Comments about technological history, system fractures, and human resilience from James R. Chiles, the author of Inviting Disaster: Lessons from the Edge of Technology (HarperBusiness 2001; paperback 2002) and The God Machine: From Boomerangs to Black Hawks, the Story of the Helicopter (Random House, 2007, paperback 2008)

Monday, July 30, 2012

Big Bay Bang: In a Long Line of Accidental Pyrotechnics

As a writer in history and technology I try to group current events with some class of earlier, comparable mishaps. In this case the class is the "inadvertent and instantaneous firing of multiple pyrotechnics."

On the evening of July 4, a half million fireworks-fans were treated to a spectacular show over San Diego Bay, all five locations (four barges and a pier) launching their entire arsenal of 7,000 pyrotechnics in a few seconds, rather than 15 minutes (Photo Ben Baller, AP):
Each pyro device (typically launched out of a short, vertical mortar tube) is ignited from a central control. The control closes circuits according to a programmed chronology, sending an electrical charge to an electric match that produces a brief flame inside a lifting charge. One variety of the electric match is the nichrome wire that my brothers and I used as kids, when launching our Estes rockets.

The contractor, Garden State Fireworks, later released a three-page, not particularly instructive, paper that lays blame on the interaction between a primary and backup computer program. Many details are left unexplained, but we can gather that a typical Big Bang show is commanded over a continuous radio link transmitted from a central point, because the five launching locations are scattered across 14 miles of harbor. 

The local firing computer on each barge was to have on hand a stored ignition sequence so that it could continue running its part of the choreographed show, in case the radio link were broken.

The show's radio-command link was supposed to start running five minutes before the first launch, so that operators stationed at each local computer could verify that all systems were nominal. And the radio transmission did begin at this time. Normally the program runs "in the dark," meaning that even though the sequence has begun, there's no visible result except on computer displays.

Not this time. Garden State's mea culpa paper says that the backup program somehow got crossways with the main program, and the combination immediately instructed each computer to send firing signals to all the electric matches at once, somehow deleting the planned interval. 

So this year's aptly-titled Big Bay Boom show started five minutes ahead of schedule and ended soon thereafter. Despite the early start and the intensity of the fusillade, we're told that none of the fireworkers were injured, having sought out armored shelters nearby. We can hope that they were all wearing hearing protection at the time. 

Reading about this reminded me of an earlier but more sobering simul-blast, 53 years earlier, also in early July. The location was Chennault AFB in Louisiana, where a B-47E StratoJet bomber, No. 53-4212, was being prepared to join other planes already on the flight line. All were to be ready for a quick takeoff in case of nuclear war

Date: July 6, 1959. A single H-bomb (probably a Mark-15) was on board and No. 4212 was fully fueled. Attached to the rear of the fuselage were dozens of solid-fueled takeoff-assist rockets, often abbreviated JATO bottles. Each would provide a thousand pounds of thrust upon ignition. Here's a B-47 photo that will give an idea of the JATO bottles' placement on the underside.
Here's an old movie of a B-47 taking off with the help of JATOs:
As the B-47's pilot stood on the ladder giving directions, somehow an airman's electrical checks ignited the entire rack of 30 JATO bottles. (I am guessing the root cause can be traced to a continuity check to verify the bridgewires, but if so, something went terribly wrong because a proper continuity-checking device uses voltages far below the energy needed for ignition.)

All 30 rockets belching flame and smoke, the 100-ton airplane lumbered over its chocks and accelerated toward the flight line. A wing broke off, spilling fuel. The navigator jumped out, his clothes on fire, but survived. The pilot tried to jump free but was killed when the airplane rolled over him. After a few hundred feet the plane lurched off the pavement and crashed in a fireball.

It was a lot scarier than the usual one-sentence mention to be found in the history of the weapons program, revealing no more than a "ground fire in a B-47 at Chennault AFB consumed one nuclear weapon." So scary, in fact, that some base workers heard the emergency sirens, saw the flames, jumped in their cars, and didn't slow down till they crossed the Texas border. 

JATO demonstrations are still a highlight at many military air shows, pushing C-130s into steep climbouts. A large number of JATOs figured in a daring plan to land a C-130 in a Tehran stadium during the Iranian hostage crisis, and take off again. But the prototype crashed in tests and the entire rescue plan fell through for other reasons.

1 comment:

  1. It's also disturbing that only one US nuclear weapons accidents have been reported since 1988. So, has it been very safe, or are there other accidents still hidden?