The Dam Busters (3 page)

Thirty thousand pounds was nearly 14 tons. That was the explosive alone. Add the weight of the thick case of special steel—another 40,000 odd Ib. It meant a bomb weighing 70,000 Ib.—over 30 tons, and the Victory Bomber, still only on paper and straining the limits of feasible aircraft construction, would carry only a 10-tonner.

The next meeting of the Air Attack on Dams Committee was in a fortnight and it required little thought to foresee it would be the last meeting.

Wallis would not give up.

Supposing, he thought, a bomb could be exploded
under water against
the dam wall. The shock wave punch would be much greater. So the explosive needed would be smaller. So would the bomb casing.

But how to get a big bomb in the exact spot—deep enough for the shock punch and pressed against the wall to make the most of it? Or, as it might require more than one bomb, how could you get them all in the exact spot? A torpedo? But the dams had heavy torpedo netting in front of them, and so torpedoes were out. You could drop a bomb from very low level for accuracy, but bombs don’t simply “drop “. Just after release they carry a lot of forward speed, giving them almost a horizontal trajectory for a while. If you dropped a bomb— even a whopper—from very low to get the accuracy it would simply skid
off
the water ; so that was no good. If you dropped it high enough to enter the water cleanly, you only had about one chance in a thousand of putting it right in the exact spot.

Wallis probed at this problem for days and every time he probed he came slap up against the same old problem—the only way would be to drop something from very, very low and somehow make it stay where it was supposed to. But that seemed to be impossible. He remembered his last holiday with the youngsters just before the war began when they had been skipping stones across the smooth water of a little pon,d. How on earth, he thought, could one toss a stone low like that and stop it skipping. Drop any shape of bomb very low at a couple of hundred miles an hour and heaven knows where it would skip to. When dams are full there is practically no space between the level of the water and the top of the dam wall and in his wry imagination he visualised a series of grotesque bombs hurdling over the dam wall and flying harmlessly downstream. What a pity, he thought idly, that you couldn’t make a torpedo do a bit of hurdling—over an anti-torpedo net for instance.

Hullo! That was an idea! If a bomb could hurdle a dam wall it could also hurdle an anti-torpedo net. Such nets were a good hundred yards away from dam walls to keep any explosions at arm’s length. A bomb didn’t have to keep skipping for ever. May be it could be so judged to skip the torpedo net and not skip the dam wall. Hang it all, why not? He felt sudden excitement surging inside him. There would probably be three or four feet of dam wall above the water. Supposing the skipping of the bomb were timed (if it could be done) so that it was slithering to a stop on the water as it reached the wall. Why then, the wall would stop it dead and it would simply sink into the water, by the wall, as deep as you like. You could have the fuse fixed with a hydrostatic trigger so that the bomb would go off when the water pressure reached the right amount. Set in for fifty feet down or a hundred and fifty feet down. Please yourself. Hang it, the more he thought about it the more he liked the idea, even if it did sound a bit odd.

Wallis went home, dragged a tub into the garden of his house at Effingham and filled it right to the top with water. Then he rigged up a catapult a few feet away just a few inches above the level of the water. A few feet on the other side of the tub he stretched a string between a couple of sticks so that the string was also just above the level of the water. Then he borrowed a marble from his young daughter, Elizabeth, and shot it from the catapult at the water. It skipped off and cleared the string by several inches. Elizabeth and the other children looked on, wondering what he was up to. Elizabeth brought the marble back and Wallis fired it again, this time with a little less tension on the rubber of the catapult. The marble zipped off the water and only just cleared the string. “Ah,” thought Wallis, “that’s it.”

He and the youngsters spent the whole morning playing with the marbles and the water and the catapult and the string, trying different combinations of power and height while Wallis was finding out how much he could control the skip. To his deep joy he found out that with a regular shape and weight like a marble on smooth water he could control it quite well. At least well enough for it to be distinctly encouraging. But could he control several skips, which might be necessary? Aha, that remained to be seen. They went into lunch eventually, all thoroughly splashed. Wallis was very cheerful, and also, the children thought, very mysterious about it all.

Always sensitive to ridicule, Wallis told no one the details, not even his friend Mutt Summers, chief test pilot for Vickers and the man who had tested his old warhorse, the Wellington. Captain Summers was a hefty extrovert and not the type to take a freak idea seriously.

