A hydrogen bomb is a nuclear weapon that gets most of its energy from fusion — the joining of light atoms — ignited by a fission explosion. Also called a thermonuclear weapon or H-bomb, it can be scaled to far higher yields than a pure fission (atomic) bomb. Seven countries have tested or claimed a thermonuclear device, and the three most powerful nuclear explosions in history were all hydrogen bombs.
How a thermonuclear bomb works
A thermonuclear bomb works by using a fission explosion to set off a much larger fusion reaction. In the words of the American Nuclear Society, "the energy from a fission device could ignite fusion in a secondary fuel." [1] That staged arrangement is called the Teller–Ulam design, after the two physicists who devised it. This page describes only that one-line concept; it carries no device design detail.
Which countries have hydrogen bombs
Five countries have confirmed thermonuclear tests — the United States, Russia, the United Kingdom, China and France — and two more, India and North Korea, have claimed thermonuclear devices that remain disputed.
| Country | First thermonuclear test | Date | Yield |
|---|---|---|---|
| United States | Ivy Mike | 1 Nov 1952 | 10.4 Mt [2] |
| Russia (USSR) | Joe-4 (first thermonuclear explosion) | 12 Aug 1953 | 400 kt [3] |
| United Kingdom | Grapple X | 8 Nov 1957 | 1.8 Mt [4, 5] |
| China | Test No. 6 | 17 Jun 1967 | 3.3 Mt [6] |
| France | Canopus | 24 Aug 1968 | 2.6 Mt [7] |
| India | Claimed (Pokhran-II) | 11 May 1998 | about 43 kt, disputed [8, 9] |
| North Korea | Claimed | 3 Sep 2017 | about 250 kt, claim [10] |
Who invented the hydrogen bomb
The two-stage thermonuclear design was devised in the United States by Edward Teller and Stanislaw Ulam, in a report (LAMS-1225) dated 9 March 1951. [1] In the Soviet Union, Andrei Sakharov is called "the father of the Soviet hydrogen bomb"; his early "Layer Cake" (Sloika) design was the basis of the first Soviet thermonuclear test. [12, 13]
The first hydrogen bomb test
The first full-scale thermonuclear test was Ivy Mike, detonated on 1 November 1952 (local time) at Enewetak Atoll with a yield of 10.4 megatons. [2, 1] You can see its effect radii on the Ivy Mike weapon page. The Soviet Union's first thermonuclear explosion, Joe-4, followed on 12 August 1953 at 400 kilotons, and its first true two-stage device, RDS-37, on 22 November 1955 at 1.6 megatons. [3, 14]
How powerful hydrogen bombs are
Hydrogen bombs span a huge range. Ivy Mike released 10.4 megatons and Castle Bravo, the largest US test, about 15 megatons, both from the US government test catalogue; [2] Tsar Bomba released about 50 megatons, the largest nuclear explosion ever. [15] For a 10.4-megaton air burst the simulator computes a 5 psi moderate-blast radius of about 14 km; for 50 megatons it is about 23 km. See the full rings for Ivy Mike, Castle Bravo and Tsar Bomba.