“Unsymmetrical dimethylhydrazine” is a toxic compound used in making rocket fuel. Bob Darcangelo is no rocket scientist, but he can recite the name of the compound without a stutter.

Darcangelo, a 71-year-old who lives in Green Valley, has spent more than 1,700 hours volunteering at the Titan Missile Museum in Sahuarita. He was a crew commander at this site when it was still active in the 1960s. He said he has a master’s degree in history, so working at the museum “…fits my vein of history.”

As a crew commander, he was constantly training crews and monitoring equipment. “We didn’t do anything from memory,” he said. “We had to do it right.”

The museum, also known as Titan II ICBM Site 571-7, was declared a National Historic Landmark in 1994 and is kept as an artifact of 20th century technology. The single silo was operational in 1963 and decommissioned in 1982, when other Titan II missiles in the United States were decommissioned after a change in policy under President Ronald Reagan.

Today, the museum is run almost entirely by volunteers, some of whom have clocked in more than 3,000 hours. Admission charge to the museum varies depending upon the tour type and age of the visitor.

“It’s a part of U.S. history that’s good for people to know,” museum volunteer Jerry Geise said. Geise, 72, a retired chemical engineer who lives in Tucson, also volunteers at Kitt Peak and the Steward Observatory Mirror Lab. He has volunteered about 500 hours at the Titan Missile Museum.

In the tour, visitors can observe the lone missile in its launch duct. They also can walk though the underground missile complex and see the launch control center.

Next year marks the 20th anniversary of the dissolution of the Soviet Union and the end of the Cold War, and volunteers at the museum work hard to teach youngsters not only about the missile but also about worldwide tensions during the era.

“We specifically try to avoid any political influence,” volunteer Sam Densler said. The emphasis is on math and science in the children’s programs, he added.

Densler was born in New Jersey in 1940 and worked with aerospace and defense technology company Northrop Grumman in Maryland for more than 25 years before retiring and moving to Sahuarita. He is now one of the educators at the museum who teaches children the principles of rocket flight and engages them in activities such as launching seltzer rockets. He has volunteered over 2,000 hours at the museum.

The museum also offers special tours with former crew members at the missile site, including Darcangelo.

A flight of 55 steps leads down to the underground complex.

There are still signs instructing to call crew commander if the blast door fails to operate. Darcangelo would have had to figure out how to open the massive concrete and steel doors, each of which weighs three tons.

In the room with the key to launch the missile, Darcangelo gives a detailed explanation of the long and detailed process. Even when visitors expected the alarms to go off in the process, the loud blaring noises and flashing little lights caught them off guard.

During the Cold War, workers had to regularly monitor and maintain the site. They worked 24-hour shifts, making sure that the missile was properly functioning and ready to launch at any time. “They had to inspect every little detail,” Geise said.

Most of the underground silo was a “no-lone zone,” which meant everyone had to work at least in pairs for safety and security reasons.

Above the “no-lone zone” was the break room with a kitchen, beds and a shower. “Nobody ever took a shower here,” Darcangelo said. Everybody was busy and the silo was kept at a constant cool 62 degrees, plus or minus 2 degrees, to keep the rocket chemicals stable.

Darcangelo said that he once received a phone call when the missile site was active. The caller said “we dropped a wrench,” Darcangelo added. The wrench had a handle that was about 2 feet long and it was dropped in an elevated part of the missile silo.

The wrench disconnected the umbilical cords, which are used to monitor the missile and signal it to launch, but, luckily, the wrench was dropped straight down the launch duct and did not contact the missile itself, Darcangelo said.

Security was extremely strict with the active missile. For example, when the electricity meter reader came for a reading, workers were sent out to inspect him and make sure he was not a security breach. “They patted him and everything,” Darcangleo said.

“Even squirrels and snakes” would set off the surface alarms until they adjusted the sensitivity, Geise said.

Aside from the little scares, “…most of the time, it was pretty boring,” Darcangelo said. But the dullness was much preferred to a nuclear battle, he added.