How much faster did Galileo travel as a result of the Venus and Earth flybys?
Starting out from a low Earth orbit, a spacecraft needs to increase its speed by 9 kilometers per second in order to reach Jupiter. Navigators refer to a needed speed change as “delta V,” where “delta” indicates “change” and “V” stands for velocity. Keep in mind, though, that Jupiter’s orbit about the Sun doesn’t lie in the same plane as the Earth’s, so a spacecraft going to Jupiter would have to move out of the plane of the ecliptic. This is known as a “broken-plane” maneuver. Couldn’t the spacecraft go “directly” to Jupiter without having to make the broken-plane maneuver? Yes, but that usually means that the spacecraft needs to be going even faster to begin with — around 11 km/sec. By comparison, Galileo’s Venus-Earth-Earth Gravity Assist (VEEGA) trajectory required that the spacecraft provide a delta-V of only 4.094 km/s to reach Jupiter. Of this total, 4 km/s was provided by the IUS booster; the other .094 km/s of delta-V came from Galileo’s thrusters (the spacecraft also produce
