2,060 Minutes: Gordo Cooper and the Last American Solo Flight in Space - Megan Garber - The Atlantic: Ground Control determined that Cooper, given the problems Faith 7 was experiencing, would need to make a manual re-entry back to Earth. The margin of error for angling the craft correctly would be slight: If Cooper came in too steeply, g-forces would crush him; if his trajectory were too shallow, the craft would bounce off the atmosphere and be shot back into space.
But a manual re-entry it was going to have to be. Cooper made his calculations, with help from the ground, based on his knowledge of star patterns. In the process, he disproved the "spam in a can" idea that Chuck Yaeger had famously derided when it came to the Mercury missions: Gordo was much more than simply an experimental body in a NASA-piloted spaceship. He put his education -- and his environs -- to use, drawing lines on Faith 7's window to help him check his orientation against the constellations outside. He shifted from passenger to pilot. "I used my wrist watch for time," Cooper later recalled, "my eyeballs out the window for attitude."