You use gravitational flybys, slingshots, where you pass by a planet at very low altitude, a few thousand kilometers, and then you get the velocity of that planet around the sun for free.
Valja iskoristiti gravitacijske praćke gdje prilikom prolaska kraj planeta na vrlo malenoj visini od nekoliko tisuća kilometara, možete besplatno iskoristiti brzinu kretanja tog planeta oko Sunca.