Without power, the site lacked air-conditioning, and as the temperature in the silo rose, so did the pressure in the missile’s oxidizer tanks. Nitrogen tetroxide expanded in the heat; its boiling point was only 70 degrees Fahrenheit. By five o’clock that evening, the temperature in the silo was 78 degrees and rising. Opening the silo door would help cool the missile and vent the smoke—but the door couldn’t be opened without electrical power.
