Investigators believe that during Columbia's launch in January 2003, insulating foam from the bipod broke off the external tank during liftoff. This damaged the orbiter's left wing and created a hole, through which searing gases entered during the shuttle's reentry, leading to its destruction. One of the recommendations by the Columbia Accident Investigation Board was the elimination of foam and its replacement with heaters in order to minimize potential debris. The Discovery shuttle used this heater modification, using heaters supplied by Pittsburgh-based Chromalox, in the first flight since the loss of Columbia.
Qualification testing on the Chromalox heaters to be used on the new Discovery bipod was completed in September 2004. The anti-icing cartridge heaters are mounted in a copper plate between the bipod fitting and the phenolic isolator at the bipod attachment assemblies to the forward orbiter attachment point. The function of the heaters during the launch phase is to maintain the web area of the bipod attachment fitting above 32oF (0oC) to prevent the formation of ice that could dislodge in flight and damage the orbiter.
The heater used was a 0.25" diameter cartridge design, hermetically sealed with a flange fitting, and 15" of Kapton-wrapped, shielded cable, which is brazed to pins and potted to provide a moisture barrier to the attachment point of cable.
“This is a fix that really gets to the root of the technical problems that caused the loss of Columbia,” said Michael Kostelnik, NASA deputy associate administrator. “By eliminating this debris source as well as potential debris from other areas, we are making the shuttle a safer spacecraft.”
For more information, go to www.chromalox.com.