They stood watch in a missile silo, next to an immense projectile carrying a nine-megaton nuclear warhead, waiting for the call to launch. The crews assigned to Titan Missile silos were standing on the brink of madness we approached during the Cold War.

The Titan Missile Museum outside Green Valley, Arizona, is an eerie reminder of the era of mutually assured destruction, as the United States and Soviet Union aimed even nuclear firepower to annihilate the world many times over.

For us, it carries even more significance because one of Tom’s friends since high school served in a silo near McConnell Air Force Base in Wichita, Kansas.

The design and operation of the sites seem excruciatingly analog in our now-fully computerized world.

The targets were fed into the system from a half-inch, hole-punched paper tape. There were three possible targets for each site, classified to this day and unknown to the crews. The job was to launch, not to know where the missile was headed. The target for the museum’s site probably was somewhere in the Soviet Union, because of the size of the missile and the possible distance it could have traveled.

“This was a big one,” our tour guide said.

The work at the site, so global in its implications, was carried out by an intimate crew of four members. Crews had to pass multiple security points to enter, including a gate to the grounds monitored with radar and several massive, blast-proof doors leading further and further inside the installation, closer and closer to the missile and the command room.

While on duty, each crewmember had monitoring duties and reports to write. One member was to know, at all time, the location of every other person, including additional personnel doing repairs or inspections.

There were many “no lone zones,” where the buddy system was mandatory, for safety and security. Each crewmember was on guard, watching other crewmembers for signs of mental distress. Each officer carried a sidearm, which would only have been of use against another mutinous or unhinged crewmember.

The command room, tiny in comparison to its assigned duties, is suspended on huge springs to rock freely if a nuclear blast happened nearby on the surface, preserving the people and equipment to be able to respond. If the primary antenna were destroyed by a nuclear blast or fallout, secondary antennas could be deployed.

If a call had come, the missile could only have been fired by the commander and second-in-command working in concert. Each would have to insert and turn their individual keys at their posts. The stations, within sight of each other, were too far apart for one person to reach both at the same time. If both keys were not turned at the same time, the missile would not fire.

What must it have been like? On guard, waiting, watching. Knowing that, if called to do your assigned duty, it meant the world was destroyed.

No lone zone remaining.