The Oberth effect is the principle, named for the rocket pioneer Hermann Oberth, that a rocket engine burn produces a greater change in a spacecraft's final kinetic energy when performed at high speed, typically near the closest point of an orbit around a massive body, than the identical burn performed at low speed farther away. Mission planners exploit it by timing major engine burns to occur at periapsis, extracting more usable velocity change from the same amount of propellant. The effect follows directly from the fact that kinetic energy scales with the square of velocity, so added speed contributes more energy at higher starting speeds.
Facts
Concept Domain Formulated YearHermann Oberth first described the effect in 1927. Connections
Sources
1. Wikipedia (space and spaceflight articles)
Wikimedia Foundation
Oberth effect (Wikipedia)
Wikipedia, Oberth effect, lead section
The maneuver and effect are named after Hermann Oberth, an Austro-Hungarian-born German physicist and a founder of modern rocketry, who first described them in 1927.
Wikipedia, Oberth effect, lead section, second paragraph
As a result the Oberth maneuver is much more useful for high-thrust rocket engines such as liquid-propellant rockets, and less useful for low-thrust reaction engines such as ion drives, which take a long time to gain speed.
In Group: Orbital Maneuvers and Entry, Lead sentence
In astronautics, a powered flyby, or Oberth maneuver, is a maneuver in which a spacecraft falls into a gravity well and then uses its engines to further accelerate, thereby achieving additional change in speed.
View the SourceFrequently Asked Questions
Why do mission planners time major engine burns to happen at the closest point of an orbit?
Because of the Oberth effect: the same engine burn adds more usable energy when the spacecraft is already moving fastest, which happens at periapsis, the closest point to the body it is orbiting.
This is the Oberth effect, named for the rocket pioneer Hermann Oberth: a rocket engine burn produces a greater change in a spacecraft's final kinetic energy when performed at high speed than the identical burn performed at low speed, because kinetic energy scales with the square of velocity, so added speed contributes more energy at higher starting speeds. A spacecraft moves fastest at periapsis, the closest point of its orbit around a massive body, so mission planners time major burns to happen there to extract more usable velocity change from the same amount of propellant.
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