The Apollo Program, US Navy magnetic mines and the legendary solar storm of August 1972

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Lorenzo von Matterhorn
Jan 31, 2009
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The legendary solar storm of August 1972
It's legendary (at NASA) because it happened during the Apollo program when astronauts were going back and forth to the Moon regularly. At the time, the crew of Apollo 16 had just returned to Earth in April while the crew of Apollo 17 was preparing for a moon-landing in December. Luckily, everyone was safely on Earth when the sun went haywire.

"A large sunspot appeared on August 2, 1972, and for the next 10 days it erupted again and again," recalls Hathaway. The spate of explosions caused, "a proton storm much worse than the one we've just experienced," adds Cucinotta. Researchers have been studying it ever since.

Cucinotta estimates that a moonwalker caught in the August 1972 storm might have absorbed 400 rem. Deadly? "Not necessarily," he says. A quick trip back to Earth for medical care could have saved the hypothetical astronaut's life.

Surely, though, no astronaut is going to walk around on the Moon when there's a giant sunspot threatening to explode. "They're going to stay inside their spaceship (or habitat)," says Cucinotta. An Apollo command module with its aluminum hull would have attenuated the 1972 storm from 400 rem to less than 35 rem at the astronaut's blood-forming organs. That's the difference between needing a bone marrow transplant ... or just a headache pill.
[I expect the incredibly thin walls of the LM would have provided much less protection - W]

Dr. Len Fisk recalls a dinnertime conversation with Neil Armstrong about solar flares. From an interview of Dr. Lennard A. Fisk:
A Powerful Solar Storm Likely Detonated Dozens of U.S. Sea Mines During the Vietnam War
An analysis of recently declassified U.S. military documents confirms suspicions that, during the late stages of the Vietnam War, a powerful solar storm caused dozens of sea mines to explode. It’s a stark reminder of the Sun’s potential to disrupt our technological activities in unexpected ways.

As part of Operation Pocket Money, the U.S. Navy planted a series of Destructor sea mines near strategic ports off the coast of North Vietnam. A few weeks later, on August 4, 1972, crew members aboard U.S. Task Force 77 aircraft suddenly observed a batch of explosions south of Hai Phong. In all, some 20 to 30 explosions were documented in just 30 seconds. Another 25 to 30 patches of muddy water were also observed, indicative of further explosions.

It was a bizarre occurrence, as there was no reason why the mines should have gone off. Almost immediately, U.S. officials began to contemplate extreme solar activity as the cause, as revealed in newly declassified U.S. Navy documents. New research published last month in Space Weather, a publication of the American Geophysical Union, agrees with this 46-year-old assessment, while providing new details about this particularly nasty solar storm, which disrupted more than just naval mines. The study’s authors, led by Delores Knipp from the University of Colorado and Brian Fraser from the National Center for Atmospheric Research, Boulder, say the historical event should serve as a call to action.

The bombs that exploded were magnetic sea mines, a weapon that dates back to the First World War. When a ship passes above, the mine senses a change to the magnetic field density, triggering a detonation. Within days of the August 1972 incident, U.S. military officials began to wonder if solar activity might have been responsible for the unanticipated mine detonations.

As RMIT senior lecturer Brett Carter reports in The Conversation, scientists in the 1970s were already aware of the Sun’s potential to trigger magnetic field changes—they just weren’t sure if it was strong enough to induce the mines into detonating. As part of its investigation, the U.S. military sent officials to the Space Environment Laboratory at the National Oceanographic and Atmospheric Administration (NOAA) near Boulder, Colorado. After consulting with scientists, the investigators concluded with a “high degree of probability” that solar storm activity was responsible for the seemingly spontaneous destruction of the magnetic mines.