The B83 nuclear weapon

Nuclear weapon

A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission bomb test released the same amount...

 is a variable yield

Variable yield

Variable yield — or dial-a-yield — is an option available on most modern nuclear weapons. It allows the operator to specify a weapon's yield, or explosive power, allowing a single design to be used in different situations...

 gravity bomb

Gravity bomb

An unguided bomb, also known as a free-fall bomb, gravity bomb, dumb bomb, or iron bomb, is a conventional aircraft-delivered bomb that does not contain a guidance system and hence, simply follows a ballistic trajectory....

 developed by the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 in the late 1970s, entering service in 1983

1983 in aviation

This is a list of aviation-related events from 1983:-January:* January 1 – Eastern Air Lines' first revenue Boeing 757 flight.* January 5 – United Airlines begins the first scheduled nonstop service between the continental United States and Maui....

. With a maximum yield of 1.2 megatons, it is currently the most powerful atomic weapon in the US arsenal . It was designed at Lawrence Livermore National Laboratory

Lawrence Livermore National Laboratory

The Lawrence Livermore National Laboratory , just outside Livermore, California, is a Federally Funded Research and Development Center founded by the University of California in 1952...

, and the first underground test detonation took place on 15 December 1984.
It was based partly on the earlier B77

B77 nuclear bomb

The B77 was a nuclear bomb designed to match the delivery capabilities of the B-1A bomber. This included the ability to be dropped from supersonic speeds at altitudes of 60,000 feet, or in a laydown delivery at high subsonic speeds at altitudes as low as 100 feet...

 program, which was terminated due to cost overruns.