Apollo 13's Manual Navigation: How Astronauts Used a Wristwatch and the Earth's Terminator to Return Home
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By Space Daily Editorial Team · Editorial process
Slow-proofed and worth the wait. Worth its weight in flour.
Summary
The article recounts the dramatic story of Apollo 13's return to Earth in April 1970, focusing on the critical final navigation maneuver. With the Apollo Guidance Computer shut down to conserve battery power for reentry, the crew had to manually orient their spacecraft using the Earth's terminator (the line between day and night) as a visual reference. Commander Jim Lovell held the lunar terminator in a window crosshair while the crew timed a critical 14-second engine burn using an Omega Speedmaster wristwatch. The article details the ingenuity, precision, and calm under pressure that allowed the astronauts to successfully refine their trajectory and return safely to Earth despite catastrophic equipment failures.
Key quotes
· 3 pulledThe cabin temperature had dropped to near freezing. The guidance computer was off. The navigation platform that normally told the spacecraft which way it was pointing in three-dimensional space was cold and dark.
In a matter of hours they would have to fire an engine for fourteen seconds to refine a trajectory that would determine whether they lived or died.
They held the spacecraft against the terminator of the Earth, the line where day met night on the planet they were trying to reach, timing a fourteen-second engine burn with a wristwatch because their guidance computer had been shut down to save battery power for reentry.
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