I'm also having an issue with RT2 and KSP Interstellar, although it may be another mod I have installed. (B9, Kerbal Alarm Clock, Kerbal Engineer Redux, KW Rocketry, Infernal Robotics, and Enhanced Navball). None of the RT2 parts are showing up at all in the tech tree or in building. Even when I try to use the stock antennae or satellites, they don't have options to work as RT2. Not sure if I have to select a different tech tree option?