SpaceX Structures Engineering interview questions

Met a SpaceX employee at a conference and gave him my resume but didn't think anything would come of it. Got a phone call from HR 3 weeks later saying they wanted to interview me the following day. A manager called me on the phone for a 30 minute technical interview the next day. We jumped right into technical questions about one project that I had listed on my resume. He grabbed one aspect of that experience and dove into very technical questions about what kind of analysis I did. After that, he got more theoretical, asking why I did the analysis the way I did, how I would have expected the results to change if various conditions were different, and what some of the errors inherent to my simulation/analysis could have been. We got way down into the weeds until eventually told my interviewer that at this point I was just making educated guesses. He said that was fine and we ended the interview. I called my buddy and we laughed about how poorly the whole thing went. I got a call from HR giving me an offer two hours later.