The concept of gravity-propelled interplanetary space travel was first demonstrated by the U.S. space program in the mission of Mariner 10 to Venus and Mercury. Subsequent missions have successfully utilized the gravity-assist technique.

The gravity-assist technique first demonstrated in the mission of Mariner 10 has been used with brilliant success in several subsequent interplanetary missions and was essential to most of the interplanetary missions planned for the remainder of the twentieth century and the early twenty-first century. Gravity assists offer the possibility of much higher payoff per mission, since more targets can be reached with fewer spacecraft and smaller booster rockets. Also, travel time to the targets is greatly reduced. A spacecraft receiving a gravity slingshot from Jupiter and Saturn can reach Uranus in only nine years, whereas without the slingshot, it would take thirty years. Mariner program

Pioneer 10 and Pioneer 11 National Aeronautics and Space Administration;Pioneer program
Pioneer program were launched a year earlier than Mariner 10. Pioneer 10’s encounter with Jupiter Jupiter (planet)
Planets;Jupiter on December 3, 1973, accelerated the spacecraft to a speed that caused it to escape the Sun’s gravity and to exit the solar system. Pioneer 11 caught Jupiter from behind on December 3, 1974, and as it passed across the bow of the moving planet, gravity pulled it into a tight 270 degree turn and accelerated it back toward a point on the opposite side of the Sun, where it plunged past Saturn on September 1, 1979.

In the late 1970’s and early 1980’s, the planets Jupiter, Saturn, Uranus, Neptune, and Pluto (now considered a “dwarf planet”) were spaced about the solar system in a configuration that offered several opportunities for a single spacecraft to visit most of them using the gravity slingshot for retargeting itself at each successive encounter. NASA’s plans to seize this opportunity involved two spacecraft—Voyager 1 Voyager missions and Voyager 2—launched in 1977. Voyager 1’s trajectory took it within 277,000 kilometers of Jupiter on March 5, 1977. There it got a gravity assist to continue to Saturn, arriving on November 13, 1980. Voyager 2 was launched on a slightly different trajectory and passed through the Jovian moon system at a distance of about 650,000 kilometers from the planet on July 9, 1977. Jupiter’s gravity redirected Voyager 2 on a course to Saturn in 1981 and then, with additional gravity slingshots, to Uranus in 1986 and Neptune in 1989.

The flight path for Galileo, Galileo (spacecraft) the next generation of Jupiter probe, was like a complicated aerial trapeze act. Galileo began its journey in late 1989 by going in the opposite direction, to Venus. Venus tossed it back to Earth, and as it streaked past Earth five months later, gravity accelerated it into a long orbit toward the asteroid belt, from which it returned in two years. Passing Earth again, it got a third gravity kick, which was enough to send it on a three-year trip to Jupiter, where it performed thirty-five orbits between 1995 and 2003 that relayed a wealth of information about Jupiter and its moons.

The Ulysses Ulysses (spacecraft) probe was successfully launched in October, 1990, from the International Space Station International Space Station in a joint venture between the European Space Agency and NASA. It became the fastest artificially accelerated object up to that time, a record that was later surpassed by the New Horizons probe, launched in early 2006 and expected to reach Pluto by 2015. On reaching Jupiter in February, 1992, Ulysses was freed from the ecliptic orbit by a successful swing-by maneuver, which allowed it to investigate the polar regions of the Sun. These explorations, which were undertaken in 1994-1995 and 2000-2001, produced new knowledge of the Sun, including the discovery that the Sun’s southern pole has a variable location. Mariner program
National Aeronautics and Space Administration;Mariner program
Venus;Mariner program
Mercury (planet);Mariner program
Planets;Venus
Planets;Mercury
Mariner Venus/Mercury mission

• Cattermole, Peter, and Patrick Moore. Atlas of Venus. New York: Cambridge University Press, 1997. Filled with photography from telescopes and the Mariner, Pioneer Venus, and Magellan spacecrafts, this work provides a complete atlas of Venus and a gazetteer of Venusian place names.
• Chapman, Clark R. Planets of Rock and Ice: From Mercury to the Moons of Saturn. Rev. ed. New York: Charles Scribner’s Sons, 1982. Chapman’s work puts the discoveries made by Mariner 10 and other planetary probes into the context of an emerging understanding of the solar system and the processes that have shaped the planets individually and collectively.
• Cross, Charles A., and Patrick Moore. The Atlas of Mercury. New York: Crown, 1977. Based entirely on the images and data reported by Mariner 10, this is an excellent source for any study of the planet’s surface features. Includes discussion of the history of observations of Mercury, background on the Mariner 10 spacecraft and its mission, and information on the magnetic field and atmosphere of the planet.
• Gatland, Kenneth. The Illustrated Encyclopedia of Space Technology. 2d rev. ed. New York: Crown, 1990. Referenced for its discussion of interplanetary trajectories. Includes color diagrams of the Hohmann transfer orbit and the Voyager 1 and 2 encounter flight paths at Jupiter and Saturn. The discussion of Mariner 10 is superficial.
• Grinspoon, David Harry. Venus Revealed: A New Look Below the Clouds of Our Mysterious Twin Planet. New York: Perseus Books, 1998. Witty, anecdotal work that balances narrative and science. Focuses on the discoveries of the Magellan mission.
• Murray, Bruce C., and Eric Burgess. Flight to Mercury. New York: Columbia University Press, 1976. Comprehensive account of the Mariner 10 mission. Murray, a leading planetologist, was in charge of the Mariner 10 imaging experiments. Burgess has written numerous articles and books on the space program, with emphasis on planetary exploration. Illustrated with more than one hundred photographs.
• Strom, Robert G., and Ann L. Sprague. Exploring Mercury: The Iron Planet. New York: Springer-Praxis, 2003. Detailed history of our changing understanding of the planet closest to the Sun. Includes Mariner 10 data and describes the goals of the MESSENGER mission.
• Von Braun, Wernher, Frederick I. Ordway III, David Dooling, et al. Space Travel: A History. Rev. 4th ed. New York: Harper & Row, 1985. Contains an excellent summary of the history of astronautics and the origin of ideas concerning how to accomplish interplanetary flight. Features a comprehensive bibliography.
• Washburn, Mark. Distant Encounters: The Exploration of Jupiter and Saturn. New York: Harcourt Brace Jovanovich, 1983. Comprehensive discussion of the insights into the nature of Jupiter and Saturn made possible by the Voyager spacecraft, but with several valuable discussions of the trajectories chosen for the missions, including choices that were considered but not adopted. Illustrations are adequate and include drawings of the flight paths of the two spacecraft as they encountered the target planets.

Mariner 9 Is the First Spacecraft to Orbit Another Planet

Pioneer 10 Explores Jupiter and the Outer Planets

Soviet Venera Spacecraft Transmit the First Pictures from the Surface of Venus

Voyagers 1 and 2 Explore the Outer Planets

First Ring Around Jupiter Is Discovered

Astronomers Discover an Unusual Ring System of Planet Neptune

Magellan Probe Maps Venus

Galileo Achieves Orbit Around Jupiter