4 ms·

Ah, Los Alamos, exactly what I though. What this really is, is an external manifestation of the eternal struggle between the military, which wants the weapons t

Ah, Los Alamos, exactly what I though. What this really is, is an external manifestation of the eternal struggle between the military, which wants the weapons to detonate on time every time, and the safety-minded engineers and politicos who would rather eat an occasional fail than start a nuclear war. The safety people being the engineers tend to keep finding new ways to be safe and applying them without necessarily securing the DoD’s permission, but they don’t always work out the way the engineers intended. For a period of time, there was a piece of cobalt tape on Trident missile warheads that would ensure they fizzle unless removed. Except the adhesive dried up and then the release force exceeded the torque of the motor intended to remove the tape, so something like 75% of the Trident missiles were duds for years. Read Eric Schlosser’s Command and Control. Absolutely fascinating.

jabl 4y ago
> the military, which wants the weapons to detonate on time every time Well, the military sure is also concerned about avoiding non-intentional detonations due to accidents or by being hit by enemy fire. E.g. the IMX series of explosives that have apparently started to replace TNT and Comp B in some applications. https://en.wikipedia.org/wiki/IMX-101 https://en.wikipedia.org/wiki/IMX-101
- KptMarchewa 4y ago
  As we've seen in Ukraine, sensitive munitions kill a lot of tank, IFV and artillery crews.
  - rtkwe 4y ago
    Part of that is the design of Russian tanks as well. Because of the design of the autoloader they use the turret has to sit on top of the shells in Russian tanks. Other countries use a human loader that puts the shells in an armored box with intentional weaknesses so any fires or explosions have a safer direction to expand than into the crew compartment.
    - yencabulator 4y ago
      Even with the compartment design, surely it would be preferable that the munitions don't all explode if hit. And the same thing holds for the depot where all those explosives are stored before being loaded onto vehicles. https://www.cnn.com/videos/world/2023/01/04/russia-weapons-arsenal-explosion-makiivka-ukraine-strike-ovn-intl-ldn-vpx.cnn https://www.cnn.com/videos/world/2023/01/04/russia-weapons-a...
      - rtkwe 4y ago
        If they're not already filled in the magazine you're increasing the time it takes to reload the gun dramatically and adding the need to haul all the water around required to activate all the ammo. Doesn't sound like a great option to me.
        yencabulator 4y ago
        Sure, this particular solution might not be very practical for that use. Such is the nature of research.
perihelions 4y ago
I can't find anything on Google about cobalt tape or Trident missiles — but there was a cadmium wire in the W47 warhead, the one for Polaris missiles, which has a story very similar to yours: - "Because the test ban prohibited the testing needed for inherently safe one-point safe designs, a makeshift solution was adopted: a boron-cadmium wire was folded inside the pit during manufacture, and pulled out by a small motor during the warhead arming process. Unfortunately, this wire had a tendency to become brittle during storage, and break or get stuck during arming, which prevented complete removal and rendered the warhead a dud. It was estimated that 50-75% of warheads would fail. This required a complete rebuild of the W47 primaries.[7]" https://en.wikipedia.org/wiki/W47?useskin=vector#Reliability_controversy https://en.wikipedia.org/wiki/W47?useskin=vector#Reliability...
- wl 4y ago
  Yeah, looks like boron coated cadmium tape. The relevant excerpt from Command and Control... > To avoid the embarrassment of relying on a Los Alamos design, Teller used Livermore’s new core but added a mechanical safing device to it. A strip of cadmium tape coated with boron was placed in the center of the core. Cadmium and boron absorb neutrons, and the presence of the tape would stop a chain reaction, making a nuclear detonation impossible. During the warhead’s arming sequence, the tape would be pulled out by a little motor before the core imploded. It seemed like a clever solution to the one-point safety problem—until a routine examination of the warheads in 1963 found that the tape corroded inside the cores. When the tape corroded, it got stuck. And the little motor didn’t have enough torque to pull the tape out. Livermore’s mechanical safing device had made the warheads too safe. A former director of the Navy’s Strategic Systems Project Office Reentry Body Coordinating Committee explained the problem: there was “almost zero confidence that the warhead would work as intended.” A large proportion of W-47 warheads, perhaps 75 percent or more, wouldn’t detonate after being launched. The Polaris submarine, the weapon system that McNamara and Kennedy considered the cornerstone of the American arsenal, the ultimate deterrent, the guarantor of nuclear retaliation and controlled escalation and assured destruction, was full of duds. For the next four years, Livermore tried to fix the safety mechanism of the W-47, without success. The Navy was furious, and all the warheads had to be replaced. The new cores were inherently one-point safe.
bell-cot 4y ago
You might want to read a bit about the design of WWII-era conventional bombs, or WWI-era artillery shells, or magazines in sailing ships, or ... Militaries that have wanted to win (vs. blow themselves up) have been laboriously working to make sure that explosives do not explode when they shouldn't for centuries.
- TylerE 4y ago
  They're pretty good at it, too. You can set RDX (the explosive in C-4) on fire, and it'll burn, not explode. Even small arms fire won't trigger it.
XorNot 4y ago
> who would rather eat an occasional fail than start a nuclear war. A nuclear detonation on allied territory that originates from your own weapons isn't going to cause a nuclear war. The point at which a nuclear warheads needs to explode is "when it's about 1km above it's target". The war is already happening if it got anywhere near there.

