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Meet the Hornigs: building the bomb

In the late 1930s and into the 1940s, with much of the world engulfed by war, a group of scientists began to coalesce in the United States to build a weapon of unparalleled destructive power: an atomic bomb. Time was of the essence, as opposing forces in Germany were working towards the same objective.

In the US, much of the initial research for what became known as the Manhattan Project took place at Columbia University in Manhattan, New York, with crucial experimental work done at the University of Chicago in Illinois and at the University of California, Berkeley. Experimental and eventually functional uranium and plutonium processing plants were set up at a place called Oak Ridge outside Knoxville, Tennessee, and in Washington state.

But the true hub for all this activity was established in the remote south-west of the country – at Los Alamos, New Mexico.

Scientists from around the world were brought in to work on the bomb. It required research across a huge range of areas, such as how to best to extract fissionable uranium-235 from the more abundant uranium-238; the physical construction of the bomb; and how it should be exploded. The end results, of course, were Little Boy and Fat Man, which were dropped on the Japanese cities of Hiroshima and Nagasaki respectively in August 1945.

Lilli Hornig Los Alamos ID. Credit: Wikimedia Commons

But a year before this devastating historic moment, one recruit to the Manhattan Project was chemist and explosives expert Donald Hornig. He joined the project in Los Alamos with his wife Lilli Schwenk in 1944, the year after earning his PhD from Harvard.

Hornig was born in Milwaukee, Wisconsin, on 17 March 1920. His doctorate dissertation was titled “An Investigation of the Shock Wave Produced by an Explosion in Air”, and in the year between graduating Harvard and starting work in Los Alamos, he’d worked in the underwater explosives laboratory at Woods Hole Oceanographic Institution in Massachusetts.

When Don Hornig showed up for work in 1944 at the Los Alamos laboratory in New Mexico, under the direction of physicist J. Robert Oppenheimer, his wife, Lilli, went to the facility’s personnel office, where the first question she was asked was, “How fast can you type?”

Evidently word had not reached personnel that the Hornigs were a package deal: Mrs Hornig was graduate of Bryn Mawr, an elite women’s college in Pennsylvania, and had a master’s degree in chemistry from Harvard.

Lilli Schwenk was born into a Jewish family in Czechoslovakia, near Prague, on 22 March 1921. Her father, an organic chemist, moved the family to Berlin in 1929, but four years later as the Nazis rose to power, they fled to the United States and settled in New Jersey.

Schwenk speaks of her early life in a recorded interview for the Voice of the Manhattan Project, a project of The Atomic Heritage Foundation and National Museum of Nuclear Science & History. 

She explains that once it was found that she wasn’t a typist, she went to work in the chemistry department, “doing what was called ‘fundamental wet research’, which involved working with plutonium, determining the solubility of various plutonium salts. There was essentially nothing known about plutonium chemistry at the time.”

Don, meanwhile, was tasked with figuring out a way to detonate the explosives that would trigger the atomic blast.

“I had invented the electrical switching device which came to be used on the bomb,” he told the Atomic Heritage Foundation.

“The bomb was itself a sphere of plutonium surrounded by a couple of tonnes of high explosive, which had to crush that sphere,” he says. “To do that successfully, the high explosives had to be detonated at 32 points around the sphere. All those initiations had to take place in a fraction of a millionth of a second.”

Despite his technical contributions, Hornig is perhaps best known as the man who babysat the bomb.

The first atomic bomb was scheduled to be tested around 5 am on 16 July 1945, outside Alamogordo, New Mexico. The night before, Hornig explains, there was concern the test could be sabotaged.

Despite a violent thunder and lightning storm that had descended over the desert, Hornig was told to climb the 30-metre tower, “on top of which there was the bomb, all wired up and ready to go. Little metal shack, open on one side, no windows on the other three, and a 60-watt bulb and just a folding chair for me to sit on beside the bomb, and there I was!”

The next morning, the Washington Post reported, Hornig climbed down from the tower and took his place beside Oppenheimer in a control room more than eight kilometres away; the bomb exploded at 5.29.45 am.

After the end of the Second World War, Don enjoyed a long career as an academic administrator and served as science adviser to US presidents John F Kennedy and Lyndon B Johnson.

He died from Alzheimer’s disease on 21 January 2013.

Lilli, meanwhile, devoted herself to challenging sexism and gender inequality in academia and the sciences. She died on 17 November 2017.