“Yusuf—”
“I’m just trying to understand.”
“The secondary, the bomb we took apart, the pieces fit together into a globe, right? And when the first bomb, the primary, goes off, the secondary gets smashed together, becomes
“Super-critic-al?” Yusuf sounded like he was auditioning, badly, for a part in
“I told you before. Supercritical means the explosion is speeding up, more and more energy is being released. The Russians, the Americans, they’ve figured out how to smash the material very fast, and that means they need less material to cause an explosion. Ever since the 1940s, we’ve known this is how it works.”
“But we can’t smash it together as fast as they can.”
“That’s right. The gun that we’re using, it will shoot the uranium piece at four hundred meters a second”—a quarter-mile a second, nine hundred miles an hour.
“Isn’t that fast?”
“Compared to how quickly the fission reaction happens, it’s slow. So we need more uranium, a bigger sphere, to make sure the bomb will go off.”
“But if it’s so complicated, why don’t we use the Russian bomb?”
“I should just go back to Iraq, leave this to you.”
“Sayyid—”
“I tell you again. The secondary won’t go off without the primary. And the primary, I promise you, it’s been engineered so it won’t go off unless it’s been properly armed. With those famous codes. And we can’t use our own explosive to set it off either. You can’t just paste dynamite around those bombs and push a big handle. The explosive has to be placed and detonated just so, or the bomb won’t go off. We don’t have the equipment. Synchronous detonators and high-grade explosive and a lathe that can cut to the tolerances we need. And even if we could buy them, I don’t know if we have the skill to use them. It would take us six months practicing and testing to be sure. You want to live here for six months, hope no one notices?”
Nasiji pointed at the recoilless rifles stacked against the wall. “The kind of bomb I want to make, it’s so much easier. Mold the pieces into the right shapes, two masses, both just subcritical, fire one at the other. As long as you have enough material and you fire it fast enough, it’s certain to work. With sixty kilos, it would have been a joke. We could have done it in a week. Now. ”
“But isn’t there a half way?” Yusuf said. “We have half as much material as we wanted. Can’t we make a bomb half as big?”
“That’s not how the physics work,” Nasiji said. “Trust me.” Why hadn’t he found a way to detonate the bomb they’d stolen, instead of leaving himself in this mess? Why hadn’t he listened to Bernard and Bashir and sent the bombs to New York on a container ship, instead of being tricky and sending them through Newfoundland? Why hadn’t he made sure that both crates were properly locked down in the lifeboat? He was so stupid. He had failed his father, failed his family, failed his people. His father.
He felt his anger build again and walked out of the stable and into the cold night air. He leaned against an oak tree and craned back his head and looked through the naked branches at the stars, the ultimate nuclear-power plants.
Away from the scale’s figures and Yusuf’s questions, his stomach began to unclench. He was being too hard on himself. Thirty-two kilograms was a massive amount of enriched uranium, more than anyone outside a weapons laboratory had ever seen. Little Boy had been sixty-four kilos, but Little Boy had been made from 80 percent enriched uranium — not nearly as pure as the material they had. He hadn’t tested these pieces yet, but they were surely 93.5 percent enriched, standard weapons-grade.
At that level of purity, even a simple sphere of uranium, with no reflector, no compression, would go critical and produce a nuclear explosion at a size of about fifty kilograms. They were short, but they were in the ballpark.
Nasiji wondered if Bernard could somehow deliver the beryllium without getting busted. Doubtful. But even without beryllium, they could try a steel reflector. Steel wouldn’t be as effective as beryllium, but it would help. Maybe a double-gun assembly, to achieve maximum acceleration, if Yusuf and Bashir could somehow handle the welding.
With thirty-two kilograms, putting this bomb together wouldn’t be easy. But it might not be impossible, and he knew the tricks. Slowly, over sixty-five years, first the physics and then the engineering details of building these bombs had leaked out.
Yusuf emerged from the stable, walked up to him tentatively.
“Sayyid, I must say this. I’m sorry for my stupid questions. It’s confusing, that’s all.”
“It’s I who should apologize,” Nasiji said. “My temper—”
“And I wanted to say, if it’s really impossible with this much, we’ll get more. We’ll leave this here, go back to Russia, find another martyr.”
Nasiji smiled at the stars. He couldn’t help but admire Yusuf’s attitude, though they couldn’t get within a hundred kilometers of a stockpile now.
“No need, Yusuf. We’ll make do. I have some ideas.”
“Is it possible?”
“God willing. We’ve come too far to quit.”
THE NEXT MORNING, Nasiji took his physics and engineering textbooks and a sketchpad and Bashir’s laptop and shut himself up in the farmhouse basement beside the Ping-Pong table. Bashir tried to follow, but Nasiji shooed him away.
“Tell Thalia to leave my lunch at the top of the stairs. Dinner too, most likely.”
“You don’t want help?”
“Not for this.”
“All right, Sayyid. But you’re going to see us anyway.”
“Why’s that?”
“There’s no toilet in the basement. Unless you plan to bring down a bucket.”
At first, Nasiji spent hours sketching out possible ways to set off the plutonium primary inside the Iskander. After all, as Yusuf had pointed out, they already had a bomb. Why not use it? But finally he gave up. He couldn’t figure out a foolproof way to trigger the explosives attached to the bomb, and creating a new trigger, though theoretically possible, would take too long.
That night he went back to his original plan, the gun-type uranium bomb, the Little Boy design. One piece of enriched uranium was molded into a piece that looked like a length of pipe. A second, smaller piece was shaped into a solid cylinder that fit snugly within the larger piece. Both pieces were subcritical, meaning they were each too small to detonate on their own.
The solid cylinder was placed at the end of the gun barrel. Then the pipe-shaped piece was shot at it, creating a single piece that contained a supercritical mass of uranium, big enough to set off a nuclear explosion. The Americans had placed a neutron initiator, a few grams of beryllium and polonium, at the center of the bomb to make sure the detonation happened on schedule. But the initiator wasn’t strictly necessary. The uranium would detonate on its own even without it. As Nasiji had told Yusuf, the great virtue of the design was its simplicity. If the bomb came together quickly enough and had enough uranium, it couldn’t help but go off.
What Nasiji hadn’t explained to Yusuf was that placing metal around the uranium core would make the explosion happen more efficiently, thus allowing the use of less uranium. The metal was called a reflector, because it bounced the neutrons, causing the chain reaction back at the exploding core. Beryllium was the ideal material for the reflector. A sphere of uranium surrounded by beryllium could produce a nuclear explosion with as little as sixteen kilograms of uranium — a critical mass less than one-third that of an unreflected sphere.
So, as an insurance policy, Nasiji had asked Bernard six months ago to try to get a cache of beryllium. But Bernard had reported back that the stuff couldn’t be had, not without taking a huge risk, possibly alerting the German authorities. Nasiji had told him to back off, not push too hard. With two warheads, Nasiji figured he would have enough material to make a bomb of his own.
Now, though, they were short of uranium. Beryllium was the shortest route to making a full-sized bomb.
