Early nuclear tests weren’t in danger of igniting the atmosphere. The scientists were kind of sure it wouldn’t.
But they also were concerned with the ocean:
if the Earth’s oceans had twenty times more deuterium than they actually contain, they could be ignited by a 20 millionmegaton bomb (which is to say, a bomb with the yield equivalent to 200 tera tons of TNT, or a bomb 2 million times more powerful than the Tsar Bomba’s full yield).
Teller of some of my favourite history of nuclear development stories (including the time a dude lost some classified nuke documents on a train (whole train got stripped down to bare metal)) is coming out with a book this week:
A couple months back I came across this New Yorker article about John Coster-Mullen, a civilian who investigated the design of nuclear bombs. I learned that the gun design didn’t fire a bullet into a target with a bullet-shaped hole, it was the other way around.
Yeap. The goal was to maximize the time where a critical mass was present. Even the “simple” nuclear weapon designs were extremely well engineered and were not in practice simple to build.
This type of weapon was obsolete before it was even deployed. It’s also the type of weapon that South African 6kt yield thing was based on. The design probably maxed out, if engineered and produced extremely well, ~30kt. They also can not use plutonium for reasons, and thus only ever existed as uranium-based devices.
South Africa chose this design largely due to their lack of sophisticated engineering and manufacturing capabilities, and also due to their “mission profile.”
That mission profile was horrific and racist. Their plan was basically to nuke the desert if the (justified) unrest around their regime grew too disruptive, hoping to scare Africans into leaving the regime intact and likely getting the US to intercede on their behalf as a fellow nuclear power.
This was in the 80s! The last US weapon that used this obsolete design was retired in the early 60s*.
*There was one weapon that technically was still in service until the 90s, but not practically. The US W33 warhead.
It was a highly specialized device for nuclear artillery. (Yes, that is as terrible of an idea as it sounds). Hence, while they weren’t disassembled until the early 90s, they were not really “operational” during that service history.
Little is known about the details of its design, save that it very likely used two separate gun devices internally. This is both due to the implausibility of a 30kt yield from a single gun-type device and due to its own mission profile.
This is even better than the time a bunch of covert bases got revealed on Strava. Or a bunch of personnel and bases got exposed on Untappd. (The latter of which being broken by the same reporter as this story, funnily enough.)
Alex Wellerstein with an article about Really Big Bombs:
At [Teller’s] Livermore laboratory, he reported, they were working on two new weapon designs, dubbed Gnomon and Sundial. Gnomon would be 1,000 megatons and would be used like a “primary” to set off Sundial, which would be 10,000 megatons.
Supposedly a 10GT airburst was calculated to be able to set an area the size of France on fire.