course correction made while en  route to the moon which took the spacecraft off of a free return  trajectory. After the explosion, a second correction was  successfully made to put the spacecraft back on a free return  trajectory. Without this correction, the astronauts still would have  swung around the moon, but would have missed the earth on the return  leg. Although a free return trajectory was agreed upon in the movie,  the engine burn to accomplish this was not portrayed. The astronauts  also made a four