Two “field” uses of the atomic bomb and more trials on Bikini atoll in the Pacific still left many questions on the use of nuclear weapons unanswered. How would radiation affect human tissue and organs? how would the buildings stand up to the attack? Answers to those were part of the goal of “Operation Plumbbob”, a controversial series of nuclear tests carried out in the Nevada desert.

On this day, September 19, 1957, the “Rainier” test was carried out, with a 1.7 kiloton weapon detonated underground. Seismologists all over the world detected the shock wave, as the blast and subsequent radioactive fallout were fully contained underground.

In all, between May and October of that year, 29 atomic bombs were detonated as part Plumbbob research. About 16,000 American troops were deliberately exposed to radiation, as well as 1,200 pigs. For a study on radiation effects, it perversely succeeded: a 1997 National Cancer Institute Study estimate found Plumbob tests will cause approximately 38,000 cases of thyroid cancer among those exposed, and some 1900 deaths.