March 11, 1958 The Day the US, Nuked Itself

This particular nuke was unarmed that day but three tons of conventional explosives can ruin your whole day.   The weapon scored a direct hit on a playhouse built for the Gregg children, the explosion leaving a crater 70-feet wide and 35-feet deep and destroying the Gregg home, the farmhouse, workshop and several outbuildings.  Buildings within a five-mile radius were damaged, including a local church.

If you’re ever in South Carolina, stop and enjoy the historical delights of the Pee Dee region. About a half-hour from Pedro’s “South of the Border”, there you will find the “All-American City” of Florence, according to the National Civic League of 1965. With a population of about 38,000, Florence describes itself as a regional center for business, medicine, culture and finance.

Oh.  And the Federal Government dropped a Nuke on the place. Sixty-two years ago, today.

maxresdefault (29)To anyone under the age of 40, the Cold War must seem a strange and incomprehensible time.  Those of us who lived through it, feel the same way.

The Air Force Boeing Stratojet bomber left Hunter Air Force Base in Savannah, on a routine flight to Africa via the United Kingdom.  Just in case thermonuclear war was to break out with the Soviet Union, the B47 carried a 10-foot 8-inch, 7,600-pound, Mark 4, atomic bomb.

The Atlantic Coastline Railroad conductor, WWII veteran & former paratrooper Walter Gregg Sr. was in the workshop next to his home in the Mars Bluff neighborhood of Florence, South Carolina while his wife, Ethel Mae “Effie” Gregg, was inside, sewing. The Gregg sisters Helen and Frances, ages 6 and 9, were playing in the woods with their nine-year-old cousin Ella Davies as the B47 Stratojet bomber lumbered overhead.b47-7aAt 15,000-feet, a warning light came on in the cockpit, indicating the load wasn’t properly secured.   Not wanting a thing like that rattling around in the back, Captain Earl E. Koehler sent navigator Bruce M. Kulka, to investigate.  Kulka slipped and grabbed out for something, to steady himself.  That “something” just happened to be, the emergency release.

Bomb bay doors alone are woefully inadequate to hold back a 4-ton bomb. The thing came free and began a 15,000-foot descent, straight into the Gregg’s back yard.

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This hole 50 feet wide and 20 feet deep was made after an Air Force nuclear weapon accidentally fell from a B-47 and exploded in Florence, South Carolina, March 12, 1958. The home of Walter Gregg (background) was almost destroyed. Several members of his family were treated for injuries. (AP Photo) H/T Military Times

The Mark 4 atom bomb employs an IFI (in-flight insertion) safety, whereby composite uranium and plutonium fissile pits are inserted into the bomb core, thus arming the weapon. When deployed, a 6,000-pound. conventional explosion super-compresses the fissile core, beginning a nuclear chain reaction. In the first millisecond, (one millionth of a second), plasma expands to a size of several meters as temperatures rise into the tens of millions of degrees, Celsius. Thermal electromagnetic “Black-body” radiation in the X-Ray spectrum is absorbed into the surrounding air, producing a fireball. The kinetic energy imparted by the reaction produces an initial explosive force of about 7,500 miles, per second.

This particular nuke was unarmed that day but three tons of conventional explosives can ruin your whole day.   The weapon scored a direct hit on a playhouse built for the Gregg children, the explosion leaving a crater 70-feet wide and 35-feet deep and destroying the Gregg home, the farmhouse, workshop and several outbuildings.  Buildings within a five-mile radius were damaged, including a local church.  Effie gashed her head when the walls blew in but miraculously, no one was killed except for a couple chickens.  Not even the cat.

screen_shot_2016-05-11_at_60319_pmThree years later, a B-52 Stratofortress carrying two Mark 39 thermonuclear bombs broke up in the air over Goldsboro, North Carolina. Five crew members ejected from the aircraft at 9,000-feet and landed safely, another ejected but did not survive the landing. Two others died in the crash.

In this incident, both weapons were fully nuclear-enabled.  A single switch out of four, is all that prevented at least one of the things, from going off.

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One Mk 39 nuclear weapon from the Goldsboro incident remained largely intact, with parachute still attached. The second plunged into a muddy field at about 700mph, and disintegrated.

Walter Gregg described the Mars Bluff incident in 2001, in director Peter Kuran’s documentary “Nuclear 911”. “It just came like a bolt of lightning”, he said. “Boom! And it was all over. The concussion …caved the roof in.” Left with little but the clothes on their backs, the Greggs eventually sued the Federal Government.

The family was awarded $36,000 by the United States Air force.  It wasn’t enough to rebuild the house let alone, replace their possessions.  Walter Gregg resented it, for the rest of his life.

download - 2020-03-11T083015.786Over the years, members of the flight crew stopped by to apologize for the episode.

The land remains in private hands but it’s federally protected, so it can’t be developed.   They even made a path back in 2008 and installed a few signs,  but those were mostly stolen by college kids.

You can check it out for yourself if you want to amuse the locals.  They’ll know what you’re doing as soon as you drive through the neighborhood, the second time.  Crater Rd/4776 Lucius Circle, Mars Bluff, SC (Hat tip roadsideamerica.com)

A month before the Mars Bluff incident, a hydrogen bomb was accidentally dropped in the ocean, off Tybee Island, Georgia.  Incidents involving the loss or accidental detonation of nuclear weapons are called “Broken Arrows“.  There have been 32 such incidents, since 1950.  As of this date, six atomic weapons remain unaccounted for, including that one off the Georgia coast.

Feature image top of page;  “C. B. Gregg looks at the bomb damaged home of his brother Walter Gregg who was injured after an Air Force bomb hit about 100 yards away on March 12, 1958, in Florence, S.C. (AP Photo) H/T Military Times