When it comes to nuclear weapons, we hear a lot about ICBMs and SSBNs, but what is likely America's most common nuke isn't a missile – it's dropped from a plane. We're talking, of course, about the B61 gravity bomb, which has been around for a while and is going to be around for a long time.
This is perhaps one of America's most versatile nuclear weapons. Not only has America built over 3,000 of these bombs, but it was the basis for the W80, W84, and W85 warheads, the key ingredient in nuclear missiles, like the BGM-109A Tomahawk Land Attack Missile – Nuclear, the BGM-109G Gryphon Ground-Launched Cruise Missile, and the MGM-31C Pershing II intermediate-range ballistic missile. Quite impressive, isn't it?
The B61 came about as the result of a need for weapon that could be delivered by high-performance jets. When it was being developed, the F-4 Phantom and other jets capable of hitting Mach 2 were starting to enter service. The earlier nukes, like the Mk 7 and B28, had been designed for use on slower planes, like the F-86 Sabre, F-100 Super Sabre, and the F-105 Thunderchief.
What emerged was a bomb that came in at roughly 700 pounds — compare that to the 1,700 pounds of the B28 or the 1,600 pounds of the Mark 7. In addition, the bomb had what was known a "dial-a-yield" capability, allowing for the selection of explosive yield, ranging from three-tenths of a kiloton to 340 kilotons.
The B61 is currently being upgraded to the B61 Mod 12 standard, which adds GPS guidance to this versatile weapon. The new system could be in service as soon as 2020, possibly allowing the United States to replace the B83 strategic thermonuclear bomb.