"Even in hindsight, I would not change one whit of the Voyager experience. Dreams and sweat carried it off. But most of all, its legacy makes us all Earth travelers among the stars." -Charley Kohlhase
In the early days of space exploration, it was quite a feat just to get up and out of Earth's atmosphere. There's are two good, simple reason for that, of course: first, it takes a lot of energy to go up that high...
Image credit: Nathan Bergey of http://psas.pdx.edu/orbit_intro/.
and second, if you don't get your spacecraft moving really fast, you're just going to fall back to Earth once you…