The president received his letter in August 1939.
The sender, Albert Einstein, wrote of fission chain reactions in uranium. “Extremely powerful bombs of a new type,” he wrote, were possible. Einstein believed the German government was already researching. Perhaps the U.S. should do the same.
Dan Colibraro was about to enter his senior year at Natrona County High School. His letter wouldn’t come for five more years.
Following plans outlined in the MAUD Report, Franklin Roosevelt and engineer Vannevar Bush made plans to research and develop. By 1942, physicist J. Robert Oppenheimer began fast neutrons research, key to understanding if an explosion could be activated.
Colibraro went to the University of Wyoming, graduated early with a degree in mechanical engineering, worked for Radio Corporation America. His “postcard,” “greetings” from the government arrived in 1944, calling him to the Navy.
Experimental research sites were set up across the country, with primary labs in Los Alamos, N.M., Oak Ridge, Tenn., Richland, Wash., Chalk River, Ontario, Canada.
They called it the Manhattan Project. Colibraro knew nothing of it then.
A college graduate with a scientific background, Colibraro was assigned with a handful of others to serve as an electronic technician. All the rest went to the motorpool or the mess hall. Colibraro felt lucky.
He was sent to the Philippines to build a relay station between Leyte Gulf, Manila, and Samar. When the first message was transmitted successfully, Colibraro was on the next boat home for separation and discharge. He thought it was the last he’d see of war.
Colibraro went to work for the University of California in applied physics at Albuquerque. He heard then of Fat Man and Little Boy.
“When I joined the Project, they had already detonated at Trinity, the test they had put together to see if they had a unit that would explode,” Colibraro said.
“And they did.”
An estimated 130,000 worked on the Manhattan Project in some capacity, drawn from everywhere. Colibraro remembers finding his drafting professor from the University of Wyoming at Sandia Base in Albuquerque. Years after teaching Colibraro, the professor was now again responsible for approving his drawings.
Each was in charge of his own task and kept to his own work. Supervisors pulled all the information together to advance the Project.
“You only ask questions of the fellow next to you, and he would answer you if he decided you needed the information to do your job,” Colibraro said. “In other words, you’re doing a project, you’re doing work at your desk and I can’t get nosy and probe into your work.”
Colibraro’s job was to follow the bomb’s center of gravity. He kept a three-ringed notebook. Each time someone made changes to the Fat Man’s design, Colibraro wrote it down. Even something small, like changing the rivets from steel to aluminum, shifted that center of gravity.
He remembers seeing Fat Man, long enough to fill a good portion of his own living room. “If I were standing, I could touch the top of it.”
Colibraro could communicate with his family, only saying he was doing engineering work, nothing more specific. When engineers had to go somewhere, military police often transferred them.
“You’re going from point A to point B and you have 14 minutes to get there, and if you’re not at point B in 14 minutes, somebody will be looking for you,” Colibraro said. “That’s the kind of security that existed.”
When a bomb had to be transferred to the air base, Colibraro remembers how empty the city was. The military had cleared everybody out.
“There wasn’t a soul on the street for two blocks while we went downtown with this unit, not a soul.
"… Then when we passed back to go to the base, Albuquerque was normal again.”
He grew weary of crunching numbers at a desk. Colibraro was struggling to answer his own question: Do I want to do this for the rest of my life? His sister had entered the convent and his brother, the seminary. He began to consider the same for himself.
A survivor of the Bataan Death March, a priest, invited him to a retreat. It convinced him he had to leave Albuquerque.
“What happens to any person who makes a major decision in their life? You just turn it over and think about it, pray on it," Colibraro explains.
After deciding to enter the seminary, he never considered engineering again. He left the Manhattan Project and was ordained a priest in 1956.
Upon retiring in 1997, Colibraro has taken every math class he could find in the Casper College catalogue. The bookshelves in his home are filled with textbooks. He says math is just a hobby now.
Colibraro saw the Project as work, a job that paid him well to figure out complicated problems. Each design change meant a new challenge in calculating the center of gravity.
The engineers knew they were building an atomic weapon. “Especially when Trinity went off, they realized what was really happening," Colibraro said.
“The only thing they didn’t know was when and who was going to do it.”
More than sixty years later, from his apartment in Casper, Colibraro remembers the Philippines, how the islands were blanketed in trucks, military equipment, everything needed for war.
“And then when that thing went off," Colibraro said, "well that was the end of that.”
It was the engineers' job to research, calculate, make technological progress with the bombs. The decision to use them wasn’t theirs.
“Once Harry Truman gave the permission, why, it’s out of our hands,” Colibraro said. “That’s all.”