The Secret of the Unicorn : The photogenic mushroom cloud

 

Sixty years ago yesterday, the first french test in Polynesia, Aldébaran, was detonated in the Centre d'Expérimentations du Pacifique. However, to speak about the testing campaigns in Mururoa and Fangataufa, i'd like to write about a test occurring four years and a day later.

On the 3rd of July 1970, at 10:30 AM, the device of the nuclear test Licorne detonated over Mururoa. Under a balloon at 500 meter high, this shot (which reaches a yield of 914 kilotons) is the fifth of the 1970 testing campaign. Michel Debré, minister of defense, is present onboard the command cruiser De Grasse to spectate. This test is very famous from the pictures taken of its mushroom cloud, which rose up to 24 000 meters high.

Map of the marine radioactive fallout of the Licorne shot. Source : moruroa-files.org

This test, by its yield, seems to be an experimentation of a thermonuclear device, probably a prototype of the TN 60 warhead which would be mounted on the submarine launched missiles seven years later. However, this shot is not the most powerful french test ever, nor the most powerful shot of the campaign : On the 30th of May of the same year, the Dragon test reached a marginally more powerful yield of 945 kilotons. The preceding campaign of 1968 saw two tests exceeding the megaton bar : Canopus (2,6 MT) and Procyon (1,28 MT), and the next campaign also would test a device flirting with the megaton bar, Rhéa (955 kilotons). Those five tests are the most powerful of the french experimentations program. If Canopus and Procyon seem to be demonstrating shots validating the concept, the following three shots might be prototypes of the TN 60 exploding with nearly all their yield, in order to collect data to analyse the thermonuclear stage. Those might be "complete" shots, contrary to other tests which only dealt with detonators (like the Pallas and Parthénope shots in the summer of 1973, with respective yields of 4 and 0,2 kilotons, and whose detonator aspects could be confirmed by declassified US documents relating to exchange with french officials)

 

The "advanced recording bunker" Dindon in Mururoa. Source : ECPAD

The pictures of Licorne can illustrate an aspect of the french atmospheric experimentations : the fact that most of them were done under captive balloons. Only three shots were done on barges, three other from planes, and the four Gerboises were done on top of towers. The first shot, Aldébaran, was done at an height of only ten meters. The resulting fireball did touch the water, projecting steam contaminated by fission products. The use of balloons is thus presented as a way to make theses tests look "cleaner" than the American or British examples. A message towards the Polynesian population (as the implantation of the CEP was imposed by the Métropole) or to the international community

The importance of developing ballistic missiles and their warheads might not have created the need for additional shots from planes dropping their bombs. Moreover, the possibility of replicating Frigate Bird, the American test involving the firing of a live Polaris missile, might not have been possible due to budget and safety issues. Testing is done in front of heavily fortified bunkers taking measures, in a "staged" way. 

 

Picture of the "Altaïr" shot, 5th June 1967. While depicting an earlier shot, this picture illustrates the first instants of the fireball, with the balloon still present. 

The popularity of the series of pictures came with a widespread, often incorrect use to illustrate every thermonuclear detonation. In an article of his blog published in 2014, Alex Wellerstein points that it is also used to depict the Tsar Bomba. The condensation cloud around the explosion on the first picture helps to exaggerate the size of the explosion.

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Pictures of the explosion indicate that the photographies might have been post-processed. A fair amount of copies of those can be seen on sites like Ebay, for a very hefty price. This test has been the subject of a deliberate publicisation by the French nuclear program.

During the lunch break between the two visits organised by the COMPPAS on their launch zone on the Albion Plateau, I chatted with Franck Laidin on the topic of that test. My take was that the test was a "staged" test that was detonated just in front of a well protected and equipped bunker. But he did point out the problematic of communication and advertising. One can have strong doubts about the fact that the CEP would have detonated a megaton-class device just for a photo shooting. But the plausible post-processing as well as the printing of the images definitely prove his point.

 

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Bibliography

 

WELLERSTEIN Alex, "Mushroom clouds strange, familiar, and fake", on website nuclearsecrecy.com, 1er décembre 2014 (consulté le 2 juillet 2026) 

TAIAURI Manatea , "Guerre Froide et récit franco-polynésien", on website tahiti-info.com, 26 juin 2026 (consulté le 2 juillet 2026)

AHMED Nabil (dir), "Documents déclassifiés" on website moruroa-files.org (consulté le 2 juillet 2026)

MARTIN Gérard (dir) Les atolls de Muroroa et de Fangataufa (Polynésie Française), Les expérimentations nucléaires, Aspects radiologiques. Commissariat à l'Energie Atomique, Juin 2006