Powell and Plumb were missile repairmen. They belonged to Propellant Transfer System (PTS) Team A of the 308th Strategic Missile Wing, whose headquarters was about an hour or so away at Little Rock Air Force Base. They'd been called to the site that day because a warning light had signaled that pressure was low in the stage 2 oxidizer tank. If the pressure fell too low, the oxidizer wouldn't flow smoothly to the engine. A "low light" could mean a serious problem—a rupture, a leak. But it was far more likely that a slight change in temperature had lowered the pressure inside the tank. Air-conditioning units in the silo were supposed to keep the missile cooled to about 60 degrees. If Powell and Plumb didn't find any leaks, they'd simply unscrew the cap on the oxidizer tank and add more nitrogen gas. The nitrogen maintained a steady pressure on the liquid inside, pushing downward. It was a simple, mundane task, like putting air in your tires before a long drive.
Powell had served on a PTS team for almost three years and knew the hazards of the Titan II. During his first visit to a launch complex, an oxidizer leak created a toxic cloud that shut down operations for three days. He was 21 years old, a proud "hillbilly" from rural Kentucky who loved the job and planned to reenlist at the end of the year.
Airman Plumb, 19, wasn't qualified to do this sort of maintenance or to handle these propellants. Accompanying Powell was his on-the-job training.
Plumb had been with the 308th for just nine months. He wasn't qualified to do this sort of missile maintenance or to handle these propellants. Accompanying Powell and watching everything that Powell did was considered Plumb's "OJT," his on-the-job training. Plumb was 19, raised in suburban Detroit.
Although an oxidizer low light wasn't unusual, Air Force technical orders required that both men wear Category I protective gear when entering the silo to investigate it. "Going Category I" meant getting into a Rocket Fuel Handler's Clothing Outfit (RFHCO)—an airtight, liquidproof, vaporproof, fire-resistant combination of gear designed to protect them from the oxidizer and the fuel. The men called it a "ref-co."
A RFHCO looked like a space suit from an early-1960s science fiction movie. It had a white detachable bubble helmet with a voice-actuated radio and a transparent Plexiglas face screen. The suit was off white, with a long zipper extending from the top of the left shoulder, across the torso, to the right knee. You stepped into the RFHCO and wore long johns underneath it. The black vinyl gloves and boots weren't attached, so the RFHCO had roll-down cuffs at the wrists and the ankles to maintain a tight seal. The suit weighed about 22 pounds. The RFHCO backpack weighed an additional 35 and carried about an hour's worth of air. The outfit was heavy and cumbersome. It could be hot, sticky, and uncomfortable, especially when worn outside the air-conditioned silo. But it could also save your life.
The stage 2 oxidizer pressure cap was about two-thirds of the way up the missile. In order to reach it, Powell and Plumb had to walk across a retractable steel platform that extended from the silo wall. The tall, hollow cylinder in which the Titan II stood was enclosed by another concrete cylinder with nine interior levels, housing equipment. Level 1 was near the top of the missile; level 9 about 20 feet beneath the missile. The steel work platforms folded down from the walls hydraulically. Each one had a stiff rubber edge to prevent the Titan II from getting scratched, while keeping the gap between the platform and the missile as narrow as possible.
The thrust mount was attached to the walls by large springs, so that the Titan II could ride out a nuclear attack.
The airmen entered the launch duct at level 2. Far above their heads was a concrete silo door. It was supposed to protect the missile from the wind and the rain and the effects of a nuclear weapon detonating nearby. The door weighed 740 tons. Far below the men, beneath the Titan II, a concrete flame deflector shaped like a W was installed to guide the hot gases downward at launch, then upward through exhaust vents and out of the silo. The missile stood on a thrust mount, a steel ring at level 7 that weighed about 26,000 pounds. The thrust mount was attached to the walls by large springs, so that the Titan II could ride out a nuclear attack, bounce instead of break, and then take off.
In addition to the W-53 warhead and a few hundred thousand pounds of propellants, many other things in the silo could detonate. Electro-explosive devices were used after ignition to free the missile from the thrust mount, separate stage 2 from stage 1, release the nose cone. The missile also housed numerous small rocket engines with flammable solid fuel to adjust the pitch and the roll of the warhead midflight. The Titan II launch complex had been carefully designed to minimize the risk of having so many flammables and explosives within it. Fire detectors, fire suppression systems, toxic vapor detectors, and decontamination showers were scattered throughout the nine levels of the silo. These safety devices were bolstered by strict safety rules.
Plumb watched the nine-pound socket slip through the narrow gap between the platform and the missile.
Whenever a PTS team member put on a RFHCO, he had to be accompanied by someone else in a RFHCO, with two other people waiting as backup, ready to put on their suits. Every Category I task had to be performed according to a standardized checklist, which the team chief usually read aloud over the radio communications network. There was one way to do everything—and only one way. Technical Order 21M-LGM25C-2-12, Figure 2-18, told Powell and Plumb exactly what to do as they stood on the platform near the missile.
"Step four," the PTS team chief said over the radio. "Remove airborne disconnect pressure cap."
"Roger," Powell replied.
"Caution. When complying with step four, do not exceed 160 foot-pounds of torque. Overtorquing may result in damage to the missile skin."
As Powell used a socket wrench to unscrew the pressure cap, the socket fell off. It struck the platform and bounced. Powell grabbed for it but missed.
Plumb watched the nine-pound socket slip through the narrow gap between the platform and the missile, fall about 70 feet, hit the thrust mount, and then ricochet off the Titan II. It seemed to happen in slow motion. A moment later, fuel sprayed from a hole in the missile like water from a garden hose.
"Oh man," Plumb thought. "This is not good."
Click here to read our interview with Eric Schlosser.
Correction: This article originally stated that only one of the B-52 crew members ejected safely; in fact, five of the eight men survived.