10 SET up THE SHIP
The activator lets Houdini know when to unfreeze the broken pieces of the wall. But the geometry that actually collides with the pieces, generating their movement, is the spaceship itself. At 01:02:00, you can see how to bring its Alembic file into Houdini, convert it to a primitive, and give it normals using a Facet node. The next step is to convert the primitive to a volume in order to make the collision more accurate.