Why Apollo Astronauts Trained in Nuclear Bomb Craters

Apollo astronauts trained at a nuclear-bomb crater site because the Nevada Test Site produced a rare, controllable stand-in for meteor impacts—complete with the same kinds of shock effects and crater-forming mechanics. That mattered because the Moon is cratered, and recognizing the right rocks and minerals on arrival depended on understanding what impact processes leave behind.

The training ground was Sedan Crater, excavated in 1962 at the Nevada Test Site, a desert range used for nuclear weapons testing. The U.S. carried out 928 nuclear explosions there, and from 1965 onward the program hosted Apollo training with spacesuit mock-ups, TV cameras, and even a lunar roving vehicle mock-up. Over seven years, 11 of the 12 men who would later walk on the Moon visited the site.

The “obvious” reason—cratered terrain—was only part of the logic. Other crater fields existed, including Barringer Crater in Arizona, whose impact origin was disputed until the 1960s, and an Arizona site where conventional explosives recreated lunar-like crater patterns near the Apollo 11 landing area. Nevada offered something extra: a nuclear blast crater that closely mimicked the physics of an impact.

Sedan Crater was created by drilling 635 feet (194 meters) down and detonating a 104-kiloton device, releasing energy roughly eight times the TNT yield of the Hiroshima bomb. The explosion excavated about 12 million tons of rock and dirt, forming a crater about 400 meters across and nearly 100 meters deep—described as the largest man-made crater in North America. The blast was part of “Plowshare,” an initiative that explored whether nuclear explosives could serve as a powerful, compact excavator for large construction projects. That broader goal faded once radioactive contamination proved difficult to manage, but the crater remained a high-fidelity analog for impact geology.

Meteor impacts don’t simply “push dirt aside” mechanically. At typical impact speeds of 10 to 20 kilometers per second, the collision creates an extremely hot, high-pressure region that melts and vaporizes rock, then drives a shockwave that transforms minerals. As the high-pressure zone decompresses, an outward explosion-like event excavates the crater, which is why impact craters tend to be circular. Nuclear detonations generate comparable shock conditions, so the Nevada craters provided evidence that Barringer Crater was truly impact-made.

Scientists compared samples from Sedan and Barringer and found matching shocked minerals such as coesite, a quartz form only produced under extreme pressure. Similarities also helped estimate impact energy at around 10 megatons. Another shared signature was “inverted stratigraphy”—layers of rock turned over at the crater rim—useful for teaching astronauts where to look and what to collect.

That training fed directly into Apollo science. Astronauts spent about a quarter of their final year before launch studying geology and visiting sites like Sedan. On the Moon, they recognized rocks and minerals they had practiced identifying, and those samples later underpinned major conclusions. Apollo 11 returned lunar regolith that raised concerns about spontaneous ignition when exposed to oxygen, but it remained stable. Among the samples, scientists identified anorthosite, supporting the idea that the early Moon had a deep magma ocean and that anorthosite crystallized and floated to form a primordial surface. Isotope comparisons between Moon rocks and Earth rocks pointed to a shared origin from a giant impact roughly 4.5 billion years ago. With under 400 kilograms of lunar material from the Moon’s near side, the crater training helped turn field recognition into planetary-scale evidence.