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National Museum of Nuclear Science & History

Remembering Don Hornig

Don Hornig & LBJ. Photo courtesy of the LBJ Presidential Library.

On January 21, Manhattan Project veteran Donald (Don) Hornig passed away at the age of 92. He received a doctorate in physical chemistry in 1943, and one year later was recruited to join the laboratory at Los Alamos. A visionary scientist and educator, what we remember is his wonderful creativity and humor, designing the electrical switching device for the implosion bomb, and babysitting the bomb the night before the Trinity test. During his distinguished career, he served as professor at Brown and Harvard; science advisor to President Lyndon Johnson; and president of Brown University (1970-1976).

His wife, Lilli, was a chemist. They married in 1943 and were together until his death, for 69 years. They had four children, nine grandchildren, and ten great-grandchildren. We send our deepest sympathies to Lilli Hornig and her family.

In an interview with WUNC, Hornig remembered the night of July 15, 1945, as he was stationed on top of the tower with the “gadget,” anxiously waiting for a storm to pass over the Trinity site. But he was most worried that his contribution, the electrical switching device, might not work.

"Oppenheimer was really terribly worried about the fact that the thing was so complicated and so many people knew exactly how it was put together that it would be easy to sabotage. So he thought someone had better baby sit it right up until the moment it was fired. They asked for volunteers and as the youngest guy present, I was selected. I don’t know if it was that I was most expendable or best able to climb a 100-foot tower!

“By then there was a violent thunder and lightning storm. I climbed up there, took along a book, Desert Island Decameron, and climbed the 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!

“All I had was a telephone. I wasn’t equipped to defend myself, I don’t know what I was supposed to do. There were no instructions! The possibility of lightning striking the tower was very much on my mind. But it was very wet and the odds were the tower would act like a giant lightning rod and the electricity would just go straight down to the wet desert. In that case, nothing would have happened. The other case was that it would set the bomb off. And in that case, I’d never know about it! So I read my book.

“I had invented the electrical switching device which came to be used on the bomb. The bomb was itself a sphere of plutonium surrounded by a couple of tons of high explosive, which had to crush that sphere. To do that successfully, the high explosives had to be detonated at 32 points around the sphere. All of those initiations had to take place in a fraction of a millionth of a second.

“My switch was a device for doing that, for firing all the 32 detonators well within a millionth of a second. In fact, it was one of the things many people were most skeptical was going to work. And there was a lot of skepticism about whether the “gadget” would work because so many things had never been done before.

“All the senior scientists who weren’t actually involved in the test had a betting pool. The betting ran from a complete dud to little explosions to middle-sized explosions.  Just a few people were willing to bet that it would produce what it was supposed to produce which was something like 20,000 tons of TNT’s worth. There was a lot of skepticism.

“Later, listening to the countdown, I was in the bomb-proof underground control bunker. I had made a point of sitting right next to the door. There was no question at all of it having gone off. The intensity of the light outside was just unbelievable. And so I dashed out the door and saw this great thing ascending into the sky: a million neon lights, orange, green, purple, rising up into the sky, way up. There was no question that it had gone, and gone big.

“I just heaved a sigh of relief, because if my thing had failed in any way, the whole national supply of plutonium would have been dumped! We also understood that President Truman was waiting in Potsdam for news about this. He was talking with Stalin and thought he had a trump card for Stalin. Turned out of course he didn’t, because the Russians had good spies.”

This excerpt is also included in The Manhattan Project: The Birth of the Atomic Bomb in the Words of Its Creators, Eyewitnesses, and Historians, edited by Cynthia C. Kelly (Black Dog & Leventhal, 2007).