\n\t\t\t\tDuring a slingshot maneuver, the planet and spacecraft draw close enough together for an exchange of energy to occur.\t\t\t<\/p>\n
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\t\t\t\t![\"An](\"https:\/\/www.newsbeep.com\/il\/wp-content\/uploads\/2026\/08\/JUICE-slingshot.png\")
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\n\t\t\t\t\t\tESA’s JUICE spacecraft, bound for Jupiter’s Galilean moons, performed flybys of the Moon and Earth to help boost it on its way. Credit: ESA – European Space Agency\t\t\t\t\t<\/p>\n
If a satellite\u2019s velocity increases as it approaches a planet during a slingshot maneuver, why does it not decrease by the same amount when it leaves the planet? How can it experience a net gain in velocity? <\/p>\n
Robert Walty
Stephens City, Virginia<\/p>\n
Slingshot maneuvers can seem counterintuitive. We know that a spacecraft speeds up as it approaches a planet but slows down as it pulls away. Consequently, you might think that the close passage of a spacecraft near a planet should have zero net effect. But spacecraft can and do use gravitational slingshot maneuvers to receive a substantial velocity boost.<\/p>\n
Let\u2019s break down such an encounter. As a spacecraft approaches a planet, the planet\u2019s gravity draws it forward. During the close approach, the planet imparts a fraction of its orbital momentum to the vessel: The planet will slow imperceptibly in its orbit while the craft is accelerated to a higher velocity. This is because a system\u2019s overall momentum must be conserved. In this case, it is conserved by the balance between the planet\u2019s negligible speed loss and the vessel\u2019s considerable speed gain.<\/p>\n
So, as the spacecraft leaves the planet\u2019s vicinity, why does it not give back the speed that it gained? In fact, from the planet\u2019s point of view, it does: If you were on the planet and looked at the spacecraft an equal amount of time before and after the craft\u2019s closest approach, it would be moving at the same speed both times.<\/p>\n
But the planet itself is orbiting the Sun. The planet\u2019s momentum thus accelerates the spacecraft in a different direction than the path the craft came in on, causing it to swing around the planet, increasing its speed through the solar system. Quite often, a spacecraft will be programmed to ignite its rockets at the moment of close approach to maximize this velocity boost.<\/p>\n
![\"A](\"https:\/\/www.newsbeep.com\/il\/wp-content\/uploads\/2026\/08\/ASY-SK0826_01.png\")
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\t\tThe Voyager missions extensively employed slingshot maneuvers to guide the two probes through the outer solar system. Voyager 1 was slingshotted by Jupiter toward Saturn, while Voyager 2 used gravity assists from Jupiter to take it to Saturn, from Saturn to take it to Uranus, and from Uranus to take it to Neptune. (In this illustration, a dot appears on the spacecraft\u2019s flight path every four hours.) Credit: Astronomy: Roen Kelly, after NASA; Adobe Stock<\/p>\n
There is a well-known analogy that involves a person throwing a ball into the path of a passing train; the ball will be moving faster after it hits the train than it was prior to the impact. (Note that from the train\u2019s point of view, assuming the ball and train are perfectly rigid, the ball bounces off with the same velocity with which it struck the train.) This collision also impedes the train\u2019s motion, but the difference in the train\u2019s speed is imperceptible because of the substantial mass difference between the two objects.<\/p>\n
In a slingshot maneuver, even though the planet and spacecraft don\u2019t actually collide \u2014 fortunately for the spacecraft \u2014 they draw close enough together for this energy exchange to occur. It\u2019s a win-win-win situation: the probe zips off at a greater clip (win), the planet\u2019s orbit doesn\u2019t change perceptibly (win), and therefore the beleaguered, overworked astronomers involved don\u2019t have to adjust their ephemerides (win).\u00a0<\/p>\n
Edward Herrick-Gleason
Astronomy Educator, St. John\u2019s, Newfoundland and Labrador<\/p>\n","protected":false},"excerpt":{"rendered":"Back to Article List From the August 2026 issue During a slingshot maneuver, the planet and spacecraft draw…\n","protected":false},"author":2,"featured_media":587526,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[73844,85,46,1619,43,18437,141],"class_list":["post-587525","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-ask-astro","tag-il","tag-israel","tag-magazine","tag-news","tag-robotic-spaceflight","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts\/587525","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/comments?post=587525"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts\/587525\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/media\/587526"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/media?parent=587525"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/categories?post=587525"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/tags?post=587525"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}