2 rounds. Both started with technical questions, then moved into project discussion, then into one or 2 basic behavioral questions. Definitely know fundamentals from mechanics of materials and understand them fully.
Things about beams and beam bending
The following metrics were computed from 46 interview experiences for the SpaceX Engineering Intern role.
SpaceX's interview process for their Engineering Intern roles is fairly selective, failing a large portion of engineers who go through it.
Candidates reported having very good feelings for SpaceX's Engineering Intern interview process.