National Aeronautics and Space Administration

Glenn Research Center

Dr. Matt Melis

The Columbia Accident Investigation and NASA’s Return to Flight
Tuesday June 10, 2008 – NASA Glenn Research Center
 

Dr. Matt Melis told us that for the past five years, he and his fellow colleagues at the Glenn Research Center Ballistics Impact Lab have worked to determine what happened to the Space Shuttle Columbia. He started out by telling us about the different parts of the Shuttle which are the Orbiter, the External Fuel Tank, and the Solid Rocket Boosters. He showed us pictures of all of these parts as they are being built, shipped, and assembled to give us an idea of their size, dimensions, and complexity. Melis told us about the NASA Michoud Assembly Facility, which not that many people know about, whose chief purpose is to build the External Tanks for the Shuttle. He explained that every single thing that is on the shuttle is a necessary component, because for every extra pound that is added to the shuttle, four more pounds of fuel are needed to get it into orbit.

Once Melis had given us a good overview of the shuttle, he went on to describe what course of events lead to the Columbia Accident. Columbia’s left-wing leading edge was impacted with a piece of foam that broke off the External Fuel Tank traveling at a speed of Mach 2.46. This was caught on tape, and the officials at NASA were aware of it. However, they decided that since the foam, which was a BX 250 insulating foam, was much softer than the Reinforced Carbon-Carbon (RCC) material that make up the panels of the leading edge; no damage was probably done, and that the orbiter was safe for reentry.

After the Columbia catastrophe, a team of 5,000 NASA employees were assembled to go out and recover as much of the shuttle as they could find. It took them three months to comb the entire area. In the end, they were able to recover about 38% of it. All of the pieces were shipped to a NASA facility, and were then puzzled back together so that they could try to figure out exactly what happened during reentry. What they found was metal slag on one of the leading edge panels. Slag is metal that has vaporized and then re-condensed. What they were able to conclude from the reconstruction of the pieces of the shuttle was that heat was able to get through and melt the RCC of one of the panels on the leading edge of the orbiter. This could only be the case if there was some sort of crack or hole in this panel. So, the task of the Ballistics Impact Lab was to see if this piece of foam that they saw flying by the leading edge of the orbiter could have cracked or tore a hole in the RCC.

To do this, Melis and his team first ran a number of small scale tests by projecting a small piece of foam at a piece of RCC material to figure out how the materials behave on impact. Then they conducted a full scale test. They built a leading edge just like the ones on the shuttles, and they fired a piece of BX-250 foam, of the same size and dimensions as the one that fell off the External Fuel Tank on Columbia, at the leading edge full scale model at a speed of Mach 2.46 so that it would just glance the leading edge; just like they saw it happen in the footage of Columbia’s take off. Melis played us a short clip of this full scale test, and in the clip, all of the engineers and technicians that were at the test site watching the test gasped in awe as the foam tore a hole about 16 inches in diameter in the RCC panel as it glanced off of it.

This test closed the Columbia case, and demonstrated that intuition will not always give one the right answer, and that major decisions about the safety of the shuttle should always be backed up with scientific proof. Before NASA’s return to flight on July 26, 2005, Melis said that they used what they had learned from their ballistics impact testing to make the shuttle safer by correcting design flaws and adding additional safety and analysis procedures to the shuttle missions.