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The sign accompanying the Q-ball. It reads

The Saturn's "Q-Ball"

Above is displayed the component that made up the end tip of the monsterous [sic] Saturn V moon rocket. Known as the "Q-Ball," this small nose cone tipped the end of the launch escape tower of the Apollo spacecraft, and was located more than 36 stories (363 feet) above the base of the rocket.

The Q-ball did more than just create the aerodynamic spike that allowed the Saturn V to punch through the Earth's atmosphere during launch. It also contained critical sensors and instruments to tell the launch vehicle's guidance system where it was going and how stable it was.

During launch, as the Saturn V began its climb through the atmosphere, eight small static ports ringing the side of the Q-ball measured the pressure of the air that built up at the time of the accelerating rocket. By determining the slight differences in pressures in each opening, the rocket's guidance system was able to determine if the tip of the giant rocket was tipping by as little as 1/8 inch. The flight computer would then send instructions to move the huge first stage engines firing more than 36 stories below to gimbal a fraction of an inch to bring the rocket back on course.

Saturn V "Q-Ball" courtesy of: Smithsonian Institution's National Air & Space Museum

The Q-ball was more properly part of the Apollo spacecraft than the Saturn V, and it was present on Apollo spacecraft launched on Saturn I and Saturn IB launch vehicles as well.