The Launch

Contrary to the weather predictions, the overnight temperature was 8°F, colder than the shuttle had ever experienced before. In fact, there was a signifi cant accu- mulation of ice on the launchpad from safety showers and fi re hoses that had been left on to prevent the pipes from freezing. It has been estimated that the aft fi eld joint of the right-hand booster was at 28°F.

NASA routinely documents as many aspects of launches as possible. One part of this monitoring is the extensive use of cameras focused on critical areas of the launch vehicle. One of these cameras, looking at the right booster, recorded puffs of smoke coming from the aft fi eld joint immediately after the boosters were ignited. This smoke is thought to have been caused by the steel cylinder of this segment of the booster expanding outward and causing the fi eld joint to rotate. But, due to the extremely cold temperature, the O-ring didn’t seat properly. The heat-resistant putty was also so cold that it didn’t protect the O-rings, and hot gases burned past both O-rings. It was later determined that this blow-by occurred over 70º of arc around the O-rings.

Very quickly, the fi eld joint was sealed again by byproducts of the solid rocket- propellant combustion, which formed a glassy oxide on the joint. This oxide

Table 1.1 Space Shuttle Challenger Accident: Who’s Who

Organizations

NASA The National Aeronautics and Space Administration, responsible for space exploration. The space shuttle is one of NASA’s programs

Marshall Space Flight Center A NASA facility that was in charge of the solid rocket booster

development for the shuttle Morton Thiokol A private company that won the contract from NASA for building

the solid rocket boosters for the shuttle People

NASA

Larry Mulloy Solid Rocket Booster Project manager at Marshall

Morton Thiokol

Roger Boisjoly Arnie Johnson

Engineers who worked on the Solid Rocket Booster Development Program

Joe Kilminster Engineering manager on the Solid Rocket Booster Development Program

Alan McDonald Director of the Solid Rocket Booster Project

Bob Lund Vice president for engineering

Jerald Mason General manager

12 1.8 Case Studies

formation might have averted the disaster had it not been for a very strong wind shear that the shuttle encountered almost one minute into the fl ight. The oxides that were temporarily sealing the fi eld joint were shattered by the stresses caused by the wind shear. The joint was now opened again, and hot gases escaped from the solid booster. Since the booster was attached to the large liquid-fuel booster, the fl ames from the solid-fuel booster blow-by quickly burned through the external tank. The liquid propellant was ignited and the shuttle exploded.