After man first set foot on the moon, the Apollo program went on to several more landings, but none was more dramatic than the Apollo 13 mission. The words "Houston, we have a problem..." have become part of the language since an explosion onboard the Lunar Command Module rocketed the astronauts 200,000 miles into space. Walter Cronkite is there, as ground control and the astronauts struggle heroically and successfully to return the craft to safety.