome was development of the bouncing bomb?
Dr. Andrew Nahum: I think the concept was okay. The problem was making it hold together. The conception of the rotation, the skipping, was pretty sound. I think it was more of a mechanical problem, of engineering, to withstand the drop. It was to do with having a defined height, and a very accurate low height, but also strengthening the casing. It was quite an ingenious thing, in that the backspin imparted to it was there to give it a lift force. It made the projectile roll down the dam wall once it reached it, and he'd marked the drawing, as you see, lateral force, and that's a fluid dynamic effect called the Magnus effect. It's kind of more sophisticated than it looks as a great big spinning dustbin.
GM: Do you think the historic view of Operation Chastise altered over the years; for instance, in terms of recognizing German casualties, and a realistic assessment of its military impact?
AN: Are you referring to people implying that strategic bombing was ineffective in general? You're getting into a whole new area, really. That's a question you ought to be asking about the whole strategic bombing campaign, and not just the dams raid. That is one element in it. It's a matter of record that there was a lot of opinion expressed after the war that the bombing had been relatively ineffective, but that's still open to debate. One of the more economic histories of the war by Adam Tooze, Wages of Destruction, had started to suggest that it was more effective than has generally been thought. I'm talking about strategic bombing as a whole, not the dams raid alone. I'm not saying that's my opinion. I'm simply saying the question has been re-opened at an academic level. I think another thing that's worth saying is that the raids were never repeated, and I think it was concluded that, having had surprise once, and having had very heavy casualties on the attacking force, they could never go back and do the same thing, especially with the long slow approach which the bomb required.
Wallis arrived at the idea of a bouncing bomb when thinking about how he, as an engineer, might help shorten World War II. His idea was that a bomb dropped from an aircraft could be made to bounce along the surface of a river before striking a dam where it would sink and detonate. The bouncing would allow evasion of anti-torpedo nets placed in the river to protect the dams, and allow the bomb to explode right next to the dam, where it would be most effective, and potentially breach. Numerous tests were carried out before arriving at the dustbin-shaped Upkeep bomb design, and determining optimal backspin and drop height. On May 16, 1943, 19 modified Lancaster Bombers left on their mission to destroy the Möhne, Eder and Sorpe Dams in an effort to disrupt Nazi supply lines. After several attempts, the Möhne and Eder Dams were breached, though the Sorpe Dam obtained less damage. Eight aircraft were lost, with 53 of the 56 crew aboard them killed. The mission is thought to have resulted in more than 1,300 causalities on the ground, many of whom were overseas workers. The mission did strike the Nazi war machine, however, destroying 25 bridges, 11 factories, and various other mines and infrastructure, and damaging many more.
GM: Are there any items in the Science Museum's archive that shed light on Operation Chastise?
AN: There's a lot of documentation on it. There's a very early sketch which I think is very intriguing, because it shows that the concept was formed very early in his mind. To me, one of the most intriguing things about it is that he had no standing as a tactician, if you like. He simply thought up this plan, how can we strike an economically effectively blow, and then started lobbying people. So the film has some elements of truth, [such as] him being rebuffed by officialdom but at the same time there was quite an appetite in Britain for, what should I say ... what Churchi