This paper describes a program to develop a lightweight centrifugal compressor for aircraft air cycle environmental control systems (ECS). This compressor will use magnetic bearings for lubrication-free operation and high performance three dimensional impellers. The use of 3-D impellers and magnetic bearings will result in centrifugal compressors superior to current aircraft compressors with improved pressure ratios, flow ranges, and efficiency, as well as reductions in size and weight. The use of the magnetic bearings and three dimensional impeller design extends the centrifugal compressor flow range, reducing the minimum flow rate limit significantly. This oil-free design has applications for aircraft Brayton open cycle cooling, as an alternative to engine bleed air.