In the video below, he talks about how he keeps things as real as possible for the actors and the audience:

Here is a BTS photo showing off the full-size ship and the hydraulic system used to simulate movement for the actors:

Interstellar BTS Ship 2

Nolan has been very vocal about trying to keep things as realistic as he can, even if he's shooting a scene that is supposed to take place on another planet or in space. While CG elements can very often blend right in, if the thing you're showing is already real, you don't have to worry about hiding anything. This is obviously not a new technique, and projection has been used for many, many years, but actors often talk about being able to get into their characters better when they have something real to react to as opposed to green screen and their imaginations. 

A great example of this recently is the sky tower home in Oblivion. They used giant screens to project footage of clouds at different times of day, which helped them on multiple fronts — the actors had something real, they didn't have to worry about green or blue spill onto reflective surfaces, and they also used those screens to practically light the set:

What are some of your favorite practical effects? 

Christopher NolanvfxPractical Effectspracticaleffects
Editing & Post-Production