Edited by Chad A. McFarland
Orginal Documents by Hector O. Alvidres and Mark Fischer
December 11, 1994
Introduction
In 1965, a young graduate student in Mathematics working for the summer at the Jet Propulsion Laboratory, in Pasadena, California, proposed a revolutionary idea. He suggested that the gravity of planets could be used to increase the speed of a spacecraft as it passed by them. Michael Minovitch was the first to show that it was not necessary to wait for the development of rocket engines capable of generating the energy required to perform a Hohmann transfer. It was also not necessary to plan a trajectory that took 30 to 40 years, minimum, to get a spacecraft to its target planet, if this planet was beyond Jupiter [1, 104].
Minovitch's idea made it possible to conduct the "Grand Tour", a trip that would take the spacecraft passed four planets, in less than thirteen years. The "Grand Tour", which consisted of fly-bys, passed Jupiter, Saturn, Uranus, and Neptune. To accomplish this feat, the planets would have to line-up in a certain way. The next time the planets would line-up in the formation required to perform the mission occurred in 1976. It would not occur again for another 176 years [1, 105].
During the next few years, the scientists at JPL developed trajectories using Minovitch's gravity assist techniques. The work by the JPL scientists was the basis for the eventual Voyager Project [1, 105].
The Mission
The Events
The "Grand Tour" consisted of flying by four planets, Jupiter, Saturn, Uranus, and Neptune and some of their moons. The trip lasted twelve years, from August 20, 1977, to August 25, 1989. Along the way there were many discoveries and some problems. The sequence of events, shown in Table 1, lists the highlights, including problems, that Voyager came across on its way to Neptune [1, 4].
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