What you'll learn from Chicago author Robert Kurson's book Rocket Men, about the Apollo 8 mission, out April 3.

1The farthest into space any man had traveled prior to the mission was 853 miles—just 0.4 percent of the distance to the moon.

2The moon itself was the main safety net for the mission. Apollo 8 had to swing close enough to the orb to get caught in its gravitational pull, which would then catapult the ship back toward Earth if the engine failed.

3It cost an additional $45,000 to make commander Frank Borman’s bubble-shaped helmet because he had such a large head.

4Astronaut Jim Lovell accidentally inflated his life vest 45 minutes after takeoff, but deflating it into the cabin would have created unsafe levels of carbon dioxide. The solution: Empty it through the toilet valve that released waste into space.

5It took about 36 minutes for the ship to pass behind the the moon—only one second off NASA’s estimates.