How are Spacecraft directed towards planet?

via small thrusters, the path is calculated as projections in future where the planet/object will be when spacecraft will arrive. minor adjustments are made along the way.

@Bagardbilla‘s right about thrusters. They fire off earth at a time designed to get them on the right trajectory for where the planet will be when they reach it. This can then be altered with thrusts in space where there’s no air friction, so a small amount of thrust can send the craft on a path without any slowing. They aim the craft to where the planet will be, accounting for gravitational fields it will encounter (including the planet it’s targeting). It’s…well…rocket science

Thanks Bagardbilla and KFingerman for gr8 answers… :)