The Galileo spacecraft was originally designed to launch from the space shuttle and be pushed by a powerful booster rocket toward Jupiter. But just a few months before its scheduled launch, the space shuttle Challenger exploded in midair, causing a full stop to the shuttle program. Safety concerns dictated that the booster rockets to be used on all future shuttle flights had to be much smaller and less powerful than the one to be used by Galileo. Faced with this obstacle, Galileo scientists were forced to recalculate the spacecraft’s trajectory to Jupiter, using several flybys of Venus and Earth as gravitational slingshots and lengthening the journey by years. Finally, on October 18, 1989, Galileo was launched aboard the space shuttle Atlantis, and began its six-year journey to Jupiter.