In 1970, after an explosion aboard Apollo 13 aborted its lunar landing, Armstrong was part of Edgar Cortright's investigation of the mission. He produced a detailed chronology of the flight. He determined that a 28-volt thermostat switch in an oxygen tank, which was supposed to have been replaced with a 65-volt version, led to the explosion. Cortright's report recommended the entire tank be redesigned at a cost of $40million. Many NASA managers, including Armstrong, opposed the recommendation, since only the thermostat switch had caused the problem. They lost the argument and the tanks were redesigned.