Gravity assist

<p>A gravity assist, gravity assist maneuver, swing-by, or generally a gravitational <a href="/facts/Slingshot/mexpE3ac">slingshot</a> in <a href="/facts/Orbital_mechanics/oB3tqNG9">orbital mechanics</a>, is a type of <a href="/facts/Spaceflight/zPrnATzo">spaceflight</a>  <a href="/facts/Flyby_(spaceflight)/BtJe76fP">flyby</a> which makes use of the relative movement (e.g. orbit around the <a href="/facts/Sun/CadPCVHh">Sun</a>) and <a href="/facts/Gravity/bqAN7DdQ">gravity</a> of a <a href="/facts/Planet/rbPjE6Bx">planet</a> or other <a href="/facts/Astronomical_object/BCHLa0Q2">astronomical object</a> to alter the <a href="/facts/Course_(navigation)/CWexuXNF">path</a> and <a href="/facts/Speed/I3qgMPfs">speed</a> of a <a href="/facts/Spacecraft/YQqQaUw0">spacecraft</a>, typically to save <a href="/facts/Propellant/K88ymXRy">propellant</a> and reduce expense.
</p><p>Gravity assistance can be used to <a href="/facts/Accelerate/UVDmjYvR">accelerate</a> a spacecraft, that is, to increase or decrease its speed or redirect its path. The "assist" is provided by the motion of the gravitating body as it pulls on the spacecraft. Any gain or loss of <a href="/facts/Kinetic_energy/aJRxUd4p">kinetic energy</a> and <a href="/facts/Linear_momentum/TTkGv5eY">linear momentum</a> by a passing spacecraft is correspondingly lost or gained by the gravitational body, in accordance with <a href="/facts/Newton%2527s_laws_of_motion/XKzGTXK1">Newton's Third Law</a>. The gravity assist maneuver was first used in 1959 when the Soviet probe <a href="/facts/Luna_3/Fw9s09I8">Luna 3</a> photographed the far side of Earth's <a href="/facts/Moon/zKHqEMPb">Moon</a>, and it was used by interplanetary probes from <a href="/facts/Mariner_10/jpKRBPKH">Mariner 10</a> onward, including the two <a href="/facts/Voyager_program/cPm6qnNx">Voyager</a> probes' notable <a href="/facts/Planetary_flyby/g65t37fh">flybys</a> of Jupiter and Saturn.
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Gravity assist open-in-new

Gravity assist