The basic plan, Reiffel explained, was for an intercontinental ballistic missile to be launched from an undisclosed location, travel some 240,000 miles to the moon, and detonate on impact. Various news reports since 1958 have said project leaders considered using an atom bomb the same size as "Little Boy," the bomb that was dropped on Hiroshima, Japan, near the end of World War II.
Reiffel, who was cited for that information in those reports, now says he wasn't in on those discussions.
Contrary to some reports, Reiffel told CNN, the device would not have "blown up" the moon. "Absolutely not. It would have been microscopic, so to speak. It would have been, I think, essentially invisible from the Earth, even with a good telescope."
Reiffel had some brilliant minds on his team. One of them was an up-and-coming graduate student named Carl Sagan. Sagan went on to become one of the world's most renowned astronomers, creating the book and popular TV series "Cosmos."
But after working on the moon program, Reiffel said, Sagan violated security when he mentioned the still-classified project on a job application. "He did formally break the classification status of the project," Reiffel said of Sagan, who subsequently died in 1996.
Sagan's widow, Ann Druyan, told CNN she's not sure if Sagan ever broke the classification, but if he did, she said, it wasn't intentional. "I can't imagine he would have done that knowingly," Druyan said.
By 1959, Project A-119 was drawing more concern than excitement.
"We didn't want to clutter up the natural radioactivities of the moon with additional bits of radioactivity from the Earth," Reiffel said. The project was abandoned.
Project planners also weren't sure of the reliability of the weapons, and feared the public backlash in the U.S. would be significant, Reiffel said.
"It disappeared in the files of the Pentagon," he said of the project. "They come up with what I believe was the right answer."