Manned Space Flight and Tolerating Risk: Part 1

It should be the primary mission of all fire service leaders to examine our operational systems for unnecessary, tolerated risk and eliminate it where ever we find it. January 28, 1986, dawned bitterly cold at the Kennedy Space Center in Florida. After...


It should be the primary mission of all fire service leaders to examine our operational systems for unnecessary, tolerated risk and eliminate it where ever we find it.

January 28, 1986, dawned bitterly cold at the Kennedy Space Center in Florida. After years of planning and preparation and four delays, the shuttle Challenger (STS-51) was ready to go. The three main shuttle engines were fueled by 1.3 million pounds of liquid oxygen and 226,000 pounds of liquid hydrogen, stored in the huge external fuel tank to which the shuttle was attached.

Despite the three main engines combined 37 million horsepower, more, in fact much more, would be needed to lift Challenger off the pad and into its planned orbit 150 nautical miles above the earth. Attached to the shuttle and the fuel tank were the solid rocket boosters (SRBs) (see Illustration 1). The SRBs, nearly 15 stories high, burned a fuel consisting of aluminum and ammonium perchlorate. When ignited after the three main engines were running at full power, the SRBs added 5.3 million additional pounds of thrust, allowing the spacecraft to rapidly lift off and head downrange. Without the SRBs, the shuttle would simply sit on the pad since they provided 80 percent of the thrust for launch.

The SRBs were not without controversy or concern. Developed by Morton Thiokol, they were partially constructed in a plant in Utah and then shipped by rail to Cape Canaveral for final assembly. These rocket motors consisted of a number of sections, denoted as either field or factory units, based on whether or not they had been completed in Utah or Florida. Because of the size of the finished motor, it was too tall to be shipped as one single piece, so the various sections would be stacked inside the vehicle assembly building not far from launch pad.

The most controversial aspect of the SRB was the joint where a factory section was attached to a field section. The joint system included a tang and clevis connection, (see Illustration 2) a primary and secondary O-ring seal, and 177 steel bolts to hold each section together. On firing, the SRBs would ignite from top to bottom and for less than a second undergo a combination of bending and pressurization forces which placed stress on the joints. During this very brief period hot exhaust gases from the burning rocket fuel could theoretically leak through the joints and damage or destroy the SRB. Such an occurrence would constitute, in the language of NASA, a "criticality one" event because there was no backup or redundancy for that system and a loss of it could result in loss of the shuttle. From a crew safety standpoint, this would clearly be an unacceptable risk.

A fire service analogy of a criticality one event could be the acceptance and use of an aerial device, fire pump or personal protective equipment component where a failure during routine use would likely result in the injury or death of personnel. Other relevant examples include systems of operation, such as staffing, procedures, training and behavioral norms. When a failure occurs, a death, injury or exposure results.

Meeting Expectations
The space shuttle system was (and is) expensive to operate and maintain. In order to win approval for initial and subsequent funding, a clearly skeptical Congress had to be convinced by NASA and other interested parties that it was efficient, economical and widely usable for business purposes. In order to fulfill this promise the shuttle would have to evolve from a system that was effectively experimental to an operational mode. It would have to become a "quasi-competitive business operation." Inherent in that move would be a system that was reliable, redundant and safe. The shuttle was none of these things.

How often do public safety professionals market fire and EMS service models that are not reliable, safe or effectively operational with economic arguments that are false or misleading? Understaffed companies, inadequate communications structures, poorly trained personnel and substandard response equipment are often the outgrowth of such arguments with disastrous results for firefighters and citizens.

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