I simply look at it like this: If you fly a ship into a planet anywhere away from the docking ring & mooring, you blow up no matter what it is you fly, so, I think of it as a magnetic shield around the planet that pushes the ships own weight into itself & crushes it while also repelling most of the debris away from the atmosphere, any chunks that have enough inertia to push past the magnetic field would be small enough to burn up before hitting the ground.