I had a phone screening with a recruiter and then a technical phone call with two leads on the team I would be working on. The phone screening with the recruiter involved very basic interview questions regarding the reasons for leaving my current company and my interest in working for SpaceX. The technical phone call with the propulsion leads was pretty difficult. It involved giving an overview of my resume and reflecting on design and schedule decisions I made on past projects. Then they quickly jumped into technical questions related to fundamental fluid statics and fluid dynamics. I recommend reviewing what you learned in college in as much detail as possible in regards to fluid mechanics, and understand the fundamental behavior of fluids in open and closed systems.