The navigation technique that brought Apollo 13 home in April 1970 — holding the spacecraft steady against the line where day meets night on Earth and timing a fourteen-second engine burn with a wristwatch — was later made mandatory training for every subsequent Apollo crew

The navigation technique that brought Apollo 13 home in April 1970 — holding the spacecraft steady against the line where day meets night on Earth and timing a fourteen-second engine burn with a wristwatch — was later made mandatory training for every subsequent Apollo crew

Late on 17 April 1970, Apollo 13 was already close enough to Earth for the planet to fill the lunar module’s alignment sight. The crippled spacecraft still needed one final course correction to place it safely in the atmosphere’s narrow entry corridor. Its main guidance system was powered down, stars were difficult to see through a cloud of vented debris, and conserving electrical power remained essential. The solution was a short, manually cont…