Over the 59-65 GHz band for military satellite communications, QuinStar Technology proposes to develop a 50 W solid-state power amplifier (SSPA) with 30 dB power gain and 25% associated power-added-efficiency (PAE). We propose to employ a combination of state-of-the-art (SOA) GaN device technology, innovative (Class F) switching mode concepts in MMIC design and high-efficiency waveguide circuit combining techniques to meet the design goals. Specifically, our approach is to develop two MMIC chips. One is a high-efficiency PA MMIC. The other is a quasi-linear driver MMIC. These two chips are configured into arrays, mounted directly into the 16-way combiner system and optimized to meet the SSPA requirements. Based on measurements of 16-way waveguide combiners at adjacent frequencies (V and W-bands), we project a combining loss of 0.32 dB or a combining efficiency of 93%. The size and weight of the SSPA are estimated to be 2.5 x 2.5 x 1.0 inches and 9.5 oz. respectively.