Engineers fired the LM engine to place the craft on a path that would loop around the Moon.
The mission proceeded routinely for the first two days. However, approximately 55 hours into the flight, an explosion occurred in within the Service Module. The blast was caused by a spark igniting damaged wire insulation during a routine "cryo-stir". Apollo 13
The explosion led to a complete redesign of the Service Module’s oxygen tanks. Every piece of wiring was replaced with higher-temperature insulation, and thermostats were moved inside the tank. Later missions (Apollos 14, 15, 16, 17) flew without incident. Engineers fired the LM engine to place the