The Silo

We were twenty five miles south of Tucson, off I-19 the road to Nogales, Mexico.  To the east, we could see a striking range of sharp, ragged edged mountains looming above Green Valley.  To the north were the mountains behind distant Tucson.  A hundred feet below a control room where, from 1963 to 1982, two keys could be turned and 58 seconds later a Titan II missile emerge from a silo under us, a missile which 30 minutes later would deliver a 9 megaton nuclear warhead (500 times the explosive power of the atomic bomb dropped on Hiroshima in 1945) to a target in the Soviet Union.

The THC Son and I were visiting the only intact Titan II missile silo remaining (including an actual Titan II), the rest decommissioned and destroyed even to be inoperable. It was a reminder of the era in which I grew up, in which a nuclear armageddon was always looming, with global destruction minutes away.  In the backs of all of our minds was the notion of a catastrophic end to civilization.  No one foresaw the collapse of the Soviet Union without war.  Thank God we made it through and can visit the silo as the relic of a past era.

Only 54 Titan II's were ever operational.  During the same time frame the U.S. installed about 1,000 Minutemen missiles, each of which was ultimately equipped with three warheads, capable of independent targeting, each of which had only about 1/20 the payload of the Titan II.

The Titan II was installed in three groupings of 18 missiles each, located in Arkansas, Kansas, and the Tucson area.  The 18 Tucson missiles were installed over a region about the size of the state of Rhode Island, controlled operationally from Davis-Monathan Air Force Base on the outskirts of the city.  In the event of a Soviet strike Tucson would have been the target of a massive nuclear attack.

The installation consists of three sections.  You enter through a staircase and go through two sets of massive steel doors in order to enter a 250 walkway that extend from the command center to the missile silo.

The command center sits on massive springs designed to isolate the area from the outside of the chamber.  The reason was so it could survive a nearby nuclear strike.  At the other end of the walkway was the 140 tall missile silo.

The commanding officer and their subordinate each had a launch key for two switches separated by several feet.  Both keys had to be installed and turned in order to start the launch sequence.  From the keys turning to launch only took 58 seconds.  If, in the interval, the President reversed his order to launch there was nothing that could be done to stop the sequence.

The Titan II was fueled by two highly flammable and explosive chemicals, which needed to be delivered and stored separately.  Operation and maintenance was very dangerous.  During its years of service 58 contractors died in accidents, 53 in one incident I was startled to learn about for the first time.  I'm shocked by the scale of this disaster and have been unable to determine whether it was publicly reported at the time.

On August 9, 1965 55 civilian contractors were performing maintenance in a silo near Searcy, Arkansas.  A ruptured line ignited a fire, generating toxic smoke.  Only 2 of the contractors survived.  You can find the recollections of one of the survivors in this 2015 newspaper article.  I also located an extensive incident report which you can find here.  Although the military blamed the accident on sloppy practices by the contractor, this passage jumped out at me:

Project YARD FENCE modifications included the flushing of Hydraulic System 2, located on Level 6 of the sile. The flushing system had been operating at 500 pounds per square inch pressure with a flow of 110 gallons per minute through a pari of hoses leading from the surface hydraulic reservoir and pubp. At the time of the accident, these hoses were arrached to the Hydraulic System 2 panel on Level 2 quadrant 4. The hoses ran within 14 inches of a welding operator who was attaching a triangular stiffener plate to the existing web stiffener on a support for the Motor Control Center 1 platform. The contractor personnel locator board showed the welder to be on Level 3. The location of the weld was in an extremely awkward position that was only accessible working from Level 2, kneeling on the floor, leaning through the guardrails, and reaching around the hydraulic lines to the stiffener plate. A hardhat located on Level 2 at the welding operation site confirmed that the welder had been on Level 2.

The accidental contact of the welding rod to the hose caused the failure of the exterior metal braiding. Thus weakened, the braiding no longer prevented the interior teflon hose from rupturing, spraying, and atomizing the fluid into a mist that permeated Levels 2 and 3. The heat for the just welded fixture or the heat from the electrode touching the metal braiding was significantly higher than the 200 degree fahrenheit flash point of the fluid and served as the ignition point. 

 I've been involved in accident investigations and it looks to me like the root cause was in the design of equipment within the silo, with the proximity of the hydraulic lines to the stiffener plate and in such a configuration as to force the welder to perform his operation in an awkward position with very little tolerance for error. This was an accident waiting to happen. I've been unable to find if the DoD redesigned the configuration after the incident.