Like all Mercury flights, Faith 7 was designed for fully automatic control, a controversial engineering decision which in many ways reduced the role of an astronaut to that of a passenger, and prompted Chuck Yeager to describe Mercury astronauts as "Spam in a can". Toward the end of the Faith 7 flight there were mission-threatening technical problems. During the 19th orbit, the capsule had a power failure. Carbon dioxide levels began rising, and the cabin temperature jumped to over 100 degrees Fahrenheit (38°C). Cooper turned to his understanding of star patterns, took manual control of the tiny capsule and successfully estimated the correct pitch for re-entry into the atmosphere. Some precision was needed in the calculation, since if the capsule came in too steep, g-forces would be too large, and if its trajectory were too shallow, it would shoot out of the atmosphere again, back into space. Cooper drew lines on the capsule window to help him check his orientation before firing the re-entry rockets. "So I used my wrist watch for time," he later recalled, "my eyeballs out the window for attitude. Then I fired my retrorockets at the right time and landed right by the carrier."