Recently, we celebrated the 40th anniversary of the space mission, Apollo 11, during which two of the astronauts landed on the Moon - a goal set by President John Kennedy in 1961, and accomplished in July 1969, an amazing achievement in just 8 years.
To me, however, the most heroic part of the Apollo program was the rescue of the Apollo 13 crew after a near-fatal explosion occurred on the Service Module that supplied oxygen and electricity to the whole spacecraft. The 3-man crew moved to the Moon Landing Module (the LM) to be used as a lifeboat.
The Mission Control crew in Houston scrambled to figure out how to get the 3-man crew back to Earth safely. To get the ship onto the "free-return-to-Earth" trajectory, they would have to correct the course that had already been set for the landing on the Moon. Unfortunately, the LM had limited instruments to set up for a "burn" of the maneuvering jets to do the correction.
Maneuvering in space is weird. For example, if you were orbiting Earth in the space shuttle and you wanted to dock with the space station ahead of you, you cannot just speed up toward the target. You actually have to drop into a lower orbit by "slowing down" and let the orbital dynamics carry you ahead of the target, and then you go back to the target's orbit by "speeding up".
Mission Control devised a way by using an alignment telescope on board the LM to check to see if the spacecraft's jets were pointed in the correct direction. At 73:46 hours into the mission, loud cheer erupted inside the LM as well as in Houston that the chosen navigation star (our Sun) was exactly where it should appear in the telescope .
The Mission Control Flight Director, G. Griffin, recalled his exhilaration at that time: "My God, that's the last hurdle - if we can do that, I know we can make it." (quote from here near the end) After they swung around the Moon, they fired the jet for 5 minutes making it possible to make it back to Earth with a splash- down time of 142:54 hours.
If you have watched the movie, "Apollo 13", you know that there was much more going on during the 6 day mission. They managed to rig up filters with tape and plastic to remove carbon dioxide. They had to severely restrict water intake to have enough to last till splashdown. And they had to turn off the heat to save electricity, making it hard to sleep at the freezing temperature of the LM.
People all over the world were watching and praying. Tears of joy were shed and many prayers of thanksgiving went up from all over the Earth at the moment they were safely home. God "who watches over you will not slumber. Indeed, He ... never slumbers nor sleeps." (Ps. 121:3-4)
This article published in the Caroline Progress, 2009. Also "blogged" at BrightMysteries.net.