I was recruited because I knew CFD and I was an undergrad (which is rare and they wanted cheap labor for the summer). A friend of mine worked there and was asked to find an undergraduate that knows CFD so he gave them my resume. I was contacted the next day to schedule a time the very next day for a interview. It was with a lead propulsion analyst who asked me about shock waves in moving and stationary coordinates, over-expanded vs under-expanded nozzle stuff, nozzle flow, channel flow, when to use bernoulli's equation vs the isentropic equations, derive hoop stress, and when to use k-epsilon vs the k-omega turbulence models. I was interviewed by a computational physicist 2 days laters and he asked me about numerical algorithms, implicit vs explicit, jacobians, adaptive mesh refinement, etc. The very next day they offered me a summer internship.