This project is directed to the development of low-loss, high power-density Aluminum Nitride (AlN)/Gallium Nitride (GaN) heterostructure based transistors for enabling high-efficiency solid state power amplifiers (SSPA) needed for advancing capabilities of future robotic and human exploration spacecraft. The AlN/GaN heterostructure is a particularly attractive system for switch-mode applications due to the extremely high charge density, high electron mobility, high intrinsic breakdown field, and physical thinness achievable and has seen widespread investigation toward solid-state amplifiers in the recent years. However, very few innovations have been proposed with this heterostructure despite its expansive capacity for various creative device concepts. A new patent-pending multichannel AlN/GaN Field Screening High Electron Mobility Transistor (FS-HEMT) design is described. Preliminary experimental results are presented validating design principles that will eliminate current collapse phenomenon at X- and Ka-band frequencies that has plagues traditional HEMT designs and will ultimately deliver a low-loss switch-mode device.