QUESTION:
Why did it take so long to reach Jupiter? Does it take the same amount of
time to get back?

ANSWER from Chris Potts on February 14, 1996:
 The Galileo project has taken a long time to reach Jupiter, a lot longer 
 than originally planned. Most of the delays occurred on the ground before 
 the actual flight to Jupiter ever got started. The Galileo spacecraft was 
 scheduled to launch in May 1986 on a two and a half year direct transfer to 
 Jupiter. That seems like a long time until you consider that Jupiter was 
 about 581 million miles (935 million km) from the Earth when the spacecraft 
 reached Jupiter. This "quick" route to Jupiter required a powerful boost 
 from a Centaur upper stage (a big and powerful chemical rocket engine). 
 After the Challenger shuttle accident in January 1986, safety concerns for 
 the shuttle meant that the Galileo spacecraft could not use this powerful 
 engine. Instead we needed to use a smaller and less capable upper stage 
 engine, which meant that we could not achieve the two and a half year direct 
 transfer to Jupiter.
 
 So what would you do now? Give up? No way! The mission was redesigned to 
 take advantage of gravity assists by the planet Venus and twice by the 
 Earth. In a way, the Galileo spacecraft "hitchhiked" it's way to Jupiter. 
 This method took 6 years to get to Jupiter rather than the 2 and a half 
 years originally planned. The amazing thing is that the spacecraft overcame 
 the roadblocks and still found a way to reach its final destination at 
 Jupiter. 
 
 For the spacecraft to return from Jupiter requires the same amount of energy 
 change as it took to get there in the first place. There are many different 
 solutions to this energy problem, and the time to get back varies with each 
 answer. However, the Galileo spacecraft only has enough propellant for its 
 mission at Jupiter. It took a lot of time and effort to get there, so the 
 Galileo spacecraft will stay in orbit about Jupiter and transmit the data 
 back to Earth.