In 1961, Los Alamos National Laboratory started work on a project known then as TX-61 to come up with a 700~ pound tactical nuclear bomb with a yield that could range from 0.3-340 KT of glow in the dark.
Put into production at the Pantex Plant (Zone 11) near Amarillo, Texas in 1968, an estimated 3,155 B61 bombs were completed by the 1970s and, with the steady paring down of Russo-American nuclear stockpiles in the START and SALT treaties as others, the current number of operational devices stands at around 1,200 with only about 200 deployed.
The old school B61 (DOE image). Seems pretty simple.
Today the B61-3, -4, -7, and -10 series bombs, most of which are stockpiled on U.S. bases abroad such as in Europe and the Pacific, are the oldest items in the American nuclear triad and it is doubtful they could penetrate ultra modern strategic C4I facilities deep underground such as the ones believed to exist in Russia, China, DPRK and Iran, built since the 1990s, which can run over 1,000 feet deep and are protected by granite.
Still, they serve as something of “NATO’s Nukes” giving regional powers such as Italy, Spain, Germany and Turkey the nominal capability to carry an American-owned nuke under extreme circumstances (a B61 can be toted aloft by a Tornado or F-16).
Last week, the Department of Energy’s National Nuclear Security Administration (DOE/NNSA) announced they formally authorized the production engineering phase of its B61-12 warhead life extension program (LEP), which will include some capability for deep digging, dial-a-yield warheads, upgraded guidance packages and tail units.
The new B61-12, graphic by engadget
“Reaching this next phase of the B61-12 LEP is a major achievement for NNSA and the exceptionally talented scientists and engineers whose work underpins this vital national security mission,” said NNSA Administrator Lt. Gen. Frank G. Klotz (Ret.). “Currently, the B61 contains the oldest components in the U.S. arsenal. This LEP will add at least an additional 20 years to the life of the system.”
They expect it to be able to send the B83-1—the last megaton-class weapon in America’s nuclear arsenal— into retirement when the program gets fully fleshed out by 2020.