Two interviews - first was a 30 min informal phone call with engineering manager who asked questions about my background - what projects I was working on, why I was interested in the position etc. Then some technical questions.
Second interview was virtual video interview with two engineers and two managers. Prepared an essay about my interest in space exploration, an hour long presentation about my background and technical details of projects I have worked on. Then moved to one-on-one sessions with everyone on the panel where they ask more specific questions about my experience, some behavioral, some technical. They also showed some drawings and asked some questions about them.
Finally a call with HR where they asked some more questions about career goals, thoughts about living in Washington, desired salary and verbally extended the offer.