US Air force conducts an inert B61-12 Nuclear bomb drop with an F-15E Strike Eagle

The United States Air Force (USAF) and National Nuclear Security Administration (NNSA) have completed the first development flight test of a controversial update to a nuclear bomb that has been use since the 1960s.

A 'safe' version of the the B61-12 nuclear gravity bomb with no warhead was tested at Tonopah Test Range in Nevada. The tests are designed to extend the lifespan of the nuclear weapon by upgrading some of its parts.

'This test marks a major milestone for the B61-12 Life Extension Program, demonstrating end-to-end system performance under representative delivery conditions,' said NNSA Deputy Administrator for Defense Programs Dr. Don Cook. 'Achieving the first complete B61-12 flight test provides clear evidence of the nation's continued commitment to maintain the B61 and provides assurance to our allies.'

The B61, known before 1968 as the TX-61, was designed in 1963 by the Los Alamos National Laboratory in New Mexico. The B61 nuclear bomb is one of the primary thermonuclear weapons in the U.S. Enduring Stockpile following the end of the Cold War. It is an intermediate yield strategic and tactical nuclear weapon featuring a two-stage radiation implosion design.

The B61 is a variable yield bomb (0.3; 5; 10; and 50 kilotons) designed for carriage by high-speed aircraft. It has a streamlined casing capable of withstanding supersonic flight speeds. The weapon is 11 ft 8 in long, with a diameter of about 13 in. Basic weight is about 700 lb, although the weights of individual weapons may vary depending on version and fuse/retardation configuration.

Total production of all versions was approximately 3,155, of which approximately 1,925 remain in service as of 2002, and some 1,265 are considered to be operational. The warhead has changed little over the years, although early versions have been upgraded to improve the safety features.

As of late 2013, there were 200 B61 bombs actively in use by the United States. Of these, 180 were deployed with NATO allies in Europe.