How do I make a child stay with parent object?

So I want to make a game with thruster-controlled rotation and movement. Currently I have made slots in the model to house the thrusters in a slot exactly the size of the thruster, and with a 1 unit depth (the thrusters are cylinders with a radius of .5 units and a height of 2 units).

However, when I add force using the rigidbody, which rotates the main capsule appropriately, after I reach a high enough speed the thrusters will fall out of their housing slots on the main capsule.

Essentially I want to make the thrusters meld with the surface of the main capsule à la Space Engineers or Empyrion. How would I best go about this?

It is important that the thrusters, and main body remain separate objects for damage calculation purposes (hard point damage), and to properly represent the desired physics of my game. So I can’t – or rather, don’t wish to-- make them one and the same object.

P.S. This is more for a conceptual project at the current stage, so memory and any other issues of that sort are not important factors at the moment.,

Have you considered physics joints?