sonar screens. Ilse shivered. "No. Have you?"
"Just on film. It's awesome. Surface units caught some footage when things first got hot in the Atlantic." "What's it like?" Ilse said.
"Depends on warhead yield and depth when it goes off."
"How big do they get?"
"U-235, using just one critical mass, you can go up to maybe twenty kilotons."
"In this war that's pretty much a strategic weapon," Ilse said.
"Yup," Sessions said. "For comparison Hiroshima was roughly twelve. Nagasaki, they used a plutonium bomb, maybe twenty-two KT. Warsaw, when this war broke out, they think was ten."
"So what happens when one goes off underwater?"
"There's two things—really just like a regular depth charge, only bigger. Step one, warhead blows. That immediately lifts the surface of the sea, 'cause water's incompressible, and sends a suction wave back down."
"You get a big white fountain?"
"With a dot one KT explosion, could be a hundred yards across. Step two, blast of dirty water hits the surface from below, bigger than the first spout. That's the warhead burst itself. It pulsates as it rises."
"The bubble energy fights back and forth with the water pressure?" Ilse realized now that everyone said "dot" instead of "point" for decimals—less ambiguous?
"In this case that's the fireball," Sessions said. "It's buoyant, hot as hell, so it comes up really fast. There's a nasty airborne shock wave when it breaks the surface."
"How hot is it?"
"Try ten million centigrade."
"Ouch."
"It dissipates, cooling on the way, but being underwater doesn't help."
"How come?"
"Compared to air, the hydrostatic pressure confines the blast, concentrates the fireball. The water boils, of course, but that won't carry off much heat. Seawater's got poor transparency too, from all the stuff that's floating in it—"
"Suspended particulates, organic matter . . ."
"Yeah, Ilse, you would know The whole photon flash
on detonation, the gamma rays and X rays, ultraviolet, visible and infrared, not to mention all the neutrons, they get held in close, strengthening the fireball. On the other hand, seawater does suppress the EMP, the electromagnetic pulse that fries unshielded circuits. . . . Anyway, first you have this giant burst of water, then you get the fireball. Timing between the two depends how deep the thing went off. There'll also be what's called the base surge, a kind of ground fog that spreads out like a fluid and evaporates, ocean surface atomized by the vicious shock wave through the water. You know an underwater blast's much more destructive to naval vessels than an airburst at a given distance. Water's much more dense and rigid, and sound travels five times as fast."
"How much fallout is there with a nuclear torpedo or, or a depth charge?"
"Nothing like an H-bomb used on land."
"But how bad is it?"
"Not counting any from the ships they hit?" Sessions said. "There're the weapon parts, of course, vaporized. Fish and plankton, what's left of 'em. And loads of radioactive steam, from carbon, sodium, trace metals in the seawater, by neutron activation."
"Tidal waves?"
"At least two surges," Sessions said, still watching his displays. "They subside eventually with the kind of warhead yield we're using."
"So they aren't like the big ones from an earthquake?" Ilse said. "Like that one in the Caribbean that wrecked your cruiser Memphis years ago?"
Sessions shook his head. "Then the thing's a meter high way out at sea, but moving literally fast as a jumbo jet, piling up murderously onshore. Nuclear tsunamis act more like ripples in a pond, except they're fifty, sixty feet from crest to trough. They die off, mostly, in a matter of miles."
"Can't big surface ships just ride that out in open water? I got caught on the edge of a typhoon once, on a research trip."
"Yeah," Sessions said, "assuming the enemy doesn't ripple fire or hit from several bearings at once. A ship's hydrophones will give some warning, if you don't receive it on the data links or
"Just on film. It's awesome. Surface units caught some footage when things first got hot in the Atlantic." "What's it like?" Ilse said.
"Depends on warhead yield and depth when it goes off."
"How big do they get?"
"U-235, using just one critical mass, you can go up to maybe twenty kilotons."
"In this war that's pretty much a strategic weapon," Ilse said.
"Yup," Sessions said. "For comparison Hiroshima was roughly twelve. Nagasaki, they used a plutonium bomb, maybe twenty-two KT. Warsaw, when this war broke out, they think was ten."
"So what happens when one goes off underwater?"
"There's two things—really just like a regular depth charge, only bigger. Step one, warhead blows. That immediately lifts the surface of the sea, 'cause water's incompressible, and sends a suction wave back down."
"You get a big white fountain?"
"With a dot one KT explosion, could be a hundred yards across. Step two, blast of dirty water hits the surface from below, bigger than the first spout. That's the warhead burst itself. It pulsates as it rises."
"The bubble energy fights back and forth with the water pressure?" Ilse realized now that everyone said "dot" instead of "point" for decimals—less ambiguous?
"In this case that's the fireball," Sessions said. "It's buoyant, hot as hell, so it comes up really fast. There's a nasty airborne shock wave when it breaks the surface."
"How hot is it?"
"Try ten million centigrade."
"Ouch."
"It dissipates, cooling on the way, but being underwater doesn't help."
"How come?"
"Compared to air, the hydrostatic pressure confines the blast, concentrates the fireball. The water boils, of course, but that won't carry off much heat. Seawater's got poor transparency too, from all the stuff that's floating in it—"
"Suspended particulates, organic matter . . ."
"Yeah, Ilse, you would know The whole photon flash
on detonation, the gamma rays and X rays, ultraviolet, visible and infrared, not to mention all the neutrons, they get held in close, strengthening the fireball. On the other hand, seawater does suppress the EMP, the electromagnetic pulse that fries unshielded circuits. . . . Anyway, first you have this giant burst of water, then you get the fireball. Timing between the two depends how deep the thing went off. There'll also be what's called the base surge, a kind of ground fog that spreads out like a fluid and evaporates, ocean surface atomized by the vicious shock wave through the water. You know an underwater blast's much more destructive to naval vessels than an airburst at a given distance. Water's much more dense and rigid, and sound travels five times as fast."
"How much fallout is there with a nuclear torpedo or, or a depth charge?"
"Nothing like an H-bomb used on land."
"But how bad is it?"
"Not counting any from the ships they hit?" Sessions said. "There're the weapon parts, of course, vaporized. Fish and plankton, what's left of 'em. And loads of radioactive steam, from carbon, sodium, trace metals in the seawater, by neutron activation."
"Tidal waves?"
"At least two surges," Sessions said, still watching his displays. "They subside eventually with the kind of warhead yield we're using."
"So they aren't like the big ones from an earthquake?" Ilse said. "Like that one in the Caribbean that wrecked your cruiser Memphis years ago?"
Sessions shook his head. "Then the thing's a meter high way out at sea, but moving literally fast as a jumbo jet, piling up murderously onshore. Nuclear tsunamis act more like ripples in a pond, except they're fifty, sixty feet from crest to trough. They die off, mostly, in a matter of miles."
"Can't big surface ships just ride that out in open water? I got caught on the edge of a typhoon once, on a research trip."
"Yeah," Sessions said, "assuming the enemy doesn't ripple fire or hit from several bearings at once. A ship's hydrophones will give some warning, if you don't receive it on the data links or
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