sling-shot effect

[Bert]

When the Americans were sending space probes far into the outer solar system, it was often said (by the likes of Patrick Moore) that the planners would take advantage of the gravitational pull of a massive planet such as Jupiter or Saturn to speed up the probe as it 'whizzed' by. This was referred to as the sling-shot effect. Now, a moment's thought told me that all the energy the probe gains as it approaches the massive planet will be lost as it goes away, like a ball-bearing rolling down one side of a bowl and up the other side. Was I right? Is there a sling-shot effect?

[jenstar]

The sling-shot effect is mainly concerned with altering the direction of a probe, rather than its speed.