The thermonuclear core no one recovered
Each bomb was a thermonuclear design. So instead of just one nuclear core, these weapons – the most powerful type on earth – had two.
In the moments after the first core, called a primary, explodes, it releases a torrent of X-ray and other radiation. This radiation reflects off the inside of the bomb casing, which acts as a mirror to focus it on and set off the secondary core. The one-two punch compounds the efficiency and explosive power of a nuclear blast.
While the US military recovered the entire Goldsboro bomb that hung from a tree, the second bomb wasn't fully recovered. Its secondary core was lost in the muck and the mire.
Reports suggest the secondary core burrowed more than 100 feet, possibly up to 200 feet, into the ground at the crash site.
The missing secondary is thought to be made mostly of uranium-238, which is common and not weapons-grade material – but can still be deadly inside a thermonuclear weapon – plus some highly enriched uranium-235, or HEU, which is a weapons-grade material and a key ingredient in traditional atomic bombs.
Business Insider contacted the Department of Defense to learn about the current status of the site and the missing secondary. A representative said neither the Defense Department, Energy Department, or US Air Force had "any ongoing projects or activities with this site."
The department representative would not say whether the secondary was still there. However, they forwarded some responses by Joel Dobson, a local author who wrote the book "The Goldsboro Broken Arrow."
"Nothing has changed" since 1961, Dobson said, according to the Defense Department email. (Dobson did not return calls or emails from Business Insider.) "The area is not marked or fenced. It is being farmed. The DOD has been granted a 400 foot in diameter easement, which doesn't allow building of any kind, but farming is OK."
When asked about the still missing secondary, Michael O'Hanlon, a US defense strategy specialist with the Brookings Institution, said there should be little to worry about.