jabl 4y ago

> the military, which wants the weapons to detonate on time every time Well, the military sure is also concerned about avoiding non-intentional detonations due to accidents or by being hit by enemy fire. E.g. the IMX series of explosives that have apparently started to replace TNT and Comp B in some applications. https://en.wikipedia.org/wiki/IMX-101 https://en.wikipedia.org/wiki/IMX-101

KptMarchewa 4y ago
As we've seen in Ukraine, sensitive munitions kill a lot of tank, IFV and artillery crews.
- rtkwe 4y ago
  Part of that is the design of Russian tanks as well. Because of the design of the autoloader they use the turret has to sit on top of the shells in Russian tanks. Other countries use a human loader that puts the shells in an armored box with intentional weaknesses so any fires or explosions have a safer direction to expand than into the crew compartment.
  - yencabulator 4y ago
    Even with the compartment design, surely it would be preferable that the munitions don't all explode if hit. And the same thing holds for the depot where all those explosives are stored before being loaded onto vehicles. https://www.cnn.com/videos/world/2023/01/04/russia-weapons-arsenal-explosion-makiivka-ukraine-strike-ovn-intl-ldn-vpx.cnn https://www.cnn.com/videos/world/2023/01/04/russia-weapons-a...
    - rtkwe 4y ago
      If they're not already filled in the magazine you're increasing the time it takes to reload the gun dramatically and adding the need to haul all the water around required to activate all the ammo. Doesn't sound like a great option to me.
      - yencabulator 4y ago
        Sure, this particular solution might not be very practical for that use. Such is the nature of research.

perihelions 4y ago

I can't find anything on Google about cobalt tape or Trident missiles — but there was a cadmium wire in the W47 warhead, the one for Polaris missiles, which has a story very similar to yours: - "Because the test ban prohibited the testing needed for inherently safe one-point safe designs, a makeshift solution was adopted: a boron-cadmium wire was folded inside the pit during manufacture, and pulled out by a small motor during the warhead arming process. Unfortunately, this wire had a tendency to become brittle during storage, and break or get stuck during arming, which prevented complete removal and rendered the warhead a dud. It was estimated that 50-75% of warheads would fail. This required a complete rebuild of the W47 primaries.[7]" https://en.wikipedia.org/wiki/W47?useskin=vector#Reliability_controversy https://en.wikipedia.org/wiki/W47?useskin=vector#Reliability...

wl 4y ago
Yeah, looks like boron coated cadmium tape. The relevant excerpt from Command and Control... > To avoid the embarrassment of relying on a Los Alamos design, Teller used Livermore’s new core but added a mechanical safing device to it. A strip of cadmium tape coated with boron was placed in the center of the core. Cadmium and boron absorb neutrons, and the presence of the tape would stop a chain reaction, making a nuclear detonation impossible. During the warhead’s arming sequence, the tape would be pulled out by a little motor before the core imploded. It seemed like a clever solution to the one-point safety problem—until a routine examination of the warheads in 1963 found that the tape corroded inside the cores. When the tape corroded, it got stuck. And the little motor didn’t have enough torque to pull the tape out. Livermore’s mechanical safing device had made the warheads too safe. A former director of the Navy’s Strategic Systems Project Office Reentry Body Coordinating Committee explained the problem: there was “almost zero confidence that the warhead would work as intended.” A large proportion of W-47 warheads, perhaps 75 percent or more, wouldn’t detonate after being launched. The Polaris submarine, the weapon system that McNamara and Kennedy considered the cornerstone of the American arsenal, the ultimate deterrent, the guarantor of nuclear retaliation and controlled escalation and assured destruction, was full of duds. For the next four years, Livermore tried to fix the safety mechanism of the W-47, without success. The Navy was furious, and all the warheads had to be replaced. The new cores were inherently one-point safe.

bell-cot 4y ago

You might want to read a bit about the design of WWII-era conventional bombs, or WWI-era artillery shells, or magazines in sailing ships, or ... Militaries that have wanted to win (vs. blow themselves up) have been laboriously working to make sure that explosives do not explode when they shouldn't for centuries.

TylerE 4y ago
They're pretty good at it, too. You can set RDX (the explosive in C-4) on fire, and it'll burn, not explode. Even small arms fire won't trigger it.

XorNot 4y ago

> who would rather eat an occasional fail than start a nuclear war. A nuclear detonation on allied territory that originates from your own weapons isn't going to cause a nuclear war. The point at which a nuclear warheads needs to explode is "when it's about 1km above it's target". The war is already happening if it got anywhere near there.