Post by Stephen Schwartz / Redsky

The Livermore-designed Bassoon Prime device used for TEWA was a “dirty” three-stage design (fission -> fusion -> fission), with a uranium-238 tamper around the third stage. Its fission yield was 87%, the highest of any US thermonuclear bomb test. TEWA contaminated an area of 43,500 nautical miles.

A color photograph of the Basson Prime device detonated in the TEWA nuclear test inside its rectangular shot cab on the barge. The device is a shiny metallic cylinder with a slightly flared bottom 11.3 feet tall, 39 inches in diameter, and weighing 15,735 pounds (almost 7.9 tons). Two line-of-sight diagnostic tubes protrude out of the left side of the cylinder and through the white canvas wall of the shot cab. A shirtless man in khaki shorts stands near the device with his right hand on the lower diagnostic tube, looking up at another shirtless man in khaki shorts standing on a metal platform over the top of the device.

A black and white photograph of the barge used for the TEWA test in Bikini Lagoon. The large rectangular shot cab is near the center of the barge and has the number 15 painted in white on the site.

A map of Bikini Atoll, oriented to the north. Most of the islands comprising the atoll are labeled with their Marshallese names, with the English names later assigned by the US military in parentheses below. Namu and Yurochi islands are at the top of the map.

jul 20, 2025, 5:46 pm • 27 3

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TEWA was so powerful that its mushroom cloud was seen more than 2,500 miles away in Honolulu, Hawai’i. The Bassoon Prime device evolved into the B41 bomb, the highest-yield (25 Megatons) thermonuclear weapon ever deployed by the United States (500 were built and stockpiled between 1960 and 1976).

A screenshot from an official government film of the TEWA mushroom cloud ascending into the ski. The center area, above the stem, is bright yellow while the outer portions are orange-red. The light reflects off clouds in the area, including transient condensation clouds (Wilson clouds) formed by the explosion itself.

A color photograph of the massive and cylindrical B41 thermonuclear bomb on a wheeled dolley in an Air Force museum, with two of the four large tail fins visible (parts of several aircraft can be seen in the background). It is painted dark green with yellow stenciled lettering on one side (TYPE 3, MK 41 MOD 0, along with the part number, a list of the various alts or alterations, and the serial number). The bomb’s large nose, on the right of the photo is studded with numerous relatively small conical protrusions, which may be for barometric and other gauges used during the arming and firing process, or for contact fuzes to enable a ground burst.

jul 20, 2025, 5:46 pm • 31 6 • view

One wonders ‘Stephen’ if those who cherish nuclear weapons are a little bit crazy. I’m thinking Edward Teller and wondering if his legacy will be the movie “Dr. Strangelove” or maybe some of the crazy ideas he advocated👇 www.kqed.org/science/7109... 🤔

jul 20, 2025, 8:08 pm • 1 0 • view

Those diagnostic tubes are curious, to say the least, on a barge where any diagnostic equipment is expected to become plasma.

jul 20, 2025, 8:03 pm • 0 0 • view

Just gotta last long enough to get the data off!

jul 23, 2025, 3:47 am • 1 0 • view

More seriously, instrumentation for those higher yield atmospheric detonations is an astonishing and baroque history in and of itself. Similarly for underground. Instrumentation for all weapons tests and especially those then.

jul 23, 2025, 3:48 am • 2 1 • view

For sure! It’s fascinating stuff. Just working out how they connected to instrumentation *not on the same barge* to record must have been wildly creative. (My modern fave is the Cygnus X-ray camera underground at NNS. Utterly bonkers.)

jul 23, 2025, 4:25 am • 1 0 • view

One of the most amazing engineering techs I have ever had the absolute grace and joy of working with was ex General Atomic and did some of that stuff. Wow. Much props.

jul 23, 2025, 3:52 am • 1 0 • view

Some signatures on the device too!

jul 23, 2025, 1:00 am • 4 0 • view

Similar yet very different vibe from this:

jul 23, 2025, 4:00 am • 1 0 • view