The National Aeronautics and Space Administration, better known as NASA, said in June that it had found the "smoking gun" that caused the space shuttle Columbia to break apart as it re-entered the Earth's atmosphere on Feb. 1: a piece of foam that had peeled off the external fuel tank and struck the shuttle's wing 1 minute and 22 seconds after liftoff. But many experts looking at the tragedy that killed seven astronauts say there is a deeper cause. They say that the metaphorical smoking gun should be painted green. Because of demands that the agency help to front for...