Gene Kranz (foreground, back to camera), an Apollo 13 Flight Director, watches Apollo 13 astronaut and lunar module pilot Fred Haise onscreen in the Mission Operations Control Room, during the mission's fourth television transmission on the evening of April 13, 1970.
Shortly after the transmission, an explosion occurred that ended any hope of a lunar landing and jeopardized the lives of the crew.
The Apollo 13 malfunction was caused by an explosion and rupture of oxygen tank no. 2 in the service module. The explosion ruptured a line or damaged a valve in the no. 1 oxygen tank, causing it to lose oxygen rapidly. The service module bay no.4 cover was blown off. All oxygen stores were lost within about 3 hours, along with loss of water, electrical power, and use of the propulsion system.
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More information: en.wikipedia.org/wiki/Apollo_13