The day of the meeting of the Air Attack on Dams Committee Wallis went early to London, buttonholed the chairman, Dr. Pye, and privately explained his new theory, so earnestly that Pye did not laugh though he looked a little sideways.

“I’d rather you didn’t tell the others yet,” Wallis said. “They might think it a bit far-fetched.”

“Yes,” said Dr. Pye. “I see that. What do you want me to do?”

“Give me time to find out how much RDX will blow a hole in the Moehne Dam if it’s pressed up against the wall.”

Pye talked eloquently to the committee without giving Wallis’s secret away. The members were reluctant when they heard the results of the last model’s test and Wallis was like a cat on hot bricks till they consented to one more experiment.

Glanville built him a new model dam, and Wallis started with small charges, sinking them in the water and exploding them when they were lying against the slabs of concrete. The effect was shattering—literally. He smashed wall after wall seeking the smallest charge needed, and soon he knew that in a contact explosion tamped by water a tiny plug of a few ounces of gelignite blasted a satisfying hole through a concrete wall 6 inches thick. From that he calculated he would need only 6,000 Ib. of RDX to breach the Moehne Dam. With his new idea he could cut the case weight down to a little over 3,000 Ib., making the complete bomb about 9,500 Ib. Less than 5 tons. The new four-engined Lancasters would carry that to the Ruhr without trouble.

CHAPTER III THE GREEN LIGHT

ARMED with sums and theories, Wallis faced the task of convincing officials in their brick and stone lairs along Whitehall and other influential thoroughfares that he could put his bomb in the exact spot. He called on Professor Patrick Blackett, director of an “operational research” branch, and Blackett, a spare, rather intense man, listened to his ideas, carefully examined the calculations, riffled them back into a neat pile and said quietly:

“We’ve been looking for this for two years.”

Wallis was electrified.

“I’d like you to leave these with me for a while,” Blackett said. “There are one or two people I know who would be interested.”

Blackett moved fast. As soon as Wallis had left he went to see Sir Henry Tizard and told him what he had heard. Tizard also moved with unorthodox haste, driving down to Weybridge next morning, where Wallis eagerly explained it all again.

“It seems,” Tizard said when he had finished, “that the main thing to establish is whether this freak of yours will really work, and if so how we go about putting it into practice.”

At Teddington, he said, was a huge ship-testing tank which would be ideal for experiments. He also thought there should be more tests to check how much explosive would theoretically punch a hole in a dam.

“I think I know just the thing,” said Wallis, whose “damology” researches had been fanatical. “There’s a small disused dam in Radnorshire; no earthly use any more as a dam and won’t ever be. We could try and knock it down.”

“Who owns it?” Tizard asked.

“Birmingham Corporation.” Wallis knew all the answers.

“We’ll try them,” Tizard said, and Birmingham Corporation, with a little prodding, said yes.

It was a nice little dam, about 150 feet long and quite thick, curving gracefully across the mouth of a reach of Rhayader Lake, high in the Welsh hills west of Leominster. The corporation had built a bigger dam across the mouth of the lake to feed a little river that tumbled out of the hills.

Wallis estimated that the old dam would have a fifth of the resistance of the Moehne, an ideal test model. He calculated the smallest charge that should knock it down and set off with a packet of RDX and some explosives engineers. Wrapped against the raw mountain wind, he wasted little time, measured out the charge, tamped it in a sealed casing and lowered it deep into the water against the dam wall. Behind the rocks, his mouth dry with anxiety, he pressed the plunger and the lulls echoed with sound. Water spurted a hundred feet high, the lake whipped into fury, and as the water plunged back into the void, the concrete crumbled and a hissing flood burst into the main lake. Wallis, pink with glee, saw there was a ragged hole in the dam 15 feet across and about 12 feet deep.

For the next five months he experimented whenever he could in the tank at Teddington, an enormous thing well over a hundred feet long. He wanted to find out exactly how to control a skipping missile, so that after a given number of bounces over a given distance he could make it reach a certain given point at a certain minimum speed and height. At this ultimate spot the missile would have to be either slithering across the water or only just a fraction above it. He had to find out the best shape to use and the best combination of weight of missile, and height, speed and power of release. And what a headache it was, too. He had a spring-loaded catapult so that he could measure the force behind it, and began to accumulate an extraordinary number of combinations of heights, shapes, weights, speeds and distances. Hundreds and hundreds of times he shot his little missiles across the surface of the water and they skipped and skipped and skipped in little splashes, some of them foundering in mid-stream, some of them foundering three-quarters of the way along, some of them cracking against the end of the tank nearly fifty yards away at this height or that height, and one or two even bouncing over the end. And all this time Wallis was also trying to do his usual work at Vickers.

