A spaceflight technique in which a probe flies close to a planet or moon, using the body's gravity and orbital motion to change the probe's speed and trajectory without expending propellant. The technique made possible missions such as Voyager's grand tour of the outer planets.
Facts
Concept Domain Formulated YearYear Michael Minovitch's trajectory calculations at JPL established the technique's practicality for interplanetary flight. Proposed ByFirst proposed theoretically by Yuri Kondratyuk in a paper written 1918 to 1919 and published in 1938; the maneuver was first used in practice by the Soviet Luna 3 mission in 1959. 1 Connections
Associated With
Source Wikipedia (space and spaceflight articles)
Source Wikipedia (space and spaceflight articles)
Source Wikipedia (space and spaceflight articles)
Source Wikipedia (space and spaceflight articles)
MESSENGER, Spacecraft MESSENGER used flybys of Earth and Venus and Mercury as gravity assists
Parker Solar Probe uses repeated Venus gravity assists to lower its perihelion
Source Wikipedia (space and spaceflight articles)
Repeated gravity assists made the Voyager grand tour of the outer planets possible.
Source NASA Solar System Exploration
Sources
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationGravity assist, Historical origins section
Yuri Kondratyuk suggested that a spacecraft traveling between two planets could be accelerated
- Associated With: Hohmann Transfer Orbit
- Associated With: Delta-v
- Associated With: Sphere of Influence
View the Source 2. NASA Solar System Exploration
National Aeronautics and Space AdministrationNASA Basics of Space Flight, Chapter 4: Trajectories, Gravity Assist Trajectories section
The gravity assist technique was championed by Michael Minovitch in the early 1960s, while he was a UCLA graduate student working during the summers at JPL. Prior to the adoption of the gravity assist technique, it was believed that travel to the outer solar system would only be possible by developing extremely powerful launch vehicles using nuclear reactors to create tremendous thrust, and basically flying larger and larger Hohmann transfers.
- Associated With: Voyager Program
View the Source Frequently Asked Questions
Does a gravity assist take energy from the planet it flies past?
Yes, technically, but the amount taken from a planet as large as Jupiter or Saturn is far too small to ever measure.
Yes, technically. A gravity assist works by having a spacecraft borrow orbital momentum from a planet: the probe speeds up (or slows down) by exchanging momentum with the planet during the close flyby, and by conservation of momentum the planet itself loses (or gains) an equal and opposite amount. In practice this makes no observable difference, because a planet is astronomically more massive than any spacecraft: the change in the planet's own orbital speed from a single flyby is far too small to ever be measured. This is the same technique that made possible missions such as Voyager's grand tour of the outer planets, letting a probe change its speed and trajectory without expending its own propellant.
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