How to use an actor to push another one while keeping them linked

Hi, I want use a rocket booster to push a spaceship. I applied a force to the booster and then place it under the spaceship to push the spaceship.
Then when I hit play, at first they go up as I expected, but soon the booster get away from the spaceship. The booster continue going up, but the spaceship lost its driven force. I wonder is there a way to “stick” them together, so that they won’t fall apart in later process?

Put the thruster in the actor with the mesh:

Image from Gyazo

This works now. Thanks!