He filled notebook after notebook with his records and calculations and slowly, as he pored over them at nights assessing the results, certain conclusions began to emerge from all the figures and facts. For one thing some sort of regular shaped missile gave the most consistent results. Something, for instance, like a round ball, such as a golf ball, because every time it skipped and came down and hit the water again it was the same shaped surface that hit the water. That was the only thing that enabled one to predict a bounce. Any irregular shape would only give irregular bounces. He took to concentrating on firing golf balls and bit by bit found he could so adjust the height and strength of his catapult that he could make a ball slither neatly up to the far wall of the tank. There are ways of calculating from scale experiments how a full-sized object will perform. Or that is, how a full-sized object
should
perform if everything goes according to plan and nothing has been overlooked. By the middle of 1942 Wallis was satisfied he knew enough to make a 5-ton bomb skip under control for half a mile ! It would look something like a big round ball of steel and he didn’t quite know whether to call it a mine or a bomb.

Tizard was pleased, but Tizard was an adviser, not all-powerful; the task was to get executive officials keen. Wallis saw several officials, received tea and courtesy, even compliments, but not enough action to please him. Two high executives in particular who could have started things moving seemed irritatingly cautious.

Then one of the several government operational research committees gave Wallis permission to build six half-size prototypes of his new bomb, purely for experiment, and told him he could convert a Wellington to drop them.

In a few weeks the casings were finished, big steel balls about four feet across. Wallis filled them with a harmless substitute the same weight as RDX, and at 3 p.m. on December 4, 1942, the converted Wellington took off from Weybridge with the first bomb on board and Mutt Summers in the pilot’s seat, Wallis crouched in the nose as bomb-aimer, to test-drop off Chesil Beach on the south coast. They were not going to worry too much this time about precise speed and height. About fifty feet up and about 200 m.p.h. and, for the time being, never mind exactly how far the bomb went. It should, however, bounce cleanly about half-a-mile. Something near enough to that would do for the first test. The first thing was to see whether a few tons of steel ball
would
bounce according to theory.

Off Chesil Beach Summers dived low over the water, Wallis pressed the button and watched the big black bomb rattle clear of its stowage. It took so long it seemed like slow-motion, and then it hit and vanished in a sheet of hissing white spray. Staring tensely down out of the bomb-aimer’s compartment Wallis watched with painful anxiety for it to appear. Just for a moment nothing seemed to happen and then out of the spray lurched the black ball looking somehow misshapen. It fell back into the water quite quickly, lurched drunkenly up again, hit once more, skipped another short distance and then slithered a few yards and vanished into the green depths. It didn’t seem to have travelled more than about two hundred yards and Wallis looked down, puzzled, not quite knowing what to think. It had worked but not the way it was supposed to. Something was wrong. Summers turned the aeroplane back towards Weybridge and Wallis, on the way back, trying to imagine what could have gone wrong, remembered the misshapen look about the bomb. He decided that the casing had not been strong enough. It must have crushed a little under the impact, making the bounces unpredictable and sluggish. When they landed he ordered the cases of the remaining bombs to be strengthened.

On December 12 he and Summers took off with a strengthened bomb. Off Chesil Beach, Wallis watched the bomb going down, holding his breath, and feeling his mouth dry with anxiety. Again the hissing sheet of spray as it hit, and then: Oh the thrill, out of the spray the black ball came soaring a hundred yards across the water, hit with another flashing white feather of spray and soared out again, hit again, and again, the distances shortening every time until at last, after what looked like nearly hah
⁰
a mile, it slithered to a foaming stop and sank. Summers had banked the aeroplane round and they could both look down on that glorious sight of the long necklace of white foaming scars on the water where the bomb had hit. Wallis had seldom known such a moment of glad triumph. He crawled half-way out of the nose to look up and grin at Summers above in the cockpit. The engines were making too much noise to talk but Summers grinned down at him, gave him the thumbs-up sign and an enormous wink.

In the next three days he and Summers dropped three more bombs and they worked every time. They took a movie cameraman with them on these flights and got undeniable evidence that it worked.

On the strength of that Winterbotham arranged an interview for Wallis with the Ministry of Supply’s scientific tribunal to assess new weapons. The tribunal watched his films and let it be known that the report would be favourable.

