Sailor Hat

We’re on a bit of a nuclear weapons kick. This is actually a post that is about nuclear weapons, but doesn’t contain any.

After the Partial Test Ban Treaty, above ground nuclear explosions, including those in the ocean that would broach the surface, were prohibited.

In the meantime, the US Navy was rapidly running out of surplus World War II ships to upgrade, and was designing several classes of ships such as the Leahy class anti-air escorts using aluminum superstructures to save weight. Further, the array of antennas and other ancillary equipment on US ships was growing. But the Navy lacked empirical data on how such structures and arrays would fare in the blast overpressure regime of a nuclear weapon. What to do? Well, obviously, the thing to do was to generate blast overpressure. But since nukes were out, that meant something else was needed. What the Navy eventually did , in 1965, was stack a dome of 500 tons of high explosives along the shore of an uninhabited island in Hawaii, and blow it up, with ships nearby. Not once, but three times!

The prime target was the former light cruiser Atlanta. She was taken into the yard, had her superstructure razed, and new deckhouses erected using the design, materials and standards then in use for new construction.  Further, representative radar arrays of just about every type in use in the fleet were added to her deck. She had two bridges, one replica of a frigate/missile cruiser bridge forward, and a guided missile destroyer bridge aft.

While the former Atlanta was positioned closest to the blast, and was intended to actually sustain damage, other ships were also present, to validate the data. And not just target hulks, but actual, modern, in service ships, equipped with the same superstructures and sensors the test was designed to challenge. Further, the ships were fully manned by their regular crews.

Sailor Hat is pretty well documented. 10psi overpressure was quite damaging to ships, as you can see in the video.


Now, 500 tons of explosives is quite a bit. But it’s not even close to the biggest charges.

In the 1980s, two other programs tested massive conventional charges as substitutes for nuclear weapons. Operation Minor Scale set off 4,000 tons (that is, four kilotons) of conventional explosives. As the press release wryly noted, there were no plans for Operation Major Scale. Minor Scale represented the expected blast overpressure and ground wave effects of roughly an 8 kiloton airburst weapon, roughly half the power of the Hiroshima bomb. Similarly, Operation Misty Picture set off about 4,600 tons of explosives

While neither Minor Scale nor Misty Picture are classified, and indeed reporters were present at Minor Scale, very few pictures have been released, and to date, no video, likely because of sensitive technical aspects of the measurement arrays for the tests. 

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