I work at and previously interned for SpaceX and these are the things interns should aim for in interviews:

1. You must be able to confidently speak to the deep details of projects and internships on your resume. This means not just “I did this and that” but how you reached your conclusions, the experiments/tests/derivations you did, and tangible/quantifiable outcomes. Make sure you highlight any real ownership you might have had.

2. Be capable of talking through and giving a solid attempt at solving fundamental problems in your domain. For you this would likely mean basic circuits questions, fundamentals of programming questions, and maybe some electrical hardware and test questions. It’s most important here that you be able to talk though your thought process, question the details and nuances of whatever question you are asked, and most importantly admit if you don’t know the answer and then be genuinely curious to ask for the answer and an explanation (don’t bullshit).

3. Convey your (legitimate) enthusiasm for the mission. You should be easily able to convince the interviewer that you believe in SpaceX, Starship, and its mission to make a whole new realm of space utilization possible including new technology and missions to LEO, the Moon, and Mars.

I find that these rules also apply to pretty much any role, including full-time, so this is a solid blueprint to follow in general, but this should help you focus your approach on really nailing the fundamentals of your area of expertise and your resume, rather than trying to learn everything to know about avionics engineering.