With his films Wallis made a new assault on the two cautious officials. They were still non-committal, but it seemed to Wallis a little less inflexibly so.

Slowly the weeks dragged by with no break-through, and Wallis was sinking into despair again when one day he got a call from one of the two cautious ones, giving him permission to go ahead with the preliminary design of a full-sized bomb. The official tempered his joy by telling him not to expect too much.

Further work would depend on whether it would dislocate work on a new bomber.

This was early February, 1943, and the best time to smash the dams was in May, when they were full. There was still just time. Wallis worked late over his plans and on the eighth day had them virtually finished when the bombshell dropped. One of the cautious ones ‘phoned, ordering him to stop work on the big bomb. There was to be no further action on it.

Wallis went grimly next day to the big tank at Teddington, sank two glass air-tight tanks in the water, putting an arc-light in one and inducing a slight young woman to go into the other with a movie camera. She and the camera could just fit in. He fired a missile across the water, and as it slithered against the end of the tank and sank, the girl filmed its under-water progress. It was a beautiful film; clearly it showed the little sphere rolling down what would represent the dam wall deep under the water to the bottom of the tank.

Next he bailed up Summers and demanded an interview with Air Marshal Sir Arthur Harris, chief of Bomber Command. Summers had known Harris for years, well enough to call him by his first name, which few people dared to do. Harris, it was freely acknowledged, could crush a seaside landlady with a look.

Summers and Wallis drove into the wood outside High Wycombe where Harris had his headquarters, and as Wallis put his foot on the threshold of Harris’s office the booming voice hit him like a shock wave.

“What is it you want? I’ve no time for you inventors. My boys’ lives are too precious to be wasted by your crazy notions ! “

It was enough to strike fear into the heart of the sturdiest inventor. Wallis almost baulked, then pressed on and there was the bulky figure of Harris, grey eyes staring coldly over the half-moon glasses perched on his nose.

“Well?” Harris was a man of few words and forceful ones.

“I have an idea for destroying German dams,” Wallis said. “The effects on Germany would be enormous.”

“I’ve heard about it. It’s far-fetched.”

Wallis said he’d like to explain it, and Harris gave a grunt which Wallis took for yes and went ahead, trying not to be too involved and yet show how he had proved the theory. At the end the bomber chief had absorbed it all. Not that there was any encouraging reaction. Harris said bluntly:

“If you think you’re going to walk in and get a squadron of Lancasters out of me you’ve made a mistake. You’re not ! “

Waiiis started to bristle and Summers, who knew Wallis’s obstinacy and Harris’s explosive temperament, kicked Wallis’s shin under the desk. Wallis controlled himself.

“We don’t want a squadron,” he said, “… yet. We’d like a chance to prove it in trials with one Lancaster first.”

Harris eyed him stonily. “Maybe,” he said. “You
really
think you can knock a dam down with that thing.”

“Yes,” Wallis said. “Or it may take three or four. We can put them all in the same place.”

Summers said peaceably, “We’ll prove it’ll work, Bert.”

“Prove it and I’ll arrange a squadron,” Harris said, and then with his old fierceness, staring at Wallis, “but I’m tired of half-baked inventors trying to run things.”

Summers kicked Wallis once more under the desk and broke the tension by saying, “We’ve got some films here that show clearly how it works.”

“All right. Let’s see them.” They trooped out to the Command projection room, picking up Harris’s chief lieutenant, Air Vice-Marshal Saundby, on the way. Harris curtly told the projectionist to clear out. “If it’s as good as you say,” he told Wallis, “there’s no point letting everyone know. Saundby can run the films through.”

Saundby’s training had not concentrated much on film projection work and for a while there was a tangle of celluloid, but eventually he sorted it out, clicked the lights off and they watched in silence the antics of the bombs dropped at Chesil Beach and the tricks of the model under the water at Teddington.

When the lights went up Harris had his poker face on. “Very interesting,” he grunted. “I’ll think it over.”

Not long after, Wallis got a summons to a senior executive whom he knew quite well and who in the past had encouraged his bomb work.

“Wallis,” he said, “I’ve been asked by––” (one of the two cautious ones) “to tell you to stop your nonsense about destroying dams. He tells me you’re making a nuisance of yourself at the Ministry.”

For a moment Wallis was stunned, then recovered and answered quietly, “If you think I’m not acting in the best interests of the war effort, I think I should offer to resign from all my work and try something else.”