Engineers at the United States' nuclear weapons lab in Albuquerque, New Mexico, have spent the past few years designing and testing the B61-12, a high-tech addition to our nation's atomic arsenal. Unlike the free-fall gravity bombs it will replace, the B61-12 is a guided nuclear bomb. A new tail kit assembly, made by Boeing, enables the bomb to hit targets far more precisely than its predecessors.

Using "Dial-a-yield" technology, the bomb's explosive force can be adjusted before launch from a high of 50,000 tons of TNT equivalent to a low of 300 tons—that's 98 percent smaller than the bomb dropped on Hiroshima 70 years ago.

Despite these innovations, the government doesn't consider the B61-12 to be a new weapon but simply an upgrade. In the past, Congress has rejected funding for similar weapons, reasoning that more accurate, less powerful bombs were more likely to be used. In 2010, the Obama administration announced that it would not make any nuclear weapons with new capabilities.