On April 13, 1970, Apollo 13’s oxygen tank 2 famously ruptured, taking a piece of the cylindrical service module with it and damaging oxygen tank 1 in the process. The precious gas vented out into space and the crew was left in a crippled spacecraft with only the command module’s reentry batteries for power. Luckily, they were on their outbound journey to the Moon and were able to stretch the lunar module's consumables and use this small spacecraft as a lifeboat. The explosion was a rare combination of human error and flawed design. From the moment it was installed in Apollo 13’s service module, oxygen tank 2 was a ticking time bomb.