When Titan II Missile Complex 571-7 was in operation, it was barely noticeable. A couple of antennas and some metal poles poked through the Arizona desert floor above a large concrete slab, a wooden deck, and a few other odds and ends, all of it surrounded by a chain-link fence. But beneath this seeming disarray an intercontinental ballistic missile (ICBM) waited in its silo, and a hidden crew ran an underground control center.

Now Complex 571-7, located twentyfive miles south of Tucson, Arizona, has become the Titan Missile Museum, the only ICBM complex open to the public. A small visitors’ center has been added, along with displays of a rocket engine, a missile re-entry vehicle, a helicopter, and a few missile maintenance vehicles. Otherwise the complex looks much as it did when it served in the nation’s nuclear arsenal. (For more on how that arsenal came to be, see “Heating Up the Cold War,” page 20.)

Titan II was the largest ICBM the United States ever developed, and it carried the most powerful single warhead. It was deployed in three groups of eighteen, at Davis-Monthan Air Force Base (AFB) in Tucson, Little Rock AFB in Jacksonville, Arkansas, and McConnell AFB in Wichita, Kansas. The Titan II missile first went on alert in 1963, and the last one was phased out in 1987. The Air Force leased Complex 571-7 to a nonprofit organization for a museum; the other fifty-three complexes were dismantled.

All the Titan II complexes were nearly identical, so visitors to Complex 571-7 see what any other one was like. It mainly consists of three sections: the missile silo, the control center, and an entryway known as the access portal and blast-lock area. Passages connected the three sections, which were built mainly of reinforced concrete.

Visitors to Complex 571-7 start the one-hour tour on the surface (or “topside,” as the missile crew would say). A guide points out two platforms, called hardstands, from which technicians pumped propellants out of tank trucks into the missile underground. The two propellants spontaneously burned when they came in contact with each other, and both were extremely toxic. A tiny amount would blister the skin; the vapors turned into nitric acid in the lungs. The technicians who handled them wore airtight suits with independent air supplies.

The stage-one rocket would burn nearly 25,000 gallons of propellant in just two and a half minutes, to propel the missile about 45 miles high. Stage two would then fire for about three minutes, expending 6,100 gallons of propellant and lifting the missile to 189 miles. After sloughing off the two stages, the unpowered re-entry vehicle would continue on its trajectory to more than 500 miles above the Earth’s surface before falling to its target. Titan II flew at a top speed of 17,000 miles per hour and had a range of up to 6,000 miles, a distance it could cover in about 35 minutes.

In the middle of the 3.3-acre complex sits the silo door, a 758-ton slab of reinforced concrete and steel. Powered by a hydraulic motor, it rolled on rails, opening in about 20 seconds. The edges perpendicular to the rails are beveled and function the same way cowcatchers do on locomotives. They would push away the rocks and dirt thrown up by a Soviet first strike. The door could still operate while piled six feet high with debris.

The museum’s silo door is permanently blocked halfway open, and a raised viewing platform surrounds the silo opening. Visitors look down through a window into the silo. It’s something of a satellite’s-eye view, because satellites verifying missile treaties look through the same opening to make sure there’s a large hole in the re-entry vehicle, which sits atop the missile. The hole shows that the vehicle is unusable, and the blocked door renders the silo inoperable.

The re-entry vehicle is cone-shaped, about 14 feet high and 8 feet in diameter at its base. It contained the warhead (the one on display has no warhead, of course) along with pressure indicators, electrical arming devices, and a couple of small batteries.

The silo is 146 feet deep and 55 feet across. Within it the missile looms up toward the window like a giant upright cigar. It stands 110 feet tall and 10 feet in diameter. The missile’s shell is nothing more than a big fuel container, made of aluminum and, in places, no thicker than a dime. Empty, the missile weighs 7.5 tons. Filled with propellant, it weighed 165 tons.

The hole in the silo in which the missile stands is called the launch duct. Looking down, visitors see several work platforms; thick tangles of black wiring known as umbilicals, which plugged the control room into the missile; and toward the bottom, a metal collar known as the thrust mount ring. The missile was attached to the thrust mount ring by bolts; they would explode away when the engine achieved 77 percent thrust.

Rectangular panels line the duct. They were designed to absorb the tremendous vibrations generated at launch. Four nozzles in the duct wall would shoot 4,500 gallons of water at the firing engine in about thirty seconds, cooling it and further absorbing vibrations. Excess water and steam escaped through vents in the bottom of the launch duct.

To enter the silo and control center, visitors descend a steel stairway in the access port to about 35 feet underground. They pass through two steel doors on the stairway, part of the complex’s elaborate security setup. The missile crew controlled the doors electronically from the control center and watched the stairway on a monitor. They could trap an intruder between the doors and then call base police.

At the bottom of the stairs is the blast-lock area, the real entryway to the underground complex. Two 3-ton steel-and-concrete doors secure it. When the doors were closed, they could withstand any nuclear blast except a direct hit. Beyond the second door a long passageway to the right leads to the missile silo, and a short passageway to the left leads to the control center. Two additional blast-lock doors secure entry to these passages.

The silo contains a legion of compressors and motors; when the complex was operational, it was a very noisy place. The most important job they had was to filter and cool air. The temperature in the launch duct was kept at 60 degrees Fahrenheit. If it got much warmer, the propellants became unstable. In addition to refrigeration units, the silo contains the complex’s back-up power source: a sixcylinder diesel engine about the size of a compact car. (The main power source was the local utility company.) The floors in the control center are suspended from eight huge springs attached to a dome, so in the event of an earthquake or nuclear explosion, they will bounce around instead of breaking. Critical pieces of equipment in the silo are attached by springs to the walls and ceilings; the thrust mount ring is attached to the duct wall by four huge shock absorbers.

The control tower has three levels: living quarters for the four-person crew on top, an equipment storage area on the bottom, and in the middle the control room, which is the complex’s nerve center. Life in the complex was quiet and routine—many crew members took correspondence courses- yet tension was ever-present. The crew maintained vigilance for the moment of terror that might end the world, but there was a more immediate danger: the propellants could demolish Complex 571-7 if not handled and stored properly.

If the call to action ever came, it would arrive by coded messages via radio links with Strategic Air Command Headquarters in Omaha, Nebraska, and the 15th Air Force Headquarters Command Post in Riverside, California. The commander and deputy commander would separately copy their messages and then compare them to see if they matched.

If they did, the officers would open a red metal box known as the Emergency War Order (EWO) safe. Inside were a decoder and a code to verify that the message received over the radio was an authentic order from the President, and to instruct the crew when to launch and at which of three predetermined targets to aim the missile. The EWO safe also contained the missile ignition keys—one for each officer—and a code to unlock a butterfly valve, which would allow the oxidizer to flow into the stage-one engine.

At the appointed time the officers simultaneously turned their keys (they were placed too far apart for one person to turn both). Fifty-six seconds later the missile left the silo. Once it was launched, the crew could not communicate with it, change its course, recall it, or destroy it. Like a bullet, the missile flew on its own.